Comissioning

SHE MANUAL

COMMISSIONING

LARSEN & TOUBRO LIMITED E & C DIVISION

SAFETY CONTROL DEPARTMENT POWAI

E & C Division SHE Manual (Commissioning)

Contents 1

Contents

Part III: Commissioning of plant

1. Corporate Policy

2. Safety responsibilities

2.1 Safety Control Department

2.2 Commissioning Team Leader

2.3 Commissioning Team members

3. Rules and regulations

3.1 Safety practices operating personnel

3.2 Safety Rules Contractors/Sub – Contractors

4. Safety during Pre-commissioning

5. Technical Measures for common Refinery Operations

5.1 Plant Layout

5.2 Alarms / Trips / Interlocks

5.3 Control Systems

5.4 Corrosion / Selection of Materials

5.5 Drum / Cylinder Handling

5.6 Pressure Plants/Reactors

5.7 Static Electricity

5.8 Causes of Plant failure

5.9 Explosion Relief

5.10 Hazardous Area Classification / Flame proofing

5.11 Inerting

5.12 Isolation

5.13 Leak / Gas Detection

5.14 Active / Passive Fire Protection

5.15 Quench Systems

5.16 Raw Materials Control / Sampling

5.17 Reaction / Product Testing

5.18 Reliability of Utilities

5.19 Relief Systems / Vent Systems

5.20 Roadways / Site Traffic Control

5.21 Secondary Containment

5.22 Segregation of Hazardous Materials

5.23 Warning Signs

5.24 Protective Devices


Contents 2

6. Material Safety Data Sheet

6.1 MSDS Contents

6.2 National Fire protection Association (NFPA) Hazard diamond

Interpretation

6.3 MSDS of various chemicals generally used in refinery

7. On site Emergency plan

8. The Environmental Preservation Acts in India

8.1 The Water prevention and Control of pollution Act, 1974

8.2 The Water Prevention and Control of Pollution Cess Act, 1974

8.3 The Air Prevention and Control of Pollution Act 1981

8.4 The environmental Protection Act,1986

8.5 Hazardous Waste Management and Handling Rules,1989

8.6 The Manufacturer Storage and Import of hazardous Chemical

Rules,1989

9. Procedural Control

9.1 Procedure for Sample Collection

9.2 Procedure for the disposal of Waste

9.3 Procedure for pipeline cleaning, gas freeing, purging, draining

of equipment and lines.

9.4 Procedure for isolation of flare header, safety valve

9.5 Permit to work system

10. Personnel Protective Equipment (PPE)

10.1 Non – Respiratory

10.2 Respiratory

11. Gas Detection Devices

11.1 Combustible/Combustible gas Detector

11.2 Toxic gas detectors

11.3 Oxygen Indicator

LARSEN & TOUBRO LIMITEDEngineering & Construction Division

CORPORATE POLICYCORPORATE POLICY

1. To Engineer and Execute projects with consistent quality, cost and delivery inline with the requirements of our customers, and to exceed or meet theirexpectations, whilst enhancing our shareholder value.

2. To set and review quality objectives for Continual Improvement of ourproducts and services, whilst implementing the globally recognisedmanagement systems for Quality, Safety, Environment and InformationTechnology, and integrating these systems with our business partners andcustomers.

3. To design / operate and maintain safe and environmentally friendly plantswhich meet all applicable statutory and regulatory requirements.

4. To advance / ensure the use of better and cleaner technology to minimiseadverse environmental impacts.

5. To continually reduce the risk of pollution through setting environmentalobjectives in our design / operation and maintenance processes, based on thefeedback.

6. To deploy Information Technology for increasing the efficiencies of ourbusiness processes, while ensuring its security by protecting information asvaluable assets and ensure availability, integrity and confidentiality of allinformation.

7. To comply with all applicable occupational Health & Safety legislation andcontinually improve safe working practices through setting health and safetyobjectives and ensure good health, safety and security of all our people, ourbiggest asset.

8. To encourage enthusiasm, innovation and empowerment whilst developinginspiring leaders to make working at L&T a rich experience and create newglobal benchmarks in whatever we do.

9. To promote a culture of mutual trust, caring and sharing achievements, withour people, our society, our stakeholders and our customers for the growthand benefit of our Nation.

10. As an undisputed leader in the Indian context, we continue to make thingsthat make India proud, and shall strive to be amongst the globallyoutstanding companies, which the World is proud of.

_____________________________Issue : Jan , 2002 K . VENKATARAMANAN ( Member of the Board & President )


____________________________________________________Responsibility 1

2. SAFETY RESPONSIBILITIES

2.1 Responsibility of the safety control department

The responsibility of the Safety Control is to develop safety

consciousness amongst the commissioning team. The Safety Control will

function in an advisory capacity. The Safety Control Department will

ensure that:

- The commissioning team members have access to and are familiar

with the HSE Manual for Commissioning.

- The commissioning team is familiar with the process hazards and the

hazards of chemicals being used / handled during commissioning. The

Safety Control will assist SBU for the procurement of Personnel

Protective Equipment.

- The Safety Control will co-ordinate with the Safety Department of

client / owner on the safety related issues in consultation with the

commissioning team leader.

- A representative from the Safety Control will be present during the

commissioning of the plant. His responsibilities would include :

- Identifying the requirement of safety equipment and

Personnel Protective Equipment (PPE), ensuring its

availability at site, and enforcing use of the PPE as the job

requirement.

- Ensure functioning of the Fire and Safety equipment.

- Ensure functioning of Fire Alarm System and Gas Detector

System before entry of Hydrocarbons into the unit.

- Check availability of proper emergency lighting and wind

cock.

- Ensure availability of Display Boards at site, detailing the

safety precautions, the important telephone numbers, the

escape route in case of any emergency like fire or emission

of toxic gases etc.


____________________________________________________Responsibility 2

- Enforcement of Safety Procedures in dealing with hazardous

jobs like Hot Work, entry / work in Confined Space / Vessels

etc.

- Ensure availability of First Aid kit. In consultation with the

Commissioning Team Leader, will co-ordinate for the medical

assistance for the commissioning team.

- Monitoring the environment as and when necessary for

toxicity level and noise level. The HSE department of the

client can be asked for assistance in this regard.

- Formulation of proper evacuation plan in co-ordination with

client safety department.

- Organise regular safety meetings with client safety

department and the commissioning team.

- Carryout Emergency Mock Drill in co-ordination with the

client's fire fighting / safety / operation departments.

- Organise training of the commissioning team with respect to

use of fire fighting equipment and first aid measures.

- Will carry out the Safety Audit before start of commissioning

activities.


____________________________________________________Responsibility 3

2.2 Responsibility of the commissioning team leader

1. Person responsible for overall commissioning, regardless of his

designation, will be designated as Commissioning Team Leader to

ensure safety during commissioning.

2. The Commissioning Team Leader (CTL) will be responsible to ensure

safety of the commissioning team and the facility being

commissioned.

3. The CTL will ensure that:

a) The HSE manual for commissioning is accessible to the

commissioning team.

b) The Personnel Protective Equipment necessary for the safe

execution of job is inspected and is in order.

c) The commissioning team members are briefed on the

availability and use of PPE.

d) The commissioning team members are briefed on process

hazards and that they are following the safe method of

working.

4. Co-ordinate with the safety department of the client.

5. Obtain copies of the safety manual and other safety related

documents from the client. This is more so in case of project site

within or near an operating plant.

6. Ensure availability of medical help and facility for the treatment in

case of:

a) Exposure to hazardous chemical.

b) Physical Injury

c) Asphyxiation

7. The CTL will, before the start of commissioning, ensure that the

safety audit (Check) of the plant is completed and the checklist

neutralized (Corrective action completed).


____________________________________________________Responsibility 4

8. The CTL will ensure that the commissioning team members are

aware of overall plot plan and familiar with the emergency escape

routes.

9. The CTL will ensure that a mock emergency drill is conducted and

emergency procedures followed.

10. The CTL will ensure before undertaking the commissioning that he

has all emergency phone numbers with him.

11. The CTL will ensure that he has the copy of the "On-site Emergency

Management Plan " and is conversant with its requirements.


__________________________________________________Responsibility 5

2.3 Responsibility of the commissioning team members

All the members of the commissioning team will ensure that:

1. They have read and familiarized themselves with the HSE

commissioning manual.

2. They have read the HSE protocol of the Operations Manual.

3. They have read and have access to the Material Safety Data

Sheet of the Hazardous Chemicals being handled.

4. They are aware and conversant with the Process Hazard of the

Plant being commissioned.

5. They have the list of PPE and familiar with the use of these

equipments.

6. They have read and understood the safety procedure of the

operating plant.

7. They are familiar with the plant layout and knowledge of the

escape routes.

8. They are using the right PPE.

9. They are familiar with the exposure symptoms of the hazardous

chemicals being handled.

10. They have access to the emergency telephone numbers.

11. They are physically fit and mentally alert during the work.


____________________________________________________Rules & Regulations 1

3.0 BASIC SAFETY RULES OPERATING PERSONNEL

Basic Safety rules to be followed by the operating personnel within the

plant limits are given below. The commissioning team is required to know

and observe these rules.

Whenever specific safety rules are provided by the client, (the

commissioning team leader is required to procure such rules) the same

shall be adhered to. This will ensure safety of the personnel, plant and

equipment.

1. Smoking is not permitted in any part of the operating plant / areas

except in smoking booth / locations specifically designated and

permitted for smoking.

2. Wearing of loose clothes is unsafe.

3. Walk through or across operating plants not to be practiced.

4. Operation of machine / equipment by authorized personnel only.

5. Use of personnel protective equipment to comply with.

6. To take proper precautions and use of fall protection equipment

when working at heights.

7. Compliance to confined space entry procedures when entering

empty tanks / vessels / reactors or closed locations.

8. To obtain necessary safety permit before start of any repair

maintenance work.

9. To provide and maintain protective guards on moving machinery

and parts to replace protective guards after completion of

maintenance work.

10. Not to use compressed air for blowing dust, drying of clothes it is

unsafe.

11. Use of empty drums / barrels as support or workbench is unsafe.

12. Removal of left over material / junk after completion of work.

13. Keep plant area clean and free of junk.

14. Keep stairways / platforms / walkways clean.

15. Use of approved safety lights and torches. Use of only flame proof

24 V portable lamps inside tanks / confined locations.


____________________________________________________Rules & Regulations 2

16. In case of contamination of clothes with chemicals to follow proper

safety instructions according to the chemical's Material Safety Data

Sheet (MDDS) supplied by the manufacturer / supplier

17. Not to use solvents for cleaning clothes / hands.

18. Use of only authorized vehicles only with in the plant premises and

to driven by licensed persons within the speed limits.

19. Use of photo Flash unit in the operating plant is unsafe .

20. Use of camera only on authorization.

21. Use of drugs / alcoholic drinks / narcotic within the premises

prohibited.

22. Carrying of arms and ammunition prohibited.

23. In case of accident / injury follow the procedure as per the E&C

HSE Manual.


__________________________________________________Rules and Regulations 3

SAFETY CODES FOR CONTRACTOR / SUB-CONTRACTOR

Following are the general safety codes to be imposed on contractors /

subcontractors to ensure safety within the operating plant. These codes

should be followed by the commissioning team. In case specific safety

codes are available from the client for any specific job, the same should

be governing.

1. Smoking and smoking requisites within the plant B/L is strictly

prohibited.

2. No spark or flame-producing gadgets like lighter, photo-flash, torch

light, electronic equipment is allowed inside the plant area.

3. Entry of automotive vehicles within the plant is restricted.

4. Safety clearance procedure: Any work carried out within the plant

must be covered by the work permit system prevailing in the

plant- Following types of work normally require work permits.

A. Any work involving open flame and sparks such as welding, gas

cutting, soldering, grinding (hot working).

B. Sand blasting (cold working)

C. Use of gasoline, diesel, electric power driven engine and tools.

D. Entry of vehicles inside the battery limits of process area, tank

dykes, pump house, API separators and loading gantries.

E. Entry of personnel into hazardous areas like TEL building,

floating roof of storage tanks.

F. Entry of personnel into confined space.

G. Radiography

H. Working on Electrical lines/equipment

5. All conditions stipulated in the safety permit must be read carefully

and complied with.

6. When using gas cylinders they should be used in upright position

and complied with safety rules for use of gas cylinders.

7. All personnel to use personnel protection equipment suitable for

the job.


__________________________________________________Rules and Regulations 4

8. All personnel to follow dress code.

9. All personnel to follow personnel conduct rules.

10. Vehicles to comply with traffic rules regarding speed limit, parking,

number of passengers and vehicle fitness with regard to breaks

horns, lights, muffler etc.

11. Vehicle to be driven by authorized person only.

12. When welding is being done proper screen must be provided to

proven? Eye injury and guards against fire hazard due to sparks

and hot slugs.

13. All electrical equipment used are properly grounded and fitted with

proper 3 pin plugs. All cables in one piece preferable.

14. Workplace to be clean and tidy good housekeeping to be practiced.

15. Ensure that existing fire fighting equipment are not to be

obstructed and no material is piled to cause blockage or hindrance

to operation.

16. Use barricades during (i) excavation (ii) hoisting (iii) areas

adjudged hazardous by shift in charge (iv) existing property

subject to damage by work.

In addition to above basic safety codes, the commissioning team may

have to undergo safety induction training, which will be imparted by the

Safety Control.


__________________________________________________ Precommissioning Activities 1

4. Safety during Pre-commissioning

Pipework erection

All pipes shall be inspected before erection to ensure that they are free

from loose contamination.

Pipework shall be erected on permanent supports designated for the

line. Temporary supports shall be kept to an absolute minimum, but to

an extent sufficient to protect nozzles and adjacent piping from

excessive loads during the erection.

Pipework shall be fitted in place without springing or forcing to avoid

undue stressing of the line or strain being placed on a vessel or item of

equipment, etc.

All temporary pipe spools and supports that are an aid to erection,

testing/flushing, sea fastening, etc. are to be specially marked for

removal identification.

Flanged joints

Before assembly flanges shall be clean and free from any detritus

matter (e.g. rust, dirt or other contamination). The joints shall be

brought up flush and square without forcing so that the entire mating

surfaces bear uniformly on the gasket and then mated-up with uniform

bolt tension.

Valve and equipment flange connections

Flange covers shall be retained on all flange connections to valve or

equipment, until ready to connect the mating piping.

All equipment shall be blanked, either by pressure test blanks, spades

or blinds, to stop the ingress of internal pipe debris.

Flanges connecting to strain sensitive mechanical equipment e.g.

pumps, compressors, turbines, etc. shall be fitted-up in close parallel

and lateral alignment prior to tightening the bolting.



In general, flange connections to equipment shall be the last

connection made on completion of a line or interconnecting system of

lines.

With the piping flange fitted and prior to bolting-up the joint, the

following tolerances shall be maintained:

• Bolting shall move freely through accompanying bolt-holes at

right angle to the flange faces.

• There shall be a clear gap between two flange faces before

gasket installation. There shall be sufficient flexibility to install

and replace gaskets.

Gaskets

Gaskets shall be treated in accordance with manufacturers'

instructions. Gaskets shall be replaced after opening or dismantling of

flange connections.

RTJ gaskets are to be lightly smeared on the mating surface with a

propriety anti-friction lubricant prior to fitting between the flange

grooves. Anti-friction lubricant, compatible with the flange material

and process fluid shall be used.

Bolting

Bolting shall be in accordance with the requirements in the Piping and

valve material standard.

Manually pulled flange bolts and studbolts shall extend fully through

their nuts with minimum one, maximum five threads.

All flanged stud bolts shall be progressively controlled to equalise bolt

pressure on the gasket. A detailed procedure shall be developed prior

to start.

Hydraulic bolt thigthening shall be used on all bolts greater than 1"

diameter.

Calculation of the required bolt tension value shall be in accordance

with the DIN 2505, with the following exeptions:

• Minimum required bolt tension value shall be multiplied with 1.5.



• Maximum bolt tension value shall not exceed 2/3 of the specified

yield of the bolt or maximum allowable stress for the gasket.

Nuts and bolts shall have their grade marks visible after installation.

Studbolts cut from long lengths of studding shall have material grade

stamped on end of each cut.

Bolts larger than 1" shall be protected against mechanical damage and

corrosion.

Pipe support

Pipe supports shall be in accordance with the relevant pipe support

detail drawings developed for the project.

Piping shall not be forced to fit with support locations in such a manner

that additional stress is introduced.

Where spring support are installed the spring shall locked gagged until

commissioning/start up.

All piping shall be arranged to facilitate supporting, and shall be

planned for ease of removal of equipment for inspection and servicing.

Pipes shall not normally be supported by other pipes, i.e. individual

supporting is required.

Vent holes in wear plates and trunnions are generally not required.

However, when the wear plate or a trunnion covers a circumferential

weld that has not been pressure tested, a vent hole is required for leak

detection.

Global tolerances, installation

Hook-up termination points shall be within ±25mm in all directions.

Over length may be provided where required.

Installation tolerances of piping components shall be as required by

the individual service of the piping component including requirements

for:

• Maintenance access.

• Position relative to surrounding steelwork, equipment, cable tray

and HVAC duct routings.



• Positioning of pipe supports relative to the structural steel.

• Pipe stress.

FLUSHING

General

The initial flushing shall be carried out prior to pressure testing. For

austenitic steelwork flushing can be performed after pressure testing,

upon agreement.

General requirements for flushing for specific systems are listed in

table 1, annex B.

Procedures for flushing shall be developed prior to start.

All pipework shall be free from dirt, grease and temporary protective

coating upon completion of flushing.

Hydro flushing

Items of equipment that would be sensitive to damage during hydro

flushing shall be removed, blocked off or isolated. A list shall be

prepared and be part of the flush & test procedure.

Ball valves shall be flushed in fully open position.

All piping systems shall be flushed using high-pressure jet flushing

equipment, such as rotating hose or rotating nozzle. Minimum

pressure shall be 600 bar.

Below 4", High Velocity Water Flushing (HVWF) may be used. Water

velocity shall be a minimum of 10m/s. On systems where high

pressure jet flushing cannot be used due to complicated shapes and/or

long runs HVWF may be used.

The flushing medium shall in general be fresh water. When flushing

stainless steel lines, the chloride ion content shall be less than 200

ppm.

After flushing, the piping systems shall be completely drained and

protected against corrosion.



Ball valves shall be flushed fully open.

Pressurised air shockblowing

This method may be used as an initial cleaning method for instrument

air, plant air and as an alternative method for initial cleaning of small-

bore pipe (less than 2 inch). This method may also be used when

there are problems removing trapped liquid in the circuit, or to verify

cleanliness of small-bore pipe where video inspection is impossible or

inadequate due to pipe dimension or configuration.

When using PAS method for cleaning or verification the procedure shall

be repeated until cleanliness is acceptable.

The air shocking pressure shall never exceed the working pressure of

the system and shall never be more than 8 bar. Safety precaution shall

be taken like warning to all the personnel working nearby as well as

effective barrication to avoid unauthorised entry when this method is

used.

Pneumatic flushing

In cases where water is not desirable in the piping system (e.g.

instrument/utility air), flushing by pressurised air or PAS shall be

carried out. When pressurised air is used, the minimum velocity shall

be 35m/s. Procedure covering all safety aspects shall be established.

PRESSURE TESTS

General

The test pressure shall, unless otherwise specified, be in accordance

with ASME B31.3.

Testing shall not take place with system temperatures 4°C or less or

where the ambient temperature during test falls by 5°C or more, nor

during rain or fog unless under suitable cover. Hydrostatic pressure

test may however be performed under a lower temperature with a

proper frost preventive added to the test water.

The following are excluded from pressure tests:



• All small bore instrument control piping downstream of the first

piping block valve.

• Open drains and vents to atmosphere (leak test only).

Test preparation

Pressure, temperature and time recorders shall be used for all

hydrostatic tests. The pressure shall be shown in bar. Pressure gauges

and recorders used to indicate and record test pressure shall be dead

weight tested for accuracy according to a procedure, dependent of

type of equipment.

Minimum of one gauge shall be positioned at the highest point and one

recorder to be positioned at the lowest point. Accuracy of pressure

gauge shall be at least 1-2% at full scale and 1-2% for the recorder.

The test pressure shall be within 60% of the gauge range (20% from

top and 20% from bottom).

If there is a deviation of more than 2% between gauge and recorder

during test, the test shall be stopped and the equipment recalibrate.

Piping joints and welds shall not be insulated or physically covered

until satisfactory completion of testing in accordance with this

specification, except for painting of prefabricated welds.

All piping shall be adequately supported before the pressure test.

Spring or other variable type supports shall be blocked to prevent

movement.

Unless otherwise noted, all valves are to be through body tested. First

block valve for pressure instruments shall be included in the test.

Piping containing check valves shall have the source of test pressure

on the upstream side. If this is not possible, the check valve disc shall

be removed or jacked open.

Ball valves shall be pressure tested in the half open position. Other

valves shall be tested in the fully open position.

Where the test pressure to be applied to the piping is greater than the

maximum allowable test pressure for valves, the valves shall be

blinded off on the side to be tested, or removed and replaced by

dummy spools.



Turbines, pumps, compressors and vessels shall be blinded off prior to

pressure testing.

A list shall be prepared for sensitive equipment that shall be removed,

blocked off or isolated during testing, such as relief valves, inline

instruments, turbines, pumps, compressors and vessels. This list shall

be a part of the test procedure.

Test media

For hydrostatic testing the test medium shall in general be fresh

water, except that other suitable liquid may be used if:

• The piping or inline equipment would be adversely affected by

water.

• If the liquid is flammable, it's flash point shall be at least 49°C

and consideration shall be given to the environment.

• The liquid is approved to be used.

The chloride ion content of the water used for pressure testing

stainless steel lines shall be less than 200 ppm and the line shall be

properly drained soon after testing. pH value of the water shall be

between 6.5 and 7.5.

Carbon steel systems as defined in table 1, annex B shall be tested

with an acceptable preservation fluid. The preservation fluid shall be a

water impellent and emulsifiable rust preventive lubricating oils that

contain detergents and inhibitors that have been specially formulated

to prevent rust.

For pneumatic testing, the test media shall be oil free, dry air or any

inert gas. The use of air for testing shall be limited to a maximum

pressure of 7.0 barg. Above this pressure nitrogen shall be used. The

extent of pneumatic testing shall be approved.

For instrument/utility air systems, where the introduction of water is

undesirable, test media shall be air or inert gas.



Hydrostatic testing

The test pressure shall be maintained for a sufficient length of time to

permit visual examination to be made of all surfaces, welds and

connections, but not less than thirty minutes. A one hour test duration

shall apply for piping systems with pressure rating class 600# and

above. Care shall be taken to ensure that overpressuring due to static

head does not take place.

The piping systems shall not show any sign of plastic deformation or

leakage.

Pneumatic testing

The sequence of test pressuring installed systems shall be as follows:

• A pressure of 0.5 bar shall be introduced in the system and a

leak test performed. The pressure shall gradually be increased to

50% of the specified test pressure and kept for minimum 10

minutes to equalise strain.

• The pressure shall then be increased in steps of 10% of the

specified test pressure, until the specified test pressure is

reached. At each step, the pressure shall be kept for 10 minutes

minimum to equalise strain.

• The specified test pressure shall be kept for one hour. The

pressure shall than be reduced to the design pressure before

examining for leakage.

The piping systems shall not show any sign of plastic deformation or

leakage.

After completion of test

The tested systems shall be depressurised by opening the

depressurising valve in the test rig. After depressurisation, all vents

and low point drain valves shall be opened and the system shall be

thoroughly drained where the test medium is water. Where required,

blowing by dry air or Pressurised Air Shock Blowing to remove any

trapped water to be performed.



Systems with drying requirement as defined in table 1, annex B shall

be dried out after hydrotesting with dry oil free air with a dew point of

-10°C. Drying can be terminated when the dew point at the outlet is

equal to the dew point at the inlet.

Other methods, such as vacuum drying or air shocking, may also be

used if the same dryness can be documented.

Requirement for drying as defined in table 2, annex C shall take in to

consideration the time for start up of system. If more than 3 months

to commissioning, drying shall be followed by preservation with

nitrogen to keep the pipe system completely dry and to avoid

condense. Other alternatives are subject to agreement.

Reinstallation of the system shall be performed in accordance with the

test procedure.

Where permanent or temporary strainers have remained in place for

the hydrostatic pressure test, they shall be removed following the test

and thoroughly cleaned before reinstalling.

Ends of pipes and nozzles shall be fully protected against the ingress

of foreign material by the use of caps, plugs or plate blinds sealed with

gaskets. These shall not be removed until just prior to final assembly.

Flange parallellity and alignment to equipment shall be checked prior

to reinstatement.

Vent holes in reinforcing pads shall be sealed upon completion of

pressure test.

Verification of cleanliness

All systems shall be internal visual inspected for acceptable cleanliness

by spot check. Internal visual inspection includes the use of

Boroscope, video etc.

If pipe configuration in critical parts of systems as defined in table 1,

annex B is too complicated for visual inspection, the PAS method or

other suitable methods shall be used for verification of cleanliness.



CHEMICAL CLEANING

Lines to be chemical cleaned shall be identified on the P&ID's and Line

Index.

A procedure shall describe in detail the steps for chemical cleaning.

Chemical cleaning shall include:

• Degassing.

• Chemical cleaning/descaling.

• Neutralisation.

• Passivation.

• Water flushing.

• Drying.

The end result shall be a clean smooth surface.

Maximum temperatures used during these operations shall not exceed

maximum design temperature for the systems as listed in the Line

Index.

For equipment such as turbines, generators, pumps and compressors,

the piping to be cleaned shall have all sensitive items that can be

damaged by the cleaning medium removed or blanked off.

Generally, the following items shall not be chemically cleaned (items

shall be identified on chemical cleaning are):

• All instrument tubing downstream the first piping block valve.

• Piping systems with copper alloy materials.

• Flexible hoses.

• Vessels.

• Exchangers.

• Pumps.

• All bolted/screwed valves and instruments.

Removed or blanked off items shall be cleaned separately prior to

reinstallation.



The systems to be cleaned shall have high and low point vents and

drains installed. "Dead legs" shall be avoided.

Cleaning shall be carried out after pressure testing unless otherwise

specified.

If more than 3 months to start up of commissioning activities, system

shall be preserved with nitrogen. Overpressure shall be 0.5 bar.

HOT OIL FLUSHING

General

Required cleanliness for systems subject to hot oil flushing shall be in

accordance with table 1, annex B.

A detailed procedure for hot oil flushing shall be developed out prior to

start.

Filters used for hot oil flushing shall be:

• 3µm ABS for hydraulic systems.

• <=10µm ABS for lube and seal oil.

Filling of lubricant oil shall take place through filters with 10µm ABS.

Flushing and sampling to verify cleanness shall take place at turbulent

flow, upstream any filters.

The Reynolds number shall be min. 4000.

The level of cleanness shall be documented from an automatic particle

counter or a membrane checked in a microscope before a flushing

operation is considered finalised.

A flowmeter shall be installed to verify flow used during flushing

operation.

Maximum water content in oil used for flushing shall be less than

500ppm.

Marking

Piping spools or systems that have been chemical cleaned or hot oil

flushed shall be marked in a unique manner.


__________________________________________________Plant Layout 1

5.1 Plant Layout

This Technical Measures Document refers to Plant Layout.

General Principles

Plant layout is often a compromise between a number of factors such as:

• The need to keep distances for transfer of materials between

plant/storage units to a minimum to reduce costs and risks;

• The geographical limitations of the site;

• Interaction with existing or planned facilities on site such as

existing roadways, drainage and utilities routings;

• Interaction with other plants on site;

• The need for plant operability and maintainability;

• The need to locate hazardous materials facilities as far as possible

from site boundaries and people living in the local neighbourhood;

• The need to prevent confinement where release of flammable

substances may occur;

• The need to provide access for emergency services;

• The need to provide emergency escape routes for on-site

personnel;

• The need to provide acceptable working conditions for operators.

The most important factors of plant layout as far as safety aspects are

concerned are those to:

• Prevent, limit and/or mitigate escalation of adjacent events

(domino);

• Ensure safety within on-site occupied buildings;

• Control access of unauthorised personnel;

• Facilitate access for emergency services.

In determining plant layout designers should consider the factors in

outlined in the following sections.

Inherent Safety

The major principle in Inherent Safety is to remove the hazard

altogether. The best method to achieve this is to reduce the inventory of


__________________________________________________Plant Layout 2

hazardous substances such that a major hazard is no longer presented.

However, this is not often readily achievable. Other possible methods to

achieve an Inherently Safer design are:

• Intensification to reduce inventories;

• Substitution of hazardous substances by less hazardous

alternatives;

• Attenuation to reduce hazardous process conditions i.e.

temperature, pressure;

• Simpler systems/processes to reduce potential loss of containment

or possibility of errors causing a hazardous event;

• Fail-safe designs e.g. valve position on failure.

Plant layout considerations to achieve Inherent Safety are mainly those

concerned with domino effects (see below).

The Dow / Mond Indices

These hazard indices are useful for evaluating processes or projects,

ranking them against existing facilities, and assigning incident

classifications. They provides a comparative measure of the overall risk of

fire and explosion of a process, and are useful tools in the plant layout

development stage since they enable objective spacing distances to be

taken into account at all stages.

Although these are useful rule-of thumb methodologies for first

consideration of plant layout, they do not replace risk assessment. The

distances derived between plant units using these systems are based

upon engineering judgement and some degree of experience rather than

any detailed analysis.

Domino Effects

Hazard assessment of site layout is critical to ensure consequences of

loss of containment and chances of escalation are minimised. Domino

may be by fire, explosion (pressure wave and missiles) or toxic gas cloud

causing loss of control of operations in another location.


__________________________________________________Plant Layout 3

Fire

A fire can spread in four ways:

• Direct burning (including running liquid fires);

• Convection;

• Radiation;

• Conduction.

The spread of fire from its origin to other parts of the premises can be

prevented by vertical and horizontal compartmentation using fire-

resisting walls and floors. Consideration should also be given to the

spread of flammable material via drains, ducts and ventilation systems.

Delayed ignition following a release may result in spread of flames

through such systems via dispersed flammable gases and vapours.

Protection against domino effects by convection, conduction and radiation

can be achieved by inherent safety principles i.e. ensuring that the

distances between plant items are sufficient to prevent overheating of

adjacent plants compromising safety of those plants also. Where this is

not possible due to other restrictions, other methods such as fire walls,

active or passive fire protection may be considered.

Explosion

Explosion propagation may be directly by pressure waves or indirectly by

missiles. As for fires, inherently safe methods that should be

considered are:

• arranging separation distances such that damage to adjacent plants

will not occur even in the worst case;

• provision of barriers e.g. blast walls, location in strong buildings;

• protecting plant against damage e.g. provision of thicker walls on

vessels;

• directing explosion relief vents away from vulnerable areas e.g.

other plants or buildings, roadways near site boundaries.

Toxic Gas Releases

Toxic gas releases may cause domino effects by rendering adjacent

plants inoperable and injuring operators. Prevention/mitigation of such

effects may be affected by provision of automatic control systems using


__________________________________________________Plant Layout 4

inherently safer principles and a suitable control room (see section below

on Occupied Buildings).

Reduction of Consequences of Event On and Off Site

In addition to the measures described above, Plant Layout design

techniques applicable to the reduction of the risks from release of

flammable or toxic materials include:

• Locating all high-volume storage of flammable / toxic material well

outside process areas;

• Locating hazardous plant away from main roadways through the

site;

• Fitting remote-actuated isolation valves where high inventories of

hazardous materials may be released into vulnerable areas;

• Provision of ditches, dykes, embankments, sloping terrain to

contain and control releases and limit the safety and environmental

effects;

• Siting of plants within buildings as secondary containment;

• Siting of plants in the open air to ensure rapid dispersion of minor

releases of flammable gases and vapours and thus prevent

concentrations building up which may lead to flash fires and

explosions;

• Hazardous area classification for flammable gases, vapours and

dusts to designate areas where ignition sources should be

eliminated.

Risk management techniques should be used to identify control measures

that can be adopted to reduce the consequences of on or off site events.

See references cited in further reading material.

Positioning of Occupied Buildings

The distance between occupied buildings and plant buildings will be

governed by the need to reduce the dangers of explosion, fire and

toxicity. In particular, evacuation routes should not be blocked by poor

plant layout, and personnel with more general site responsibilities should

usually be housed in buildings sited in a non-hazard area near the main

entrance. Consideration should be given to siting of occupied buildings


__________________________________________________Plant Layout 5

outside the main fence. In all cases occupied buildings should not be

sited downwind of hazardous plant areas.

Aggregation / Trapping of Flammable Vapours

To avoid aggregation and trapping of flammable / toxic vapours which

could lead to a hazardous event, buildings should be designed so that all

parts of the building are well ventilated by natural or forced ventilation.

Flammable storages should be sited in the open air so that minor leaks or

thermal outbreathing can be dissipated by natural ventilation.

Segregation of Incompatible Substances (particularly in warehouses /

storage areas)

This is detailed in the Technical Measures Document on Segregation of

Hazardous Materials.


__________________________________________________Alarms/Trips/Interlocks 1

5.2 Alarm Systems

Alarm systems alert operators to plant conditions, such as deviation from

normal operating limits and to abnormal events, which require timely

action or assessment.

Alarm systems are not normally safety related, but do have a role in

enabling operators to reduce the demand on the safety-related systems,

thus improving overall plant safety.

However, where a risk reduction of better than 10-1 failures on demand is

claimed then the alarm system, including the operator, is a safety related

system, which requires a suitable safety integrity level.

EEMUA 191 ‘Alarm systems - a guide to design, management and

procurement’ considers alarm settings, the human interface (alarm

presentation), alarm processing and system management controls for

both safety related and other alarm systems. It provides the following

guidance in regard to safety related alarm systems:

• The alarm system should be independent from the process control

system and other alarms unless it has also been designated safety

related;

• The operator should have a clear written alarm response procedure

for each alarm which his simple, obvious and invariant, and in

which he is trained;

• The alarms should be presented in an obvious manner,

distinguishable from other alarms, have the highest priority, and

remain on view at all times when it is active;

• The claimed operator workload and performance should be stated

and verified.

Alarms which are not designated as safety should be carefully designed

to ensure that they fulfil their role in reducing demands on safety related

systems.

For all alarms, regardless of their safety designation, attention is required

to ensure that under abnormal condition such as severe disturbance,

onset of hazard, or emergency situations, the alarm system is remains

effective given the limitations of human response. The extent to which



the alarm system survives common cause failures, such as a power loss,

should also be adequately defined.

Alarm settings

The type of alarm and its setting should be established so as to enable

the operator to make the necessary assessment and take the required

timely action. Settings should be documented and controlled in

accordance with the alarm system management controls.

Human interface (alarm presentation)

The human interface should be suitable. Alarms may be presented either

on annunciator panel, individual indicators, VDU screen, or programmable

display device.

Alarms lists should be carefully designed to ensure that high priority

alarms are readily identified, that low priority alarms are not overlooked,

and that the list remains readable even during times of high alarm

activity or with repeat alarms.

Alarms should be prioritised in terms of which alarms require the most

urgent operator attention.

Alarms should be presented within the operators field of view, and use

consistent presentation style (colour, flash rate, naming convention).

Each alarm should provide sufficient operator information for the alarm

condition, plant affected, action required, alarm priority, time of alarm

and alarm status to be readily identified.

The visual display device may be augmented by audible warnings, which

should at a level considerably higher than the ambient noise at the signal

frequency. Where there are multiple audible warnings, they should be

designed so that they are readily distinguished from each other and from

emergency alarm systems. They should be designed to avoid distraction

of the operator in high operator workload situations. Where both constant

frequency and variable frequency (including pulsed or intermittent)

signals are used, then the later should denote a higher level of danger or

a more urgent need for intervention.



Alarm processing

The alarms should be processed in such a manner as to avoid operator

overload at all times (alarm floods). The alarm processing should ensure

that fleeting or repeating alarms do not result in operator overload even

under the most severe conditions.

The presentation of alarms should not exceed that which the operator is

capable of acting upon, or alternatively the alarms should be prioritised

and presented in such a way that the operator may deal with the most

important alarms without distraction of the others. Applicable alarm

processing techniques include grouping and first-up alarms, eclipsing of

lower grade alarms (e.g. suppression high alarm when the high-high

activates) suppression of out of service plant alarms, suppression of

selected alarms during certain operating modes, automatic alarm load

shedding and shelving.

Care should be taken in the use of shelving or suppression to ensure that

controls exist to ensure that alarms are returned to an active state when

they are relevant to plant operation.

Alarm system management procedures

Management systems should be in place to ensure that the alarm system

is operated, maintained and modified in a controlled manner. Alarm

response procedures should be available, and alarm parameters should

be documented.

The performance of the alarms system should be assessed and monitored

to ensure that it is effective during normal and abnormal plant conditions.

The monitoring should include evaluation of the alarm presentation rate,

operator acceptance and response times, operator workload, standing

alarm count and duration, repeat or nuisance alarms, and operator views

of operability of the system. Monitoring may be achieved by regular and

systematic auditing.

Matters which are not worthy of operator attention should not be

alarmed.



Logging may be a suitable alternative for engineering or discrepancy

events to prevent unnecessary standing alarms. A system for assessing

the significance of such logged events to ensure timely intervention by

maintenance personnel may be required.

Protection Systems (Trips and Interlocks)

Protective tripping systems provide a defense against excursions beyond

the safe operating limits by detecting a excursions beyond set points

related to the safe operating limits (i.e. the onset of a hazard) and taking

timely action to maintain or restore the equipment under control to a safe

state. Trips should not be self-resetting unless adequate justification has

been made. Protective interlocks prevent those control actions which

might initiate a hazard from being undertaken by an operator or process

control system, and are by nature self-resetting.

Protection systems should indicate that a demand to perform a safety

function has been made and that the necessary actions have been

performed.

Independence

Protective systems should be sufficiently independent of the control

system or other protective systems (electrical/electronic or

programmable). Where there is an interface between systems (e.g. for

indication, monitoring or shared components) or shared utilities (e.g.

power), environment (e.g. accommodation, wiring routes) or

management systems (maintenance procedures, personnel), then the

method of achieving independence should be defined, and common cause

failures adequately considered.

Measures to defend against common mode failures due to environmental

interactions may include physical separation or segregation of system

elements (sensors, wiring, logic, actuators or utilities) of different

protective systems.

Independence will also be required for protection against systematic and



common mode faults. Measures may include use of diverse technology

for different protective systems. Where more than one E/E/PES protective

system is used to provide the required risk reduction for a safety

function, then adequate independence should be achieved by diverse

technology, construction, manufacturer or software as necessary to

achieve the requires safety integrity level.

Dependence on utilities

The action required from the protective system depend upon the nature

of the process. The actions may be passive in nature, such as simple

isolation of plant or removal of power, or they may be active in that

continued or positive action is required to maintain or restore a safe

state, for example by injection of inhibitor into the process, or provision

of emergency cooling.

Active protective measures have a high dependence upon utilities, and

may be particularly vulnerable to common mode failures. The scope of

the protective system therefore includes all utilities upon which it

depends, and they should have an integrity consistent and contributory to

that of the remainder of the system.

Measures taken to defend against common mode failure of utilities will be

commensurate with the level of safety integrity required, but may include

standby or uninterruptable/reservoir supplies for electricity, air, cooling

water, or other utilities essential for performance of the safety function.

Such measures should themselves be of sufficient integrity.

Survivability and external influences

The protective system should be adequately protected against

environmental influences, the effects of the hazard against which it is

protecting, and other hazards which may be present. Environmental

influences include power system failure or characteristics, lightning,

electromagnetic radiation, flammable atmospheres, corrosive or humid

atmospheres, ingress of water or dust, temperature, rodent attack,

chemical attack, vibration physical impact, and other plant hazards.



Degradation of protection against environmental influences during

maintenance and testing should have been considered and appropriate

measures taken. e.g. Use of radios by maintenance personnel may be

prohibited during testing of a protective system with the cabinet door

open where the cabinet provides protection against EMR.

Protection against random hardware faults

The architecture of the protective system should be designed to protect

against random hardware failure. It should be demonstrated that the

required reliability has been achieved commensurate with the require

integrity level. Defensive measures may include high reliability elements,

automatic diagnostic features to reveal faults, and redundancy of

elements (e.g. 2 out of 3 voting for sensors) to provide fault tolerance.

Protection common mode failures

Diversity of elements is not effective for protection against random

hardware faults, but is useful in defense against common mode failures

within a protective system.

Protection systematic failures

Protection against systematic hardware and software failures may be

achieved by appropriate safety lifecycles.

Sensing

Sensors include their connection to the process, both of which should be

adequately reliable. A measure of their reliability is used in confirming the

integrity level of the protective system. This measure should take into

account the proportion of failures of the sensor and its process

connection, which are failures to danger.

Dangerous failures can be minimised by a number of measures such as:

• Use of measurement which is as direct as possible, (e.g.

pneumercators provide an inferred level measurement but actually

measure back pressure against a head and are sensitive to changes

in density due to temperature variations within the process, and to

balance gas flow, upon which they are dependant);



• Control of isolation or bleed valves to prevent uncoupling from the

process between proof tests or monitoring such that their operation

causes a trip;

• Use of good engineering practice and well proven techniques for

process connections and sample lines to prevent blockage,

hydraulic locking, sensing delays etc.;

• Use of analogue devices (transmitters) rather than digital

(switches);

• Use of positively actuated switches operating in a positive mode

together with idle current (de-energise to trip);

• Appropriate measures to protect against the effects of the process

on the process connection or sensor, such as vibration, corrosion,

and erosion;

• Monitoring of protective system process variable measurement (PV)

and comparison against the equivalent control system PV either by

the operator or the control system.

Proof testing procedures should clearly set out how sensors are

reinstated and how such reinstatement is verified after proof testing.

Maintenance procedures should define how sensors/transmitters are

calibrated with traceability back to national reference standards by use of

calibrated test equipment.

Other matters which will need to have been considered are:

• Cross sensitivities of analysers to other fluids which might be

present in the process;

• Reliability of sampling systems;

• Protection against systematic failures on programmable

sensors/analysers.

• The measures taken will depend on the level of variability and track

record of the software. ‘Smart’ transmitters with limited variability

software which are extensively proven in use may require no

additional measures other than those related to control of

operation, maintenance, and modification, whereas bespoke

software for an on-line analyser may require a defense in depth

against systematic failures ;



• Signal conditioning (e.g. filtering) and which may affect the sensor

response times;

• Degradation of measurement signals (distance between sensor and

transmitter may be important);

• Accuracy, repeatability, hysteresis and common mode effects (e.g.

effects of gauge pressure or temperature on differential pressure

measurement);

• Integrity of process connections and sensors for containment

(sample or impulse lines, instrument pockets are often a weak link

in process containment measures).

Use of ‘SMART’ instruments requires adequate diagnostic coverage and

fault tolerance and measures to protect against systematic failures

(software design/integration, inadvertent re-ranging during

maintenance). Measures may include use of equipment in non-smart

mode (analogue signal output, no remote setting) and equipment of

stable design for which there is an extensive record of reliability under

similar circumstances.

Actuators and signal conversion

Actuators are the final control elements or systems and include

contactors and the electrical apparatus under control, valves (control and

isolation), including pilots valves, valve actuators and positioners, power

supplies and utilities which are required for the actuator to perform its

safety function, all of which should be adequately reliable. A measure of

their reliability is used in confirming the integrity level of the protective

system. This measure should take into account the proportion of failures

of the actuator under the relevant process conditions which are failures to

danger.

Actuators are frequently the most unreliable part of the tripping process.

Dangerous failures can be minimised by a number of measures such as:

• Use of ‘fail-safe’ principles so that the actuator takes up the tripped

state on loss of signal or power (electricity, air etc.). e.g. held

open, spring return actuator;

• Provision of uninterruptable or reservoir supplies of sufficient

capacity for essential power;



• Failure detection and performance monitoring (end of travel

switches, time to operate, brake performance, shaft speed, torque

etc.) during operation;

• Actuator exercising or partial stroke shutoff simulation during

normal operation to reveal failures or degradation in performance.

Note this is not proof testing but may reduce probability of failure

by improved diagnostic coverage

• Overrating of equipment.

Other matters which should have been considered are:

• Valves should be properly selected for their duty, and it should not

be assumed that a control valve can satisfactorily perform isolation

functions;

• Actuators may also include programmable control elements (e.g.

SMART instruments) particularly within positioners and variable

speed drives and motor control centers. Modern motor control

centers may use programmable digital addressing. This introduces

a significant risk of introduction of systematic failure and failure

modes which cannot be readily predicted. Such an arrangement

should be treated with caution. It is normally reasonably practicable

for trip signal to act directly upon the final contactor;

• Potential for failure due to hydraulic locking between valves (e.g.

trace-heated lines between redundant shutoff valves).

Logic systems

Commonly, the logic systems for protective systems are electronic, but

programmable and other technology systems (magnetic or

fluidic/pneumatic) have been used.

The architecture of the logic system will be determined by the hardware

fault tolerance requirements, for example dual redundant channels.

Where a high level of integrity for the system is required (SIL3 or SIL4)

then diverse hardware between channels may be employed. This should

not be confused with diversity of independent protective systems.

Logic systems are likely to incorporate provisions for fault alarms and



overrides, for which there should be suitable management control

arrangements. They may also provide monitoring of input and output

signal lines for detection of wiring (open circuit, short circuit) and

sensors/actuators (stuck-at, out of range). Such monitoring may initiate

an alarm, a trip action or, in a voting arrangement, disable the faulty

element.

Software based systems should be adequately protected against

systematic failures, for example by an appropriate hardware and software

safety lifecycles, and suitable techniques and quality systems.

Wiring and communications (signal transmission)

Transmitters, communications devices and wiring systems should be

arranged to meet the requirements for survivability, protection against

External influences and independence.

Independent systems or redundant channels should not share multicore

cables with each other or power circuits, and may require diverse routes

depending upon the safety integrity level to be achieved.

Measures to protect against failures include:

• Use of fail-safe principles such as DC model (e.g. 4-20 ma loop) for

analogue signal transmission diagnosis and alarm of out of range,

abnormal, or fault states (such as stuck-at) with defined control

system responses for both the sensor and transmitter;

• Cable selection (screening etc.);

• Protection of cables against fire, chemical attack, physical damage

etc.;

• Physical separation or segregation of cables and cable routes;

• Routing in benign environments;

• Use of optical fibres to protect against electrical interference;

• Careful attention to lightning protection of data links between

buildings.

Use of fieldbus or other digital communication protocols in protective

systems should be considered a novel approach requiring a thorough

evaluation and demonstration of the safety integrity.



Utilities

Utilities which are required for the protective system to perform its safety

function may include power supplies such as electricity, air, inhibitor

materials and their propellants, inert gas such as nitrogen, cooling water,

steam, pilot flames and their gases all of which should be adequately

reliable. Measures such as redundancy, and uninterruptable/reservoir

supplies, and availability monitoring (e.g. loss of air alarm) may be

required. Confirmation that the designed capacity of reserves is adequate

should be demonstrated by test.

Utilities may also introduce external influences into the protective

systems (e.g. from electrical supplies).

Measures to protect against external influences may include:

• Under/Over voltage protection;

• Overcurrent and short circuit protection;

• Use of an uninterruptable power supply or voltage conditioning or

filtering;

• Careful attention to lightning protection and equipotential bonding.

Proof testing

The probability of failure on demand, or the failure rate of a protective

system is critically dependent upon the frequency of proof testing and its

ability to detect previously unrevealed failures of the system. The proof

test interval should therefore be established accordingly, and as a rule of

thumb for low demand systems, should be an order of magnitude less

than the mean time between failure of the system and the demand rate.

Proof test procedures should be available which specify the

success/failure criteria and detail how the test will be performed safely,

including any management arrangements, operating restrictions and

competence of personnel.

The tests should be arranged to reveal all dangerous failures which have

been unrevealed in normal operation including the following measures:



• Tests performed at the conditions which would be expected at trip.

(Where test under trip conditions cannot be performed, for example

for safety reasons, then measures to ensure that potential failures

at trip conditions will be revealed should be clarified);

• End to end tests at appropriate intervals, including proving

sample/impulse lines. (Different elements of the protective system

may require proof testing at different intervals).

Operation

Procedures should be available which detail the operation of the

protective system including:

• Override management (authorisation, security, recording,

monitoring and review of overrides, reset requirements);

• Operating instruction for trips;

• Instructions for response to equipment faults including fault alarms.

(There should be procedural arrangements in place to ensure timely

repair so that mean time to repair criteria can be met).

Maintenance

Procedures should be available for maintenance activities including:

• Maintenance instructions;

• Control of spares (segregation of faulty or non-conforming parts,

identification to prevent interchange of similar parts etc.);

• Competence of maintenance personnel;

• Operating restriction during maintenance;

• Control of software back-ups and memory media (floppy disks, files

on hard disks on portable PCs etc.);

• Post maintenance reinstatement and proof testing.

For systems where a high diagnostic coverage is claimed, for example

high integrity high systems, the probability of failure (expressed as

failure rate) is critically dependent upon the mean time to repair the

faults revealed. For such systems, the repair performance should

monitored and reviewed against the design criteria.



Modification

A management system for control of modifications should be available to

ensure that:

• Unauthorised modifications are prevented;

• Authorised modifications are not ill conceived;

• Safety verification to confirm that the required safety function and

integrity have been maintained;

• Designed and implementation is carried out by competent persons.

Remote diagnostic systems

Remote diagnostic systems have the potential to cause danger by

initiating unexpected operations or by affecting safety functions by

software/parameter modification or by diverting the control system

processor from time critical functions.

The need for remote diagnosis should be justified, a risk assessment

completed, and measures taken to ensure that safety is not affected by

normal operation or malfunction of the diagnostic system, including the

remote diagnostic terminal and software, communication link, and the

control system diagnostic interface and software.

Consideration should be given to:

• Security and control of access;

• Communication between diagnostician and plant personnel;

• Restricted mode of operation; passive (monitoring only), active

(control/operator functions), interactive (software change

possible);

• Potential for operation outside restricted mode under fault

conditions;

• Protection of safety functions from unauthorised modification;

• Change control;

• Competence of personnel.

E & C Division SHE Manual (Commissioning)____________________________________________________

______________________________________________________________________

Control System 1

5.3 Control Room Design

This Technical Measures Document refers to codes, standards and bestpractice applicable to the design of control rooms.

General PrinciplesThere are two major aspects of control room design that should be takeninto account in the Safety Report these are:

• the suitability of the structure of the control room to withstandpossible major hazards events; and

• the layout of control rooms and the arrangement of panels, VDUsetc to ensure effective ergonomic operation of the plant in normalcircumstances and in an emergency.

Control Room StructureFor large plants, control rooms are likely to be situated in separatebuildings away from the process plant which they serve. For medium orsmall plants control rooms may be within the plant building or controlpanels may be located local to the plant. Whatever the location, controlrooms should be designed to ensure that the risks to the occupants of thecontrol room are within acceptable limits and that it is suitable for thepurposes of maintaining plant control, should the emergency responseplan require it, following any foreseeable, undesirable event within theplant.

Events that may affect the control room are:• Vapour Cloud Explosions (VCEs)• Boiling Liquid Expanding Vapour Explosions (BLEVEs)• Pressure bursts• Exothermic reactions• Toxic gas releases• Fires, including pool fires, jet fires, flash fires and fire balls.

The threat from explosions and pressure bursts should be considered inthe structural design of control building. A methodology for this ispresented in the recent CIA/CISHEC guidance CIA Guidance for thelocation and design of occupied building on chemical manufacturing sites.This considers the vulnerability of the building to possible overpressuresassociated with particular events. Buildings should be designed towithstand an overpressure that will ensure that risks to individuals withinthe building are below acceptable limits. Particular attention should begiven to the provision of windows, the presence of heavy equipment onroofs (e.g. air conditioners) and the ability of internal fixtures towithstand the building shaking. If windows are present, considerationshould be given to the use of laminated or polycarbonate glass, toprevent serious injury to occupiers of the control room in the event of anoverpressure. ALARP principles should be applied in these considerations


______________________________________________________________________

Control System 2

and cost benefit used to determine if additional measures should beapplied.

In consideration of toxic gas releases the control room should provide asafe haven for its occupants. This will include arranging that the buildingis adequately sealed to prevent ingress of gases to levels of concentrationthat will affect the health and thereby the ability of the operators tomaintain control of the plant. Careful consideration of the buildingventilation system is required to ensure that air intakes are situated awayfrom areas that may be affected or to arrange that there is no air intakeduring an incident, preferably by closure of an automatic valve linked to agas analyser.

Measures for protection from fires should ensure the control room willwithstand thermal radiation effects without collapse and that smokeingress is controlled. Materials of construction should be fire resistant forthe duration of any possible fire event. Smoke ingress may be controlledin a similar manner to toxic gas ingress.

Each of these methodologies should be applied to control rooms withinbuildings as well as separate control buildings. Control panels on theplant itself cannot be so easily be protected, therefore diversity andredundancy should be applied to ensure that plant control can bemaintained in an emergency. Risk Assessments should be undertaken todemonstrate that primary and secondary (domino) risks are withinacceptable limits.

Human Factors/ErgonomicsOperators should be able to demonstrate that appropriate human factorsconsiderations have been given to the design, commissioning, andoperation of control rooms under both normal and abnormal plantoperating conditions to reduce the frequency of human error due tocontrol room deficiencies.

It is vitally important that a control room and its operators are consideredas a whole system and not in isolation of each other. For example a welldesigned control room for use by 4 operators is dangerous when staffedby 3 operators. Similarly, the best-trained operators cannot guaranteehigh reliability in a poorly designed control room.

Factors to be taken in account are included on the following paragraphs.

Environmental issuesLayout

• Control room dimensions should take into account the 5th and 95thpercentile user.


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Control System 3

• The design of the control room should be derived from anappropriate task analysis method, such as link analysis orhierarchical task analysis.

• Emergency exits should accommodate egress by the 99thpercentile user.

• Access and egress should be considered for disabled operators.• Adequate access should be provided throughout the control room.

However, the layout should discourage flow from general circulationareas to ensure that necessary lines of sight are not obscured.

• If there are a number of control rooms operating on the samesystem they should adopt similar layouts to ensure consistency.

• Operational links between control room operators, such ascommunications and lines of site should be considered during thedesign stage.

• The layout should not hinder verbal and non-verbal communicationand should facilitate team working.

• The layout of the control room should reflect the allocation ofresponsibility and the requirements for supervision.

• The layout should be effective under high and low staffing levels.• Circulation of all personal should be achieved with the minimum of

disruption to operators.• Where supervisory positions will increase the amount of personnel

circulation, it is recommended that these positions are located closeto main entrances.

• Distances between workstations should mean that operators arenot sitting within each other’s ‘intimate zones’. As a guide theminimum spacing distance should be between 300 - 700 mm.

Maintenance• Adequate access should be provided so that inadvertent operation

of equipment during maintenance is not possible.• Behind panel equipment should be appropriately coded to reduce

the potential for human error.

Thermal environment• Temperature and airflow should be adjustable. As a guide,

‘comfortable’ temperature for office work should be between 18.3°Cand 20.0°C with airflow between 0.11 and 0.15 m/s.

Visual environmentLighting should be such that it does not create veiling reflections on VDUsor other reflective surfaces that require monitoring.

The type of lighting should be adequate for the task. i.e. for office work alux (lux is the unit of illuminance - measured using a light meter at thework surface) figure of between 500 - 800 is suggested.There should be no perceptible flicker from strip lighting.


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Control System 4

It is desirable to provide adjustable lighting for control rooms that aremanned 24 hours a day. During night-time operation lighting is oftendimmed.

Windows in control rooms should not cause veiling reflections onreflective surfaces. Adequate means of blocking out direct sunlight shouldbe provided.

Auditory environment

The average noise level within the control room shall not exceed 85dB(A) during the length of the working day.

For office work a noise level below 40 dB(A) is not desirable as it cancause interference between operators.Prolonged, very low or very high frequency noises should be avoided.

Noise levels should not interfere with communications, warning signals,mental performance (i.e. be distracting).

Man Machine Interface (MMI)For mental workload, conditions of over and under-arousal should beavoided. The duration of tasks that have an associated low or high levelof mental workload should be limited. Both these extremes will increasethe likelihood of human error affecting the system. The design of the MMIshould be based on a full Task Analysis.

An interface should provide the operator with the general followinginformation:

• After initiating an action within a system the operator should beclearly informed of the result of their action.

• If there is a delay in the system that prevents the operator frombeing informed of the result of his/her action, the system shouldinform the operator of this fact.

• If an action is made in error then it should be possible to reversesuch an action where it would not be detrimental to plant safety todo so.

• The system should inform the operator of any deviations from safeoperating levels.

Alarms• All employees and contractors on site should know what each alarm

means and what the required response is, if the cause of the alarmhas the potential to affect them.

• An alarm should reset automatically if the fault that generated it isrectified.


______________________________________________________________________

Control System 5

• Alarm messages should be presented in a standard format, basedupon existing conventions.

• Alarm messages should clearly inform the operator of the reasonfor the alarm.

• Following an alarm response required by the operator should beclear.

• The coding of alarms should not be based purely on colour, ascolour blind operators will be unable to recognise what the alarmindicates.

• Alarm signals should be at least 10 dB(A) over the backgroundnoise of the control room.

• Alarms should not prevent effective communication within thecontrol room.

• An alarm log should be provided to for diagnostic purposes.• The design of the alarm system should prevent masking and

flooding of alarms. Masking is where one alarm noise masks asimilar sounding alarm preventing the operator from detecting thesignal. Flooding happens when a system alarms which has a ‘knockon’ effect on other related systems, the result of which is thetriggering of myriad other alarms - flooding the control room withsound.

Coding techniques• Coding should follow international conventions. Arbitrary coding by

operators can actually propagate, rather than mitigate, humanerror if not carried out correctly.

• Coding should be consistent across plant.• Coding should be used appropriately.• Example methods of coding are:

• Colour• Flash• Brightness• Inverse video/highlighting• Sound frequency• Sound type• Shape 2D/3D• Symbols

• Coding should be used redundantly where colour is one of thecoding methods.

Designing displays

Text• The language used should always be capable of being easily

understood by the operator.• Active rather than passive language should be used.• Text should be left justified.


______________________________________________________________________

Control System 6

• Sans serif fonts should be used as these have been found to be themost legible. An example of a sans serif font is Ariel.

Labels• Labelling should be used consistently across plant.• Labels should be used appropriately.• The relationship between labels and the equipment they refer to

should be clear.• Labels should be easily read.• Standard abbreviations should be used where abbreviations are

required.

Display devices• Display devices should be appropriate for the type of information

they are presenting.• Display devices should be grouped logically to improve signal

detection. It is recommended that formal task analysis methods beperformed to determine the optimum arrangement for displays andtheir associated controls.

• The relationship between a control and its associated display shouldbe obvious.

• The operator should be able to easily understand display feedback.• The response to this feedback should be obvious, wherever

possible.• The control method provided for navigation around displays should

be appropriate for the task.

Graphics• Appropriate presentation methods should be used for information.

A simple guide is presented below:

Method Advantage Disadvantage

Numeric • Accuratequantitativeinformation

• Quickly read

• Cannot illustrate rate of change orapproach to limit

• Rapidly changing data is unreadable• Difficult to locate individual data

items if presented in a list or table.

Barcharts/analogue dials

• Easy to checkwhether data iswithin limits

• Possible to markalarm limits

• Displays rate ofchange well.

• Easily compared toother similarlypresented data.

• Movement can potentially distractoperators.

• Slow read time.• Inaccurate if numerical value has to

be derived.


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Control System 7

• Provides at a glanceappreciation ofoperating conditions

Pictorialdisplays

• Ideal for showingplant configurations.

• Can improveoperator situationalawareness of plant.

• Operator’s mental model of theplant may differ from the mimic.

• Can be very difficult to learn.

Trenddisplays

• Ideal for presentingcontinuouslychanginginformation.

• Presents rate ofchange in an easilyunderstood format.

• Good for comparingdata plots

• Provides historicaldata over time

• Inaccurate if numerical value has tobe derived.

• Only four parameters can bedisplayed

• Mimics should follow current conventions for symbols etc.• Mimics should be user tested prior installation to ensure that they

are compatible with the end users mental model of the plant.

Anthropometry

Reach• Control desk/panels should conform to reach distances for the 5th

percentile operator.

Seating• Seating should be anthropometrically sound and should be usable

by both 5th and 95th percentile operators.• Adjustment should be provided to allow the operator set up the

chair to a configuration that is comfortable.• Seating should not promote a slumped posture.

Posture• The workstation should be designed so that it allows the operator to

regularly change their posture or move around the room. Thisshould not however, be during primary control duties or during anemergency scenario.


__________________________________________________Corrosion / Selection of Material 1

5.4 Corrosion / Selection of Materials

This Technical Measures Document covers the corrosion of materials and

the selection of materials of construction. Reference is made to relevant

codes of practice and standards.

Introduction

Corrosion is the largest single cause of plant and equipment breakdown

in the process industries. For most applications it is possible to select

materials of construction which are completely resistant to attack by the

process fluids, but the cost of such an approach is often prohibitive. In

practice it is usual to select materials which corrode slowly at a known

rate and to make an allowance for this in specifying the material

thickness. However, a significant proportion of corrosion failures occur

due to some form of localised corrosion, which results in failure in a much

shorter time than would be expected from uniform wastage. Additionally,

it is important to take into account that external atmospheric corrosion

leads to many instances of loss of containment and tends to be a greater

problem than internal corrosion. All these aspects of corrosive behaviour

need to be addressed both at plant design time and during the life of the

plant.

General Principles

The operator should demonstrate that procedures are in place to ensure

that corrosion and the selection of the correct materials of construction

are considered at the process design stage. Additionally the operator

should demonstrate that it has appropriate inspection and maintenance

programmes in place in order to prevent corrosion causing loss of

containment from its process operations. In doing so the following should

be considered:

Process Fluid Corrosion

Corrosion in metallic components occurs when pure metals and their

alloys form stable compounds with the process fluid by chemical reaction

or electrochemical processes resulting in surface wastage. Appreciable

corrosion can be permitted for tanks and piping if anticipated and allowed

for in design thickness, but essentially no corrosion can be permitted in



fine mesh wire screens, orifice plates and other items in which small

changes in dimensions are critical. Rates of corrosion can be heavily

affected by temperature changes and whilst a material of construction

may be suitable at one temperature it may not be appropriate for use at

a higher temperature with the same process fluid.

The corrosion of non-metallic materials is essentially a physiochemical

process that manifests itself as swelling, cracking or softening of the

material of construction. In many instances non–metallic materials will

prove to be attractive from an economic and performance view.

The use of various substances as additives to process streams to inhibit

corrosion has found widespread use and is generally most economically

attractive in recirculation systems, however it has also been found to be

attractive in some once through systems such as those encountered in

the petroleum industry. Typical inhibitors used to prevent corrosion of

iron or steel in aqueous solutions are chromates, phosphates, and

silicates. In acid solutions organic sulphides and amides are effective.

Localised Corrosion

There are many forms of localised corrosion than can lead to early failure

of equipment. The prevention of corrosion should be addressed at the

mechanical design stage and proper design to minimise local corrosion

should include free and complete drainage, minimising crevices, no dead

spots in pipework and ease of cleaning and inspection. Some of the more

common types of local corrosion are briefly discussed in this section.

Pitting often occurs where certain impurities such as chlorides are present

in process streams and cooling waters. This is an extreme form of

localised corrosion. Once initiated pits are usually self-accelerating and

can result in rapid failures.

Many metals suffer from stress corrosion cracking under certain

conditions. In piping the most frequent failures from stress corrosion

cracking occur with austenitic stainless steels in contact with solutions



containing chloride. Even trace quantities of chlorides can cause problems

at temperatures above 60°C.

Crevice corrosion may occur where liquid is trapped between close fitting

metal surfaces, or between a metal surface or a non metallic material

such as a gasket. Attention to detail at the design and fabrication stage

should be given to areas such as jointing to prevent crevice corrosion.

Localised erosion can occur where equipment orientation causes fluid

velocities to accelerate such as at bends. Some chemicals can be handled

in carbon steel piping because they form protective coatings of ferric

compounds in pipework. Careful design to ensure the coating is not

eroded is necessary.

External Corrosion

Exterior surface corrosion or rusting of pipework occurs by the formation

of iron oxides. Painting to an appropriate specification will significantly

extend the period to the onset of corrosion but the durability of the paint

finish is largely dependent on the quality of the surface preparation.

Improperly installed insulation can provide ideal conditions for corrosion

and should be weatherproofed or otherwise protected from moisture and

spills to avoid contact of the wet material on equipment surfaces.

Application of an impervious coating such as bitumen to the exterior of

the pipework is beneficial in some circumstances.

Cathodic protection is an electrochemical method of corrosion control

which has found widespread application in the protection of carbon steel

underground structures such as pipelines and tanks from soil corrosion.

The process equipment metal surface is made the cathode in an

electrolytic circuit to prevent metal wastage.

Anodic protection is less commonly used and relies on an external

potential control system to maintain the metal in a passive condition. This

form of corrosion protection has found practical application in the

sulphuric acid manufacturing industry.



Materials Selection

Corrosion rates are expressed in terms of inches per year of surface

wastage and are used to provide a corrosion allowance in the design

thickness of equipment such as vessels and pipework. Operators will

often use data based on historical experience from plant operations to aid

them in determining appropriate corrosion allowances. Alternatively

corrosion charts are widely available that give corrosion rates for many

combinations of materials of construction and process fluids and normally

a range of values will be provided for various process temperatures. In

some instances, particularly where there is a mixture of chemicals

present, appropriate data may not exist and corrosion tests may be

necessary in order to determine the suitability of equipment. Operators

should be able to demonstrate the use of corrosion allowances in

equipment specification and design. The sources of data used should be

traceable.

Whilst carbon and stainless steels are commonly used materials of

construction, increasing use is being made of non- metallic and lined or

plastic process equipment. The selection of the material of construction

should taken into account worst case process conditions that may occur

under foreseeable upset conditions and should be applied to all

components including valves, pipe fittings, instruments and gauges. Both

composition (e.g. chlorides, moisture) and temperature deviations can

have a significant direct effect on the rate of corrosion. The operator

should demonstrate that procedures are in place to ensure that potential

deviations in process conditions such as fluid temperature, pressure and

composition are identified by competent persons and assessed in relation

to the selection of materials of construction for pipework systems.

A wide range of plastics are available for use as materials of construction

and can be used in areas such as handling inorganic salt solutions where

metals are unsuitable. The use of plastic linings is widespread in

equipment such as tanks, pipes, and drums. However, their use is limited

to moderate temperatures and they are generally unsuitable for use in

abrasive duties. Some of the more commonly used plastics are PVC, PTFE

and polypropylene.



Special glasses can be bonded to steel, providing an impervious liner.

Glass or 'epoxy' lined equipment is widely used in severely corrosive acid

duties. The glass lining can be easily damaged and careful attention is

required. The thin paint like coatings are unlikely to give full protection

due to defects and the most dependable barrier linings are those which

are built up in multiple layers to a depth in the region of 3 mm.

Performance Tests

Normally testing is carried out in order to determine the suitability of a

material of construction for handling a process fluid. However, testing can

be used for different purposes. Typically this might be to justify a

modified inspection frequency of equipment on an existing plant.

There are a variety of test methods available. Commonly test specimens

consisting of a small strip or 'coupon' of the material of interest are

exposed to the process fluid. The weight loss of the test specimen over a

time period is measured in order to determine the corrosion rate. Testing

can be carried out on the plant, in the laboratory, or on a pilot plan

depending on the situation.

Where laboratory testing is carried out using standard test methods there

are difficulties in interpreting results and translating them into plant

performance. Care is required to ensure that the test fluid is exactly the

same as on the process plant. Discrepancies in test conditions such as

trace impurities, dissolved gases, velocity, and turbulence can lead to

erroneous results.

Maintenance Requirements

Process equipment handling hazardous materials should be inspected at

regular frequencies, both internally and externally. Localised corrosion

can be unpredictable and fabrication defects such as poor welds can be

present. Linings can deform or be damaged. Typically the glass lining on

a jacketed reactor can suffer thermal shock or a static discharge may

occur through the lining. The frequency of inspection can be amended

once an inspection history has been built up and the condition of a piece

of equipment can be reasonably predicted. The operator should



demonstrate that it has inspection and maintenance programmes in place

for hazardous process equipment including lagged systems. Where

equipment is lined electrical continuity tests for lining defects should be

carried out where appropriate. Cathodic and anodic protection systems

should be regularly checked to ensure continued protection.

Control of Operating Conditions

Where control of corrosion is dependent on the concentration of

contaminants or moisture the operator should demonstrate that

procedures and the necessary controls are in place to maintain a safe

operating condition. Similarly where inhibitors are added or systems such

as cathodic protection are used the operator should demonstrate that

these systems are inspected and adequately maintained to ensure

continued protection of the process.

Industry Applications

Chlorine

The flow rate of liquid chlorine through pipework is restricted to 2 m/s to

avoid removing the ferric chloride coating on the pipe surface which

protects against erosion / corrosion of carbon steel. Wet chlorine gas

corrodes mild steel and ebonite or rubber lined steel is used for this duty.

Chlorine gas handled at temperatures in excess of 200°C in carbon steel

can result in chlorine / steel fires. Zinc can be used for this duty, but for

low temperature chlorine special steels are required to avoid

embrittlement.

Bromine

PVDF pipework and PVDF lined steel are commonly used for handling

bromine. If the bromine is 'dry' then metals such as monel and hastelloy

can be used. Vessels are normally constructed of either lead, PVDF or

GRP lined steel.

Sulphuric Acid

Corrosion protection of mild steel vessels occurs by the formation of an

iron sulphate coating. Any condition leading to excessive turbulence can

result in the removal of the coating and corrosion. Additionally the

temperature influence on corrosion rate varies with different strengths of

acid and consequently it is necessary to define maximum operating



temperatures. Chemical lead is widely used where steel is unsuitable and

PVC can be used in certain applications.

Hydrochloric Acid

This acid is very corrosive towards most of the common metals and

alloys. This is exacerbated where aeration or contamination by oxidising

agents is present. Copper is particularly prone to this problem. Also many

failures occur due to the presence of minor impurities such as ferric

chloride. Plastics and rubber-lined steel are widely used for pipework and

small vessels.

Ammonia

Materials of construction for ammonia are dependent on the operating

temperature. Whilst mild steel may be used at ambient temperature

special steels are required at low temperatures to avoid embrittlement.

Impurities in liquid ammonia such as air or carbon dioxide can cause

stress corrosion cracking of mild steel. Ammonia is highly corrosive

towards copper and zinc.

Hydrofluoric Acid

Bulk storage of 70% acid or greater may be in mild steel or PVDF tanks.

Polyethylene, polypropylene, and PVDF are commonly used for

construction of major components. PTFE is often used for smaller

components such as gaskets. Glass or GRP should never be used.

Oxygen

Materials suitable for liquid oxygen service are nickel steel, austenitic

stainless steels, and copper or aluminium alloys. Carbon steels and

plastics are brittle at low temperatures and should not be used on liquid

oxygen duty. PTFE is the most widely used sealant.

Hydrogen

At temperatures below 120°C carbon steel can be used up to high

pressures. At elevated temperatures and significant pressures hydrogen

will penetrate carbon steel and react with the carbon to form methane.

This results in a loss of ductility and cracking or blistering of the steel. For

high temperature applications steel alloys containing molybdenum and

steel are satisfactory.


__________________________________________________Drum / Cylinder Handling 1

5.5 Drum / Cylinder Handling

Introduction

A variety of toxic and flammable chemicals are frequently stored and

transported in drums and cylinders. Although individual containers hold

relatively small inventories, a single cylinder of a compressed or liquefied

toxic gas can present a significant hazard to personnel. Additionally large

quantities of drums and cylinders are often stored together giving rise to

potentially large inventories of hazardous materials. The movement and

connection / disconnection of drums and cylinders to process plant

requires the direct involvement of operating personnel giving rise to the

potential for human error to cause incidents.

General Principles

Storage Location

Both the hazards of the material and the size of the inventory need to be

considered in determining where a store should be located.

Considerations should include the distance from other stored materials,

process plant, traffic routes and occupied buildings.. Where separation

distances are inadequate measures such as fire walls can be employed to

reduce the impact of incidents. The operator should demonstrate that the

storage location and design has taken into account site specific security

requirements and the potential for vandalism.

Ventilation

The preferred location for the storage of drummed flammable liquids and

compressed / liquefied gases is in the open air, to allow vapours to be

dispersed effectively. When located in buildings, the operator should

demonstrate that there is an adequate level of ventilation achieved by

either the presence of a sufficient size and number of permanent

openings such as louvres or mechanical ventilation. If stored indoors,

flammable gases such as LPG may only be stored in purpose built

compartments or buildings constructed with fire resistant walls and

explosion relief.



Compatibility With Other Stored Materials

Toxic, flammable or self reactive materials should not in general be

stored in the same location (see Technical Measures Document

(Segregation of Hazardous Materials). The operator’s risk assessment

should demonstrate the compatibility of the substances stored and the

suitability of the arrangements.

Layout

Drums and cylinders should be stored in a safe manner. Both the height

and method of stacking should take into account the hazard of the

material stored and the construction of the container. Racking or free-

standing multi layer stacks can be used for drummed materials storing

low hazard liquids. Consideration should be given to the detection of

leaks from containers and the method for collection and disposal of such

spills to reduce the possibility of cross-contamination and domino effects.

Training should be provided to operators on dealing with spills and

emergency procedures. Adequate access for fork lift trucks should be

provided. Pressurised cylinders and drums should be stored with their

valves uppermost in secure manner. The size of any particular stack

should be limited and separation distances should be provided between

stacks. Drums should not be filled or emptied within the storage area.

Transportation

Whilst drums containing flammable liquids can be transported securely on

a simple pallet, cylinders and drums containing compressed or liquefied

gases require careful and appropriate means of transport such as cylinder

trolleys or purpose designed attachments for fork lift trucks should be

used at all times. The operator should maintain records demonstrating

that personnel involved in the movement of drums and cylinders have

received training in the hazards involved in handling them and in the

operation of any machinery involved such as cranes and fork lift trucks.



Containment of Spills

Suitable precautions should be in place for the containment of leaked

materials. Where liquids are handled suitable spillage containment such

as bunding and drainage sumps should be in place. Arrangements should

be in place for the routine drainage of rainwater from sumps. Where

materials that react with water are stored outdoors, the operator’s risk

assessment should demonstrate the suitability of the arrangements For

the storage of toxic gases, location of the containers in a purpose

designed indoor store will reduce the rate at which gas is released to the

environment.

Control of Ignition Sources

Where flammable liquids or gases are stored, the area should be subject

to hazardous area classification for the control of ignition sources. This

requirement should be reflected both in the equipment installed and in

the control of operational and maintenance activities in the location. The

movement of drums and cylinders often involves the use of fork lift

trucks, which can provide a source of ignition for flammable vapours. Any

vehicle operating in a zoned area should be protected to an appropriate standard.


Flammable Liquids

Containers should be stored in the open air where practical, but if stored

inside five air changes per hour is considered a sufficient ventilation rate.

Standard 205 litre metal drums should be stacked no more than three

high and preferably on pallets or racking. The maximum stack size should

be 300,000 litres with at least 4 metres between stacks. Storage should

be on an impervious surface such as concrete and be bunded with

drainage towards a sump or other suitable handling system.



LPG Cylinders

Cylinders should be stored preferably in the open air on a concrete or

load bearing surface. Flammable liquids, combustible, corrosive, oxidising

materials, toxic materials or compressed gas cylinders should be kept

separate from LPG containers in general. Containers should be stored

with their valves uppermost. The maximum size of any stack should not

exceed 30,000 kg. For storage indoors, no more than 5000 kg may be

stored in each purpose designed building compartment and a maximum

of five compartments may exist in a single building.

Chlorine Cylinders

The vast majority of chlorine cylinder and drum stores are located

indoors and should be solely used for storing chlorine. Access doors

should fit closely to help contain any leak. These stores should be

protected from any nearby radiant heat hazards. The store should be at

least 5 m from any roadway. A cylinder store should be at least 20 m

from the site boundary and a drum store 60 m. Chlorine gas detectors /

alarms should normally be provided.

Risk assessments should be carried out to consider hazards arising from

mishandling (dropping of containers in transport/handling), incorrect

operation of valves and failure to connect correctly, maintenance errors

and damage by external sources (domino, vehicle impacts, etc.)


______________________________________________________________________

Pressure Plants / Reactors 1

5.6 Pressure Plants / Reactors

Introduction

If pressure equipment fails in use, it can seriously injure or kill peoplenearby and cause serious damage to property.

To minimise the risks when working with systems or equipment whichcontain a liquid or gas under pressure. It does not cover gas cylinders(now called transportable pressure receptacles or transportable pressurevessels), or tanks and tank containers.

As an employer or self-employed person, you have a duty to provide asafe workplace and safe work equipment. Designers, manufacturers,suppliers, installers, users and owners also have duties. Employers havea further duty to consult any safety or employee representatives onhealth and safety matters. Where none are appointed, employers shouldconsult the workforce direct.

Examples of pressure systems and equipment are:

• boilers and steam heating systems;• pressurised process plant and piping;• compressed air systems (fixed and portable);• pressure cookers, autoclaves and retorts;• heat exchangers and refrigeration plant;• valves, steam traps and filters;• pipework and hoses; and• pressure gauges and level indicators.

Principal causes of incidents are:

• poor equipment and/or system design;• poor maintenance of equipment;• an unsafe system of work;• operator error, poor training/supervision;• poor installation; and• inadequate repairs or modifications.

The main hazards are:

• impact from the blast of an explosion or release of compressedliquid or gas;

• impact from parts of equipment that fail or any flying debris;• contact with the released liquid or gas, such as steam; and• fire resulting from the escape of flammable liquids or gases.


______________________________________________________________________


Reduce the risk of failure:

The level of risk from the failure of pressure systems and equipmentdepends on a number of factors including:

• the pressure in the system;• the type of liquid or gas and its properties;• the suitability of the equipment and pipe work that contains it;• the age and condition of the equipment;• the complexity and control of its operation;• the prevailing conditions (eg a process carried out at high

temperature); and• the skills and knowledge of the people who design, manufacture,

install, maintain, test and operate the pressure equipment and systems.

Provide safe and suitable equipment

To reduce the risks you need to know (and act on) some basicprecautions,

• When installing new equipment, ensure that it is suitable for itsintended purpose and that it is installed correctly. This requirementcan normally be met by using the appropriate design, constructionand installation standards and/or codes of practice.

• The pressure system should be designed and manufactured fromsuitable materials. You should make sure that the vessel, pipes andvalves have been made of suitable materials for the liquids or gasesthey will contain.

• Ensure the system can be operated safely – without having to climbor struggle through gaps in pipe work or structures,

Example.

Be careful when repairing or modifying a pressure system. Following amajor repair and/or modification, you may need to have the wholesystem re-examined before allowing the system to come back into use.

Know the operating conditions• Know what liquid or gas is being contained, stored or processed (eg

is it toxic/flammable?).• Know the process conditions, such as the pressures and

temperatures.• Know the safe operating limits of the system and any equipment

directly linked to it or affected by it.• Ensure there is a set of operating instructions for all the equipment

and for the control of the whole system including emergencies.


______________________________________________________________________


• Ensure that appropriate employees have access to theseinstructions, and are properly trained in the operation and use ofthe equipment or system (see the section on training).

Fit suitable protective devices and ensure they function properly

• Ensure suitable protective devices are fitted to the vessels, orpipework (eg safety valves and any electronic devices which causeshutdown when the pressure, temperature or liquid or gas levelexceed permissible limits).

• Ensure the protective devices have been adjusted to the correctsettings.

• If warning devices are fitted, ensure they are noticeable, either bysight or sound.

• Ensure protective devices are kept in good working order at alltimes.

• Ensure that, where fitted, protective devices such as safety valvesand bursting discs discharge to a safe place.

• Ensure that, once set, protective devices cannot be altered exceptby an authorised person.

Carry out suitable maintenance

• All pressure equipment and systems should be properly maintained.There should be a maintenance programme for the system as awhole. It should take into account the system and equipment age,its uses and the environment.

• Look for tell-tale signs of problems with the system, eg if a safetyvalve repeatedly discharges, this could be an indication that eitherthe system is overpressurising or the safety valve is not workingcorrectly.

• Look for signs of wear and corrosion.• Systems should be depressurised before maintenance work is

carried out.• Ensure there is a safe system of work, so that maintenance work is

carried out properly and under suitable supervision.

Make provision for appropriate training

Everybody operating, installing, maintaining, repairing, inspecting andtesting pressure equipment should have the necessary skills andknowledge to carry out their job safely –so you need to provide suitabletraining. This includes all new employees, who should have initial trainingand be supervised closely.


______________________________________________________________________


Additional training or retraining may be required if:• the job changes;• the equipment or operation changes; or• skills have not been used for a while.

Have the equipment examined

You must not allow your pressure system to be operated (or hired out)until you have a written scheme of examination and ensured that thesystem has been examined.

• The written scheme of examination must cover all protectivedevices. It must also include every pressure vessel and those partsof pipelines and pipework which, if they fail, may give rise todanger.

• The written scheme must specify the nature and frequency ofexaminations, and include any special measures that may beneeded to prepare a system for a safe examination.

• The pressure system must be examined in accordance with thewritten scheme by a competent person.

• For fired (heated) pressure systems, such as steam boilers, thewritten scheme should include an examination of the system whenit is cold and stripped down and when it is running under normalconditions.

The key steps are:• Decide what items of equipment and parts of the plant should be

included in the scheme. This must include all protective devices. Itmust also include pressure vessels, and parts of pipework, which ifthey failed could give rise to danger.

• The scheme must be drawn up (or certified as suitable) by acompetent person. It must specify whether the examination is in-service or out-of service and how often the system is to beexamined.

• The system must be examined by a competent person inaccordance with that scheme.

Choose a competent person

• You must assure yourself that the competent person has thenecessary knowledge, experience and independence to undertakethe functions required of them.

• The competent person carrying out examinations under a writtenscheme does not necessarily need to be the same one whoprepares or certifies the scheme as suitable.


______________________________________________________________________


A competent person may be:• a company's own in-house inspection department; an individual

person (eg, a self-employed person); or• an organisation providing independent inspection services.

The competent person undertaking an examination of a pressure systemin accordance with the written scheme of examination takes theresponsibility for all aspects of the examination. For example, on systemswhere ancillary examination techniques (eg non-destructive testing) areundertaken, the competent person must assume responsibility for theresults of these tests and their interpretation even though the tests mayhave been carried out by someone else.


__________________________________________________Static Electricity 1

5.7 Earthing

This Technical Measures Document refers to codes and standards

applicable to earthing of plant.

General Principles

Earthing can classified in two ways:

• System earthing;

• Equipment earthing.

System earthing is essential to the proper operation of the system,

whereas equipment earthing concerns the safety of personnel and plant.

A key function of equipment earthing is to provide a controlled method to

prevent the build up of static electricity, thus reducing the risk of

electrical discharge in potentially hazardous environments. Generally, a

resistance to earth of less than 106 � will ensure safe dissipation of static

electricity in all situations.

Flammable Liquids Transfer

The major hazard involved with the transfer of flammable liquids is the

build up of static due to charge separation with potential for discharge

resulting in fire and subsequent loss of containment. Certain non-polar

liquids can be charged, e.g. while flowing through pipelines. Detectable

and hazardous charges must be expected if the specific resistance of the

liquid exceeds 108 �.m.

The potential for accumulation of static charges may strongly increase if

the liquid contains a non-miscible component or a suspended solid.

Examples include:

• Crystallisation processes in toluene;

• Quantities of water in toluene.

With the presence of a second phase, velocities less than 1 m/s should be

employed.



Measures that can be employed to reduce these hazards include:

• Ensure that the pipe transferring the liquid is completely filled to

exclude the formation of explosive mixtures;

• Wherever possible ensure no contaminants / solids are present;

• Utilise inert gas blanketing;

• When transferring flammable liquids by ‘blowing across’ use an

inert gas;

• Avoid mechanical mixing or agitation of low conductivity liquids

wherever possible;

• Use of ball valves with earthed metal spheres;

• Employ low transfer velocities. For only partially filled pipes, or

pipes which discharge into containers, the velocity is to be limited

as follows:

• For chargeable esters: maximum 10 m/s;

• For mineral oil products (e.g. gasoline, petrol, kerosene, paraffin,

jet fuel) and for other chargeable liquids (excluding carbon

disulphide and ether):

Nominal pipe

diameter, mm

�40 50 80 100 200 400 600

Velocity, m/s 7.0 6.0 3.6 3.0 1.8 1.3 1.0

Quantity, l/min �600 800 1100 1600 3500 10000 17000

If these velocities are adhered to, no hazardous charges will be generated

within homogenous liquids. But when suspensions of crystals in non-

conductive liquids are conveyed, hazardous charges may always be

generated, even at velocities below 1 m/s.

• For ether and carbon disulphide in pipelines up to a diameter of 25

mm, the maximum velocity should not exceed 1m/s. Larger pipes

require lower velocities;

• A general rule for all homogeneous liquids (except carbon

disulphide and ether) and all pipelines: at velocities below 1 m/s,

no dangerous charges will be generated;

• Flanges should be earth bonded;

• Use sub-surface dip pipes or bottom entry filling when discharging

into vessels;

• Ensure regular inspection and testing of earth bonding.



Powder Transfer

Powder transfer can be carried out by several different methods:

• Screw conveying;

• Vacuum transfer;

• Pneumatic conveying;

There are two distinct types of pneumatic conveying used for powder

transfer, namely low pressure / dilute phase or high pressure / dense

phase. Low pressure / dilute phase systems tend to employ high system

velocities ranging from 10 to 25 m/s, whereas high pressure / dense

phase systems tend to employ low system velocities ranging from 0.25 to

2.5 m/s.

Intensive charging of the conveyed material and pipeline is possible

during pneumatic powder transfer potentially resulting in:

• Electrostatic discharge between conductive parts (e.g. between

metal flanges and a part of the steel structure of the building);

• Entrapment of considerable charges into receiving containers.

Powders can be divided into three groups depending upon the volume

resistivity of the material of which the particles are composed. These

groups are:

• Low resistivity powders, e.g. metals having volume resistivities up

to about 106 �.m;

• Medium resistivity powders, e.g. many organic powders, such as

flour, having volume resistivities in the approximate range 106 �.m

to 109 �.m;

• High resistivity powders, e.g. certain organic powders, many

synthetic polymers and some minerals, such as quartz, having volume

resistivities above about 109 �.m.



Measures that reduce these hazards include:

• Ensure pipelines used for pneumatic conveying are made from

metal with good earth bonding. Resistance to ground for all

conductive components should be < 10 ohms;

• Ground all operators loading powder so that their resistance to

ground is < 1 x108 ohms;

• Avoid use of insulating coatings on the inner surfaces of metal

containers and pipelines;

• Use plastic flanges with plastic transfer lines;

• Avoid use of coating or sheathing on pipelines constructed of

insulating material;

• Use antistatic plastic or paper bags in or around flammable gases,

vapours or dusts having minimum ignition energies of < 4 mJ;

• Discharge powder into the container or silo via intermediate loading

equipment, e.g. a cyclone fabricated from conductive material to

reduce velocities and earth charge. (Alternatively rotary valves, bag

dump hoppers or scroll feeder systems can be employed).

Offloading

Stringent precautions are required to prevent accumulations of static

electricity and to give protection against lightning. Standard copper strip

(25 mm x 3 mm section or equivalent) is usually employed for the main

earthing system. This should be connected to at least one copper-

earthing rod that has been tested and shown to have a total resistance to

earth of <10 ohms.

The operator should employ a bulk loading and offloading procedure. This

should include written instruction that state when offloading flammable

liquids, the driver must first connect the tanker to the earthing

connection at the off-loading point. The electrically conducting discharge

hose can then be connected to the liquid intake point on the storage. The

electrical resistance between the two couplings on a flexible hose must

not be higher than 106 ohms.



Temporary Storage

Before temporary storage is brought on line for storage of flammable

liquids or explosible powders, an assessment of earthing provision with

associated earth testing should be undertaken. This should encompass

the storage vessel and all supporting ancillary equipment.

Flexible Pipelines

When flexible hoses are employed, measures that can be adopted

include:

• Where velocities exceed 1m/s hoses should be made of conductive

material or non-conductive material with embedded fine wire mesh.

The mesh should be bonded to the metal flanges or coupling of the

hose;

• If a metal hose with a liner is employed, the metal mantle and

flanges or couplings must be bonded to each other;

• The electrical resistance between the two couplings must not be

higher than 106 ohms. This resistance is to be measured at regular

intervals;

• Use of ball valves with earthed metal spheres.


__________________________________________________Causes Of Plant Failure 1

5.8 Causes of Plant Failure

Contents

1. Corrosion2. Erosion3. External Loading4. Impact5. Pressure6. Temperature7. Vibration8. Wrong Equipment9. Defective Equipment10. Human Error

1. CORROSION

Corrosion is caused by electro-chemical processes in which a metal reactswith its environment to form an oxide or compound by the formation ofcells comprising an anode (the deteriorating metal), a cathode (adjacentmetal) and a conducting solution (acid / salts). It can occur bothinternally and externally to pipelines, vessels, plant, machinery,structures and supports.

The materials selection philosophy aspect of the design phase of all plantand structures should take into account the anticipated conditions(pressure, temperature and atmosphere) and the contents of the systemin order to either minimise corrosion or to make adequate allowances forit in the form of additional material thicknesses.

The initial corrosion on some metals creates an impervious coating, whichprevents further corrosion taking place.

Corrosion can be exacerbated by utilising different materials which thenset up an electrochemical cell which in turn causes wastage of the anode.

1.1 Types1. Oxygen pitting, bi-metallic (internal and external).2. Water lines, low velocity/stagnant conditions, under millscale

deposits, crevice-type corrosion (differential aeration), localised atareas of dissimilar metals (galvanic action).

3. Carbon dioxide uniform loss, specific through turbulence, wet gas“Mesa” type (internal). Note: Mesa type corrosion is a descriptiveword emanating from the Mesa region of Spain which is noted forits table top sharp edged plateau with shallow broad valleys.



4. Hot aerated water lines, where CO2 partial pressure is 0.2 barg,areas of turbulence (bends, tees, weld upsets), wet gas lines.

5. Hydrogen Sulphide (internal).6. Sour service, partial pressure > 0.003 barg, bacterial attack on

sulphates in low acid conditions.7. Stress Corrosion Cracking (internal and external).8. Chloride SCC in austenitic steels at temperatures above 60°C,

combined corrosive and tensile stress, externally.9. Can be associated with damaged / wet coverings and insulation

material, inadequate or maloperating cathodic protection.

1.2 PreventionAdequate design parameters.1. Choice of materials, taking into accounts all envisaged conditions

and contained fluids or products.2. Avoiding the use of dissimilar metals.3. Suitable corrosion allowances.4. Joint design and configuration.5. Applied coatings (internal and external).6. Drainage facilities.7. Inspection and monitoring facilities.8. Installation considerations.

1.3 Monitoringa) Condition Monitoring (containment system):

i) Planned inspection procedures.ii) Planned corrosion monitoring procedures, by ultrasonic thickness

measurement, probes, coupons, cathodic protection,etc.b) Condition Monitoring. (contained fluids):

i) Continuous process and operation monitoring.ii) Planned application of inhibitors to contained fluids.iii) Regular checks and monitoring that the contained fluids are

within the design parameters.c) Monitoring at manufacture and installation:

i) Storage and protection of pipework and plant at fabricationstage and prior to commissioning.

ii) Correct selection and usage of fabrication methods andconsumables.

iii) Satisfactory installation to avoid deadlegs, moisture traps,environmental hazards.

iv) Proper selection and application of monitoring and inspectionprocedures during fabrication and installation.

v) Suitable insulation and protection during installation. Equipmentand installation drainage points etc.



1.4 Examples1. External Chlorine induced SCC of Oil/Gas HP Separator due to

warm, (90°C) wet insulation attached to solid stainless steel(duplex).

2. Stress Corrosion Cracking in duplex stainless steel pipe welds dueto low pH, high chloride and high hydrogen sulphide environment(Acid washing downhole safety valves).

3. Pin-point corrosion of heat exchanger tubes in fin-fan coolers onclosed circuit cooling water systems due to inadequate addition ofcorrosion inhibitors and tested alkalinity of the medium.

4. External corrosion of pipework, vessels and storage tanks in placesthat usually are covered, but where insulation breaks haveoccurred, particularly in harsh environments. e.g. coastal locations,(gas terminals etc.)

5. External corrosion of boiler blowdown elbows and associatedpipework, located in floor sumps, which become fouled with wetwarm debris.

6. Cavitational corrosion caused by bubble collapse in process systemsand more commonly in boiler water tubes as scab pitting.

7. Internal corrosion occurring in dead-legs on systems which do nothave adequate draining facilities, or are not operated as frequentlyas required.

8. Floor plate and lower shell plate corrosion due to smothering withwet acidic/chlorinated waste material and debris.

9. Preferential corrosion attack in the heat affected zone (HAZ) ofwelds in carbon steel gas flow lines, initiated from a fairly benigngas output at start up of production to an inclusion of degrees ofcorrosive trace elements without proper degrees of inhibition beingimplemented.

1.5 Key WordsTrace elements, corrosive extraction products, oxygen bubbling, H2Sattack, damp warm conditions (under insulation), sub-surface (soil),acidic, chlorine content, preferential attack, drainage, design, monitoring.

2.EROSION

Caused by internally by excessive fluid velocity, change in phase,cavitation, change in flow direction, presence of particulates.

Caused externally by sand, salt, water (rain and sea), wind, cavitation,venturi effect round buildings etc. Pressure leaks can cause impingementand have a lancing effect at the leak itself and at areas where the leakingfluid strikes another surface.



2.1 PreventionAdequate design parameters:

i) Choice of materials.ii) Plant layout and siting.iii) Coverings and coatings.iv) Filtration.v) Reduction of dissolved gases in fluids.vi) Avoidance of abrupt changes in pipe section and short radius

bends.

2.2 MonitoringRoutine inspection programmes (visual supported by ultrasonic thicknessmeasurements where appropriate).

i) Non-intrusive internal inspection and monitoring at suspectedsystem sites (bends, Tees, elbows etc.).

ii) Intrusive inspection and monitoring at areas where erosion isprobable.

2.3 Examples1. Failure of bends on 50 mmNB pipework carrying pulverised

anthracite to the combustion chamber of a fluidised bed steamgenerator at the Grimesthorpe European power station project.

2. Thinning of swept bends of flowlines carrying first oil from offshoreextraction due to the scouring effect of sand particulates.

3. Perforation of “U” bends in tubular heat exchangers.4. Rapid perforation of adjacent boiler downcomer tubes from

tubewall leak through cracking.5. Thinning of exposed pipe through sand blasting in desert and

seaside locations.6. Turbulence effect created by incorrectly fitted / incorrectly sized

flange gaskets.

3. EXTERNAL LOADING

Can be caused by the effects of snow, winds, ice, floods, support failure,system/equipment failure, environmental failures (earth movements),filling / emptying, change in contained fluids.

3.1 PreventionAdequately considered design parameters.

i) Adequate consideration of environmental factors, (wind, snow, iceformations, earth tremors).

ii) Provision of spiral deflector vanes on pipework, tall vessels etc.iii) Provision of guyed supports for tall structures.



iv) Design considerations for supports and hangers (to includeperceived environmental loadings).

v) “Golfballing” of large spherical or cylindrical storage and processvessels.

vi) Adequate foundations provision.vii) Provision of trace heating for the prevention of ice or snow build-

up.

3.2 Monitoring1. Regular, scheduled external inspection regimes with dedicated

methods and reviews.2. Regular scheduled maintenance of trace heating facilities etc.3. Documented procedures for information sharing in the event of a

change of use, including change in contained fluids.

4. IMPACTFrom road and rail vehicles, failed equipment, or other sources, includingaircraft, and dropped or swinging loads or objects.

4.1 Prevention1. Adequate provision to ensure surrounding equipment, building

attachments, are safe and secure.2. Avoid siting plant within the arc of cranes, winches, gantries, etc.3. Avoid crossing roads with pipelines, and ensure sufficient clearance

for all foreseeable vehicle travel (including JCBs with elevatedbuckets).

4. Employ rigid guarding where necessary (likelihood, possibility).5. Adequate distance between plant and road, railways, rivers and

canals etc.6. Careful siting of small bore pipework in relation to walkways and

access points.

4.2 MonitoringSurveillance of plant, surroundings and adjacent equipment.

4.3 ExamplesDistorted and ruptured pipelines on overhead pipetrack resulting fromimpact by JCB raised bucket during travel (illegal).Indented pipelines from equipment miss-handling duringremoval/replacement for refurbishment or inspection during refinerydowntimes (numerous).Sheet steel cladding of crane structures becoming detached andimpacting on pipework during fall.Distortion and severance of unprotected small bore pipework in way ofregular human access.



5. PRESSUREFailure due to over-pressure caused by control failure, external fire,internal explosion, excessive reaction rate, liquid expansion, exothermicreaction, or collapse caused by vacuum.

5.1 Prevention1. Design parameters to include suitable process pressure controllers

for systems, particularly where multi-system inter-action isrequired.

2. Installation of suitable additional pressure controlled shutdown orwarning devices where operational environments deem this anecessity (Gas terminals, chemical plant etc.).

3. Design parameters should ensure conditions where there may be apotential for internal explosion (e.g. through mixture of gasses) arefully considered.

4. Design and operating procedures should take account of thepossibility of excessive reaction rates and limit the resulting rises inpressure and / or temperature to acceptable limits.

5. Design and operating procedures should take account of thepossibility of liquid expansion to limit the resulting rises in pressureand / or temperature to acceptable limits.

6. Design and operating procedures should take account of thepossibility of exothermic reaction and limit the resulting rises inpressure and / or temperature to acceptable limits.

7. Design parameters should include suitable prevention devices(vacuum breakers) and structural strength where vacuumgeneration is possible unless the plant has been designed to safelywithstand vacuum conditions.

8. Fitting of suitable relieving devices to the systems and vessels(pressure safety valves, bursting discs, fusible plugs) which haveadequate margin between system operating pressure and actuationpressure and which prevent design parameters being exceeded.

9. System dump facilities in case of over-pressure.

5.2 Monitoring1. Regular programmed and audited testing and calibration of

pressure control, relieving, indicating and warning devices.2. Regular review of design codes and guidance for pressure systems.3. Regular review of safety notices regarding incidents to pressure

systems.4. Regular review of the operators awareness and skills.5. A formal procedure to review operating procedures in the event of

change of use or contents of a pressure system.6. Regular and formal testing and maintenance of vent and flare

headers.



6. TEMPERATURE

Excessive excursions of high and low temperatures due to processupsets, fire, adverse weather conditions, fouling, blockages or phasechanges can lead to failure due to rapid or large temperature variations.Rapid temperature changes or low temperatures can lead to cracking.High temperatures can lead to failure due to loss of structural strengthwithout the design pressure being exceeded.

6.1 Prevention (internal)1. Adequate thermostatic control of the system contents.2. Design parameters adequate for predictable temperature

variations.3. Provision of insulation where required.

6.2 Prevention (external)1. Temperature sensors, gas sensors.2. The provision of blast and fire walls where required.3. Deluge systems provision.4. Insulation to the system’s vessels and pipe work.

6.3 Monitoring1. Implement regular inspection and testing of all alarm, control and

shut down devices.2. Regular surveillance and monitoring of insulation, fireproofing etc.

7. VIBRATION

Vibration can be generated through changes in phase, water hammer,liquid slugs in gas systems, gas bubbles or pockets in liquid systems,high pressure drop, cavitation, incorrect siting of rotating machinery,incorrect pipe supports, loss of buffer gas in damper vessels, damagedsupports and hangers, all of which can give rise to fatigue failure.

7.1 Prevention1. Ensure that system operation and contained fluid flow

characteristics are constantly monitored for prevention ofmechanical shocking caused by fluctuations.

2. Ensuring that provision is made for liquid systems to be vented toprevent gas entrainment.

3. Accurately determined siting of mechanical and rotating machinery.4. Pipelines and pipework layout is are such that the effect of vibration

is minimised.5. All pipelines and pipework is properly supported, and such supports

and hangers are suitable for the purpose.



6. All equipment and piping holding down devices are adequate andsecure.

7. Adequate shock / vibration mountings are fitted to plant andmachinery.

8. There is adequate provision of damper vessels at pump/compressordischarges, (especially reciprocating type).

7.2 Monitoring1. Adequate, programmed, audited surveillance by visual and

electromechanical means.2. Machinery vibration analysis exercises carried out, results reported

and acted on.3. Monitoring and recording of damper vessel precharge pressure.

8. WRONG EQUIPMENT

Wrong equipment can be fitted at installation or be supplied as areplacement during the life of the plant or at a modification. Theequipment may be wrong because it has been incorrectly specified, orbecause the supplier has not supplied in accordance with thespecification.

Wrongly supplied equipment can lead to failure due to incompatiblematerials, wrong design, or it may have a rating or duty other than thatwhich it is intended to fulfil.

8.1 Prevention1. Formal system for ensuring that only equipment specified under the

design approval process is supplied and fitted.2. Adequate system design parameters from inception to first

fabrication.3. Audited and auditable “TIPS” (Technical Integrity Procurement

System) in place for new and replacement items, includingpipework, steelwork, fixtures and fittings.

4. Auditable obedience to design procedures during build, to includeformal design change procedures and engineering query routes tofulfilment.

5. Manufacturer, supplier, installer, operator and maintainerknowledge assessment and awareness systems are in place andaudited.

6. Auditable maintenance procedures, check lists, equipment lists inplace.

7. Permit to work systems in place.



9. DEFECTIVE EQUIPMENT

Defective equipment can be supplied when the plant is initially installedor subsequently as a replacement or during a modification.

This category covers circumstances where the equipment was correctlyspecified, but was defective in some way, such as the materials, theduty, or it may have been wrongly assembled. It may not work inaccordance with the specification, in terms of performance, or the trips,interlocks, protective devices etc. may not function as required.

The materials of construction may not be as per the specification, or itmay be intended for a duty other than that which was specified.Such defects can lead to the system failing or at least not perform asrequired.

9.1 Prevention1. Formal system for ensuring that only equipment specified under the

design approval process is supplied and fitted.2. Plant and equipment purchased from approved suppliers only.3. Audited and auditable “TIPS” (Technical Integrity Procurement

System) in place for new and replacement items, includingpipework, steelwork, fixtures and fittings.

4. Recorded vendor inspections at the supplier’s or manufacturer’sworks on all major plant and equipment.

5. Adequate and recorded commissioning tests on all new andrepaired equipment.

6. Manufacturer, supplier, installer, operator and maintainerknowledge assessment and awareness systems are in place andaudited.

7. Auditable maintenance procedures, check lists, equipment lists inplace.

8. Permit to work systems in place.

10. HUMAN ERROR

Many of the causes of plant failure already discussed have elements ofhuman error built in to them, from the design stage through to operationand maintenance. The types of failure directly covered here are thoseassociated with the operation of the plant, where errors of judgement orignorance form a major hazard.

Human error can cause overfilling, overloading through lack of or mis-placed judgement and/or information giving rise to incorrect decisions by



operators. Lack of knowledge or training of operations staff giving canalso give rise to failure due to operational errors.

10.1 Prevention1. Formal written training schemes are in place with performance

tests and assessments where required.2. Formal written operating procedure manuals are available covering

normal and emergency operations.3. Formal written operating instructions with check lists as required

are on hand / displayed and signed up.4. Regular auditing of procedures to account for changes in operating

parameters etc.5. Formal permit to work systems in place.


__________________________________________________Explosion Relief 1

5.9 Explosion Relief

This Technical Measures Document refers to the explosion relief measures

that can be adopted in plant design to ensure safe operation.

General Principles

Operators should demonstrate that appropriate measures are in place

either to prevent explosions from taking place, or to protect

against/minimise the effects of explosions.

Explosion prevention is always preferable to explosion protection,

particularly where an explosion is likely to result in emission of toxic

material.

In the event of an explosion, consideration must be given to flame

propagation, pressure effects, recoil forces and the possible toxic nature

of relieving components. These factors will have a significant impact on

plant layout, design of plant and supporting structures and explosion

relief routes. Relief points from explosion protection devices should be

located in an area typically outside the plant, but certainly not in the

vicinity of plant or personnel. Restriction of explosion relief routes may

result in system back-pressures compromising the effectiveness of the

explosion relief device.

Standard relief systems are inadequate for explosion relief conditions

because explosions :

• Are too fast for a safety valve to open in time;

• Cannot be relieved through piping – only through large explosion

panels or doors with short ducts;

• Do not have uniform conditions throughout each phase at any one

moment;

• Further reaction in vent flow is important;

• Steady state flow equations may not be applicable.



Explosion prevention can be achieved by:

• Inerting (exclusion of oxygen by use of inert gases);

• Elimination of ignition sources (segregation);

• Monitoring and detection of smouldering particles with automatic

quench systems (specific to dust explosions);

• Control of concentration, i.e. outside explosive limits by ventilation;

• Replacement of combustible materials.

Explosion protection and control can be achieved by:

• Containment (explosion-resistant construction);

• High speed isolation;

• Segregation;

• Explosion pressure relief (venting);

• Explosion suppression.

Sizing of Explosion Panels

General principles that relate to sizing methods for bursting discs and

relief valves are covered in the Technical Measures Document Relief

Systems / Vent Systems. Rates of pressure rise of dust explosions are

generally slower than those of gas or vapour explosions, therefore design

requirements are different for each case.

Explosion Panels for Gases and Vapours

The size of vent area required for effective control depends upon a

number of factors including:

• The type of gas or vapour;

• The concentration;

• The geometry of the hazardous region;

• The distance of the ignition source from the vent.

Various general rules are available for predicting vent areas based on

plant or vessel volumes. However, there is some discrepancy between

these general rules, so they should only be used with utmost caution.



These methods also depend upon the physical properties of the material

in the vessel. Two of the most common general rules are:

• The Fire Protection Association suggest 1 ft2 of vent area should be

allowed for every 20 ft3 of plant volume (equivalent to 1 of vent

area per 7 m3 of plant volume);

• API RP 521 suggests a relief area of 6.6 m2 per 100 m3 of vessel

volume as an empirical guide.

Explosion Panels for Dusts and Powders

HS (G) 103 quotes 1 m2 per 6 m3 of plant volume for up to 30 m3, and 1

m2 per 25 m3 of plant volume for greater than 300 m3 as a rule of thumb

for dusts.

For more considered sizing of vent areas for dust explosion, several basic

methods exist. These include:

• The Kst Nomograph Method;

• The ST Group Nomograph Method;

• The NFPA 68 Method;

• The Vent Ratio Method

• The K-Factor Method

• The NFPA Randstadt Alternative Method;

• The Scholl Method.

Selection of the appropriate explosion panel sizing method is dependent

upon the configuration of the vessel to be protected, the physical

properties of the dust or powder being handled, the prevailing process

conditions, whether pneumatic conveying is involved (homogeneous or

heterogeneous dust distribution), and whether vent ducting is employed.

Each individual method outlines the requirements that need to be fulfilled

for the method to be valid.

Any attempt to apply a single method indiscriminately may lead either to

uneconomic and impracticably large vents or, more seriously, to

inadequate vents which could result in extensive damage and injury. It is

good practice to undertake sizing of explosion panels by implementation

of several methods to corroborate the ultimate size selected.



Explosion Relief from Buildings

Consideration should be given to the provision of lightweight roofs and

relief panels in walls which vent to a safe place so as not to injure people

or damage neighboring property. This is particularly relevant to

warehouses storing drums/cylinders of flammable substances

Dust Explosions (especially in powder transfer and dryers)

A dust explosion can take place only if a number of conditions are

simultaneously satisfied:

• The dust must be explosible (refer to table on dust explosion

classes);

• The dust must have a particle size distribution that will allow the

propagation of flame;

• The atmosphere into which the dust is dispersed as a cloud or

suspension must contain sufficient oxidant to support combustion;

• The dust cloud must have a concentration within the explosible

range;

• The dust cloud must be in contact with an ignition source of

sufficient energy to cause an ignition.

Dust may be grouped into dust explosion classes as determined using

standard test apparatus. These groupings are as follows:

Dust Explosion

Class

Kst (bar m s-1) Characteristics

St 0 0 Non-explosible

St 1 0 < Kst < 200 Weak to moderately

explosible

St 2 200 < Kst

<300

Strongly explosible

St 3 300 < Kst Very strongly explosible



Separate ignition prevention precautions for dryers are detailed in

references although typical precautions include:

• Maintaining the temperature of flammable materials below the

relevant ignition temperatures;

• Regulating heat input during the start-up and shut-down to prevent

the exhaust air temperature exceeding a predetermined value;

• Earthing of equipment;

• Elimination of points where dust can accumulate;

• Regular cleaning of dust spills and accumulation;

• Avoidance of non-conducting or low conductivity materials.

Dryers may present specific fire or explosion risk due to:

• The combustion of the fuel used for heating them;

• The ignition of the material being processed in them;

• The proximity of hot surfaces to other processes and materials.

Where explosion protection measures have to be adopted, in some cases

it may be more appropriate to employ explosion suppression instead of

explosion venting. These cases typically include:

• When equipment is located indoors;

• The dust is particularly explosible or a hybrid mixture (i.e. dust and

flammable vapour);

• The vessel has insufficient area for vent installation;

• The dust is toxic and emissions are unacceptable;

• There is no safe vent discharge point;

• To prevent propagation of the explosion from one piece of

equipment through the interconnection to other equipment.

A combination of preventative and protective measures should be

employed to minimise risk of escalation due to flame propagation

between interconnected vessels. A common approach is to employ

isolation methods.



Separation Distances (Layout)

Consideration should be given to the location and layout of plant areas in

which potentially explosive conditions could develop to ensure reduction

of on-site and off-site risks.

Exothermic Reactions

Overpressurisation of reactors is addressed in the Technical Measures

Documents Relief Systems / Vent Systems.

Hazards from exothermic reactions occur in the event of thermal runaway

of the reaction mixture in which the rate of generation of heat is greater

than the available cooling capacity of the system.

Various testing strategies and experimental methods are commonly

available for determination of thermal decomposition hazards. The

operator should have shown due consideration of these hazards and

taken appropriate measures to provide pressure relief. Measures for

provision of pressure relief in these cases are addressed in the Technical

Measures Document on Relief Systems / Vent Systems.

Unstable Substances

When unstable substances are in use, the operator should demonstrate

that at the research stage of the product a systematic approach to the

identification of hazards relating to the nature of the materials has been

followed. These hazards should be identified and documented, with

subsequent evidence of implementation of control measures. Hazards

that merit consideration include:

• Explosibility;

• Thermal and pressure conditions;

• Flammability;

• Toxicity;

• Environmental problems.

The assessment is specifically concerned with the physical properties of

the products, and possible by-products.


__________________________________________________Hazardous Area Classification/Flameproofing 1

5.10 Hazardous Area Classification / Flameproofing

This Technical Measures Document refers to the classification of plant into

hazardous areas, and the flameproofing measures that can be adopted

for electrical apparatus.

General Principles

The methodology for classification of hazardous areas is covered by

appropriate British and European standards. All likely ignition sources

must be considered, and only equipment designed to an appropriate

standard should be employed in designated zones.

Catastrophic failures, such as vessel or line rupture are not considered by

an area extent and classification study. These abnormal events should be

considered by a Preliminary Hazard Analysis and a Hazard and Operability

Study.

Zoning

A hazardous area may be defined as an 'Area in which an explosive

atmosphere is, or may be expected to be, present in quantities such as to

require special precautions for the construction, installation and use of

electrical apparatus'.

Area classification is a method of analysing and classifying the

environment where explosive gas atmospheres may occur so as to

facilitate the proper selection an installation of apparatus to be used

safely in that environment, taking into account gas groups and

temperature classes.

Hazardous areas are classified into zones based on an assessment of the

frequency of the occurrence and duration of an explosive gas

atmosphere, as follows:

• Zone 0: An area in which an explosive gas atmosphere is present

continuously or for long periods;

• Zone 1: An area in which an explosive gas atmosphere is likely to

occur in normal operation;



• Zone 2: An area in which an explosive gas atmosphere is not likely

to occur in normal operation and, if it occurs, will only exist for a

short time.

When the hazardous areas of a plant have been classified, the remainder

will be defined as non-hazardous, sometimes referred to as ‘safe areas’.

An area extent and classification study involves due consideration of the

following:

• The flammable materials that may be present;

• The physical properties and characteristics of each of the flammable

materials;

• The source of potential releases;

• Prevailing operating temperatures and pressures;

• Presence, degree and availability of ventilation (forced and

natural);

• Dispersion of released vapours to below flammable limits;

• The probability of each release scenario.

These factors enable appropriate selection of a grouping, temperature

class, zone type and zone extent.

This information may be summarised in Hazardous Area Classification

data sheets, supported by appropriate reference drawings.

The zone so designated is a three-dimensional area of space, and thus

will extend above and below the plant item under consideration (if

appropriate), as well as horizontally.

Electrical Equipment Design Codes/Selection

The classification of hazardous areas where flammable gas or vapour

risks may arise allows the selection and subsequent installation of

electrical apparatus that is appropriate for use in such hazardous areas.

Design codes related to classification of electrical apparatus are listed in

the table shown on next page



Zone 0 Zone 1 Zone 2

Ex ia – Intrinsic safety

(IEC 79-11)

Methods suitable for Zone

0

Methods suitable for

Zone 0 or 1

Ex s – Special protection

if specifically certified for

Zone 0

Ex d – Flameproof

enclosure (IEC 79-1)

Ex n – Type of

protection N (IEC

79-15)

Ex p – Pressurised or

purging (IEC 79-2)

Ex q – Powder filling (IEC

79-5)

Ex o – Oil immersion (IEC

79-6)

Ex e – Increased safety

(IEC 79-7)

Ex ib – Intrinsic safety

(IEC 79-11)

Ex m – Encapsulation (IEC

79-18)

Ex s – Special protection

It should be noted that references in the table are to the equivalent IEC

79 standard Selection of electrical equipment for hazardous areas

requires the following information:

• classification of the hazardous area (as in zones shown in the table

above);

• temperature class or ignition temperature of the gas or vapour

involved according to the table next page:



Temperature

Classification

Maximum Surface

Temperature, °C

Ignition Temperature of gas or

vapour, °C

T1 450 >450

T2 300 >300

T3 200 >200

T4 135 >135

T5 100 >100

T6 85 >85

• Where applicable, gas or vapour classification in relation to the

group or sub-group of the electrical apparatus as in the table

below.

Group Representative Gas

I Methane

IIA Propene

IIB Ethylene

IIC Hydrogen

For particular gases, the group classification provided in BS EN 50014: 1998

should be used. This is based upon the comparison of the Maximum

Experimental Safe Gaps (MESG) for flameproof enclosures or Maximum

Ignition Currents (MIC) for intrinsically safe equipment with Group I

methane. The sub-groups in Group II are derived as shown in the table

below:

Sub Division MESG MIC Ratio

A > 0.9 mm > 0.8

B 0.5 - 0.9 mm 0.45 - 0.8

C < 0.5 mm < 0.45



If several different flammable materials may be present within a

particular area, the material that gives the highest classification dictates

the overall area classification. Consideration should be shown for

flammable material that may be generated due to interaction between

chemical species.

Ignition Sources Identification and Elimination

Ignition sources may be:

• Flames;

• Direct fired space and process heating;

• Fires involving waste materials allowed to accumulate;

• Use of cigarettes/matches etc;

• Internal combustion engines;

• Cutting and welding flames;

• Large scale fires started elsewhere on site

• Hot surfaces;

• Heated process vessels such as dryers and furnaces;

• Hot process vessels;

• Space heating equipment;

• Mechanical machinery;

• Electrical equipment and lights

• Spontaneous heating;

• Friction heating or sparks;

• Impact sparks;

• Electric sparks;

• Electrostatic discharge sparks:

• Lightning strikes.



Sources of ignition should be eliminated from all hazardous areas by:

• Avoidance of the use of direct fired heating;

• Prohibition of smoking/use of matches;

• Control of the use of internal combustion engines (see Technical

Measures Document on Permit to Work Systems;

• Control of cutting and welding activity through a Permit to Work

system;

• Elimination of surfaces above autoignition temperatures of

flammable materials being handled/stored (see above);

• Using electrical equipment classified for the zone in which it is

located (see above);

• Control of maintenance activities that may cause sparks/hot

surfaces through a Permit to Work System;

• Earthing of all plant/ equipment

• Provision of lightning protection.

Lightning Protection

Protection against lightning involves installation of a surge protection

device between each non-earth bonded core of the cable and the local

structure.

Dust Explosions

Hazardous area classification for flammable dusts may be undertaken in

the same manner as that for flammable gases and vapours. Zoning as

described above may be applied, replacing 'gas atmosphere' with

'dust/air mixtures'.

Classification of dusts relating to autoignition and minimum ignition

current is undertaken similarly to gases/vapours, but involves additional

complications.



The explosibility of dusts is dependent upon a number of factors:

• chemical composition;

• particle size;

• moisture content;

• oxygen concentration;

• inert dust admixture.

In general, dusts with a particle size greater than 500 µm are unlikely to

cause an explosion, and particle sizes below 50-74 µm do not result in a

reduction of explosibility as size reduces. For this reason, most tests are

carried out on 75 µm samples as the worst case.

Ignition due to a hot surface is particularly likely to occur. The minimum

surface temperature which can cause ignition is about 100-200°C in most

cases.

Factors for assessor to consider

• Identification of Hazardous Areas

• Effectiveness of management and control of hazardous areas, with

respect to elimination of ignition sources;

• Demonstration that by design, operation and location extent of

hazardous areas has been minimised;

• Completeness of existing area extent and classification studies;

• All flammable substances present have been considered during area

classification, including raw materials, intermediates and by

products, final product and effluents;

• The appropriateness of the standards adopted for area

classification;

• Reference to impact upon area extent and classification due to

plant modification Control measures in hazardous areas required

during maintenance;

• Procedures for change/temporary works


__________________________________________________Inerting 1

5.11 INERTING

General Principles

The partial or complete substitution of the air or flammable atmosphere

by an inert gas is a very effective method of explosion prevention.

Inerting is normally only considered when the flammable or explosive

hazard cannot be eliminated by other means i.e. substitution of

flammable material with non-flammable, adjustment of process

conditions to ensure substances are below flammable limits. Typical uses

are within storage tanks where a material may be above its flashpoint

and within reactor systems when excursions into flammable atmospheres

may occur. Inert gases are also used to transfer flammable liquids under

pressure. Inerting is applicable to enclosed plant, since plant that is

substantially open to atmosphere cannot be effectively inerted because

the prevailing oxygen concentration is likely to vary.

A major risk associated with use of inerting is that of asphyxiation,

particularly in confined spaces. In those events where people are required

to enter a confined space, a formal management control system in the

form of a Permit to Work should be in place so that appropriate

precautions and control measures can be implemented. The Permit to

Work system is covered separately.

Gases that can be used for inerting include:

• Nitrogen;

• Carbon Dioxide;

• Argon;

• Helium;

• Flue gases.

The practice of inerting is also employed in explosion suppression

systems, where typically a quick acting pressure switch responds to the

initial comparatively slow increase in pressure due to initiation of

explosion conditions. This in turn triggers injection of an explosion

suppressant such as chlorobromomethane or carbon dioxide into the path

of the advancing flame front. This technique can also be employed to


__________________________________________________Inerting 2

provide protection to interconnected plant by inerting plant items

downstream of the explosion.

In most inerting systems a slight positive pressure should be maintained

within the enclosed plant to reduce the possibility of air ingress. Inert

gases may be generated on site, or via bulk storage of cylinder facilities.

Flammable Limits

To produce an explosion, three key 'ingredients' are required

simultaneously. These are:

• Fuel;

• Ignition;

• Oxygen.

The fuel must be within its range of flammability, i.e. at a concentration

above the lower flammable limit, but below the upper flammable limit.

This means that it is perfectly acceptable to have an environment with

the flammable material above the upper flammable limit provided

appropriate control protocols are in place since the potential for further

dilution would bring the material within its flammable range.

If the fuel cannot be eliminated or minimised, steps must be

implemented to eliminate or minimise the source of ignition (see the

Technical Measures documentation on Hazardous Area Classification). The

final measure that can be adopted involves reducing the oxygen levels

necessary to sustain combustion. This can be achieved by pressurising /

purging with an inert gas such as nitrogen.

The flammable limits for individual materials with air are readily available

in standard references, however appropriate methods should be

employed to determine the flammable limits for mixtures of materials.

Where flammable dusts are handled in an atmosphere containing

flammable gas or vapour, determination of flammable limits is difficult

and use of inerting should be considered wherever possible.

Reliability / Back-up / Proof Testing

In many applications, the maintenance of an inert atmosphere is a

safety-critical measure, in the absence of which many potential hazards


__________________________________________________Inerting 3

could be realised. Reliability of the supply of inert gas is therefore of vital

importance, and the system should be regularly inspected and

maintained.

Consideration should be given to the possibility of failure of the inert gas

supply and the acceptable unavailability. This will involve calculations to

determine the rate of leakage / replacement in all process conditions

encountered to find the worst case that must be considered.

Back up of supplies with alarm systems to bring about operator

intervention or automatic change-over should be provided as required to

meet the required availability determined. Consideration should also be

given to the reliability of the control systems employed for operation and

change-over. Back-up facilities may be via alternative bulk storage or

cylinder provision.

A major consideration when designing plant to be protected by inerting is

the need for continuous monitoring of oxygen and flammable gas or

vapour concentrations.

Operating / Maintenance Procedures

Inert gases are often used to purge tanks and vessels which normally

contain flammable substances prior to maintenance, commissioning or

decommissioning. The presence of inert atmospheres should always be

taken into consideration during operational or maintenance activities

since potential hazards could arise from:

• Asphyxiation;

• Loss of inert atmosphere.

Control systems based upon the use of ‘explosimeters’ and oxygen

analysers should protect against asphyxiation if entering such areas.

Maintenance activities should only be undertaken by suitably trained and

authorised personnel, and controlled by a Permit to Work system.


__________________________________________________Leak/ Gas Detection 1

5.13 LEAK / GAS DETECTION

This Technical Measures Document refers to issues surrounding the

detection of leaks and gases and what type of containment control

systems have been designed to manage unplanned releases.

General Principles

The following aspects should be considered with respect to Leak/Gas

Detection:

• Human Factors;

• Objectives of leak/gas detection systems;

• Types of leak/gas detectors required;

• Maintenance of leak/gas detectors; and

• Management of leak/gas detector systems.

The following issues may contribute towards a major accident or hazard:

• Unrecognised high-risk areas, where detectors could be used;

• No detectors or the wrong types in place in high risk areas;

• Detectors incorrectly positioned and installed on site;

• Poor level of maintenance and control of detection systems;

• Too heavy a reliance on ineffective detectors.

Contributory Factors for an Assessor to Consider Concerning

Leak/Gas Detection

The Report should address the following points:

• The appropriateness of the types of detectors being used (UV

detectors, IR. detectors, smoke detectors, intrinsically safe

detectors, heat detectors, specific substance detectors,

explosimeters) in terms of the environment in which they are

located and to perform the duty expected;

• The effectiveness of using the detectors in terms of their

positioning relative to the possible leak sources, taking account of

dispersion and dilution of the released gases/vapours;



• The effectiveness of the detectors for the types of substances to be

detected (flammable substances, acid gases, smoke, explosive

substances, toxic substances) at the concentrations required.

Detectors may be chosen to react to more than one substance;

• The types of protective devices linked to the detection systems

(alarms, warning lights, reaction quenching systems, isolation

systems, fire retardant systems, plant shutdown systems, trip

devices, emergency services);

• The reliability of each detector (range of detection, response time

of detection, level of maintenance, calibration frequency,

performance testing frequency, proof testing);

• The detectors can be clearly seen, heard and understood,

(appropriate warning signs, lighting, noise recognition), on plant, in

the control room and off-site (if appropriate);

• The procedures to respond to alarms, as a result of a leak/gas

being detected (emergency evacuation plans, fire drills, risk

assessing existing emergency evacuation plans), to confirm that

the release has actually occurred and to record and investigate

false alarms and take action to change the system to maintain the

confidence of operators;

• The level of risk associated with each potential leak source (risk

assessments, risk-rating systems) and the reduction in that

assessed risk value achieved by the use of detectors;

• The provision and accessibility (to operators, maintenance staff

etc)of a sufficient site plan which maps all potentially hazardous

areas (zones 0, 1 & 2, segregation of compatible hazardous

substances);

Contributory Factors for an Assessor to Consider Concerning Fire

Detection and Control


• The types of fire detector systems in place (infrared detectors,

ultraviolet light detectors, temperature detectors, smoke

detectors);

• The area covered by the detection system;



• The reliability of the fire detection systems (fail-to-danger faults,

spurious alarms); and

• The types of fire protection systems in place (fire proofing, water

sprays, foam/filming agents, monitor guns, combustible gas

monitors, foam on tanks, fire walls/barrier walls, emergency relief

venting for buildings, dust explosion control).

Major Hazards


• Detector fails to detect in time (i.e. response time of instrument

and/or response to high reading/alarm failing to prevent a major

accident),

• Detector fails in undetected unsafe state (reading zero),

• Alarms, warning devices and protective devices fail to operate on

demand,

• A leak occurs which cannot be detected (due to position of sensor

or weather conditions), and

• Maintenance procedures not followed, increasing unavailability of

system or rendering system ineffective.


__________________________________________________Active / Passive fire protection 1

5.14 Active/Passive Fire Protection

Introduction

Active fire protection systems such as water sprinkler and spray systems

are widely used in the process industries for protection of storage

vessels, process plant, loading installations and warehouses. The duty of

the fire protection system may be to extinguish the fire, control the fire,

or provide exposure protection to prevent domino effects. For some

applications foam pourers or fixed water monitors may be a more

appropriate method of delivery than sprays or sprinklers. Other more

specialised systems using inert gases and halogen based gases are used

for flooding enclosed spaces.

Passive fire protection can provide an effective alternative to active

systems for protecting against vessel failure. This generally consists of a

coating of fire resistant insulating media applied to a vessel or steel

surface. It is often used where water or other active protection media

supplies are inadequate, such as in remote locations, or where there are

difficulties with handling firewater run-off. Firewalls are another form of

passive fire protection that are used to prevent the spread of fire and the

exposure of adjacent equipment to thermal radiation. An important

criterion in deciding which system is most appropriate for fire exposure

protection is the likely duration of the exposure to fire as passive fire

protection is only effective for short duration exposure (1-2 hours).

General Principles

The operator should be able to demonstrate that it has an effective and

practical plan for the containment and fighting of fires on its process

installations. The following site factors should be considered in

determining whether active and passive fire protection measures are

required:

• fire hazard posed by substance;

• toxicity of substances and the smoke produced;

• inventory size;



• frequency of hazardous operations;

• distance to other hazardous installations;

• available access to fight fire;

• fire fighting capability of on site emergency response team;

• response time of nearest fire brigade;

• resources available to fire brigade.

Design of System

Active fire fighting systems need to be reliable and the design of the

system should demonstrate this. The design of fire fighting systems

should conform to specified standards such as Teriff Advisory Committee

(TAC) and Fire Offices Committee 'Tentative rules for medium and high

velocity spray systems'.

The location of items such as the foam and water sources should be a

safe distance from any hazardous installation. Critical valving and

instrument cabling located on the protected installation should be capable

of withstanding the effects of fire and heat.

The system should be supplied by a secure water supply, which should

include items such as backup diesel pumps where appropriate. The

design must ensure that the active fire protection system is not starved

of water due to other demands on the water supply system during a fire.

Choice of Fire Fighting Media

The selection of media will depend on the required duty. This may be to

extinguish the fire, control the fire, or provide exposure protection. Types

of fire fighting media are:

• Water;

• Foams;

• Inert gases;

• Chemical powders;

• Halons.



Water is not recommended as an extinguishing media for low flash point

liquids, but it is used widely throughout industry for fire control and

exposure protection.

Foam is a more effective extinguishing media for low flash point

substances and is widely used against liquid fires. There are various types

of foam available, but the most widely used is protein foam. Alcohol

resistant foam is used for application on polar solvents where the foam

stability is affected. Other more specialist foams have been developed to

give improved extinguishing properties such as fluoro-protein and

aqueous film forming foams. Foam can be delivered as low, medium or

high expansion depending on the required duty.

Other agents such as inert gases, chemical powders and halogen based

gases (Halons) can be delivered by active fire protection systems, but

these tend to be installed where process equipment is contained within

an enclosure such as a gas turbine enclosure. A common use for these

systems is in the protection of switch rooms and control panels. There

has been movement away from the use of Halons over recent years due

to their potential effect upon the ozone layer and other undesirable

environmental effects.

Standard Material Safety Data Sheets should also specify appropriate fire

fighting media.

Choice of Passive Fire Protection

For the protection of vessels from fire exposure there are a number of

types of passive fire protection that can be applied.

1. mortar based coating

2. intumescent coating

3. sublimation coating

4. mineral fiber matting

5. earth mounds

The protective systems based on coatings are normally sprayed onto the

surface following mixing of the required components. A reinforcing glass

fiber scrim or steel wire gauze is applied to prevent cracking and peeling



of the coating under fire conditions and to provide additional strength to

resist the impact of high pressure water jets. The fire protective coating

is further protected by a weather protective top layer. The fire resistant

performance of the coatings is dependent on the thickness of the coating.

Fiber matting systems consist of fireproof mineral fiber matting clad with

a protective galvanised steel sheet. The protective capability of the

system is provided by the poor heat conductivity of the system.

Earth mounds are commonly used in the LPG industry, where vessels are

either fully or partially buried in an earth mound. The presence of the

earth mound effectively prevents a fire from developing around the

vessel.

Fire walls are sometimes employed in process and storage areas to

prevent the spread of fire and protect adjacent equipment from thermal

radiation. These may be an integral part of a process building or

warehouse structure or may consist of a free-standing wall specifically

built for the purpose. Firewalls are normally built of brick, concrete or

masonry and the number and size of openings should be kept to a

minimum.

Performance of the Protective System

For active fire protection systems required delivery rates and durations

for various types of application are specified in BS 5306. For fire

engulfment protection a water rate of 9.81 litres/min/m2 over the

exposed vessel surface and its supports is standard. For protection from

lower levels of thermal radiation from fires on adjacent units lower rates

of water application are allowable.

For passive fire protection systems the operator should have supplier or

manufacturer information demonstrating that the fire protective system

employed meets defined performance criteria based on standard tests

that replicate the fire conditions likely to be encountered in the work

place. Typically the criteria will be that a protected surface will not reach

a certain temperature in a defined time period during a standard test.

The protective system should meet the requirements of a pool fire test or

a jet fire test .Jet Fire resistance for Passive Fire Protection Materials'.




Active fire protection systems require to be well maintained to ensure

reliability. In particular systems using water and water based foam are

prone to rust deposits which can block sprinkler heads and spray nozzles.

Procedures should be in place to ensure regular maintenance and testing

of systems. Maintenance contracts are often placed with the supplier of

the fire protection system. Records of these activities should be kept by

site operators.

The performance of passive fire protection systems can deteriorate in

time due to weathering and corrosion. Plant operational and maintenance

activities may damage or remove the fire protection. Additionally the

protected surface itself can corrode beneath the fire protection.

Procedures should be in place to ensure that both the passive fire

protective system and the protected surface are regularly inspected and

repaired as appropriate.

Containment of Firewater

Foam and water based active fire protection systems can generate

considerable amounts of effluent with significant potential environmental

damage. Where active fire protection systems are installed the overall

design of the facility should cater for the collection of fire fighting

effluents. Operating sites should have effluent disposal plans in place as

part of their emergency plans.

Supporting Measures

Where active or passive fire protection is installed, these systems should

be supported by hydrants at suitable locations as specified in BS 5908.

Suitable portable fire fighting equipment should also be located on the

plant.

Mortar based fire protection fire protection is commonly used to protect

load bearing steel work from collapse under fire exposure. The application

of this to vessel supports and supporting structures for process



equipment is standard where flammable substances are handled in

quantity.


LPG Industry

The use of water deluge systems for the protection of bulk LPG storage

vessels and loading bays is standard in the industry for all but the

smallest installations. Passive fire protection is used as an alternative and

in particular earth mounding of LPG vessels is an established practice.

Large LPG cylinder compounds covered by canopies are normally

provided with either fixed water monitors or a sprinkler system.

Flammable Liquids / Solvent Bulk Storage

Whilst active fire protection is not a standard requirement for vessels

containing flammable and highly flammable liquids, site factors such as

inadequate separation distances from other plant or the proximity of

occupied buildings may necessitate the use of active or passive fire

protection to prevent escalation of a fire event. Where protection of

remote storage tanks is required, passive fire protection is commonly

used. However, it is not normal practice to protect storage tanks in

locations that do not represent a hazard to people directly or by domino

effect.

Process Operating Units

Both the material handled, the size of the flammable inventory and the

local fire fighting capability will influence the requirement for active fire

protection on a process structure. In particular, where process equipment

handling significant quantities of flammable material are located inside a

building and fire fighting access is poor, then fixed fire protection systems

should be provided.

Warehousing

Some significant fires have occurred in chemical warehouses, The

considerations are much the same as those for process operating units.

For the storage of high hazard materials such as organic peroxides in



warehouses, fixed sprinkler systems using either foam or water should be

provided. However, it should be noted that the effectiveness of sprinkler

systems in warehouses may be limited if stocking densities are high.

Particular care is required in designing such systems.


__________________________________________________Quench System 1

5.15 QUENCH SYSTEMS

This Technical Measures Document covers the design and use of quench

systems

Introduction

Quenching can either be used to directly control a chemical reaction or in

the treatment of an emergency vent stream. For the direct quenching of a

chemical reaction when loss of control has occurred, the quench material

both cools and dilutes the reactants, thereby slowing down the reaction

rate and the rate of heat generation to a controllable level. Quenching

may be carried out by adding the quench liquid to the reactor or by

discharging the reactants to a dedicated dump tank.

Quench systems are used in vent disposal systems for the treatment of

streams that can not be discharged directly to atmosphere or where

continuing reaction is taking place. The process involves the mixing of a

solvent with the relief stream. This results in the condensation and

removal of volatile components from the relief stream and / or the cooling

of the vent stream which prevents further reaction from taking place.

General Principles

The operator should be able to demonstrate that it has evaluated the

options for emergency protection of an uncontrolled exothermic reaction.

Where venting has been chosen as the means of protection, the operator

should demonstrate that it has considered the consequences of a vent

emission directly to atmosphere and installed appropriate vent treatment

measures where necessary.

Reactor Quenching

Where a quench system for the control of a reaction is installed the

following should have been considered:

• compatibility of the quench material with the reactants;

• reliability of the quench delivery system;


__________________________________________________Quench System 2

• availability of space in the reactor / dump tank to accommodate

quench material in addition to the reactor contents;

• the effects of level swell and foaming on quench addition;

• rate of mixing of the quench material with reaction fluids;

• the effectiveness of quenching for all conditions leading to loss of

control.

The operator should demonstrate the validity of the approach used by

appropriate test work. Consideration of the conditions leading to loss of

control of the reaction are particularly important. For instance if loss of

agitation can initiate this, the use of quenching to control the exotherm is

questionable as the cooling and dilution effects are reliant on effective

mixing. The pressure relief arrangements will need careful consideration

where a dump tank is employed.

Vent Stream Quenching

For the treatment of a vent stream there are a variety of arrangements

possible. The duty of the system to either condense volatiles or control

further reaction in the vent system will dictate the arrangement. A

commonly used arrangement for handling two phase discharge from a

reactor is a simple knockout drum containing an inventory of an

appropriate quenching agent. The vent stream is sparged into the

knockout drum below the liquid surface. The knockout drum itself then

vents to atmosphere, a scrubber or a flare stack. Alternatively the

quenching agent can be sprayed into the vessel from which the discharge

arises, or it can be injected into the vent stream in a quench nozzle to

effect partial condensation of the stream. Where a quenching agent is

used in a vent disposal system the following should be considered:

• the duty – condensation or control of reaction;

• compatibility of the quench material with the vent stream;

• reliability of the quench delivery system;

• the effects of level swell and foaming in the reactor and/or

knockout drum.


__________________________________________________Quench System 3

Design of Quenching Systems

Data produced from adiabatic tests will strongly influence the design

requirements and form the basis for mass and heat balances. The

operator should be able to show how these have been used in the design.

The design should ensure effective mixing of the quenching agent and

cater for the effects of level swell where appropriate.

As an emergency protective measure the operation of a quench system

needs to be reliable. The instrument and control features of a quench

delivery system should demonstrate this and features such as voting

systems and hard wiring of trips should be included for critical duties.

Other support systems, such as utilities, that are critical to delivery of the

quench system need similar high integrity.


Quenching systems require to be well maintained to ensure reliability.

Procedures should be in place to ensure regular maintenance and testing

of relevant instrument and control systems. The inspection and

maintenance of pipe work and vessels should be carried out to written

procedures on a regular basis. Where the quality or specification of

quenching agents may deteriorate over time so as to reduce

effectiveness, the inventory should be replenished at set frequencies.

Effluent Disposal

Control of a reaction with a quenching agent may cause irreversible

contamination of the reactants. Where a quenching agent has been used

in a vent disposal system, this will need to be removed before plant

operations can recommence. Plans should be in place for the safe

handling and disposal of effluents generated from the use of a quench

system.


Raw Material Control/Sampling 1

5.16 Raw Materials Control / Sampling

This Technical Measures Document refers to the ‘cradle to grave’

approach to prevent an unwanted chemical being used in a plant

resulting in a major accident or hazard. A chemical can be a contaminant,

raw material, reactant, intermediate, by-product or product.

See also Technical Measures Documents on Corrosion / Selection of

Materials

General Principles

The following aspects should be considered with respect to Raw Materials

Control/Sampling:

• Human factors;

• Poorly skilled work force;

• Unconscious and conscious incompetence;

• What would happen if the wrong material was used in the wrong

place; and

• What would happen if contaminated or out of specification material

was used.

The following issues may contribute towards a major accident or hazard.

• Human error during acceptance of delivery and sampling;

• Incompetent quality control staff;

• Contaminant entering the plant for example, flammables in non-

flameproof areas, oxidisers mixing with flammable solvents;

• Failure to understand the properties of substances handled;

• Failure of quality assurance procedures; and

• Failure to identify all credible contaminants and resultant reaction

pathways that could disrupt the integrity of the plant involved.

Contributory Factors for an Assessor to Consider Concerning Raw

Material Delivery, Test and Storage

The Safety Report should address the following points:

• Whether there is are sufficient management systems in place to

control the handling and use of all raw materials on site (Quality

Safety Management, Quality Control/Assurance Procedures);



• Whether staff is sufficiently informed, instructed, trained and

supervised to minimise a potential human failing during raw

material delivery, test and storage;

• Whether there a sufficient chemical inventory of all chemicals used

on site;

• The procedures in place to vet the suppliers of raw materials

(Audits, supplier history, reputation);

• The amount of information with each raw material delivery (Trem

Cards, Certificate of Analysis, Safety Data Sheets, representative

samples);

• The suitability of quality assurance procedures in place to test all

incoming raw materials on site if deemed necessary (Quarantine

procedures, quality control procedures, representative sampling

procedures);

• The suitability of validated quality control test methods and

equipment in place to identify any potentially hazardous

contaminants present within a raw material delivery; and

• The effectiveness of the systems of work in place to prevent

contamination of raw materials once placed in storage, after QC

approval (Storage procedures, QC tests to approve stored

chemicals before use).

Contributory Factors for an Assessor to Consider During Plant

Production


The possibility of a major accident as a result of a change in the process

reaction kinetics due to contaminants in the raw materials (R&D data,

safety reliability data, engineering constraints);

• Whether all raw materials, reactants, intermediates, products and

by-products known and can be retained safely without a

deterioration in plant integrity (R&D data, analytical data, safety

reliability data, engineering constraints); and

• Identification of required emergency procedures, systems and

provisions in place to deal with events resulting from raw materials

control failure.



Major Hazards


• Static discharge during sampling of flammable substances;

• Exposure to head-space gases during profile sampling of raw

material tanker;

• Overfilling of storage vessels;

• Non-compliance of quality and safety procedures resulting in a

‘Domino effect’;

• Failure of safety systems manual or automatic.


__________________________________________________Reaction / Product Testing 1

5.17 Reaction / Product Testing

This Technical Measures Document covers the identification and control of

reaction hazards

Related Technical Measures Documents are Relief Systems / Vent Systems, Raw

Materials Control / Sampling, Trips / Interlocks, and Secondary Containment.

Introduction

Chemical reaction hazards may result from loss of control of an

exothermic chemical synthesis reaction, or an undesired reaction

occurring in the reaction mixture such as the decomposition of a chemical

present. So called 'runaway reactions' are normally associated with batch

reactors however an uncontrolled exotherm may occur in many types of

equipment. Storage vessels, batch distillation units and drying operations

are some of the more common types of process equipment where

undesired exothermic reactions have resulted in severe incidents.

Thermal runaway begins when the heat generated by a reaction exceeds

the rate at which heat is lost to the surroundings. The heat generation

rate is a function of temperature and chemical composition. Whilst the

temperature of the reactants may not directly constitute a major hazard,

the pressure developed as a result of thermal runaway in a vessel or

other item of process equipment can cause catastrophic failure of the

equipment.

General Principles

The operator should be able to demonstrate that it has evaluated the

potential reaction hazards of a process and carried out reaction hazard

studies as part of an overall hazard assessment of a process. This should

involve the following activities:



• Preliminary Reviews

As a starting point for a reaction hazard assessment a literature

survey and some theoretical calculations are useful, but are no

substitute for chemical hazard testing. Thermochemical calculations

based on bond energies or heats of formation can be used to calculate

a heat of reaction or a decomposition energy. The structure of

individual molecules can be reviewed to identify potentially reactive

groups such as acetylenic compounds, peroxides and nitro

compounds. An oxygen balance of an organic compound such as

propylene oxide can give an indication of the chemical’s propensity to

decompose on heating.

• Screening Tests

The simplest and most common apparatus used are Differential

Scanning Calorimetry (DSC) and Differential Thermal Analysis (DTA).

These apparatus use a sample size of a few milligrams and are used to

for purposes such as identifying at what temperature materials

involved in a reaction decompose and the possible effects of

contaminants on thermal stability.

• Worst Case

To define the worst case foreseeable upset conditions consideration of

failure of equipment, instrumentation, utility supplies, etc is required

to identify the scenarios that could result in uncontrolled process

temperature rise and subsequent over pressurisation of process

equipment.

• Adiabatic Tests

Adiabatic calorimeters are used to mimic plant conditions and give

accurate data on rates of heat production and gas evolution under

runaway conditions. Commonly used apparatus are the Dewar

Calorimeter, the Vent Sizing Package, the Phi-Tec Calorimeter and the



Reactive Systems Screening Tool. The data from these tests is used to

determine the Time to Maximum Rate and whether the pressure

developed is sufficient to cause failure of the vessel or relevant

process equipment. The data can be used to calculate a vent size

where appropriate. The Time to Maximum Rate is the time taken from

onset of the runaway to its maximum rate of heat generation.

• Basis for Safe Operation

Where reaction hazard studies identify that a thermal runaway can

occur, the studies should clearly define the technical measures in place

to ensure the safe operation of the process. For a reaction the

important parameters of the reaction such as temperature, cooling

conditions and time of addition should be defined in order to maintain

the reaction within safe limits. The requirement for protective

measures, such as emergency relief or quench systems, should be

detailed.

Chemical Reactors

Chemical reactions are widely used in the process industries and are the

process operation commonly associated with thermal runaway. Surveys

have shown that the following types of reaction have been involved in

incidents:

• Polymerisation

• Nitration

• Sulphonation

• Hydrolysis

• Salt formation

• Halogenation

• Alkylation

• Amination



The screening test programme and the adiabatic tests should show

whether the normal reaction or a secondary reaction or decomposition

are capable of over pressurising the reactor. The test work should be

used as the basis for determining whether additional protective measures

need to be included in the plant design such as:

• emergency pressure relief devices

• redundant systems / high integrity controls and trips

• emergency cooling

• quench systems

• reaction inhibition

• containment

Typically for a batch or semi batch reactor, failures such as cooling

failure, loss of agitation, addition rate of reactants, and reactant

temperature are considered to determine the worst case scenario. In

deciding whether emergency protective measures are appropriate it is

necessary to taken into account the time available to carry out

emergency preventative measures and rectify the situation. Where

emergency relief devices are employed, the toxic and flammable hazards

of the materials in the process may require additional features to limit the

consequences of a release. Depending on the severity of the hazard these

may include liquid catchpots, scrubbing systems, quench pools or

secondary containment vessels.

Other Process Operations

The situations in which the handling of self-reactive materials may result

in thermal explosion are numerous. This can be due to the decomposition

of an energetic substance or due to contamination causing an undesired

reaction. Some of the situations common to the process industries are

given below:



Batch Distillation

In a batch distillation process loss of vacuum may result in increased

temperatures that could initiate decomposition. Additionally batch

distillation residues can be prone to thermal explosion due to the thermal

ageing process that takes place during distillation. In 1993 a severe

incident occurred at a plant in southern Ireland when an operational

change to a batch distillation process resulted in a thermal explosion

followed by a large fire.

Storage

The slow decomposition of a reactive material in storage may cause an

increase in temperature over a period of leading to a thermal explosion.

This process can occur in a variety of situations from large-scale storage

in vessels to small transport packages. Accidental contamination of

materials in storage has resulted in some significant incidents, notably

the Bhopal incident.

Drying Operations

Loss of temperature control in a powder drier may expose a self-reactive

powder to a temperature that causes it to decompose. Similarly when a

drier is shut down the thermal cladding may cause heat to be retained for

a long period and a powder build-up or residues may start to decompose

after a period of time.


__________________________________________________Reliability of Utilities 1

5.18 RELIABILITY OF UTILITIES

This Technical Measures Document covers the reliability of utility services

and reference is made to relevant codes of practice and standards.

Introduction

The reliable supply of utilities on sites operating hazardous plant is

necessary in order to prevent events that may lead to multiple failures of

equipment and potentially hazardous events. The modes of failure of site

wide utility systems are numerous and may lead to site wide or local loss

of supply or even only partial failure on a particular plant. Whilst most

plant are designed to 'fail safe' on loss of utility supplies, there are those

where failure to operate correctly will almost certainly result in a

hazardous event and local back-up facilities are required. Particular care

is required in the design of site power systems as loss of power can also

result in loss of supply of all other site utility systems as well.

General Principles

Risk Assessment

The company should demonstrate that it has assessed the risk of loss of

utility supplies to its plants and identified the hazardous events that could

occur following such loss (e.g. using relevant techniques such as

HAZOP/HAZAN). These events should not only include fire and toxic gas

emissions, but also the release of process streams hazardous to the

environment such as the overflow of effluent sumps. The numerous ways

in which loss of supply of a utility can occur – total site, part of a site, a

single plant unit, part of a plant – should all be taken into consideration

in order to identify which process streams will continue to flow or not and

any potential hazards or domino effects arising as a consequence.

Site utility systems may include:

1. Electrical Power;

2. Steam / Condensate;

3. Inerting Gases – normally nitrogen;

4. Compressed Air;



5. Vacuum Systems;

6. Cooling Water;

7. Fire Water / other Extinguishing Agents (e.g. BCF, foam,

etc.);

8. Process / Service Water;

9. Fuel (oil, gas, etc.);

10. Refrigeration.

On some sites other more specialised utility systems may exist such as

the supply of oxygen through a distribution system from a cryogenic

plant unit.

Where a hazard assessment identifies that a plant may not continue to

operate or may not shutdown safely then back-up features may be

necessary to ensure its continued safe operation. Normally, such back-up

supplies are provided local to the plant, e.g. bottled gas supplies, but

may be via a redundant or diverse system arrangement, e.g. a parallel or

alternative supply.

Design

Based on risk assessment the operator should demonstrate that utility

systems have been designed with an appropriate level of redundancy

within the system to cope with failures and maintain the required

integrity (availability) of supply. Items such as pumps and compressors

can be expected to fail occasionally and typically this would mean the

availability of back-up pumps, compressors, or steam boilers available on

an auto start basis. To improve availability diverse equipment can be

used to avoid common mode failures.

Routing of critical utility supplies should take into account the hazards on

site and the potential for fire and impact damage on the distribution

system. Appropriate shielding should be used where necessary. The loss

of supply of a utility such as steam to a plant can often be handled safely

by appropriate trip systems, but where the continued operation of a

utility system is more critical, the design of the distribution system should

demonstrate the availability of various routes to achieve supply. Routes

for duplicate distribution lines should be segregated. Often a 'ring main'



approach is used for the distribution of fire water in hydrant systems.

Compressed air and inert gases should be supplied through local receiver

vessels with sufficient volume to ensure safe shutdown or continued

operation until normal supplies have been reinstated.

Electrical power supply systems involve much complex equipment and

deserve special consideration as failure can also impact on the supply of

other utilities and directly on process equipment. Typically a system for a

high hazard site may consist of two independent Grid supply points, both

fed from different circuits. Power may be fed to sub stations in duplicate

lines with cross over connections. The distribution from local substations

to various plant switch rooms can be switched between substations.

Nominated critical drives should be capable of being fed from a standby

emergency diesel generator and should auto start-up on receiving power.

An uninterruptable power supply (often referred to as an UPS) should

feed critical control and instrumentation systems.

The operator should demonstrate an appropriate level of availability for

critical utility systems using methods such as fault tree analysis.

Preferably for such calculations site specific data should be used,

however, where this is not possible generic data may be used. Where this

is the case some consideration of its appropriateness to the actual site

should be provided. Regular reviews of the systems should be undertaken

to ensure the required availability is being achieved in practice.

Training / Emergency Plans

The operator should demonstrate that site personnel understand the

implications of loss of a utility system and that emergency plans are in

place for the safe reinstatement of critical supplies where necessary.

Competent persons should be trained in the requirements of the

emergency plans and exercises should take place to test those plans.

Maintenance / Testing

Programmes should be in place for inspection and maintenance of utility

systems at regular intervals to written procedures. The intervals for proof

tests should be based upon the required availability of the utility system.

Where back-up systems are in place the operator should demonstrate



that the test routine involves 'end to end' testing of the system. As an

example, it is insufficient to test a diesel power generator set without

testing that the auto start-up facility works and that the switchgear in the

distribution system works properly.

Examples of Industry Applications

Emergency Absorption Plants

Emergency absorption plants must be able to handle vents under all

circumstances. These plants are built with standby recirculation pumps

and suction fans. Emergency power is provided by a standby diesel

generator. This approach is used in the handling of chlorine and other

toxic gases. Operating procedures should include the shutdown of plant in

the event of failure of such systems.

Flammables Handling

Where site operations involve the handling of flammable liquids a fire

hydrant system should be provided that preferably encircles the plant and

is provided with cross over connections at appropriate points. The ring

should be maintained under pressure by e.g. 'jockey' pumps. Any fall in

pressure should automatically start the main fire pump. A diesel powered

pump should be provided on high hazard sites in case of power failure.

Centrifuging of Flammable Materials

Many industrial processes involve the centrifuging of a powder from a

flammable liquid. Centrifuges are well known for providing an ignition

source due to their high speed moving parts and a secure nitrogen source

is necessary. A local emergency back-up supply of nitrogen is often

provided from local cylinders in case of site nitrogen failure.

Steam Heating

Where a hazard can arise from the solidification of a liquid chemical on

loss of steam heating, back-up heating is often provided by an electrical

heater or trace heating. Whilst there are not many instances of this being



a direct hazard, the exposure of personnel during the process of dealing

with a solid tank of a substance such as sulphur can represent a hazard.

Reactor Cooling

Loss of water cooling to a reactor can be hazardous where the reactions

involved are exothermic. The use of site utility water supplies to back-up

a local purpose designed cooling tower-based system is common. Where

a refrigerant is used for cooling, loss of power supply to the refrigeration

package can be critical.


__________________________________________________Relief System / Vent System 1

5.19 RELIEF SYSTEMS / VENT SYSTEMS

General Principles

Process plant can be subjected to excessive overpressure or

underpressure due to:

• External fire;

• Process abnormality or mal operation;

• Equipment or service / utility failure;

• Changes in ambient conditions;

• Excess chemical reaction.

To achieve a more inherently safe design, and to arrive at the most

economical solution overall consideration should always be given to:

• Can the overpressure or underpressure hazard be eliminated by

changes in process or plant design?

• Can the overpressure or underpressure hazard be reduced by

reducing inventories or changing process conditions?

• Can the overpressure or underpressure be contained by designing

equipment to withstand maximum feasible pressure?;

• Can alternative protection to a relief system be considered?;

• Can the required relief system be minimised by mechanical or

instrumented systems?.

Explosion Relief is considered in a separate Technical Measures Document.

Relief systems considered in this document are based on systems where

pressure rise occurs over several seconds or longer, and there is no

reaction front. In these cases we may assume:

• Safety valves can open in time;

• Piping is adequately sized to provide pressure relief;

• Relief flow may be determined by steady-state flow equations;

• Conditions are approximately uniform throughout each phase at

any moment;



• Further pressure generation by reaction in the relief piping is

negligible.

General principles applicable to relief systems include:

• In all cases, relief devices must be selected and located to minimise

disturbance to plant and environment;

• Relief devices must not be isolated from equipment they protect

while the equipment is in use;

• The discharge from a relief device should pass to a safe location

which may be:

• A dump tank;

• Upstream in the process;

• A storage tank;

• A quench vessel or tower;

• A sewer;

• The atmosphere;

• A knockout drum;

• A scrubber;

• An incinerator;

• A flare stack.

Design basis and methodology of all relief stream packages must be

documented, and incorporated into plant modification and change

procedures to ensure that relief stream invalidation does not occur.

Sizing of Vents (Especially Exothermic Reactions, Storage Tanks)

One of the biggest problems in sizing vents is the availability and

accuracy of physical property data for the reaction components. It is good

practice when sizing a relief system to utilise several design methods to

achieve consistency in design.

When sizing pressure / vacuum relief systems for storage, if several

tanks are connected up to a single relief system the relief device should

be capable of accommodating the simultaneous vent loading at a

relieving pressure less than the lowest tank design pressure.



Venting can either be normal or atmospheric venting or emergency

venting. Different measures may be adopted to provide protection for the

vessel or tank in each case. The worst case scenario is generally

experienced when tanks are exposed to fire.

Normal venting requirements may be met by installation of pressure-

vacuum relief valves. Emergency venting may be accomplished by

installation of a bursting or rupture disc device. Depending upon the tank

contents and the physical characteristics of these contents consideration

should be given to the vent discharge point and configuration. Guidance

is provided in recognised industry standards.

There are various recognised methods for sizing vents. These include:

• API Methods;

• NFPA Methods;

• Vapour / Gas Only method;

• Leung’s method;

• Level Swell method;

• Stepwise method;

• Nomogram method;

• Fauske’s method;

• Two-phase method;

• DIERS method;

• Huff’s method;

• Boyle’s method.

The use of DIERS (Design Institute for Emergency Relief Systems)

methodology is becoming increasingly widespread. Detailed analysis of

relief systems using this methodology, together with experimental

testing, is now the accepted practice.



Flame Arresters

Flame arresters are commonly installed on the vent outlet of tanks

containing liquids with flashpoints below 21°C, generally where pressure-

vacuum vent valves are not in use. Their prime function is to prevent the

unrestricted propagation of flame through flammable gas or vapour

mixtures, and secondly to absorb heat from unburnt gas.

Flame arresters should be designed for each specific application, and due

to the likelihood of progressive blockage a rigorous inspection and

maintenance schedule should be in place.

Relief Valves

Relief valves are characterised by:

• Slow response times (tenths of a second up to > 1 second);

• Risk of blockage;

• Trace leakage.

Design considerations for relief valves include:

• The pressure drop before the safety valve must be low to avoid

instability;

• The design must take into consideration differences between gas

and liquid duties;

• Back pressure can affect opening / closing pressures, stability and

capacity;

• The relief valve usually solely determines relief capacity if

appropriate piping is used.

Regular proof checks are required to check lifting pressure, particularly if

located in a corrosive environment. Also valve seating checks should be

undertaken to ensure that the valve is not passing.

Bursting Discs

Bursting discs are characterised by:

• Very fast response times (milliseconds);

• Less risk of blockage than relief valves;



• Cheap to install and maintain;

• Available in a wide range of materials;

• No leakage;

• Non re-closing hence may allow large discharges even when

pressure falls below relieving (rupture) pressure;

• Potential for premature failure due to pressure pulsation, especially

if the rupture pressure is close to the operating pressure;

• Rupture pressure affected by back pressure;

• Risk of incorrect assembly.

Design considerations for bursting discs include:

• Protection against reverse pressure (vac dials);

• Differences between disc temperature and vessel temperature;

• Main factor affecting relief capacity is piping configuration;

The rupture pressure of a bursting disc is a function of the prevailing

temperature. It is common practice for an operator to specify the

required rupture pressure at a specific operating or relieving temperature

however, if the temperature cycles or changes during the process

operation the degree of protection of the vessel can be compromised.

This is because as the prevailing temperature decreases the rupture

pressure of the bursting disc will increase potentially resulting in the

rupture pressure at temperature being greater than the design pressure

of the vessel. Thus if the pressure increases at this condition, vessel

failure will occur. The converse case can also apply if the rupture

pressure is quoted for ambient temperatures, since the actual rupture

pressure will decrease under normal operating conditions which can

cause premature failure of bursting discs.

The surrounding vent pipework should be adequately sized to

accommodate relief flows in the event of bursting disc failure.

Bursting discs are a common method for fulfilling emergency venting

requirements, although a routine maintenance programme should cover

bursting disc installations.

Bursting disc installations should incorporate vent pipework that is the

same diameter as the bursting disc itself.



Combinations of bursting discs and relief valves are occasionally

employed for specific applications. Double bursting discs (back to back

arrangements) are often provided with a pressure indicator/alarm

between them in aggressive environments where failures of the initial

disc may occur. In such instances the second bursting disc is reversed to

withstand the initial shock pressure.

Scrubbers (Design for Maximum Foreseeable Flow)

In many installations, scrubbing systems provide one of the major lines

of defence against release of toxic gas. Several key factors must

therefore be taken into consideration when designing and sizing the

scrubbing system. These include:

• Composition of gas load;

• The composition of the gas load must be known with respect to:

• Solids loading, particle size distribution and chemical

composition;

• Water vapour loading;

• Toxic gas loading;

• Inerts loading.

• Variations in gas load;

• The basis of the scrubber design should take into consideration the

peak gas loading, the minimum gas loading and the mean gas

loading in addition to corresponding variations in inert gas loading.

• Depletion / saturation of scrubbing liquor;

• Analysis of the reaction stoichiometry between the gas and the

scrubbing liquor will give some indication of the minimum scrubbing

liquor strength at which the absorption process can occur for a

recirculatory system. A methodology must be in place that ensures

replenishment of the scrubbing liquor at an appropriate point.

Hence monitoring of depletion of scrubber liquor and modelling of

breakthrough concentrations is critical. Furthermore, the process

may specify a maximum concentration of absorbed gas in the

scrubbing liquor at which the scrubber liquor should be replenished.



• Provision of Back-up systems;

• In the vent of scrubber failure, it is sometimes possible to isolate

plant and process to prevent toxic gas emission by implementation

of appropriate interlocks and control systems. However, if

temporary isolation of plant and process is unfeasible a back up

system should be provided.

• Control systems;

• The control system for the scrubber operation should be interlocked

with the plant and processes that the scrubber services such that in

the event of scrubber failure process operations can be isolated and

/ or suspended. The control system should feature scrubber

diagnostics that verify and indicate that the scrubber is healthy and

working.

• Monitoring and instrumentation;

• Typical instrumentation on a toxic gas scrubbing system should

include:

• Stack gas analyser;

• Scrubbing liquor flow indicator;

• Scrubbing liquor tank level indication;

• Flow indication or DP instrumentation across scrubbing

fan;

• Process interlocks for event of scrubber failure.

Stack Heights

The concentration of waste gases at ground level can be reduced

significantly by emitting the waste gases from a process at great height,

although the actual amount of pollutants released into the atmosphere

will remain the same.

The basis for design begins with determination of an acceptable ground-

level concentration of the pollutant or pollutants. If the waste gas is to be

discharged through an existing stack, or the stack size is restricted the

ground-level concentration should be determined and if it is unacceptable



appropriate control measures should be adopted. Steps in the design

methodology include:

• For a given stack height, the effective height of the emission can be

determined by employing an appropriate plume-rise equation;

• Application of atmospheric dispersion formula enables the

downward path of the emission to be modelled. Various formulae

may be employed. These include:

• Bosanquet-Pearson model;

• Gaussian model employing Briggs formulae;

• Wilson model

• Pasquill-Gifford model;

• Sutton model;

• TVA model.

Factors affecting stack design include:

• Composition of waste gas (and changes in composition);

• Physical and chemical properties of waste gas;

• Topography (buildings, hills, lakes and rivers etc.);

• Seasonal changes in weather;

• Prevailing winds (direction and speed);

• Humidity;

• Rainfall

Flaring

Flaring may be used to destroy flammable, toxic or corrosive vapours,

particularly those produced during process upsets and emergency

venting.

Key design factors to ensure flare safety and performance include:

• Smokeless operation;

• Flame stability;

• Flare size and capacity;



• Thermal radiation;

• Noise level;

• Reliable pilot and ignition system;

• Flashback protection.

The major safety issues are the latter two items. BS 5908: 1990

recommends that permanent pilot burners should be provided with a

reliable means of remote ignition. An additional means of ignition, e.g. a

piccolo tube should be provided, independent of power supplies. Flare

header systems should be provided with an inert gas purge sufficient to

provide a positive gas flow up the stack to prevent back diffusion of air.

Forced Ventilation (Especially to Control Direction of Flow and

Dilution)

Non-pressurised systems in which fumes and vapours are generated

should have adequate ventilation to remove those fumes to a safe place.

This may be a scrubber or a stack for discharge. Consideration should

also be given to the venting of discharges from relief systems. Both

dedicated enclosed forced ventilation systems and area forced ventilation

will need to be considered.

A further purpose of ventilation is to dilute and remove the hazardous

substance to such an extent that the concentration in the protected space

is kept to acceptable levels. Ventilation rates are generally designed to

reduce the concentration to about one-quarter of these levels.

The use of forced ventilation has an impact on the area extent and

classification of hazardous areas. The methodology for assessment of

type and degree of ventilation is covered in British Standards. Although

mainly applied inside a room or enclosed space, forced ventilation can

also be applied to situations in the open air to compensate for restricted

or impeded natural ventilation due to obstacles.

Spot Ventilation

General ventilation is applied to the room or compartment as a whole

(see forced ventilation above). It may also be applied locally to the plant

or process as spot or local ventilation. Basic design principles include:



• Fume extraction inlet should be as close to the source of gas or

vapour as possible;

• The rate of extraction of fume should be greater than or equal to

the rate of generation of fume in the particular area;

• Air supply inlets should be located to provide ventilation for other

regions that may become contaminated;

• General air movement should be from areas surrounding the

emission source, across the contaminated zone and thence through

the fume extraction inlet;

• A velocity of 0.5 to 2 m/s is generally recommended (Lees 25.7).

Trunking is often used to allow operators to move the point of

extraction as required.

Special Cases: Chlorine, LPG Storage

In the event of overpressure in liquid chlorine storage tanks, the

discharge line from the pressure relief system should enter a closed

expansion vessel with a capacity of nominally 10% of the largest storage

vessel. This expansion vessel should then be manually relieved at a

controlled rate to an absorption system.

In the event of overpressure of LPG storage tanks, the tank should be

fitted with a pressure relief valve connected directly to the vapour space.

Underground or mounded vessels affect full flow capacity of pressure

relief valves.

In the event of overpressure in anhydrous ammonia storage tanks, the

tank should be protected by a relief system fitted with at least two

pressure relief valves should be fitted.


__________________________________________________Roadways / Site Traffic Control 1

5.20 ROADWAYS / SITE TRAFFIC CONTROL

Introduction

The good design of roadways and the control of traffic on-site are

important factors in the prevention of road traffic accidents and an

important consideration in the prevention of major accident hazards on-

site. Collisions between moving vehicles, collisions between pedestrians

and moving vehicles, or the impact of a vehicle with stationary plant,

vehicles or equipment can lead to physical injuries and damage or a loss

of containment of chemicals. The detailed design and construction of

roadways is outside the scope of this technical measures document but

some of the important considerations relating to roadway design are

highlighted below.

In addition the safe and correct immobilisation of vehicles during tanker

loading and unloading operations and at other times when on site is also

an important factor in the prevention of site major accident hazards.

This technical measures document considers the following elements:

• Design Codes – Roadways;

• Site Traffic Control;

• Operational Issues.

General Principles – Design Codes – Roadways

In principle the road layout, signing and marking should be such that all

road users can reasonably understand what is required of them. Roads

should be designed to accommodate the largest vehicles that may have

to use them in respect of strength, width, radius, gradient, clearance and

visibility.

Access routes on-site are required for pedestrians, cyclists and road

traffic. Access is required for the transport of equipment and materials,

for emergency vehicle access and maintenance purposes. Roadways and

access routes should be designed to avoid congestion and hence reduce

the likelihood of road traffic accidents occurring.



Road Layout & Geometry

The following are important considerations in the design of road layout:

• The surface should be firm, level and of an appropriate material;

• Consideration should be given to other physical characteristics of

the road such as the camber, width, headroom, visibility, drainage,

gradient and radius of bends etc;

• Road layouts should be carefully planned and clearly marked;

• There should be appropriate segregation between pedestrians and

road traffic;

• Parking and loading/unloading areas on site should be separated;

and

• Hazards, restrictions and directions should be clearly identified and

communicated by signs, signals and instructions.

However, for the majority of industrial sites with an existing infrastructure

road layouts cannot be readily amended.

Layout

Depending on the size of the site the road layout should preferably be a

looped arrangement, which avoids the need for reversing. In smaller sites,

a street with only one way in or out may be acceptable subject to the

provision of adequate turning facilities, which may be in the form of a

hammerhead but preferably a turning circle.

In larger sites, individual access roads should feed to the main industrial

distributor road, which should not provide direct access to individual

factory units. All two-way industrial roads should have a minimum width

of 7.3 meters with local widening on bends to cater for the swept path of

HGV vehicles. Individual premises should have an access of minimum

width of 6.1 meters.

When designing a new or improved layout it is helpful to use a “design”

vehicle to achieve efficient and uniform layouts. Most designs will operate

satisfactorily if they can cope with the requirements of a 15.5 metre long

design articulated vehicle and a 10.0 metre long design rigid vehicle.



Gradient

The maximum longitudinal gradient should be 1 in 12 and the minimum

channel gradient should be 1 in 125. A crossfall or camber of 1 in 40

provides adequate drainage. If minimum gradients are not provided,

surface water will tend to pond, which will be hazardous in freezing

conditions. Standing water can also obscure road markings and lead to an

increased likelihood of accidents.

Materials of Construction

Different types of road pavements are available including flexible

pavement where surface materials are bound with a bituminous binder, a

rigid pavement which utilises pavement quality concrete for the surfacing

layers, or a flexible pavement surfaced with block paviors.

Bituminous surfacing will degrade if exposed to oil products and other

chemical spillages. Areas where spillages are likely such as loading and

unloading areas should utilise a resistant surfacing, such as concrete or

some other appropriate material, with drainage facilities that can intercept

hazardous chemicals.

The design of the road pavement will be dependent on the ground

conditions at sub-grade level and the expected traffic flow and vehicle

type during the design life of the pavement.

Kerbing

Kerbing to roadways should be provided wherever possible to clearly

define the roadway and provide a measure of protection. Dropped kerbs

should be provided at pedestrian crossing points.

Height Restrictions

Areas that are vulnerable such as pipebridges, overhead gantries etc

should be clearly identified and height restrictions clearly marked.

The standard minimum clearance over every part of the carriageway of a

public road is 16 feet 6 inches (5.03 meters). When the clearance over

any part is less than this standard, a warning sign both on and prior to the



structure should be provided which should be at least 75mm less than the

measured height.

Heights of vehicle likely to be encountered are 4.2 meters high (i.e. A

standard container on a suitable flatbed vehicle). Minimum headroom

provided should be 4.65 meters exclusive of any additional space required

for lighting units. Additional clearance will be required if there is a

requirement for an overlay in the future. Changes in gradient may also

reduce the effective headroom for long vehicles.

Visibility

Consideration should be given to road traffic visibility. Road traffic should

have adequate forward visibility on bends to enable a driver to stop

before an obstruction in the road. In addition, there should be adequate

visibility at junctions so those drivers emerging can see and be seen by

approaching drivers.

Visibility requirements are related to vehicle speed and stopping

distances.

Lighting

There should be adequate lighting of site locations and vehicles at all

times to enable all persons to carry out their work tasks safely and in

safety.

Lighting should be provided for junctions, plant and buildings, pedestrian

routes and areas where loading/unloading is to be carried out. Signs

should either be illuminated for night-time visibility or adverse weather

conditions, or be suitably reflective. Vehicles on site should use

lights/beacons etc in darkness or poor visibility to aid detection by other

vehicles.

Consideration should be given to the difference in light levels between

internal and external areas at the points of access to and from buildings

that may hinder detection of vehicle movement.

Adequate lighting should be provided to all areas and especially to those

areas used in darkness hours.



Drainage

Roadways on site should be adequately drained to ensure that standing

water is not present on-site. Connections for rainwater run-off from roads

into drainage systems may have to include interception facilities in the

case of chemical contamination.

Bridges

Bridges and other structures, which have maximum weight restrictions,

should be clearly identified.

Parking

Parking areas on site for employees, visitors and delivery vehicles should

be clearly identified and marked. Staff and visitor car parking areas

should be separate from site access routes wherever possible. Provision

for disabled users should also be made.

Parking bays should be clearly identified by surface markings in order to

avoid random parking arrangements.

Lay-bys or similar should be considered to avoid obstruction of the main

site access roads.

Secure, convenient and adequate parking areas should be provided on-

site for vehicles such that the general roadway is not obstructed. Off-road

pull-in areas that are clearly identified should be provided wherever

possible. Random parking should be avoided and discouraged wherever

possible since this can introduce additional hazards and increase the

likelihood of a road traffic accident.

Loading/Offloading

Areas for loading and unloading should preferably be separate from

general access areas and loading bay edges should be clearly marked and

protected by barriers. Adequate space for vehicle manoeuvring should be

available in loading/unloading and delivery areas.

If reversing or manoeuvring into position is required consideration should

be given to the provision of physical barriers or the attendance of another



person to supervise the movements. In some instances audible warnings

for vehicles reversing or manoeuvring may be appropriate.

Operators in unloading areas should be provided with suitable refuges

and drivers of vehicles should be segregated from dangerous working

areas.

Special coatings to road surfaces may be required to provide resistance

against chemical attack from spillages. Raised kerbing and other

containment measures may also be required to ensure that spillages do

not spread across adjacent areas. In these areas special drainage

channels may also be required that drain to collection sumps for

reclamation purposes.

Pedestrian Walkways

Pedestrians should be kept away from access routes for vehicles

wherever possible in order to avoid possible conflict. Separate pedestrian

pavements that are clearly identified should be provided. Guard rails or

fencing should be provided where appropriate and additional protection

should be provided at pedestrian exits and entrances from buildings.

Normal road crossing points for pedestrians should be clearly identified

and consideration should be given to clearly identifying walkways by

zebra markings or other such systems. Zebra crossings can also be

incorporated into layout design. Zebra crossings are normally only

considered when traffic flows do not provide adequate gaps in the traffic

for pedestrians to cross.

Consideration should be given to the provision of pedestrian walkways

clearly segregated from adjacent roadways wherever possible.

The positioning of pedestrian crossing points should be considered

carefully to ensure the pedestrian and road user have adequate visibility.

It may be necessary to erect guardrails to stop pedestrians crossing on

corners where visibility is reduced. Guardrails should be set back a

minimum of 500mm from the kerb. Where road crossings are wide, it is

appropriate to provide central refuges to allow the roadway to be crossed

safely in two or more movements. In some circumstances overhead

pedestrian footbridges or subways may be considered necessary



The movement of pedestrians onto/off and around site should be

considered, not only for routine access between plants during the working

day but also for mass movements which may occur at the beginning or

end of the working day, during shift changeovers, at lunchtime and under

emergency evacuation conditions.

The interaction between pedestrians, cycle traffic and vehicles should be

evaluated.

Railways

Rail deliveries are generally only applicable for the bulk transfer of raw

materials or product onto or off site. Specially designed facilities for

loading/offloading are generally available. Special consideration needs to

be given to rail car movements onto and off-site in co-ordination with the

relevant railtrack operator. Whilst on-site, rail car movements may

restrict normal traffic flow arrangements, either whilst moving into

location or whilst being loaded. Special consideration should be given to

the segregation of rail traffic from other areas and the provision of

suitable barriers and warning signals for locations where rail tracks cross

pedestrian footpaths or roadways.

The legislative requirements for rail traffic are outside the scope of this

document.

Areas where road and rail lines interact should be given special

consideration to ensure that suitable signing and barriers, if required, are

provided between road and rail.

General Principles – Site Traffic Control

Site traffic control relies upon a combination of physical features such as

road layout and marking, signs and signals and other considerations such

as systems, procedures and training.

Site traffic control should typically consider the following types of traffic:

• Road traffic – commercial delivery vehicles (including road tankers,

wagons, couriers etc), internal vehicles (including fork lift trucks,

mobile cranes, bicycles), visitor and staff cars/motorbikes/bicycles

etc;



• Rail traffic – some sites may receive and dispatch goods by rail.

Rail routes may cross site access roads for vehicles or affect

pedestrian areas; and

• Pedestrian traffic– site employees, contractors and visitors either

on their way to or from their normal place of work at the beginning

or end of the working day, or as part of their work during the day.

Road users, both drivers and pedestrians, should know exactly what is

expected of them. This can be achieved by establishing a Road Hierarchy,

which is used to provide a consistent standard for each road type in

terms of design standard, signing, access constraints etc.

Traffic routes should be determined and can be classified as either

access/through routes to site for deliveries, shuttle routes between

buildings for on-site activities, or emergency access routes for fire

engines, ambulances etc. Careful planning and consideration of site traffic

control issues can result in a reduction in the likelihood of collisions

between vehicles and/or equipment.

Incompatible types of traffic should be segregated as far as possible to

avoid potential interactions between chemicals in the event of a collision

between road traffic vehicles or between road traffic and stationary

storage facilities or pipelines carrying chemicals.

This guidance is not concerned with traffic control within buildings such

as warehouses or process plant areas where special consideration needs

to be given to the potential interaction between forklift trucks and/or

pedestrians.

Road Traffic

Consideration should be given both to the hazards introduced by the

loads being conveyed and the mode of transport used. Chemical hazards

are considered elsewhere. Consideration should be given to the physical

size, the presence of ignition sources and hot surfaces, the presence of

flammable fuels, the possibility of impact caused by size or speed, and

loading/unloading issues.

The purpose of the presence of vehicles on site should be assessed.

Some vehicles may be used simply for access and the transportation of



personnel and others for the delivery of materials (solids, liquids and

gases) and equipment to/from site.

Some of the items that may be transported are given below:

• Bulk deliveries of liquids or solids;

• Small packages, containers, drums etc of solids or liquids;

• Gas cylinders;

• Mechanical equipment;

• Letters, parcels etc; and

• Personnel.

Some of the different modes of road traffic transport which may be

present on site on either a routine or an irregular basis are given below

and consideration should be given for any possible implications due to

variation in height, length, width, weight etc.

• Bulk delivery tankers;

• Wagons, trucks, lorries and vans;

• Mobile cranes;

• Cars;

• Mini-buses;

• Cyclists; and

• Fork lift trucks.

Each type of vehicle has different characteristics and introduces different

potential problems to site.

An assessment of the risks of transportation of each material/load on site

should be carried out, an estimate of the frequency of each delivery

made and the access route carefully defined in relation to the hazards

present.

Traffic Flow

In order to assist in controlling traffic flow on-site a number of additional

measures can be incorporated in order to manage traffic flow in

congested areas and reduce speeds on-site. Such techniques include:



• Traffic lights can be used to control flow at busy junctions, in

narrow locations and at entry and exit locations to the site;

• One-way systems should be considered where necessary to reduce

the likelihood of collision, reduce congestion and improve traffic

movement;

• Roundabouts may smooth traffic flow and avoid road traffic turning

directly in front of on-coming traffic;

• Traffic calming devices such as speed humps, rumble strips, width

restrictors etc can be incorporated into road design to encourage a

reduction in speed. (Such devices are not appropriate in areas

where forklift trucks routinely operate since they introduce

additional hazards for this type of vehicle). The design of such

features must be appropriate for the type of traffic envisaged;

• Physical barriers should be incorporated into road design to protect

vulnerable and hazardous installations such as storage tanks,

pipework systems, buildings or pedestrian access areas;

• Signs and road markings; and,

• Site speed limits.

Physical Barriers

Physical barriers should be installed, wherever practical, adjacent to

roadways to reduce the potential impact of road traffic accidents.

Consideration should be given to the protection of vulnerable pipework,

storage tanks and other plant and equipment.

When considering the installation of barriers it is important that visibility

is not reduced below acceptable standards for road users and

pedestrians.

Signs/Road Markings

Signs and signals should be used on-site to clearly identify hazards,

restrictions and to give directions. Chemical hazards should be identified

along with height, width and loading restrictions for pipebridges, arches,

bridges etc.



Road markings should be used to designate traffic routes, non-parking

areas, give way areas etc in accordance with standard road markings. All

signs should be unambiguous, conspicuous, clean and unobstructed.

Speed sensors and flashing warning signs can be used to improve

communication of information to traffic on-site.

A site plan should be available at the site entrance, the site speed limit

should be clearly identified and adequate sign posting to assist delivery

vehicles unfamiliar with the site layout should be provided to assist

navigation.

Speed Limits

Speed limits should be imposed on larger industrial sites to limit the

possibility and severity of accidents. A suitable site speed limit (s) should

be determined based upon consideration of what is a safe speed on-site

accounting for the layout, bends etc. Limits of 10, 15 or 20 mph may be

appropriate depending on the site layout and hazards. This should then

be effectively communicated to drivers of all vehicles who require access

to the site, sign-posted at appropriate intervals and locations to remind

drivers of the speed limit and enforced. To be effective the limits should

be enforced by site security. Speed limits should be included in the Site

Rules with appropriate disciplinary action taken as necessary.

Operational Issues

A number of on-going measures should be considered when considering

roads and traffic control.

Spillage Clean-up

Adequate facilities and materials should be readily available on-site for

clean-up of spillages. Any materials used should not directly affect the

road surface.

Maintenance

Roads on site should be adequately maintained and free from pot-holes

and other surface defects which may affect vehicles



Adequate equipment – grit/sand etc should be readily available on-site

for snow and icy conditions.

Systems and Procedures

Systems and procedures should be in place to ensure that site traffic

control issues are adequately considered and incorporated into site safety

management systems. Consideration should be given to segregating

incompatible traffic loads and organising deliveries outside busy periods.

Systems should be in place for assessing the transport requirements,

vehicles and routes to be used. Consideration should be given to the

necessity for transport, and to a vehicle selection system for the site that

considers the design, maintenance and operability of the vehicles to be

used.

Procedures for accidents to be reported and investigated should exist.

Lessons for improving traffic flow and reducing accidents should be

learnt.

Normal requirements of Road Traffic Acts should be adhered to on-site.

This includes seatbelt and alcohol policies.

Procedures should exist to deal with the increased hazards caused by

adverse weather conditions. Procedures for routine clearance of debris

from roadways and road cleaning along with adequate resources should

be available.

Standard access routes should be defined and prepared. In the event of

site roadwork, temporary construction work or other reasons why areas

may be temporarily out of use (cranes, rail delivery etc) a system needs

to be in place to ensure that alternative routes are developed, temporary

access signs installed etc. Under all circumstances access for emergency

vehicles to all facilities should be maintained.

For those sites where offloading/loading can result in temporary road

closures being necessary care should be taken that a combination of

more than one road closure at a time does not lead to areas of site

becoming temporarily inaccessible for pedestrians, or emergency



vehicles.

Visitors should be the subject of suitable reception and security checks

prior to access to site. Visitor vehicles should be separated from site

operations as far as possible. Prior to access to site visitors should be

made aware of vehicle restrictions and safety considerations. Pedestrian

visitors should be accompanied whilst on-site in operational areas.

Site based vehicles should be routinely inspected and maintained to set

standards and procedures to ensure roadworthiness and the effectiveness

of safety systems such as brakes, lights, horns, indicators etc. Daily pre-

use checks for site based vehicles such as fork lift trucks should be

considered. There should be a clear procedure for reporting and

correcting defects in vehicles and maintenance records should be

available for inspection.

Systems should be in place to ensure effective communication between

gatehouse and operators accepting delivery on-site to warn of the arrival

of delivery vehicles.

CCTV systems can be considered as a mechanism for managing and

controlling road traffic systems.

Training

Training is an essential component of site traffic control and should cover

not only those engaged in driving vehicles on site, but also pedestrians

and those responsible for monitoring and enforcing traffic control on site.

Training of site personnel engaged in driving site-based vehicles is an

essential part of the prevention of site traffic accidents. Site based

personnel should be made aware of the hazards of driving fork lift trucks

for example and should be routinely checked for competence and licensed

as appropriate. Unauthorised personnel should not be allowed to drive

vehicles on site.

Training for all site staff should cover technical issues such as – vehicles,

equipment, hazard awareness, speed limits, parking and loading

requirements, safe operating practices etc, site layout, traffic routes,

reporting procedures etc.

The competence of third party delivery drivers on site can be assessed by

checking the health & safety standards of contractors and their sub-

contractors in relation to their selection and training procedures,



maintenance of vehicles, use of regular or ad-hoc drivers, accident and

safety records etc. The company may undertake spot checks and

inspections of delivery vehicles to ensure suitable road safety standards,

driver competence and vehicle maintenance is being carried out.


__________________________________________________Secondary Containment 1

5.21 SECONDARY CONTAINMENT

This Technical Measures Document refers to secondary containment.

Temporary or mobile systems which are required to be put in place in

response to an emergency e.g. booms, absorbent materials, sandbags

are considered under the Technical Measures Document on Emergency

Response / Spill Control. Also water sprays/curtains and foam blankets are

considered under the Technical Measures Document on Active / Passive Fire

Protection.

Related Technical Measures Documents are Emergency Response / Spill Control,

Active / Passive Fire Protection, Drum/Cylinder Storage/Handling and Relief Systems /

Vent Systems.

General Principles

Secondary containment is used on plant as a second line of defense for

preventing, controlling or mitigating major hazards events. It can take a

number of forms, the most common are:

• Bunds

• Drip trays

• Off-gas treatment systems

• Interceptors/Sumps

• Expansion vessels

• Double skinned tanks/vessels

• Concentric pipes

• Building structures/ventilation

Bunds

Bunds are generally used around storage tanks or drum storage areas

where flammable or toxic liquids are held. Alternative measures may be

earth dikes (usually for very large tanks), sumps and interceptors. Bunds

are also sometimes used within plant buildings for reactors and other

process vessels. For materials that are normally gases at ambient

conditions, bunds are used where flash fractions are sufficiently low to



merit them. Therefore they are often used for refrigerated gases but not

for the same gases stored under pressure.

It is normal to limit the number of tanks in a single bund to 60,000 m3

total capacity. However, incompatible materials should have separate

bunds. Tanks often have individual bunds.

Bunds should be sized to hold 110% of the maximum capacity of the

largest tank or drum. This will allow some latitude for the addition of

foam during response to the emergency. There are no set rules on the

ratio between wall height and floor area and codes vary greatly with

respect to recommendations of bund wall height. Low wall heights (1-1.5

m) are often used to facilitate firefighting but are poor defense against

spigot flow (where a leak in the wall of a tank passes over the bund wall)

or the tidal wave effect of a catastrophic tank failure. In some cases

bunds up to height of the tank are used, but these are quite unusual. For

high walled bunds, consideration will need to be given to the possibility of

tanks floating as the bund fills, causing catastrophic failure.

Bunds are generally fabricated from brick/mortar or concrete but where

liquids are being stored above their boiling point additional insulation,

e.g. vermiculite mortar, may be added as cladding to reduce the

evaporation rate. Such materials provide adequate chemical resistance to

most liquids.

Maintenance of bunds is an important aspect, often overlooked,

particularly in remote locations. A system of inspection should be in place

to ensure the integrity of the bund. Also due consideration should be

given to drainage to allow the removal of rainwater. This is normally

achieved by incorporating a drain at a low point of a sloping floor with a

manual valve, normally kept closed. Operating schedules should include

daily opening of the valve to remove accumulated water, this will also

assist in identifying minor leaks. However, with this system there is the

problem that the valve may be left open or fail, thus reducing the

effectiveness of the bund if a tank failure occurs. Also in winter

conditions, ice may form blocking the drain. Failure to remove rainwater

will reduce the capacity of the bund and may result in overtopping and if

the substance to be contained is incompatible with water e.g. oleum, may



result in an increased airborne release. Consideration of these scenarios

should be included in the Safety Report.

Drip Trays

Drip trays are often used beneath equipment liable to small leaks, such

as pumps, in process buildings and are effectively mini-bunds. They are

intended to prevent the spread of toxic or flammable substances to other

plant areas or to sumps and drains where secondary effects resulting in a

major accident could occur by domino effect. Drip trays vary greatly in

size and design. They are normally tailored to the individual item of

equipment but may serve a number of items. Materials of construction

are often metals such as stainless steel or strong rigid plastics that can

be readily moved. Drainage is not normally provided and liquid collected

is normally removed using absorbent material, after neutralisation or

dilution (if required).

One variation on this theme is the use of sumps on drum stillages. These

are intended to hold the total contents of a drum in the event of a

catastrophic failure. They are normally limited to 1 or 2 drums and may

be used in drum transport by forklift truck.

HAZOP/HAZAN studies should determine where drip trays are required.

Off-Gas Treatment Systems

Off-gas treatment systems which may act as secondary containment

include:

• Scrubbers

• Flares

• Catchpots/Knock-out drums

• Electrostatic precipitators

These systems may be used to reduce concentrations of hazardous gases

and vapours prior to discharge of the stream to atmosphere. Apart from

scrubbers, often such systems are part of the normal process but they

may be used in a secondary containment role. The latter two are used

when discharge streams may contain liquids or solids e.g. from reactor

emergency venting, which need to be removed, prior to further

treatment. Catchpots may be chilled or contain an absorbent liquid to

remove contaminants. The worst credible case discharge rate and volume



should considered when designing such systems. HAZOP/HAZAN should

be used to establish the worst case scenario. The Technical Measures

Document Relief Systems / Vent Systems provides more detail.

Interceptors/Sumps

Design of drainage systems both within and outside process buildings

should take account of the need to segregate spillages of hazardous

materials. Drains systems to be considered may include:

• Sewers

• Stormwater drains

• Process effluent systems

• Firewater drainage systems

In many cases these functions are combined and often firewater and

process effluents are drained into main sewerage systems. Where there

is a possibility that hazardous substances could be discharged into a

drainage system, interceptors or sumps should be provided of sufficient

capacity to ensure that an offsite major accident does not occur. HAZOP

studies or an alternative hazard identification methodology should be

used to identify such hazards.

For process effluents arising from leaks or plant washdown, good practice

is to provide a local sump which is sampled before emptying. Such sumps

normally incorporate level indicators/alarms for monitoring. Discharge

can be to drums via submersible or mobile pumps for onward disposal or

via manual or manually operated automatic valves into main drainage

systems if the contents are non-hazardous. As for bund drainage

consideration will need to be given in the Safety Report on the possibility

of valves being left open.

A particular concern is the discharge of non-water miscible flammable

liquids, which form a top layer. These could ignite considerable distances

from the plant after discharge. More sophisticated interceptors can be

provided to facilitate removal of floating flammable liquids. These tend to

be designed to meet individual needs and may incorporate conductivity-

based level sensors to distinguish between layers.

Firewater run-off is likely to involve very large quantities of contaminated

water (Lees quotes 900-2700 m3/hr). Risk Assessments should be



undertaken to consider the requirement for segregation of these streams

into lagoons or other catchment systems.

Expansion Systems

Expansion systems are used to prevent pressure build up, leading to loss

of containment, in the event of overfilling or temperature increases. They

are used mainly on liquefied gas storage systems, reactors and long runs

of pipelines.

Codes of practice for chlorine systems include the use of an expansion

vessel to allow for overfilling of the main storage tank. Depending upon

the arrangement, pressure, level or weight detection/alarms on the

expansion vessel may included to alert operators if liquid reaches this

point. Capacity of the expansion vessel is recommended as 10% of the

capacity of a storage tank.

Expansion vessels are sometimes provided for atmospheric storage

tanks, particularly where substances are particularly toxic or noxious. A

liquid scrubbing medium may be included in the expansion vessel to

provide for removal of fumes from air displaced on filling. The vent

stream is sparged into vessel below the liquid surface. The expansion

vessel itself then vents to either atmosphere or a scrubber. An

alternative, where a number of tanks are used for the same substance, is

to arrange overflows from one tank to another.

Expansion tanks for reactors are described in the Technical Measure

Document Quench Systems.

Long pipelines containing liquids that have a high coefficient of expansion

should be provided with relief systems or expansion chambers to prevent

loss of containment due to overpressure. Relief systems should be

discharged into expansion vessels or off gas treatment plant if discharge

rates are within the design limits for such systems. Expansion chambers

should have a capacity of 20% of the pipeline volume. Chlorine is a

particular case to consider. Codes of practice recommend pressure relief

valves or bursting discs for liquid chlorine pipelines venting to the

expansion vessel or use of expansion chambers.



Double Skinned Vessels

Where there is particular concern about leakages occurring from tanks,

an alternative to bunding is to provide a second skin to collect material

lost. Monitoring of the annulus using specific analysers or level detection

can alert operators to the problem. Such systems are sometimes used for

underground or tanks in remote areas, where undetected leaks to the

environment may occur. Similarly tanks within process buildings may also

be doubled skinned.

Jacketed vessels including reactors and other process vessels are

primarily used to provide cooling or heating (using water, steam,

refrigerants, heating fluids etc.) to maintain temperatures of contained

substances. In some cases monitoring of the heat transfer medium is

used to detect loss of containment.

Concentric Pipes

Pipes are sometimes provided with an outer shell or secondary pipe to

protect against loss of containment. As for double skinned tanks, these

tend to be used where the substance contained is particularly hazardous

and no alternative means i.e. bunding is available to contain any release.

Such methods are used in particular to protect pipes of less robust

materials of construction such as glass or plastic which are being used for

very corrosive substances e.g. bromine, strong acids. The outer pipe may

be of much stronger material, e.g. steel, which is sufficient to provide

further containment for a short duration without failure. Again monitoring

of the annulus is used to detect the initial failure and alert operators.

Such systems are often used where there are long runs of pipe on

overhead pipebridges. Pipes can be sloped to allow drainage to a

collection pot provided with level detection/alarms.

As for jacketed vessels, coolant/heating medium flow through jacketed

pipes may be used to detect leaks also.

Building Ventilation

Building ventilation systems can be arranged such that flow is maintained

from less contaminated to areas that may become contaminated

following a loss of containment, before discharge via off-gas systems, to



provide some degree of secondary containment. Such systems are used

routinely in the nuclear industry.

The Technical Measures Document Relief Systems / Vent Systems considers

ventilation systems.


__________________________________________________Segregation of Hazardous Material 1

5.22 SEGREGATION OF HAZARDOUS MATERIALS

This Technical Measures Document refers to issues surrounding the

storing and segregation of hazardous materials and how it can be used to

minimise the foreseeable risks of a major accident or hazard.

General Principles

The following aspects should be considered with respect to the

Segregation of Hazardous Materials:

• Human factors;

• Poorly skilled work force;

• Ignorance towards physical and chemical properties of stored

substances;


• Plant lay-out; and

• Plant siting.

The following issues may contribute towards a major accident or hazard:

• Failure to understand the properties of substances handled;

• Failure to identify hazards associated with mixing substances and

domino events;

• Failure of quality assurance procedures;

• Insufficient recording of chemical inventories at each location on

site;

• Insufficient labelling of chemical storage containers (raw materials,

reactants, intermediates, products, by-products and waste);

• Poor warehousing management systems;

• Poor house keeping.

Contributory Factors for an Assessor to Consider Concerning All Aspects

of Segregation of Hazardous Materials




• Whether formal hazard identification and risk assessment has been

used to determine the need for segregation (e.g. HAZOP, HAZAN,);

• Whether there is a chemical inventory system sufficient to address

and categorise hazardous materials into compatible groups;

• Whether there is a sufficient site plan illustrating a compact block

layout system with designated zones/plots for compatible

hazardous materials (zones 0, 1 & 2, oxidising agents, flammable

substances, explosive substances, strong acids, cyanide

compounds, LPG);

• Whether hazardous areas are classified and sufficient to segregate

compatible, hazardous materials to avoid overlap of these areas.

(oxidising agents and flammable substances areas should not

overlap, strong acids and cyanide compound areas should not

overlap, peroxides should not be stored near any metallic

compounds that could cause decomposition and the liberation of

oxygen);

• Whether there are sufficient warning signs in place to inform

employees and visitors of the potentially, hazardous environments

they are approaching (no smoking signs, flammable area,

intrinsically safe zone);

• Whether there are sufficient traffic routes for the emergency

services to safely access and egress a hazardous area in the event

of an emergency;

• Whether the emergency services are aware of all risks associated

within and around the segregated areas;

• Whether the designated plots for containing hazardous substances

are sited on impervious ground with an adequate drainage slope, (1

in 40 to 1 in 60);

• Whether mixing of incompatible substance can occur within the

drainage system or anywhere that leaks/spills may accumulate (in

particular consideration of the location and routing of

pipelines/pumps etc from which hazardous substances may leak);



• Whether the processes and plant operating procedures minimise

the inventories of hazardous substances stored, handled or in

process;

• Whether plots containing flammable and toxic chemicals are

sufficiently ventilated;

• Whether enclosed plots containing flammable chemicals have

sufficient explosive relief systems within the building structure to

allow for safe relief ventilation;

• Whether the bund facilities are sufficient to contain a maximum

volume of spillage from a hazardous chemical storage vessel;

• Whether there are sufficient emergency provisions in place to

control the risks associated with leaks and spills (fire

extinguishers/blankets/hydrants, absorbent materials, PPE,

emergency services, emergency evacuation procedures); and

• Whether there are sufficient escape routes in place in the event of a

major accident or hazard (minimum of two escape routes, no dead

end should exceed 8 metres).

Major Hazards

Major hazards could arise from the following:

• Storing incompatible substances together;

• Domino effects (e.g. thermal radiation from fires);

• Direction of leaks to common sumps/manifolds;

• Incorrect labelling/delivery of raw materials, intermediates and

products;

• Introduction of ignition sources into segregated areas containing

flammable, combustible and explosive substances (e.g. smoking,

mobile equipment and vehicles, power tools);

• Use of non-intrinsically safe equipment within intrinsically safe

zones;

• Poorly managed inventory control and identification systems for

hazardous chemicals stored in drums and vessels;

• Poor house keeping.


__________________________________________________________Warning Signs 1

5.23 WARNING SIGNS

This Technical Measure Document refers to issues surrounding physical

and electronic warning signs and how they can be used to minimise the

foreseeable risks of a major accident and hazard.

General Principles

“For warning signs and alarm indications, the first requirement is to alert

the operator to the situation, and then to aid his/her accurate and prompt

diagnosis”.

The following aspects should be considered with respect to Warning

Signs:

• Human factors;


• Ergonomic design;

• Inadequate/lack of warning signs;

• Unidentifiable warning signs;

• Misinterpretation of warning signs; and,

• Wrong warning signs used.

General Issues

• Appropriate management systems should be in place to ensure that

areas of plant and plant items (valves, pipes, etc.) are identified

which require warning or instructional signs and that signs are

provided as appropriate. This also includes temporary works, such

as restricted areas e.g. for tanker offloading, lifting operations, hot

works, confined space etc.

• Appropriate risk assessments should be conducted to determine

hazardous areas/zones on site.


__________________________________________________________Warning Signs 2

• All site staff (including contractors) should be informed, instructed,

trained and supervised as appropriate to minimise a potential for

human error when recognising the meaning of warning signs.

• The system of housekeeping should ensure that all damaged or

missing labels, signs, etc are replaced swiftly

• The maintenance and calibration of electronic warning signs need to

be considered (noise/visual warning systems).

• A warning sign should be compelling but not startling.

Visual Warning Signs

• Where possible, accepted warning signs should be used so that

they conform to the reader’s assumptions.

• The types of warning signs required to be in place within the

designated zones should be appropriate for the hazard, i.e.

mandatory, warning, caution, electronic, physical, intrinsically safe,

chemical/heat resistant.

• The long-term visibility of the warning signs, i.e., lighting,

degradation due to exposure to UV, corrosion, size, positioning,

orientation should be considered.

• Improvised signs, that are laminated to protect them, are

susceptible to veiling reflections. In certain positions this can mean

that they are unreadable.

• Colour should not be used as the sole means of coding. It should

always be used redundantly. For example, apart the issue of colour

blindness, red is extremely difficult to detect under sodium lighting.

• New designs or icons or pictograms should conform to accepted

codes and widely used systems and should be user tested prior to

being put into use to ensure that the designer’s mental model of

what the icon or pictogram means is compatible with that of the

user.

• The variability in human dimensions should be considered when

placing warning signs. For example, a warning sign that is clearly


__________________________________________________________Warning Signs 3

visible to someone who is 5 ft 5 might not be visible to someone

who is 6 ft 5, or vice versa. Signs should be placed so that all the

people who need to, can see them.

• Warning signs should contain no more information than is

necessary to inform the reader of the its meaning.

• Dyslexic or illiterate employees should be considered when

considering the use of purely text based warning signs.

• Colour warning signs and labels are perceived as representing a

greater hazard than achromatic labels.

• If signs are used to indicate direction, there should be no ambiguity

as to the route the sign indicates. Wherever it is possible to take

the wrong route a sign should be positioned to reduce the likelihood

of this happening.

• The typeface used for text on warning signs should be a sans-serif

type. For example Ariel.

• All types of viewing conditions should be considered when deciding

on what types of warning sign to use.

• If the warning message is more than a couple of words long do not

use all capitals. This is because it slows down the reading time of

the message.

• The minimum size of letters within warning signs should be based

on the following:

For Non VDU applications use this table:

Viewing

distance (mm)

Height

in mm

501-900 5

901-1800 9

1801-3600 18

3601-6000 30


__________________________________________________________Warning Signs 4

Or if the viewing distance exceeds in 6000 mm use the formula: Height in

mm = Viewing distance in mm/200

For VDU applications use the following table:

Viewing

distance (mm)

Height

in

mm

500 3

700 4 .3

1000 4.8

The preferred colour contrasts on VDUs are presented in the table

below:

Character Background

Black White

Yellow Dark Blue

White Green

Black Light Grey

White Dark Grey

White Red

Non-Verbal Auditory Warnings

• All employees and contractors on site should know what each alarm

means and what the required response is, if the cause of the alarm

has the potential to affect them.

• When an alarm triggers it should provide enough time to effect

recovery where applicable.


__________________________________________________________Warning Signs 5

• Alarms should prioritised, where appropriate.

• An alarm should reset automatically if the fault that generated it is

rectified

• Following an alarm, the response required by the operator should

be clear.

• Alarm signals should be at least 10-dB (A) over the background

noise.

• Do not use alarms that have a frequency of 1 kHz if the source of

the sound needs to be detected.

• Alarms should not prevent effective communication across the site.

• The design of the alarm system should prevent masking and

flooding of alarms. Masking is where one alarm noise masks a

similar sounding alarm preventing the operator from detecting the

signal. Flooding happens when a system alarms which has a ‘knock

on’ effect on other related systems, the result of which is the

triggering of myriad other alarms, flooding the site with sound.

• There should be a noticeable difference between alarm sounds used

to alert, than for routine signals.

Verbal Auditory Warnings

Consider using verbal auditory warnings in combination with visual

warnings. Use of both methods has been found to improve compliance

with the warning message.

Verbal warnings can be more effective in crowd situations when signs can

become obscured.

Major Hazards

The safety report should address the following points:

• Adequacy of management systems to identify when/where

warnings signs are required;


__________________________________________________________Warning Signs 6

• Adequacy of management systems to deal with human failings to

obey warning signs;

• Adequacy of risk assessments programmes, which may identify the

requirement for warning signs;

• Adequacy of warning signs for emergency response, particularly for

local fire brigades/police;

• Adequacy of warning signs for visitors or intruders to site;

• Suitability of warning signs for the area in which they are located

e.g. use of non-flameproof electric/electronic signs in flameproof

areas;

• Maintenance/review of warning signs; and

• Mis-information included on warning signs.


______________________________________________________________________

Protective Device 1

5.24 PROTECTIVE DEVICES

Contents

1. Introduction

2. Pressure

3. Level

4. Temperature

1. INTRODUCTION

Process equipment, including storage tanks and vessels, are usually

provided with protective devices in order that system safe operating

limits are not exceeded. In addition to protective devices, other devices

will perform a controlling function (e.g. pressure control, level control or

temperature control) and others will perform an alarm and / or shut down

function (e.g. high-pressure alarm, high level alarm, emergency

shutdown etc.). The latter function is usually actioned as a result of the

failure of a controlling function (e.g. emergency shutdown of a process

vessel due to high liquid level). The protective devices as described here

are the ultimate devices which are the last line of defense against safe

operating limits being exceeded.

The most common processing parameters that require to be controlled,

or against which process equipment needs to be protected are:

• pressure (positive pressure and vacuum)

• temperature

• level

A range of protective devices, and protective functions (i.e. alarms,

shutdown etc.), are utilised for these parameters and these are

discussed, together with their merits, settings, installation locations etc.,

in the following sections.


______________________________________________________________________

Protective Device 2

2. PRESSURE

All pressure systems must be provided with protective devices to prevent

the system being subject to pressures in excess of the safe operating

pressure. The safe operating pressure is the pressure quoted on the last

report of thorough examination made by the competent person, which

must be the same as or below the design pressure. Where the current

condition has deteriorated since manufacture, the safe operating pressure

may have been reduced below the design pressure by the competent

person. This applies equally to positive pressure and to negative pressure

(vacuum) - some large storage tanks and vessels can fail due to

inadvertently experiencing a vacuum. The only exception to the provision

of pressure protection/relief is in the case of a vessel (or system) that

has been specifically designed to withstand the maximum (or minimum)

pressure that can be generated within it - inherently safe (pressure)

design.

Over pressure protection for process pressure vessels usually involves a

hierarchy of passive and reactive protection devices. These devices range

from simple pressure indicators or gauges, through pressure transmitters

providing alarms, to pressure switches providing alarms and invoking

automatic shutdowns, and finally through to mechanical pressure relief

devices (e.g. pressure safety valves and bursting discs). Pressure

monitoring via gauges and automatic alarms is typically used to check

that the process system is operating at, or close to, the intended

operating pressure. Automatic shutdown systems are designed to shut

the system down before the Safe Operating Pressure is reached, or to

react to loss of pressure situations (e.g. vessel leakage). Pressure relief

(protective) devices are designed to prevent the system exceeding the

Safe Operating Pressure.

2.1 Pressure Relief Devices

Pressure relief devices typically take the form of a pressure, vacuum or

pressure/vacuum relief device. There are 2 types of common relief

devices - relief valves and bursting (or rupture) discs. These devices are

normally installed at the top of the vessels or tanks that they are


______________________________________________________________________

Protective Device 3

protecting. However, it is permissible to mount these devices on pipework

which is directly attached to the item. It should not normally be possible

to isolate the pressure protective device from the vessel/tank which it is

protecting, however, it is quite common for a pressure vessel to be

protected by a pair of pressure relief valves set in parallel with ‘interlock’

controlled lockable isolation valves fitted between these relief valves and

the vessel. This arrangement allows individual relief valves to be

removed, tested, reset and refitted without shutting down the vessel.

2.2 System Operating Pressure and Relief Pressure

In order to ensure effective seating/sealing of the pressure relief device it

is necessary to have an adequate margin between the system operating

pressure and the set pressure of the pressure relief device. Conventional

pressure relief valves can ‘simmer’ when the system pressure approaches

the set pressure of the valve. This pressure setting margin is normally

not less than:

• 5% for gas service

• 15% for liquid service

2.3 Relief Capacity

Of paramount importance is for the pressure relief device to have an

adequate discharge capacity in order to limit the pressure to within the

safe operating limits. When two-phase or multi-phase flow conditions can

occur, the relief device should be designed to deal adequately with the

dynamic flow conditions of such fluids. In situations where a pair of relief

valves are fitted in parallel, and where each relief valve can be separately

isolated from the vessel, each individual relief valve must have sufficient

discharge capacity on its own.

2.4 Discharge Systems

Pressure relief devices, when they operate, discharge into either an open

system (i.e. directly to atmosphere), a containment vessel, or into a

disposal system such as a flare. Discharge systems associated with

pressure relief devices used for hazardous fluids (e.g. toxic or highly


______________________________________________________________________

Protective Device 4

flammable) require careful design and consideration. Fluids such as

chlorine, ammonia and liquefied petroleum gas (LPG) present hazards

when discharged through pressure relief systems. Chlorine, in particular,

requires the pressure relief discharge to be directed into a dedicated

expansion vessel or to a chlorine absorption system. Dual bursting discs,

placed back to back, are the preferred overpressure protection

arrangement, however, a pressure relief valve may be used for chlorine

systems if the valve is protected from exposure to the chlorine by the use

of an upstream bursting disc. Whichever system is used, a pressure

alarm and indication should always be fitted between the bursting discs

and the bursting disc and the relief valve. Use of a pressure relief valve

on its own is NOT recommended. For ammonia and LPG applications, the

discharge system should be designed to discharge the fluids safely,

typically by use of vertical extension pipework.

2.5 Back Pressure

When a pressure relief device is designed to relieve into a disposal

system, due consideration must be given to the superimposed or ‘back

pressure’ within the disposal system. Conventional pressure relief valves

are typically used in situations where the back pressure does not exceed

10% of the set pressure. In situations where the back pressure is high or

variable (e.g. in a relief valve discharge header routed to a flare) a

‘balanced bellows’ pressure relief valve will typically be used. This type of

pressure relief valve utilises a bellows to isolate the effect of the back

pressure on the valve disc, and therefore the lift pressure. Pilot operated

relief valves can also be used for pressure relief into disposal systems

subject to back pressure. Pilot operated relief valves use a pressure

tapping or pressure impulse pipe, which is connected to the underside of

the relief valve disc, to supply a pilot valve which, once activated, opens

the main valve.


______________________________________________________________________

Protective Device 5

2.6 Thermal (Pressure) Relief

When parts of a pressure system can be isolated from a protective device

and where the contents may be subject to a pressure rise due to a

temperature rise (e.g. LPG trapped in piping between shut-off valves)

then that part of the system should be protected against excessive

pressure by fitting a thermal relief valve (sometimes referred to as a

hydrostatic relief valve).

2.7 Conventional Relief Valve

A conventional pressure relief valve consists essentially of a nozzle and

disc assembly which is held together to effect a seal by means of an

adjustable spring. The seal is usually a metal to metal seal. The sealing

surfaces are lapped to a high degree of flatness and surface finish to

achieve a good quality of seal. Elastomeric seals can be used, but are

usually limited to low (ambient) temperature service applications in order

to take advantage of the use of a resilient seal.

When in service, the pressure retaining parts (i.e. nozzle and disc) of a

conventional pressure relief valve will encounter the process fluids and,

as such, require to be ‘trimmed’ (i.e. furnished in suitable material)

accordingly. Bursting (or rupture) discs can be fitted upstream

(underneath) pressure relief valves in highly corrosive or toxic services

thus enabling the pressure relief valve to be furnished with a

conventional trim. The discharge side of the pressure relief valve will be

subject to the environment into which the valve would relieve.

2.8 Balanced Bellows Relief Valve

Balanced bellows pressure relief valves are so-called because of their use

of a bellows to isolate the valve sealing components from the discharge

system’s environment and because they equalise (balance) the back

pressure forces acting on both sides of the valve disc. Their relieving

capacity is largely unaffected up to around 30% of the set pressure. Most

manufacturers limit the back pressure on balanced bellows pressure relief

valves to around 45/50% of the set pressure.


______________________________________________________________________

Protective Device 6

2.9 Pilot Operated Relief Valve

Pilot operated relief valves use a pressure tapping or pressure impulse

pipe, which is connected to the underside of the relief valve disc, to

supply a pilot valve which, once activated, opens the main valve. Pilot

operated relief valves are commonly used in clean, low-pressure service

and where a large relieving area is required. Because of the use of the

pilot valve to effect opening of the main valve, these valves do not

‘simmer’ when the system operating pressure approaches the set

pressure of the valve. The set pressure, therefore, of pilot operated relief

valves can be close to the system operating pressure - they are often

used when the system operating pressure is higher than 90% of the set

pressure of the valve.

2.10 Vacuum Relief Valve

Certain conditions may prevail (e.g. excessive condensation, process

upset) to cause a vessel to experience a vacuum. Unless the vessel has

been specifically designed to withstand partial or full vacuum, a vacuum

relief valve must be provided. Vacuum relief valves operate along the

same principle of a conventional relief valve.

Special care must be exercised when utilising vacuum relief valves on

highly flammable service since the introduction of air into a vessel, to

prevent a vacuum from developing, can present hazardous conditions.

Systems are available which supply nitrogen or fuel gas to the vessel to

prevent a vacuum occurring thus preventing hazardous conditions.

2.11 Pressure/Vacuum Relief Valve

For atmospheric and low-pressure storage tanks, pressure/vacuum relief

valves are typically used to provide the necessary pressure relief. These

devices incorporate a pressure relief valve and a vacuum relief valve

within a single assembly which will be mounted onto a single

nozzle/flange on the top of the tank. These valves allow the tanks to

operate within their normal working conditions, as caused by filling,

emptying and reacting to temperature and product variations. It is often

found that an additional, independent, pressure relief valve will be fitted


______________________________________________________________________

Protective Device 7

to the tank in order to provide pressure relief in emergency situations.

2.12 Bursting (Rupture) Disc

A bursting disc assembly consists of a circular membrane which may be

made of metal, plastic, or graphite and which is sandwiched between two

plates or holders. This assembly is usually installed between a pair of

flanges. Bursting discs operate by simply ‘bursting’ the membrane and

thus allowing instantaneous relief. The burst tolerance of bursting discs is

typically around 5% of the set pressure unlike the tolerance of pressure

relief valves which have a typical tolerance of around 3% of the set

pressure. Tighter burst pressure tolerances are possible, however,

manufacturing tolerances of the membrane tend to dictate the achievable

burst pressure tolerance. Bursting discs are sensitive to temperature

variations.

Pressure relief valves may be removed and tested to check for correct

operation (methods do exist to check valves in situ), however, bursting

discs cannot be tested without destroying them.

The major disadvantage of bursting discs is that once activated they

cannot reseat and, therefore, the process must be shutdown, the vessel

isolated, or the bursting disc isolated, to allow for replacement of the

disc.

The major advantage of bursting discs is that they are more effective

than pressure relief valves in protecting equipment from sudden

explosions. They are more resistant to corrosion or potential plugging

than relief valves and are, therefore, often used upstream of relief valves

in toxic or corrosive services. Bursting discs only burst when the set

pressure of the disc is reached which prevents any seepage or leakage of

the product during normal operation of the process.

2.13 Pressure Monitoring, Alarms and Trips

As mentioned previously, a hierarchy of alarms and trips will typically be

found on process vessels. These actions provide layers of protection

between the manual monitoring of pressure and the ultimate lifting of a

pressure relief valve or bursting of a bursting disc. These alarms and trips

are provided with pressure measurements from simple pressure sensors


______________________________________________________________________

Protective Device 8

(e.g. Bourdon tubes, diaphragm sealed sensors, differential pressure

gauges/sensors). A hierarchy of monitoring and automatic shutdown is

employed with vessels typically being provided with high pressure and

low pressure alarms and high/high pressure and low/low pressure

alarms/shutdown. These pressure alarm and shutdown protective

devices/systems are typically found on the process and instrumentation

diagrams (P&IDs) designated as PSLL, PSHH, PSL, PSH, PALL or PAHH

P indicating pressure, S indicating switch, A indicating alarm, and L&H

indicating low or high.

3. LEVEL

Correct level control, and indication, is often critical to the safe and

efficient operation of process plant. Many process vessels, such as

separators and distillation columns, require liquid levels to be strictly

controlled in order to effect product separation (e.g. separation of oil, gas

and water) and to prevent product carry over.

Level indication is usually accomplished by displacer/float instruments

and sight glasses. Other level indicators include differential pressure

gauges, ultrasonic, microwave, radiological, and fibreoptic instruments.

Providing that it is appropriate for the particular application, the method

of level indication is of less importance than the use of the level

information and / or measurement for control and protection purposes.

A typical level control function would be accomplished by using a level

transmitter which feeds control signals to a level control valve (LCV). The

LCV will open or close (modulate) to maintain the level within, say, the

vessel within pre-defined limits.

When it has not been possible to control the correct level within, say, a

process vessel, protective devices are provided to prevent hazardous

conditions arising. These protective devices, which usually take the form

of level transmitters and level switches, provide alarms and/or effect

shutdown of the process or individual vessel. A hierarchy of monitoring

and automatic shutdown is employed with vessels typically being

provided with high level and low level alarms and high/high level and


______________________________________________________________________

Protective Device 9

low/low level alarms/shutdown. These level alarm and shutdown

protective devices/systems are typically found on the process and

instrumentation diagrams (P&IDs) designated as LSLL, LSHH, LSL, LSH,

LALL, LAHH

L indicating level, S indicating switch, A indicating alarm, and L&H

indicating low or high.

Dedicated level switches may be found on vessels to protect pumps from

losing suction caused by low liquid levels and to protect compressors

from liquid carry over caused by high liquid levels. These protective

devices/systems are independent of the level control system, utilising

separate level bridles or standpipes.

Level measurement or control using differential pressure gauges should

not be used for fluids which can be subject to variations in specific gravity

since the change in the weight of the material column will affect the

operation of the instrument.

Sight (level) glasses are used for manually monitoring the levels within

the process plant. Sight glasses are, however, not recommended for

fluids which are toxic or highly flammable unless they are armoured or of

high pressure, robust design. Use of sight glasses for ammonia is not

recommended due to incompatibility.

Vessel tappings and nozzles used for level indication and control must be

located to provide accurate indication or measurement of the actual

levels within the vessels or tanks. Level indications can be affected by

movement of the product within the vessel and, therefore, tappings

should not be placed in areas that could be affected (e.g. close to outlet

piping).

4. TEMPERATURE

Temperature plays an important part in processes involving product

separation and refining. Many processes involve chemical reactions and

this reaction is sensitive to temperature variations. Materials used for

process equipment can impose temperature limitations and the structural

strength of equipment can be dramatically reduced at elevated

temperatures. Likewise, low temperatures can present material problems


______________________________________________________________________

Protective Device 10

through embrittlement. Temperature monitoring and control is, therefore,

crucial to the safe and efficient operation of process plant.

Temperature measurements are typically accomplished by using sensors

such as thermocouples. In order to protect the sensor itself from the

harmful effects of the process stream (e.g. corrosion, erosion) the sensor

is usually installed within a thermowell. A thermowell is a tube which

protrudes into the vessel or pipework through a sealed opening. The

thermowell is closed at the protruding end but is open at the other end.

The sensor can, therefore, be readily inserted or removed. The

thermowell itself may be furnished in suitable material to prevent

corrosion, however, since the thermowell protrudes into the product

stream it can be subject to structural loading due to fluid dynamics.

Failures of thermowells have been experienced due to vibration fatigue

cracking caused by vortex shedding at the thermowell.

Temperature measurements must be taken at the areas within the

process plant that are of interest. Sensors must be located in areas that

are subject to continuous movement of the process fluids and must not

be located in stagnant areas. If liquid temperature is of interest then the

thermowell complete with sensor must project into the liquid phase and if

gas temperature is of interest then the thermowell complete with sensor

must project into the gas phase.

In very much a similar way to pressure and level monitoring and control,

temperature monitoring and control may use a hierarchy of alarms and

trips to ensure safe and efficient operation of process plant.


____________________________________________________Material Safety Data Sheet (MSDS) 1

6.0 MATERIAL SAFETY DATA SHEET (MSDS)

6.1 MSDS CONTENTS

The MSDS for the chemicals are part of the process and Basic

Engineering Design Document of the licensor. As per OSHA (USA)

manufacturers, importers and distributors are required to provide the

MSDS for each hazardous chemical they produce or handle. The

purchaser of these chemicals (Client) is entitled to receive these MSDS

from the supplier.

Each member of the commissioning team is required to read the MSDS

carefully before undertaking the commissioning activity. Although the

format of MSDS can vary, they should all include the following

information:

1. Chemical and common name

2. Ingredient information

3. Physical and chemical characteristics

4. Physical hazards - Potential for reactivity, fire and/or explosion.

5. Health hazard

6. Symptoms of exposure

7. Primary route of likely entry into the body upon exposure.

8. OSHA permissible exposure levels.

9. Precautions for use

10. Waste disposal

11. Protective measures and equipment including during spills

and maintenance.

12. Emergency and first aid procedures

13. Date of MSDS preparation and last revision

14. Emergency contact of manufacturer

The OSHA standard requires that the manufacturer or distributor provide

quick and easy access to all MSDS applicable to their work place.



MSDS for chemicals generally handled during Refinery / Petrochemical /

Fertilizer plant commissioning are enclosed at the end of Chapter .

For more data on MSDS, following sites in the Internet may be

used :

1. University of California MSDS Resources at

http://www.ucop.edu/riskmgt/ohp/msds.html

2. MSDS SEARCH

http://www.msdssearch.com

3. Occupational Safety & Health Administration, OSHA, Data Base

http://www.osh.nct

4. Safety links: Material Safety Data Sheets

http://www.ksu.edu/area/irml/safetv/msds.html

5. The Hong Kong Occupational Safety & Health Association

http://www.hkosha.org.hk/weblinks.htm This site has the following

resources other than MSDS :

a. Safety related web sites.

b. Safety Magazine

c. Occupational health

d. Fire

e. Related Chemical Resources

f. Emergency

g. Lessons learnt from Accidents

h. Safety Equipment Supplies



CODE SYMBOL: NATIONAL FIRE PROTECTION

ASSOCIATION (NFPA) DIAMOND

H – Health 1 - Low

F – Fire 2 - Medium

R – Reactivity 3 – High

4 - Extreme

Note: More information can be had from the following site:

http://vvww.orcbs.msu.edu/Chemical/nfpa/nfpa.html



RATING SUMMARY:

Health (Blue):

4 – Danger May be fatal on short exposure. Specialized

protective equipment required

3 – Warning Corrosive or toxic. Avoid skin contact or

Inhalation

2 – Warning May be harmful if inhaled or absorbed

1 – Caution May be irritating

0 - No unusual hazard

Flammability (Red):

4 – Danger Flammable gas or extremely flammable liquid

3 - Warning Flammable liquid flash point below 100° F

2 – Caution Combustible liquid flash point of 100° to

200°F

1 Combustible if heated

0 Not combustible

Reactivity (Yellow):

4 – Danger Explosive material at room temperature

3 – Danger May be explosive if shocked, heated under

confinement or mixed with water

2 – Warning Unstable or may react violently if mixed with

Water



1 – Caution May react if heated or mixed with water but not

violently

0 – Stable Not reactive when mixed with water

Special Notice Key (White):

W Water Reactive

Oxy Oxidizing Agent

Note: More information can be had from the following site:

http://www.orcbs.msuedu/chemical/nfpa/nfpa.htrnl



MSDS OF VERIOUS CHEMICALS COMMONLY USED IN REFINERY

Material Safety data Sheets of verious chemicals which are generally

used in refinery are given in Annexure 1 for ready reference.


__________________________________________________On site Emergency Plan 1

7.0 ON-SITE EMERGENCY PLAN

It is recommended that the commissioning team leader and other

members of the commissioning team read and familiarize themselves

with following two documents available with the client.

These two documents are prepared and submitted to the authority in

compliance to the Manufacture, Storage and Import of Hazardous

Chemicals Rules, 1989. The formats of these two documents are given as

Schedule 8 and Schedule 11 of the rules.

1. Safety Report (Schedule 8, Manufacture, Storage and import of

hazardous chemicals rules 1989).

2. On site emergency Plan (Schedule 11, Manufacture. Storage and

import of hazardous chemicals rules, 1989).

It is recommended that the commissioning team leader procures

a copy of the On-site Emergency Plan and keeps the same at site

with access to team members.


__________________________________________________Environmental Preservation Acts in India 1

8.0 THE ENVIRONMENTAL PRESERVATION ACTS IN INDIA

1. THE WATER (PREVENTION AND CONTROL OF POLLUTION) ACT,

1974.

2. THE WATER (PREVENTION AND CONTROL OF POLLUTION) CESS

ACT, 1975.

3. THE AIR (PREVENTION AND CONTROL OF POLLUTION) ACT,

1981.

4. THE ENVIRONMENT (PROJECTION) ACT, 1986.

5. THE HAZARDOUS WASTES (MANAGEMENT AND HANDLING)

RULES. 1989.

6. MANUFACTURE, STORAGE AND IMPORT OF HAZARDOUS

CHEMICALS RULES. 1989.



ENVIRONMENTAL LEGISLATION FOR INDUSTRY IN INDIA

India is the first country, which has provided for the protection and

improvement of the Environment in its Constitution. Article 51 -(g) of

the Constitution states:

"It shall be the duty of every citizen of India to protect and improve the

natural / environment including forest, lakes, rivers and wildlife and to

have compassion for all living creatures".

The Directive Principles of State Policy, an integral and significant

element of our democratic set-up, also contains a specific provision

enunciating the State's commitment for protecting the environment.

These constitutional provisions are implemented through environmental

protection laws of the country.

Table 1 Represents various specific legislation and regulations

dealing with protection and improvement of the

environment.

Table 2 Represents the air emission standards in India.

Table 3 Represents the ambient air quality standards.

Table 4 Represents the Minimum National Standards (MINAS) for the

refinery effluents.

Table 5 Represents the Minimum National Standards (MINAS) for the

petrochemical Plants.

Table 6 Represents the General standards for Discharge of Effluent.

Table 7 Represents the effluent sample preservation conditions.



Table 1 - ENVIRONMENTAL LEGISLATION IN INDIA

The Water (Prevention & Control of Pollution) Act, 1974, as amended up

to 1988 The Water (Prevention & Control of Pollution) Rules, 1975

The Water (Prevention & Control of Pollution) Cess Act, 1977 as

amended upto 1991

- The Water (Prevention & Control of Pollution) Cess Rules, 1978 as

amended up to 1992

- The Air (Prevention & Control of Pollution) Act, 1981 as amended up

to 1987

- The Air (Prevention & Control of Pollution) Rules, 1982 and 1983

- The Environment (Protection) Act, 1986

- The Environmental (Protection) Rules, 1986

- The Hazardous Wastes (Management and Handling) Rules, 1989

- Manufacture, Storage and Import of Hazardous chemical Rules, 1989

- Manufacture, Use, Import, Export and Storage of Hazardous Micro-

Organisms, Genetically Engineered Micro-organisms of Cells Rules,

1989

- The Public Liability Insurance Act, 1991

- The Public Liability Insurance Rules, 1991

- Environmental (Protection) Rules, 1992 and 1993 - "Environmental

Statement"

- Environmental (Protection) Rules, 1993 - "Environmental Standards"

- Environmental (Protection) Rules, 1994 - "Environmental Clearance"



1.0 THE WATER (PREVENTION AND CONTROL OF

POLLUTION) ACT, 1974

Following are the specific obligations, under this Act, which are to be

complied with:

Obligations

- Provide the Pollution Control Board (PCB) any information which is

sought for preventing or controlling pollution of water regarding the

construction, installation, operation or the treatment and disposal

systems of an industrial establishment

- Provide access to the PCB, or any officer empowered by it, for taking

samples of water or effluents from the industrial establishment for

the purpose of analysis

- Allow entry to the PCB or any person empowered by it, at any time,

for the purpose of performing any of the entrusted functions; or for

seizing of any plant, records, registers, documents or any material

object, in case there are reasons to believe that provisions of the Act

are being contravened

- Not to discharge, knowingly, of any effluent into the stream, sewer or

on land, of quality which is not conforming to the standards

prescribed by the PCB

- Furnish information to the PCB and other designation agencies, of any

accidental or unforeseen event, in which effluents not conforming to

the prescribed standards are being discharged, or likely to be

discharged into a stream or sewer or on land



• Comply with the directions issued in writing by the PCB, within the

specified time, as mentioned in the order. The directions may

include:

1. the closure, prohibition or regulation of any industry,

operation or process; or

2. the stoppage or regulation of supply of electricity, water

or any other service

• Comply with the conditions as prescribed in the "Consent to

Establish" or "Consent to Operate" for discharge of effluents into a

stream or sewer or on land

Responsibilities

• Obtain "Consent to Establish", prior to taking any steps to establish

any industry, operation or process or any treatment and disposal

system which is likely to discharge effluents

• Obtain "Consent to Operate" prior to commencing operations of any

industry, or any treatment and disposal system, which is likely to

discharge effluents.

• Apply for renewal of the "Consent to Operate" before the expiry of

validity period, as specified in the consent granted earlier, in the

prescribed form and along with the prescribed fees

Rights

• Industry to ensure that specified effluent sampling procedure is being

followed by the PCB or any officer empowered by it, in case results of

analysis are to be used as evidence in legal proceedings

• A prior "Notice of Inspection" for the purpose of making an enquiry

for grant of consent to be served by the Board to the industry in the

prescribed form.



• PCS to maintain "Consent Register" containing particulars of the

consent issued, and to provide access to industry, at all reasonable

hours

• Consent to be deemed as granted automatically and unconditionally

after four months from the date of application which was complete in

all respects unless already given or refused before this period

• Refusal of "Consent" to be recorded in writing, by the PCB

• "Right to Appeal" to the "Appellate Authority" under the Act, in

case of grievance against the order of the PCB, in the prescribed form

of appeal, within the specified time limit (30 days from the date of

the order) The Appellate Authority is a grievance redressal forum,

appointed by the government, and consists of a single person or

three persons as its members

• Opportunity to file objections with the PCB against notice of proposed

directions for closure or stoppage of any essential service to the

industry, within the Specified time (15 days from the date of service

of the notice)

• PCB to record reason(s), in writing, in case it is not providing an

opportunity to the industry to file objections.



2 THE WATER (PREVENTION AND CONTROL OF POLLUTION)

CESS ACT, 1975

Obligations

• Pay water cess, as prescribed within the specified time as indicated in

the assessment order, if the industry is included in the specified

schedule under title Act.

• Affix meters of the prescribed standards for water consumption

measurements at places specified by the PCB

• Provide access to PCB, at all reasonable times, for implementing the

provisions of the Act, including testing of the meters for their

accuracy.

• Pay interest at the prescribed rates, in case of delay in paying the

water CESS.

• Pay penalty for non-payment of cess, within the specified time, not

exceeding the amount of cess, in arrears, after being given a

reasonable opportunity of hearing.

Responsibilities

• Submit the " Water Cess Return" in the prescribed form, at specified

intervals, to the PCB.

Right

• Industry is entitled to 25% rebate in Water Cess payable, provided :

i) it consumes water, in quantity less than or equal to the

maximum specified quantity in the Schedule and

ii) it complies with the provisions of "Consent to Operate" as

well as the prescribed standards under the Environment

(Protection Act), 1986



• Opportunity for hearing before imposing penalty for non-payment of

cess within the specified time.

• Right to appeal to the "Appellate Authority" in case of any

grievance(s) against any Order of Assessment in the prescribed form

and along with the prescribed fee.



3 THE AIR (PREVENTION AND CONTROL OF POLLUTION)

ACT, 1981

Obligations

• Comply with the conditions, as prescribed in the "Consent to

Establish" or "Consent to Operate" for emissions

• Not to discharge air pollutant(s) in excess of the standards prescribed

standards by the PCB

• Furnish information to the PCB and other designated agencies, of any

accident or unforeseen act or event in which emissions of air

pollutant(s) occurred in excess of the prescribed standards or are

likely to occur

• Allow entry to the PCB or any official empowered by it to the

industrial establishment, at all reasonable times, for the purposes of

carrying out any of the entrusted functions or for inspecting to

ascertain that provisions of the Act are being complied with; or for

seizing any equipment, plant, records registers, documents or any

other material object if there are reasons to believe that provisions of

the Act are being contravened

• Provide the PCB any information to enable it to implement the

provisions of the Act.

• Provide access to the PCB or any officer empowered by it, for taking

samples of air or emissions from the industrial plant for the purpose

of analysis

• Comply with the directions, issued in writing by the PCB, within the

specified time as indicated in the order. The directions may include :

1. the closure, prohibition or regulation of any industry,

operation or process or

2. the stoppage or regulation of supply of electricity, water or

any other service

• Industry to provide all facilities required by the PCB official for the

purpose of sampling.



Responsibilities

• Obtain "Consent to Establish" prior to establishing any industrial plant

in an air pollution control area, which is likely to emit air pollutanl(s)

• Obtain "Consent to Operate" prior to commencing operation of any

industrial plant which is likely to emit air pollutant(s) in an air

pollution control area

• Apply for the renewal of "Consent to Operate" before expiry of the

validity period, as specified in the consent granted earlier, in the

prescribed form, along with the prescribed fees

Rights

• Consent to be deemed as granted, automatically and unconditionally,

after four months, from the date of receipt of application, which is

complete in all respects, unless it is given or refused earlier than this

period

• Refusal of consent to be recorded in writing, by the PCB

• Opportunity for hearing before withdrawing the consent, already

granted, or in case renewal of consent is refused

• PCB to maintain "Consent Register" containing particulars of consent

issued and provide access to the industry, at all reasonable hours

• Right to appeal to the Appellate Authority, in case of a grievance

against an order by the PCB, under the Act, in the prescribed form

within the specified time limit (30 days from the date of order)

• A prior "Notice of Inspection" for the purposes of making an enquiry

for granting consent, to be served by the PCB to the industry, in the

prescribed form

• Industry to ensure that specified emission sampling procedure is

being followed by the PCB or any officer empowered by it, in case,

results of analysis are to be used as evidence in legal proceedings

• Opportunity to file objections with the PCB against notice of proposed

directions for closure or stoppage of any essential service to the



industry, within the specified time (15 days from the date of service

of notice)

• PCB to record reasons, in writing, in case it does not provide an

opportunity to the industry to file objections.



4 ENVIRONMENT (PROTECTION) ACT, 1986

Obligations

• Comply with the directions issued in writing by the Central

Government within a specified time as mentioned in the order. The

directions may include:

1. closure, prohibition or regulation of any industry, operation or

process or

2. stoppage or regulation of the supply of electricity, water or

any other service

• Prevent discharges or emissions of environmental pollutants in

excess of the prescribed standards

• Furnish information to the prescribed agencies of any accidental or

unforeseen event in which environmental pollutant(s) not

conforming to the prescribed standards are being discharged, or are

likely to be discharged into the environment

• Allow entry and inspection by any person empowered by the Central

Government into the industrial establishment at all reasonable

times, for the purpose of performing any of the functions entrusted,

or to ascertain compliance with the provisions of the Act; or for

seizing of any equipment, plant, registers, records or documents in

case there are reasons to believe and any provision of the Act is

being contravened

• Allow Central Government or any official empowered by it, to take

samples of air, water, soil or any other substance from the industrial

establishment for the purpose of analysis



Responsibilities

• Submit an "Environmental Statement" every year, before 30th

September, to the PCB, in case consent is required under the

Water/Air Act or authorization under the Hazardous Wastes

(Management and Handling) rules or both

• Obtain prior "Environmental Clearance" from MoEF, in case of a

new project or for modernization/expansion of the existing

project, if it falls under the specified schedule, subject to certain

conditions

Rights

• Ensure that specified procedure is being followed by Central

Government or any officer empowered by it, for taking samples

of air, water, soil or other substance form the industrial

establishment, in case results of the analysis are to be used as

evidence in legal proceedings

• Opportunity to file objections against the proposed directions of

closure or stoppage of any essential services to the industry, with

the Central Government, within the specified time (15 days form

the data of service of notice)

• Central Government to record reasons, in writing, in case it does

not provide an opportunity to the industry to file objections

against the proposed directions.



5 THE HAZARDOUS WASTES (MANAGEMENT AND

HANDLING) RULES, 1989

Obligations

• Ensure packaging, labeling and transportation of hazardous wastes in

accordance with the provisions of Motor Vehicles Act, 1988

• Comply with the conditions specified in the authorization granted for

handling of hazardous wastes.

Responsibilities

• Ensure proper collection, reception, treatment, storage and disposal

of hazardous wastes by the owner himself or through an operator of

the facility for specified hazardous wastes

• Obtain "grant of authorization" for handling hazardous wastes form

PCB Apply for renewal of authorization before expiry of the validity

period as specified in the authorization granted in the prescribed

form

• Maintain records of hazardous wastes handling, at the site, in the

prescribed form

• Submit "Annual Returns" to the PCB regarding disposal of hazardous

wastes in the prescribed form

• Report to the PCB any accident at site, or during transportation,

while handling hazardous wastes, in the prescribed form

Rights

• An authorization that is granted would be in force for a period of two

years form the date of issue, unless suspended or cancelled earlier

• Opportunity of hearing given to the industry before refusing grant of an

authorization

• PCB to give show cause notice to industry, stating reasons before



suspending or canceling any authorization granted under the rules

• State Government to identify sites for disposal of hazardous wastes

and publish an inventory periodically

• Import of hazardous wastes to follow specified procedures given

below :

- Exporting country or exporter to apply to the Ministry of

Environment and Forests, Government of India, in the

prescribed form for grant of permission

- Exporter and importer to follow prescribed conditions laid

down by the Ministry of Environment and Forest, Government

of India, and the PCB

- Importer to keep records of imports of hazardous wastes, in

the prescribed form

Note: Import of hazardous wastes from any country to India is not

permitted for dumping. Import of such wastes may only be allowed for

processing or reuse as raw material on a case to case basis

- Right to appeal in writing, against an order of suspension, cancellation

or refusal of authorization, to the State Government, in case of the

State Pollution Control Board and to the Central Government, in case of

the Central Pollution Control Board, within the specified time (30 days

form the date of the order).



6 MANUFACTURE, STORAGE AND IMPORT OF HAZARDOUS

CHEMICALS RULES, 1989

Obligations

• Occupier to identify major accidents, hazards related with industrial

activity involving hazardous chemicals, and to take adequate steps for

the prevention and control of such hazards

• Occupier to provide relevant information to the persons liable to be

affected by a major accident

• Occupier to develop information in the form of a safety data sheet

• Occupier to label the specified information on every container of a

hazardous chemical

• Occupier to follow specified procedures for importing hazardous

chemicals

Responsibilities

• Occupier to furnish information required to notify the concerned

authorities of a major accident occurred at the site or in a pipe line in

the prescribed form

• Occupier to furnish information regarding "Notification of Sites" for

industrial activity involving hazardous chemicals to the concerned

authority in the prescribed form at least 3 months before commencing

activity

• Occupier to submit "Safety Report" containing the prescribed

information to the concerned authority at least 3 months before

commencing activity

• Occupier to send further information, within the specified time, as

mentioned in the notice, if so desired, by the concerned authority

relating to the "Safety Report" ( refer Schedule - 8 appended here)



• Occupier to prepare up-to-date on-site "emergency plans"(refer

Schedule - 11 appended here) in case of a major accident, before

commencing an industrial activity involving hazardous chemicals

• Occupier to maintain records of imports of hazardous chemicals in the

prescribed form

• Ensure transportation of hazardous substances as per the provisions of

the Motor Vehicles Act, 1988



SCHEDULE 8 See rule 10(1) 1

INFORMATION TO BE FURNISHED IN A SAFETY REPORT

1. The name and address of the person furnishing the information.

2. Description of the industrial activity, namely –

• Site,

• Construction design,

• Protection zones explosion protection, separation distance,

• Accessibility of plant.

• Maximum number of persons working on the site and particularly

of those persons exposed to be hazard.

3. Description of the plant design, namely,

• Technical purpose of the industrial activity.

• Basic principles of the technological process.

• Process and safety-relating data for the individual process stages,

• Process description,

• Safety-related types of utilities

4. Description of the hazardous chemicals, namely-

• Chemicals (quantities, substance data, safety-related data,

toxicological data and threshold values.)

• The form in which the chemical may occur on or into which they

may be transformed in the event of abnormal conditions.

• The degree of purity of the hazardous chemical.

5. Information on the preliminary hazard analysis, namely-

• Types of accident

• System elements or events that can lead to a major accident

• Hazards

• Safety-relevant components.

6. Description of safety-relevant units, among others:

• Special design criteria,



• Controls and alarms.

• Special relief systems,

• Quick-acting valves.

• Collecting tanks/dump tank,

• Sprinkler system,

• Fire - fighting etc.

7. Information on the hazard assessment, namely

• Identification of hazards,

• The cause of major accidents,

• Assessment of hazards according to their occurrence frequency.

• Assessment of accident consequences,

• Safety systems,

• Known accident history.

8. Description of information on organizational systems used to carry on

the industrial activity safety, namely-

• Maintenance and inspection schedules,

• Guidelines for the training of personnel.

• Allocation and delegation of responsibility for plant safety,

• Implementation of safety procedures.

9. Information on assessment of the consequences of major accidents,

namely-

• Assessment of the possible release of hazardous chemicals or of

energy,

• Assessment of the effects of the released (size of the affected

area, health effects, property damage)

10. Information on the mitigation of major accidents, namely-

• Fire brigade

• Alarm systems,

• Emergency plan containing system of organization; used to fight

the emergency, the alarm and the communication rules,



guidelines for fighting the emergency, information about

hazardous chemicals, examples of possible accident sequence,

• Coordination with the District Emergency authority and its off -

site emergency plan,

• Notification of the nature and scope of the hazard in the event of

an accident,

• Antidotes in the event of a release of a hazardous chemicals.



TABLE 2: ATMOSPHERIC EMISSION STANDARDS

I. Concentration based Standard

Suspended Particular Matter (SPM) 150mg/Nm3

Sulfur dioxide 50mg/Nm3

II. Load / Mass - Based Standards - Oil Refineries

Distillation 0.25 Kg/MT of feed*

(Atmospheric and Vacuum)

Catalytic cracker 2.5 Kg/Mt of feed*

Sulfur Recovery Unit (SRU) 120 Kg/MT of sulfur in the feed*

• Feed indicates the feed for that part of the process under

consideration

III. Equipment Based Standards

For dispersion of Sulfur- dioxide, a minimum stack height has been

prescribed as:

a) Power Generation Capacity

>500MW Stack height 275 m

200/210 - 150 MW Stack height 220m

<200/210 MW Stack height H = 14 (Q) °3 meters

b) Steam generation capacity

>30 Tone / Hr Stack height H = 14 (Q) °3 meters

Here Q is Emission rate of SO2 in Kg/Hr. however, the minimum stack

height of 30 m shall be maintained in case it is less by computation using

above formula.



TABLE 3: NATIONAL AMBIENT AIR QUALITY STANDARDS

Time

weighted

Concentration in ambient airPollutants

average Industrial

area

Residenti

al , Rural

& other

Sensitive

Area

Method of

measurement

Sulfur dioxide Annual

average*

24

hours**

80 pg/m3

120 pg/m3

50 pg/m3

80 pg/m3

15 pg/m3

30 pg/m3

1. Improved West &

Gaeke

2. Ultraviolet

Fluorescence

Oxides of

Nitrogen (as

N02)

Annual

average*

24

hours**

80 pg/m3

120 pg/m3

60 pg/m3

80 pg/m3

15 pg/m3

30 pg/m3

1. Jacob & Hochheiser

(Na-Arsenite) method

2. Gas phase

Chemiluminescence

Suspended

Particulate

Matter (SPM)

Annual

average*

24

hours**

360 pg/m3

150 pg/m3

140

pg/m3

200

pg/m3

70 pg/m3

100 pg/m3

1. High volume

sampling

(Average flow rate not

less than 1.1 m3/min

Respirable

Particulate

matter (size)

less than

10pm)(RPM)

Annual

average*

24

hours**

120 pg/m3

150 pg/m3

60 pg/m3

100

pg/m3

50 pg/m3

75 pg/m3

2. Respirable

particulate Matter

sample

Lead (Pb) Annual

average*

24

hours**

1.0 pg/m3

1.5 pg/m3

0.75

pg/m3

1.00

pg/m3

0.50

pg/m3

0.75

pg/m3

1. AAS method after

2.sampling using EPM

2000 or equivalent

filter paper

Carbon Monoxide

I(CO)

8 Hours* 1

hour

5.0 pg/m3

10.0

pg/m3

2.0

pg/m3 4.0

pg/m3

1.00

pg/m3

2.00

1. Non- dispersive

infrared Spectroscope

* Annual arithmetic mean of minimum 104 measurements in a year

taken twice a week 24 hourly at uniform interval.



** 24 hourly / 8 hourly values should be met 98% of the time in a

year. However, 2% of the time, it may exceed but not on two

consecutive days.



TABLE 4: MINIMUM NATIONAL STANDARDS (MINAS) FOR OIL REFINERIES

Pollutant Characteristics Max. Permissible

Concentration*

Max. Permissible Quantum in

Kg/1000 Tonnes Crude

Processed

PH 6.0-8.5 -

Suspended solids 20 14.

BOD 5 days, 20°C 15 10.5

Oil and grease 10 7

Phenols 1 0.70

Sulphides 0.5 0.35

All values except pH are in mg/L

Note: MINAS are the Minimum National Standards or the concentration

and quantitative limits that are to be complied with. The respective state

pollution control board can specify more stringent standards than these.



TABLE: 5 MINIMUM NATIONAL STANDARDS (MINAS) FOR

PETROCHEMICAL INDUSTRIES

The standards proposed by the Central Board were reviewed by the Core

and Peer Groups constituted by the Central Board. The Standards

recommended by the Core and Peer Groups are presented below:

Parameter Concentration not to exceed (mg/1 except pH)

PH 6.5-8.5

*BOD5, 20°C 50

COD 250

**Phenol 5

Cyanide as CN 0.2

Sulphide as S 2

***Fluoride as F 15

****Hexavalent Chromium as Cr 0.1

Total chromium as Cr 2

Total suspended solids 100

* State Board may prescribe the BOD value of 30mg/l, if the recipient

system so demands

** The limit for phenol shall be conformed to at the outlet of effluent

treatment of phenol-cumene plant however, at the final disposal

point, the limit shall be less than 1mg/l

*** The limit for fluoride shall be conformed to at the outlet of fluoride

removal unit. However, at the disposal point fluoride concentration

shall be lower than 5mg /1

**** " The limits for total and hexavalent chromium shall be conformed

to at the outlet of the chromate removal unit. This implies that in

the final treated effluent, total and hexavalent chromium shall be

lower than prescribed herein



Table: - 6 GENERAL STANDARDS FOR DISCHARGE OF ENVIRONMENT

POLLUTANTS: EFFLUENT (Gazette Notification of MoEF- May 1993)

Parameter StandardsS. No.

Inland surface

Waters

Public

Sewers

Land for

Irrigation

Marine coastal Areas

(a) (b) (c) (d)

1 Colour and odour - - - -

2. Suspended solids, 100 600 200 a) For process waste water-

100

b) For cooling water effluent

10% above total suspended

matter of influent

3. Particular size of Suspended

solids

Shall pass 850

Micron Sieve

- a) Floatable solids, max.3

mm

b) Settleable solids, max

850 microns

4. pH value 5.5 to 9.0 5.5 to 9.0 5.5 to 9.0 5.5 to 9.0

5. Temperature Shall not exceed

5°C above the

receiving water

temp.

- - Shall not exceed 5°C above

the receiving water

temperature

6. Oil and residual chlorine,

Max.

10 20 10 20

7. Total residual chlorine, mg/l,

Max.

1.0 - - 1.0

8. Ammonical nitrogen (as N),

mg/l, Max.

50 50 - 50

9. Total Kjeldahl nitrogen (as

NH3),mg/l, Max.

100 - • 100

10. Free ammonia (as

NH3),mg/l, Max.

5.0 - - 5.0

11. Biochemical Oxygen

Demand(5 days at 20°C),

Mg/l, Max.

30 350 100 100

12. Chemical Oxygen Demand,

mg/l, Max.

250 - - 250

13. Arsenic (as As) mg/l, Max. 0.2 0.2 0.2 0.2

14 Mercury (as Hg), Mg/l, Max. 0.01 0.01 - 0.01

15. Lead (as Pb), mg/l, Max. 0.1 1.0 - 2.0

16. Cadmium (as Cd), mg/l, Max. 2.0 1.0 - 2.0



Table: 6 Contd.....

Parameter StandardsS. No.

Inland surface

Waters

Public Sewers Land for

Irrigation

Marine

coastal

Areas

17 Hexavalent chromium (as

Cr+6),mg/l, Max.

0.1 2.0 ^ 2.0

18. Total chromium (as Cr), mg/l,

Max.

2.0 2.0 ^ 2.0

19. Copper (as Cu), mg/l, Max. 3.0 3.0 ^ 3.0

20. Zinc (as Zn), mg/l, Max. 5.0 15 - 15

21. Swiwnium (as Se), ing/I, Max. 0.05 0.05 * 0.05

22. Nickel (as Ni),mg/l, Max. 3.0 3.0 - 5.0

23. Cyanide (as CN), mg/l, Max. 0.2 2.0 0.2 0.2

24. Fluoride (as F), mg/l, Max. 2.0 15 * 15

25. Dissolved phosphates (as P),

mg/l, Max.

5.0 - - -

26. Sulphide (as SO), mg/l. Max. 2.0 ~ ~ 5.0

27. Phenoilic compounds, (as

CgHsOH), mg/l, Max.

1.0 5.0 - 5.0

28. Radioactive materials

(a) Alpha emitter - micro curie/ml 10-7 10-7 10-8 10-7

(b) Beta emitter - micro curie/ml 10-6 10-6 10-7 10-6

29. Bio-assay test 90%survival of

fish after 96

hours in 100%

effluent

90%survival of

fish after 96

hours in 100%

effluent

90%survival of

fish after 96

hours in 100%

effluent

90%surviv

al of fish

after 96

hours in

100%

30. Manganese(as Mn) mg/l.<ax. 2 2 * 2

31. Iron (as Fe) mg/l, Max. 3 3 - 3

32. Vanadium (as V) 0.2 0.2 - 0.2

33 Nitrate Nitrogen, mg/l, Max. 10 ' ^ 20

Wastewater Sources, Characterization and Quantification of Pollution Loads



TABLE 7: PRESERVATION OF WASTE WATER SAMPLE

Parameters Preservative Maximum holding period

Acidity-alkalinity Refrigeration at 4 "C 24hrs

BOD Refrigeration at 4 "C 6hrs

Calcium None required

COD 2 ml/LH2S04(Conc.) 7days

Chloride Refrigeration at 4 "C 24hrs

Cyanide NaOH to pH 10 24hrs

Dissolved oxygen Determine onsrte

Fluoride None required

Metals, total 5 ml/L HN03 6months

Metals .dissolved Filtrate, 3 mi/11 HNOs 6months

Nitrogen .Ammonia 40 mg/l HgCh, 4 "C 7days

Nitrogen, Kjeldahl 40 mg/l HgCl2,4 "C Unstable

N itrogen-N itrate-N itrite 40 mg/l HgCb, 4 "C 7days

Oil and grease 2 ml/L H2S04, 4 "C 24hrs

Organic carbon 2 ml/L H2S04, 7days

PH None available

Phenolics 1.0 g CuS04 + H3P04 to 24hrs

pH 4.0, 4 "C

Solids None available

Specific conductance None available

Sulfate Refrigeration at 4 "C 7days

Sulfide 2 ml/L Zn acetate 7days

Threshold odour Refrigeration at 4 "C 7days

Turbidity None available

*a : Slow-freezing techniques (up to –250"C) can be used for preserving samples to be

analysed for organic content.

**b : for some methods of determination, 4 to 8 hrs preservation can be accomplished

with 0.7 ml cone. H2S04 and 20 mg NaN02. Refer to Standard Methods for prescribed

applications.


Procedural Control 1

9.0 SAFETY PROCEDURES

Safety Procedures

Note: Some of the safety procedures followed in operating chemical

complex are given here these are for information purpose. The activities are

generally carried out by the maintenance personal of the plant in

consultation with operations department.



9.1 PROCEDURES FOR SAMPLE COLLECTION

Many a times the commissioning team will be required to collect process

stream samples. Following precautions are to be observed for safe sample

collection and disposal.

1. It is preferred to obtain help from the client’s analytical laboratory for

sample collection. The scientific staff is well trained for this purpose.

2. The samples should be collected from sampling points specially

provided for.

3. The person collecting the sample should be fully aware about the

hazards of the plant and also the properties of chemical being collected.

4. When sampling hot or corrosive liquids the person collecting the sample

must wear safety equipments like face shield, gloves, goggles, apron

etc.

5. Ensure that the sampling point system is not damaged and physically in

good shape. Damaged sampling lines could be hazardous.

6. The sampling valve should be opened slowly and in stages to avoid

splashing / gushing of sample.

7. In case of plugged sampling line proper unplugging procedure to be

followed. Unplugging not to be done on open sample valve.

8. While unplugging personnel to stand upwind direction to avoid

exposure. Personnel to wear protective gear.

9. Sample collector to have unobstructed view of the sampling point. Do

not collect sample from points that are not visible.

10. Purge volume of the sampling line of toxic should be collected in sample

bottle or bladder to be disposed in a controlled manner as per

procedure 8.2.

11. While collecting toxic sample wear gas mask specified for the chemical

or use breathing apparatus.

12. While collecting samples under pressure care should be taken to avoid

splashing of liquid or toxic gas jet formation.

13. Samples should be labeled and dispatched for analysis promptly.



9.2 DISPOSAL OF WASTE

The waste material during commissioning may contain flammable, toxic and

hazardous chemicals it is recommended that the waste is disposed in

consultation with the environmental control department of the plant.

Handling precautions are as follows:

Solid Waste

Solid flakes, pellets or powder should be collected separately in appropriate

inert containers. Intermixing of waste should not be done. The waste is to

be labeled, sealed and handed over to the environmental department for

proper disposal.

Liquid

Waste samples etc., should be kept in a separate container specially made

for the purpose, duly labeled and handed over to the environmental

department for disposal when disposing liquid waste into the OWS it is to be

diluted effectively to avoid shock loading to the effluent treatment plant.

Disposal of liquid waste into the OWS done after consultation and with the

knowledge of the plants environmental central department.

Gases

Waste samples contained in SS bombs or rubber bladders should be

discharged out door in a manner to effectively dilute the contents. There

should not be a source of ignition when disposing flammable gases. Toxic

gases should be disposed extremely carefully avoiding possibility of

exposure.



9.3 PROCEDURE FOR PIPELINES CLEANING, GAS FREEING

PURGING. DRAINING OF EQUIPMENT AND LINES.

To avoid accidents of toxic gas inhalation, fire and explosion of splashing c

harmful chemicals it is essential to prepare equipment, tank or pipe line to

make free from hazardous substances.

PROCEDURE:

Media used for freeing / purging and precautions to be observed:

a) Water

b) Inert gas or N2

c) Steam

d) Air (with precautions)

Tank Cleaning:

a) Drain/pump out the contents

b) Fill the tank with water & drain.

c) Purge with steam if containing solvents or hydrocarbon liquids.

d) Purge with inert gas if containing fire hazardous gases.

e) Purge with air after purging with inert gas before entry. (Entry

with fire Safety Permit only).

f) Remove all sludge, deposits inside the tanks.

When closed piping systems are parted for replacing valves, servicing pump

replacing sections of lines etc this is called "Opening Lines". This type of

work not properly planned can lead to serious accidents.

To protect against such accidents the following rules must be followed while

performing such work:

1 Familiarize yourself with the piping system to be worked on.



2 Check to make sure all valves are properly positioned. All drain valves

should be opened.

3 Any pump on the system that could be accidentally started shall be

electrically isolated.

4 Although the previous steps have been taken, the job should be

performed as though the line is full and under pressure.

a) A sloping line may have a plug, a valve and another plug. You can

open the valve to drain the line, but it could still be full between

the plugs.

b) A horizontal line may have sag or dip in it. You can open the line

up and blow it out, but there could still be acid or other material

where the line is sagging, if that section of the line is taken out

and tilted, the material will run out.

c) You can't drain a line if the valve, you are trying to use is lower

than the discharge end of the line.

d) If a line is plugged, it may be from corrosion, which can produce

gas under pressure.

5. The area around the possible spray release of material should be

roped off.

6. Personnel performing this work shall wear protective clothing as

follows:

a) Protective suit.

b) Face shield.

c) PVC gloves.

7 Since opening a flange is the most common procedure used to open a

line, the procedure to follow is:

a) If the flange is horizontal, you want any sprays to be away from

you. If it is vertical a spray should be downward,

b) These are the edges of the flanges that should be opened first.

c) Keep the bolts near, you tight, and slowly open the ones away

from you. A quarter of a turn at a time is not too little.

d) If the flange stays tight, start a wedge between the flange on the

side where the bolts were loosened.



e) When you are sure the flange is open and that any drip is over,

remove the rest of the bolts and nuts.

8 Lines taken out or brought to the shop can also be hazardous. Further

handling or dismantling in the shop could release material. The only

fitting or section of line that is safe is one that has been blowout,

washed out and looked through and tested.

9 After a section of line has been removed the remaining open flanges

should be blinded.

Draining Of Equipment / Lines

Draining of lines, vessels and tanks is a common operation. Work of this

nature is primarily required when units or portion of unit are shut down for

the purpose of inspection and /or repair. This operation or type of work

normally can be accomplished without encountering any hazards, however,

consideration must be given to several factors, each and every time when

such work is to be performed.

The following is to serve as a guide in determining the safe method to be

used when draining materials from lines, vessels, tanks and like equipment.

1. The wind draining of toxic materials to atmosphere are prohibited

when there is the possibility of personnel over exposure.

2. The direction can be an important factor in determining personnel

exposure when releasing (draining ) toxic or obnoxious material.

3. The rate at which the material is being drained can be a factor in

determining personnel exposure.

4. The careful control of releasing (draining) flammable materials cannot

be overemphasized. Careful and thorough consideration must be

given to:

a) Rate of release.

b) Sources of ignition

c) Wind direction

d) Type of material being released, (whether it is heavier or

lighter then air, as vapour will readily disperse).



5. The use of protective equipment shall be evaluated prior to starting

the job. The supervisor shall specify the equipments required for the

safety of personnel and/or equipment.

6. When draining toxic, flammable, hot or obnoxious material, the

hazardous area involved shall be restricted (roped off). All personnel

who work in and around the area involved shall be notified of the work

being performed /precautions to be taken to avoid accidents.

7. The waste material to be drained if containing Arcylonitrile or

Hydrocyanic acid then it should be put in chemical sewer only looking

towards the possibility of the hazard involved.

8. If a hose is used to drain material from a piece of equipment or line,

the proper type of hose must be used. Many materials will deteriorate

the hoses such as these used for water and air. If this is done, serious

accidents can & will occur.

9. When draining is to be performed on/or close to ground level, the

protection of personnel must be considered, If draining through a

hose, the free end must be secured to prevent swinging action. The

direction of material release shall be downward not horizontal to the

ground.

10. Permanent and Temporary drains or bleeds on equipment such as

pumps shall be directed in a downward position. The material when

released should not be in a direction, which is horizontal to the

ground.



9.4 PROCEDURE FOR UNPLUGGING OF LINES

A plugged line is an abnormal condition. These plugs develop from some

mechanical failure and also from polymerization / or salting / congealing.

Although care is taken to avoid these conditions they still occur occasionally.

Since a plugged line is an abnormal condition it must be treated as

unpredictable.

A plug in a line is adhering to the inner surface of the pipe. This blocking

however is not firm and some change in the condition might cause it to

loosen and spray materials out of a previously dear opening. There is always

a hazard associated with the plugged line and care needs to be taken in

dealing with them

Tracing or Jacketing in a line is great help in melting out of a plug. But when

line is opened, the heat applied can cause pressure to build up and hot or

corrosive material to spray out on to anything in its path.

Due to various piping arrangement and materials handled, procedure can

not be set up to handle each specific condition, however, from past

experience we have learned many facts that must be applied when

unplugging lines.

The following are the rules to be followed when performing such a job:

1. Since a plugged is an abnormal condition and unusual hazards might

exit, the job of clearing a line should be preplanned.

2. The procedure outlined shall be to first try to clear the line by applying

a solvent directly in to the closed line. Normally this is done with

steam or water applied to permanent connection of hose.

Compatibility of the de-plugging liquid with the fluid contents

of the pipe should be verified before using the technique

(remember Bhopal)

3. The most effective means of cleaning in this manner is to pressurize

this line & then drain, repeating this process frequently. This cyclic

process helps to clear the clog. It also drains the solution from the

area of the plug facilitating unplugging.

4. Heat should be applied to the outside of the line if it is possible, this

can be in the form of steam tracing or steam applied safely from the

open hose.



5. If the plug does not respond to the above clearing procedure, probably

it will be necessary to dismantle the line.

6. The line must be depressurized as completely as possible.

7. All tracing and jacketing should be shut off and the line allowed to

cool.

8. Since the line may still be under pressure in spots or pockets,

protective equipment must. be worn when parting a line. This

equipment consist of:

a. Protective suit.

b. Face shield over the helmet and glasses (if a full cover one piece

suit is available the same should be used).

c. PVC and gloves.

This equipment is worn to protect against unexpected splashes or

released material.

9. After opening the line, the condition should be considered hazardous,

even if no material is released from the opening.

10. If the cleaning can be carried out by attaching valves and hoses and in

a closed manner the same should be attempted.

11. If the cleaning at the point must be conducted openly it should be

performed by the use of a suitable lance so that close exposure to the

opening is not required. Those performing the lancing operation shall

wear the same protective clothing used in opening the line.

12. In case of fouling / choking of the tubes of heat exchangers, following

is the procedure for caustic cleaning:

a. Isolate the fouled/choked exchanger.

b. Depressurize drain and flush the exchanger.

c. Dismantle the exchanger tube bundles using personnel protective

safety equipment.

d. Carefully put the exchanger tube bundle in caustic cleaning tank

and start heating the caustic by stream coils to 80° - 90°c. Keep

the exchanger bundles soaked for overnight preferable 24 hours.

e. Remove the exchanger carefully after caustic has cooled down.

Use all safety precautions as far as handling not alkalis is



concerned.

f. Flush he exchanger tubes bundles with large quantities of water,

till the entire caustic is washed out.

13. For de-choking of column and in case of partial choking of heat

exchanger tubes:

In process like ACN, suction/discharge lines 2" caustic connections are

provided which are normally kept blinded. In case choking problem is

experienced, a particular type of operation is isolated / by-passed as

per the procedures laid down, then the column drained / flushed out to

toxic sewer. Caustic connection can be made by hose connecting a

loop circulation and established for a period of time till choking is

removed. Than the contents can be drained out in to proper sewer and

flushing with water carried out-This is normally used in case of

polymerized material or fouling material which are responsible for

plugging of process equipments.



9.5 PROCEDURE FOR ISOLATION OF FLARE HEADER, SAFETY

VALVE Etc.

Isolation of Flare Header or Safety Valve connected to flare header requires

special safety precautions due to the following hazards associated with the

job. (Same hazards are present while installing back the isolated valve).

1. Entry of air in the flare header.

2. Fire hazard due to leakage of gases.

3. Inhalation of toxic vapors.

The following safe maintenance procedures are followed for undertaking the

job.

1. Keep the sealing plate (as per figure 1 below) and special bolts ready,

suitable for the size of the flare pipe to be isolated. The special bolts

have a small head, which will pass through the bolt-holes of safety

valve flange, but not through the holes of sealing plate.

2. Keep gaskets, nuts & bolts & proper size of spanners & tools ready for

the job.

3. Rouse one by one all the bolts & nuts of the flange of the pipe.

4. Remove all the bolts marked ‘A’ in Fig. 1 in attached drawing.

5. Slacken the bolts marked 'B' in attached drawing.

6. Quickly insert the sealing plate (shown in Fig. 2) in between the

flanges.

7. Tighten bolt 'B' to stop gas escaping.

8. Insert special bolts in the holes where bolts 'A' were to hold the seal

plate tight to the flare pipeline.

9. When the small bolts are tight remove bolts 'B' Ensure that seal plate is

holding property.

The reverse procedure as mentioned below, is to be followed while removing

slip plate and re-fixing the safety valve:

a) Position safety valve and fix bolts 'B' tightly.

b) Remove all special bolts marked "A".



c) Slacken bolts 'B' to remove slip plate.

d) Remove slip-plates quickly & tighten bolts "B" immediately.

e) Insert & tighten original bolt 'A'.

f) Ensure that no gas leak after tightening.

Special Precautions

Before undertaking removal of S. V., ensure proper access and working

platform or scaffolding.

1. Before isolation or installations work is undertaken of flare header,

ensure that plant operations are smooth (no up sets) and flare

header is on normal load.

2. Isolation & Installation work to be undertaken in the personal

supervision of responsible engineer with minimum two technicians.

3. Ensure flare header under positive pressure.

4. The job is to be undertaken under "Fire -Safety Permit".

5. Make use of Air Line gas Mask/Self contained breathing equipment or

Gas Mask organic canister while removing the bolts and putting the

sealing plate (Select safety equipment as per toxic conditions of

escaping gases).

6. Make use of Brass hammer if required or Non sparking Tools for such

jobs.

7. Do not allow any welding / cutting or spark producing job near by

while the above job is being undertaken.

8. Keep water hose & fire extinguishers ready for use, in case of any

emergency.



9.6 WORK PERMIT SYSTEM

Note:

Work Permit system specified in Oil Industry Safety Directorate guidelines is

reproduced here. The purpose is to familiarize with the work permit system

prevailing in Hydrocarbon industry. The actual formats may vary; however,

the procedure is to be based on the OISD -105 guidelines.

9.6.1 INTRODUCTION

The Work Permit System is an important tool for safety in hydrocarbon

processing / handling. In the following pages the recommended Work Permit

System is described covering various aspects like when a work permit is

required, type of permits, responsibilities, check lists, validity, etc. The

success of a work Permit System depends upon the training, motivation and

participation of all individuals concerned with its implementation. Since

several maintenance / construction jobs are often carried out with

assistance from contractors, it is essential to provide sufficient exposure to

contractor and his employees as well.

If work has to be performed in a hydrocarbon processing / handling

installation by any person other than the operating personnel of that area, a

duly authorized written permit shall be obtained by the person / agency

executing the work before commencement of the work. However, even for

operating personnel, where work has to be performed outside their normal

routine, an exclusive permit to that effect by the authorized person shall be

obtained.

9.6.2 SCOPE

The Work Permit System shall cover all hydrocarbon processing / handling

installations such as onshore / offshore processing platforms, gas treating

units, crude terminals, refineries, pipelines, marketing installations, and LPG

bottling plants.



9.6.3 DEFINITIONS

a) Hot work: Hot work is an activity, which may produce enough heat to

ignite a flammable air hydrocarbon mixture or a flammable substance.

b) Cold Work : Cold Work is an activity which does not produce sufficient

heat to ignite a flammable air hydrocarbon mixture or a flammable

substance.

9.6.4 TYPE OF WORK PERMITS

Two types of permits, one for cold work and the other for hot work, are the

minimum requirements, which must be fulfilled before commencing work.

Based on the nature of the work that is to be undertaken, permit should be

obtained either under Hot Work Permit or Cold Work Permit. For jobs like

excavation, road / dike cutting, electrical lockout / energizing etc. where the

work permit issuing authority may have to take clearances from other

sections / personnel, organizations may introduce supplement formats

for these purposes. If they wish, format for electrical lockout energizing

is given in OISD-Std. 137 (on Inspection of Electrical Equipment).

9.6.5 PROCEDURE FOR WORK PERMIT SYSTEM

Following is the procedure for the implementation of Work Permit System:

a) The Work Permit System shall always operate on Owner / In-charge

concept. (Example : Process Unit - Shift In-charge; Laboratory - Chief

Chemist; Depot - Depot Manager). The concerned management shall

issue the appropriate authority limits for various installations and type

of permits based on this concept.

b) The permit shall be in printed form.

c) Separate forms shall be used for Hot Work and Cold Work.

d) For simplification of procedure, Hot Work Permit also covers

permission for vessel entry, vessel boxing up and excavation. Cold

Work Permit shall cover all activities outside the scope of Hot

Work Permit.

e) No hot / cold work shall be undertaken without a work permit except

in the areas pre-determined and designated by the owner in-charge.

All work permits shall be issued by the person who is designated as



responsible person for the operation of the area where work is to be

carried out. In respect of work permits for handling highly critical

types of work and also for long duration work such as in construction

jobs in a running installation, the authorizing level should be elevated.

f) The work to be done may be planned either departmentally or

through a contractor. In either case, the work permit should be

received and signed by the maintenance project / construction

supervisor of the company as he is responsible for the work of the

contractor also. Where no such independent supervisor exists, for

example in small installations, the owner in-charge can issue the

permit to the contractor's supervisor directly and obtain his signature.

g) Permit should be issued only for a single shift and its validity should

expire at the termination of the shift. However, where the work has to

be continued, the same permit may be revalidated in the succeeding

shift by authorized person, after satisfying the normal checks.

In instances like plant turnaround or an activity where work is of

continuous nature involving round the clock activity, Blanket Hot Work

Permit could be given if the owner in-charge is fully satisfied that the

conditions are totally safe for the multiple jobs to be performed. But

this should not be resorted to, especially in highly integrated units.

Even when construction activity has to be undertaken in non

operating areas in integrated units, it is recommended that approval

be obtained from designated senior management for issuing Blanket

Hot Work Permit.)

h) It is recommended that both Hot Work Permit as well as Cold Work

Permit be made in the form of books with tear off facility. In the case

of Hot Work Permit the authorized Original copy shall be given to the

receiver, the Duplicate to the Fire and Safety Section and Triplicate

retained in the book. In case of Cold Work Permit, the authorized

Original shall be issued to the receiver, retaining the Duplicate in the

book.

It is recommended that plot plans of the installation and the operating



blocks should be displayed in the Fire and concerned Unit Control

Rooms respectively, and site of hot jobs under progress should be

indicated on these plot plans with fed pins. This helps the incoming

supervisor (in Fire and operating departments) to get a quick idea of

the hot jobs being undertaken and help in identifying the areas which

require inspection / attention, depending upon the criticality of the

area and job.

i) As a prerequisite to permit issue, particularly in the case of hot work /

vessel entry permit, gas test for hydrocarbons / oxygen deficiency

toxic gases shall be conducted as applicable.

j) Where gas free conditions are not fully assured for the duration of hot

work, a system of monitoring either by automatic or by manual

periodic verification shall be resorted to depending upon the prevalent

conditions of the operating area.

k) After completion or stoppage of the job, the person to whom the

permit was issued, should thoroughly check the area for clearing of

debris, removal of temporary electrical installations etc., and then

shall sign the work permit and return it to the issuer.

9.6.6 SPECIMEN WORK PERMIT FORMS

Specimen Work Permit forms for the two types of permits illustrating the

suggested colour code, layout, and size are exhibited in pages 5-14 of OISD

105.

9.6.7 EXPLANATORY NOTES TO WORK PERMIT FORMS

The check-listed items in the Work Permit Forms are elaborated below to

amplify the underlying concepts and highlight their significance.

i) Equipment / Area inspected

Equipment or area where work is to be conducted, should be

inspected to ensure that it is safe to carry out work and assess

other safety requirements / stipulations. In case of vessel box-up

permit, the inspection is required to ensure work is complete, all

personnel are out, no maintenance gear is left behind and debris is

removed.



ii) Surrounding area checked / cleaned.

Unsafe conditions for performance of work may arise from

surrounding area. It should be cleaned up to remove flammable

material such as oil, rags, grass.

iii) Sewers, Manholes, CBD etc., and Hot Surfaces covered.

Flammable gases may be released from nearby sewers. Hot

uninsulated surfaces, pipelines may provide a source of ignition.

Therefore, these are to be properly covered to prevent fires.

iv) Considered hazard from other routine / non-routine operations

and persons alerted.

Other activities (routine / non routine) being carried out near by,

which can create conditions which are unsafe for performance of the

permit work, should be taken into consideration and the concerned

persons should be alerted accordingly.

v) Equipment electrically isolated and tagged.

Before issuing permit for mechanical / electrical work in the operating

area, it should be ensured that electrical switches are locked out and

cautionary tags duly signed with date and time are attached.

Wherever local locking arrangement is provided in the field, the same

should be used. Refer format for electrical lockout / energizing given in

OISD-STD- 137 on Inspection of Electrical equipment.

vi) Running water hose / Portable extinguisher provided

Running water hose and portable fire extinguisher are required

respectively to flush / dilute in case of release of any hazardous

chemical or to quench sparks and to put out small fires immediately.

vii) Fire water system checked for readiness

In order to meet any contingency, it should be ensured that the fire

water system including fire water pumps, storage, network, etc. is

checked and kept ready for immediate use.

viii) Equipment blinded / disconnected / closed-isolated / wedged

open

Equipment / Vessel on which Work Permit is being issued, should be

completely isolated from the rest of the plant with which it is

connected during normal operation, in order to ensure that there is no



change in the work environment with respect to presence of toxic /

flammable gases, solids, hazardous chemicals etc., in the course of

the work. Blinding is one of the most effective ways of isolation. Blinds

should be installed as close to the vessel as possible. If lines cannot

be blinded, they should be disconnected and the open ends should be

made safe by installing pipe caps plugs, blind flanges, mud packing

etc.

ix) Equipment properly drained / depressurized

Equipment under pressure should be depressurized after isolation.

This will be followed by draining, purging, water flushing etc., as the

case may be.

Equipment containing liquid hydrocarbons should be drained

completely. There may be a possibility of overlooking liquid collected

in pockets or inaccessible areas such as level gauges, small nozzle-

bleeders on vessels, laterals in pipe work etc. All low point drains

should be in unplugged condition.

x) Equipment properly steamed / purged

Purging of equipment (vessels, pipelines, compressors etc.) is done to

free them of flammable hydrocarbons and toxic gases. Steam is used

for gas-freeing of vessels and pipes in refineries and processing units,

but it may not be available at other locations. Other means of purging

is by displacement with water and final traces of gas removed by air

eductor. All high point vents should be unplugged while purging.

Purging may be done continuously or in batches to conserve purge

medium. It should be done in a systematic manner to cover the entire

equipment/plant and continued till the allowable level of toxic

flammable gas concentration is attained.

xi) Equipment water flushed

Water flushing is an effective means of cooling, cleaning and even

gas-freeing of equipment. It is also employed to remove traces of

acids/chemicals. Equipment metallurgy must be considered before

using sea / saline water. Sometimes flushing with demineralised water

would be necessary depending upon the metallurgy of the equipment

xii) Gas / Oxygen deficiency test done and found OK.

Gas test includes measurement of:



(a) Hydrocarbons by Explosivity Meter

(b) Oxygen Deficiency by Oxygen Meter

(c) Toxic gases like Hydrogen Sulphide, Carbon Monoxide, Nickel

Carbonyl, Chlorine, etc. by techniques like Indicator Tube

method, Lead Acetate Paper etc.

Measurement of Lead in air is required for entering Leaded tanks.

Octal Ethyl regulations are to be followed while handling leaded

gasoline. Gas tests may be specified for vessel entry including open

excavation where head of a man will be below ground level and when

hot work is being carried out. The person carrying out gas test must

wear proper protective gear. No hot work shall be permitted unless

the explosivity meter reading is zero. Vessel entry where no hot work

is to be carried out may be permitted if combustible gases are up to

5% of lower explosivity limit (LEL). Entry with an air supplied mask,

may be permitted with LEL of up to 50%. The oxygen level should be

at least 19.5 % by volume and the concentration of toxic gases below

the threshold limits.

xiii) Shield against sparks provided

In order to protect against welding sparks, which can provide ignition

in operating areas, shields are to be provided. The shield material

should be non-flammable. In case tarpaulins are used, they should be

kept wet with water.

xiv) Proper ventilation and lighting provided

Where natural ventilation is not available, fans / air eductors are

provided. Some types of works like welding, may generate fumes.

Facilities may be required for the speedy dispersal of these fumes.

Only approved reduced voltage extension lights (24 volts) are to be

allowed for work inside vessels, from consideration of personal.

xv) Proper means of exit provided

Proper means of exit is required in case of emergencies developed on

account of the work or otherwise. Availability of an alternate route of

escape should be considered.

xvi) Precautionary tags / boards provided

To prevent any unwarranted entry in the work area and also to

caution other personnel taking actions, which may endanger people



working on the permit job, precautionary tags / boards are to be

provided. Example: "No Entry" sign on roads or "Caution — Men At

Work Inside" on the manhole of a vessel etc.

xvii) Portable equipment / Hose nozzles properly grounded

As a precaution against static electricity generation, portable

equipment hose nozzles, example: nozzle of a sand blasting gun is to

be grounded. Use of hydrocarbon lines for earthing should be avoided.

xviii) Standby person provided for vessel entry

Whenever a vessel is being entered or work is being carried out in

confined space, it may be necessary to keep standby persons

(minimum 2) at the manhole or entry point holding the rope

connected to the safety belt of the person inside. In case of any

emergence inside or outside the vessel, the standby will be able to pull

the person out.

xix) Standby personnel provided for fire watch from Process /

Maintenance / Contractor Fire Department

Depending on criticality of the job work permit issuer shall decide the

type of standby to be provided i.e., from which department, of what

level, how many and also additional fire fighting support facilities.

xx) Iron Sulphide removed / kept wet

Pyrophoric substances may be present in operating area / equipment

handling hydrocarbon. Iron sulphide scale is the most common

pyrophoric substance encountered. These should be either removed to

safe locations or kept wet all the time to prevent their auto-ignition.

xxi) Area cordoned off

In order to prevent the unauthorized entry of people and to avoid

accidents during excavation jobs. work area is to be cordoned off.

xxii) Precaution against public traffic taken

In case hot work is to be carried out in the close proximity of a public

road, for example, in the case of a trunk pipeline, it may be desirable

to block-off / divert public traffic for the duration of the job as a

precautionary measure.

xxiii) Clearance obtained for excavation from Technical / concerned

departments



For any excavation work which may affect underground sewers /

telephone lines / cables / pipelines etc. Technical Services Dept. and /

or other concerned departments should be consulted for obtaining the

co-ordinates and the depth to which excavation can be resorted to

without damaging the existing facilities. Markers should be put around

the area where excavation can be done, and the depth can be

indicated in the work permit.

xxiv) Clearance obtained for road cutting from Technical / Fire /

concerned departments

Since road cutting can hamper the movement of the fire trucks, initial

clearance should be obtained from Fire Department, and final approval

from the higher designated authorities. If the road is wide, preferably

the road should be cut half at a time. Duration of cut road should be

restricted as far as possible.

xxv) Clearance obtained for dyke cutting

When the dyke is cut. Any mishap in the tank farm can lead to a free

flow of oil to outside the bund. A high level authority should be

designated for authorizing dike cutting. Further, it should be ensured

that dike would be reconstructed in the shortest possible time. For

example, if pipes have to be laid through the dikes, the pipes should

be laid quickly and plugged / capped so that the dike can be dosed.

Thereafter, balance of pipe fabrication can continue without any risk.

Standby personnel should be available at the work site, who should

possess a suitable size steel plate for blocking the opening in case of a

mishap / tank failure. If no work is undertaken in evening and night

shifts, invariably the gap should be dosed with steel plate and mud

packing at the end of day's work.

xxvi) Checked the flame arrester on mobile equipment

Although only certified vehicles engines are permitted in operating

areas, it should be ensured that the flame arrester is not inadvertently

removed.

xxvii) Checked for oil / gas trapped behind lining in equipment

Before undertaking hot jobs a check should be done for oil / gas

trapped behind lining in the equipment. Many times oil / gas trapped

behind lining depicts itself in the form of swelling and can be



confirmed h y way of drilling holes.

xxviii) Hot tapping

While it is presumed that modification jobs will be undertaken

always with the approval of the designated authority, it is further to

be noted that hot tapping shall be undertaken only after an

approval by Inspection Personnel. Continuous flow in the line

should be ensured.

9.6.8 E&C WORK PERMIT SYSTEM

E&C division has an elaborate work permit system and has following work

permits:

1. Hot Work Permit

2. Cold Work Permit

3. Confined Space Entry Permit

4. Electrical Lines / Equipment Work Permit

5. Radiography Work Permit.

Formats:

Formats for each type of work permit are reproduced of at the end of this

Chapter.

Validity:

The permit is to be renewed each day only after checking all the compliance

jointly by the E&C Site Engineer and the contractor site-in-charge. The

permit can be renewed for not more than 7 times including the issue date.

Safety Instructions:

Specific Safety Instructions to be followed strictly during the work are

printed on the backside of the work permit and are reproduced here.

Hot Work:

1. Combustible / inflammable materials shall be removed within 30 feet of

the place of the work and also from opposite side of the partition /

structure.

2. Materials which can catch fire / get damaged due to sparks, metal

globules falling on them during Hot Work shall be covered with "Fire



blanket".

3. One DCP type 5 Kg. Capacity portable fire extinguisher shall be kept

near Hot Work Place.

4. All persons engaged in "Hot Work" shall be provided with all necessary

Personal Protective Equipment like; Welding Screen; Asbestos hand

gloves; Safety Shoes; respiratory mask; and Apron and they shall wear

these while working.

5. While doing Hot Work in confined space one stand-by person shall be

kept outside the vessel, to assist in case of emergency, and the

emergency exit shall be kept open.

6. If Hot Work is to be carried on tank / drum which contained explosive

flammable or other dangerous substances then following precautions

shall be taken:

a) Decontaminate the container by steaming or other similar method.

b) Flush / Purge the container with water having detergents.

7. Empty drums shall not be used instead of ladder for standing on it.

8. After completing the Hot Work, materials / substances shall be

removed from the working place.

9. Supervisor shall be available at welding site during the period of work.

10. This permit shall be cancelled if any deficiencies are noticed during the

work.

11. Explosimeter reading shall be taken before starting of hot work and

must be entered in the space provided in the permit.


__________________________________________________Personnel Protective Equipment(PPE) 1

10.0 PERSONNEL PROTECTIVE EQUIPMENTS

INTRODUCTION

In industrial accident prevention, in spite of all the best efforts, there

are some activities where exposure of persons to hazards can only be

minimised but cannot be totally eliminated. Hence there rises a need

for protection of our valuable body parts from injuries, even in case of

such exposure to hazard either due to nature of job or accidental.

Personal protective appliances of various types are now available in

our country and with proper planning, selection, training and use, a lot

of injuries can be avoided. Statistics prove that a high percentage of

all injuries arising out of industrial construction accidents are caused

due to non-compliance of wearing safety equipment.

SELECTION AND USE OF PERSONAL PROTECTIVE APPLIANCES

In order to have the best utilisation of available personal protective

appliances, we should have knowledge and information on the

following:

a) The nature of hazards against which a particular equipment

is required to be used.

b) Standards and occupational safety & health requirements

on various hazards in the work area.

c) Selection, procurement and inspection of different

equipments as per the required quantity.

d) Methods of procuring / maintaining and storing of

equipments.

e) Effective methods of training and motivation of employees,

so that they use as and when required.

TYPES OF PERSONAL PROTECTIVE EQUIPMENT

Personal protective equipments are mainly divided into two main

categories:

(A) Non-Respiratory

(B) Respiratory



10.1 NON-RESPIRATORY

These equipment are used to protect following non-respiratory body

parts

10.1.1 HEAD PROTECTION : INDUSTRIAL SAFETY HELMET:

Presently available with cushioned end adjustable suspension cradles

and two-three different sizes with IS certificates. These helmets are

impact resistant, electrical shock-proof & comparatively light in weight

(400 to 500 gms). This gives protection for common hazard of striking

objects, falling objects as well as chemical splashes.

Up-keep and maintenance

Safety helmets are individually issued to all employees. The

suspension cradles are washable and replaceable. Drilling of holes or

tampering with the shell is unsafe, as this will reduce the strength of

the helmet against impact. For proper fitting and grip, the chin-straps

should also be tied after wearing the helmet.

10.1.2 EYE - PROTECTION :

Industrial eye injuries are caused due to flying objects like chips,

splinters, etc. dusts, liquid chemical splashes, glares due to harmful

radiation etc. Following charts show the requirements of specific type

of goggles / eye protection for specific use:

Types Brief Description

Safely spectacles with Combustion resistant plastic or metal

frame

clear lens with or without side shields and toughened

glass

or plastic lenses.

Recommended use :

Babbiting, butting, chipping, minor dust hazards, grinding machine

shop

operations, spot and butt welding, etc.

Safety spectacles with Combustion resistant plastic or metal

frame

coloured or filter lens with side shield and toughened glass.



Impact goggles Combustion resistant plastic or metal cups,

adjustable nose-bridge. The cups may be

shallow or deep and are shaped to fit the

contours of the face. Clear toughened

glass or

plastic lenses. Ventilation is provided

through

sides of the cup and slots in the lens

retaining

rings.

Recommended use

Chipping, fitting, grinding, riveting, boiler & other fabrication work,

hand & power tools, machine shop operations, wood working, spot

and butt welding, dusts etc.

Welding goggles Combustion resistant plastic cups and

adjustable

nose-bridge. The cups may be shallow or

deep

and are shaped to fit the contours of the

face.

Filter glass of suitable grade has to be

used.

Clear cover glass is provided to protect the

filter

glass from pitting, ventilation is provided

through indirect ports.

Recommended use

Glare, furnace operations, infra red and ultraviolet radiation, molten

and red hot metals, gas welding and cutting etc.

Dust goggles Fabric cups with tufted cord binding to

provide

dust tight fitting. Clear toughened glass or

plastic through the fabric of the cups.



Recommended use

Extremely fine dusts and particles.

Chemical Goggles One piece moulded rubber frame with

rolled

edge for comfortable and air tight fit. Clear

toughened glass or plastic through the

fabric of

the cups.

Recommended use

Acids, caustic and other chemicals, dusts and particles, light impacts

etc.

Eye screens and face shields A single screen suspended in front of

the

face from a head band or cap. The

visor may

be clear or tinted plastic or fine wire

mesh or

a combination of tinted plastic and wire

mesh.

Recommended use

Babbiting, Chemicals, furnace operations spot and butt welding, flying

particles, frontal splashes, glare molten metals etc. and for additional

protection over the goggles-

Welding shields A shell of fibre-glass provided with a

window

for fitting suitable grade of fitter glass

with

clear cover glass to protect the filter

glass

from pitting. The shield may be held in

hand

or suspended in front of the face by a

head



band or bracket on a safety cap. The

shield

can be raised off the face when

protection is

not required and dropped back into

position

by a sharp downward motion of the

wearer's

head.

Recommended use

Arc welding, atomic hydrogen welding.

10.1.3 HAND PROTECTION

About 22% of industrial accidents injure hands.

The following chart gives an idea of how to select the proper type of

gloves for the

specific job and hazard.

HAZARDS MATERIALS

Sustained heat Asbestos

Asbestos reinforced with

leather

Aluminium faced fabric

Sparks Asbestos

Asbestos reinforced with

leather

Fire resistant fabric

Leather

Glass fibre

Hot metal splash Leather

Fire resistant fabric

Glass fibre

Dust Fabric

Coated fabric



Plastic

Natural rubber

Synthetic rubber

Sharp object Fabric

Abrasion Leather

Coated fabric

Teflon

NBR (Nitric Butadiene

Rubber)

Cuts Leather reinforced with

steel

staples

Metal Mesh

Electric Circuit Rubber

Moisture Coated fabric

Natural rubber

Synthetic rubber

Plastic

Glass

fibre

Acids, alkalis and other natural In some cases synthetic

materials

rubber chemicals like neoprene, Teflon etc.

Petroleum products Synthetic rubber, neoprene,

plastic

X-ray Rubber, leather or plastic with

lining.

10.1.4 FOOT & LEG PROTECTION

Manual as well as mechanical handling of materials are part of the

day-to-day industrial activities. The statistics on occupational injuries

show that about 23% of the accidents occur during material handling.



Toe and foot injuries are common in industry while handling materials

or getting struck on obstructions while working.

Adequate foot protection against impact on toes as well as exposure of

foot to chemicals, dusts, dirty materials etc. will go long way in

reducing injuries. Most common foot protection in industries are :

1) Safety shoes and boots

2) Legging

3) Foot guards and leg guards

1) Safety (Toe) Shoes:

They appear just like any other normal leather shoes except for the

additional provision of a concealed steel cap above the toe portions.

This provides additional protection from impact and crushing force. In

few cases a steel innersole is provided for protections against

punctures from nails, glass pieces etc. But, now a days, sturdy rubber

soles are available which serve the above purpose. Common utility of

safety shoes is in construction sites, engineering industries, foundries

as well as chemical operating plants. The soles are also provided with

‘Non-Slip’ strips at the bottom.

2) Natural rubber, synthetic rubber, neoprene or plastic

(PVC) shoes :

These can be with or without (overshoe type) steel toes providing

protection up to ankles knee, or same times up to thigh.

Recommended in construction sites fishing, food processing, chemicals

petroleums, water/ sewage plants, tanneries, breweries, laundries etc.

3) Rubber boots for fire fighting :

These are having felt lining thick clealed soles and metal or wood

shanks to relieve pressure of ladder rungs. They may have steel toe

caps and steel inner soles too.

4) Rubber boots with conductive soles :

These are designed to ground static charges build up in potentially

explosive atmospheres of grain, metal dusts, oil and petroleum,

chemical fumes and vapours, solvent extractions plants. It may be

noted that use of talcum powder on feet and wearing of synthetic fibre

socks will adversely affect the conductivities of the charge.



5) Asbestos overshoes:

These may be with leather sole and recommended for protection

against heat, sparks and for operation at coke, asphalt & steel plants.

6) Leggings:

The leggings may be knee high or hip high or they may be spats which

shield the lower shin, ankle and instep. Knee leggings are held in place

by metal spring clip or may wrapped round the leg and fastened with a

snap button or similar quick release device. Hip leggings are

suspended by straps from waist belt. The spats are generally held in

position by straps. The leggings and spats are made of appropriate

material depending upon the hazard as choosing gloves and shoes.

7) Foot guards & leg guards :

Foot guard is a steel / plastic guard, which may be attached to the

shoe when circumstances require. Foot guard is held in place by a heel

strap. Leg guard is similar to a foot guard. It is a metal sheet, which

protects the skin and ankle. This is strapped to the leg and offers

protection against falling weights & impacts from striking objects.

10.1.5 BODY PROTECTION :

Even after protecting head eyes, face, ears and limbs, some times

injury may occur to the trunk portion of the body. Aprons, overalls

jackets and some time complete head to toe suits are used to protect

the trunk.

Aprons :

These may be bib type, covering the chest, waist, knees, or ankles or

up to waist only. Aprons may be used to protect against heat, sparks,

hot metal splashes, impact cut hazards and liquid splashes or

radiations.

Jackets and coats:

Jackets are for protection of the general upper section of the body.

covering the body and attending to the hips. Coats are longer then

jackets and may be of knee or ankle length.



Complete suits :

These units cover the wearer from head to foot. Generally this consists

of overalls or trousers topped by short jackets and hoods. Suits may

be made of materials such as oiled fabric, plastic coated fabric, glass

fibre, conductive plastic, natural rubber, synthetic coated fabric

asbestos and fire resistant fabric.

10.1.6 EAR PROTECTION :

Continuous exposure to excessive noise can often result in serious

hearing impairment or deafness. High noise levels endured over long

period also result in fatigue, loosening of efficiency and making

persons irritable and may even result in loss of hearing. Hearing loss

varies with the type of exposure and the total duration of exposure. A

committee formed under the American Conference of Government

Industrial Hygienists in USA have agreed to the following points to

establish threshold limit values for noise :

1. Exposure to 90 dBA (i.e. 'A' scale reading of sound level meter)

for an eight hours per day, five days a week is not injurious to

about 90% of the people exposed. It may be stated here that 'A'

scale reading is used for hazard rating only but if studies are

made for the purpose of engineering control, the octave band

analysis should be made of the noise.

2. Equal energy will produce equal damage to the ear. Based on

this assumption if sound level is increased by 3 decibels the

exposure time should be reduced to half. If noise is intermittent,

ear can tolerate more acoustical energy than for a single

exposure to continuous noise.

3. Considering these two factors, the limit is increased to 5 decibels

for each halving of the exposure time.

The following table may be taken as a guide to control the noise

hazard. The

exposure should not exceed the duration shown below against each

sound level:

Duration per day (hours) Sound level (dBA)

8 90

6 92

4 95

3 97



2 100

1½ 102

1 105

¾ 107

½ 110

¼ 115 ceiling value

When noise levels exceed the above values, ear protectors have to be

used.

Common types of ear protectors are ear plugs and ear muffs. Ear

plugs attenuate a large part of the noise when properly fitted in the

outer portion of the ear canal. These are usually made of rubber,

plastic or similar non-porous pliable material. It is important that ear

plugs fit properly and remain correctly seated because even the

slightest leakage will lower the amount of attenuation. Ear plugs if

properly fitted and used, generally reduce noise reaching the ear by

25-30 dB in the higher frequencies, which are more harmful.

EARMUFFS

Earmuffs are designed to cover the external ear. These are suspended

from

adjustable head band or nape bands. The attenuation provided by ear

muffs varies due to difference in size, shape, sealing material, shell

mass and type of suspension. The type of cushion used between the

shell and the head has a great deal to do with attenuation efficiency.

Liquid or grease filled cushions give better results than plastic or foam

rubber type Better type of ear muffs may have 10-15 dB better

attenuation than that of ear plugs.

10.2 RESPIRATORY PROTECTIVE APPLIANCES

INTRODUCTION

There are three modes of entry of matter into human body.

(1) Inhalation through nose / mouth.

(2) Ingestion through mouth.

(3) Skin absorption.

In the simplest physiological term, respiration is "taking oxygen from

atmosphere, converting it into energy by circulation through blood and



venting out carbon dioxide, the by product and waste in this reaction."

The tireless lungs do this function at a rate of 20-24 times a minute

and repeats through out our life term. Since this is such an automatic

function proceeding unknowingly, many of us take it for granted that

there is nothing particular. The fact is reverse. Even a slightest change

in the flow of quality or quantity of air we breathe makes lot of

difference. As we all are aware the air we breathe is a mixture of about

22% oxygen and remaining Nitrogen with traces of carbon dioxide,

moisture, rare gases etc. A difference of 10-12%, oxygen below 20%

for about 6-8 minutes means a difference between life and death. The

chart shown below illustrates this fact in a better way.

Signs and symptoms from reduced level of oxygen in atmosphere are

as below :

% O2 in air Effect

Above 20 Normal

12-15 Muscular co-ordination for skilled

movements is lost.

10-14 Consciousness continues, but

judgement

is faulty and muscular effect leads to

fatigue.

6-8 Collapse occurs rapidly but quick

treatment prevents fatal

outcome.

Below 6 Death occurs in 6-8 minutes.

In a chemical industry where different types of toxic gas, vapours,

dusts, fumes, etc and asphyxiating gases like Nitrogen, Carbon

dioxide, etc. are likely to be present the importance of identifying the

hazards, controlling / confining and using proper effective breathing

protective gears need not be over emphasized.

10.2.1 DESCRIPTION OF HAZARDS :

i) Type of hazard-whether toxic/poisonous or asphyxiating.

Toxic / poisonous - Chlorine Ammonia, Cyanides, hydrocarbon, etc.

which react with blood and makes it impure.



Asphyxiating - Nitrogen, C02 etc. which do not react with blood but

obviously stop the oxidation process in the blood by reducing oxygen

content.

ii) Dusts, fumes, etc

Asbestos, Catalyst fine, Glass-wool Insulation fines, silica, carbon, etc.

which block the respiratory track and deposit foreign particles in the

lungs.

While choosing a personal protective equipment for respiration we

should consider the type of hazards as mentioned above and select

the correct type equipment. Remember using a wrong equipment may

mean immediate danger to life. That is why invariably respiratory

protective equipment are known as emergency equipment also.

10.2.2 DIFFERENT TYPES OF RESPIRATORY SAFETY

EQUIPMENTS

1. Canister type Gas Mask - Mask with separate canisters for

different chemicals, Organics, Acid fumes, Ammonia & Chlorine,

etc.

2. 1 Hr. MSA CHEMOX Mask.

3. ½ Hr. MSA -401 compressed air cylinder breathing apparatus.

4. 10 minutes Escape Mask with compressed air - DRAGER, SABRE

& SCOTT make.

5. Hand operated blower hose mask - MSA make.

6. On-line air hose mask.

7. Resuscitator - both, hand-operated (balloon type) and with

pressurized medical oxygen cylinder.

8. Compressed air Pressurized head to toe suits.

10.2.2.1 Canister Type Gas Mask:

Gas mask gives some emergency protection in the acid gas, organic

vapours and other poisonous gaseous atmosphere. But it does not

provide protection against oxygen deficiency. For most of the hazards

universal gas mask is provided which gives protection against organic

vapours, acid, fumes, fog, rust, etc. For Cl2, NH3 & CO separate gas

mask canisters are available. Gas masks with chemical cartridge for



organic vapours are also available, covering mouth & nose portion,

which is lighter and easy to wear.

Limitations :

i) It shall not be used where oxygen content in the

atmosphere is less than 18% by volume in the air.

ii) The gas mask should not be used where gases are

present at more than 2% by volume or the figure

indicated by the manufacturer.

Operation and Use:

i) Check for proper type of canister to be used.

ii) Remove the seal from the bottom of the canister and put

on the headpiece.

iii) Adjust the head strap until the mask fits closely and

comfortably to avoid leaking.

After Use:

Enter in the card the duration of use of canister Gas Mask.

CAUTION: NEVER USE A CANISTER WHOSE SELF LIFE (MENTIONED

ON

THE SHELL) HAS BEEN EXPIRED.

10.2.2.2 One Hour MSA CHEMOX Breathing Apparatus:

The 'Chemex' oxygen breathing set is a complete independent

breathing

apparatus, which provides oxygen. It can be used for a duration of 60

minutes (1 hour) only.

The chemical filled into the canister comes in contact with moisture

and carbon dioxide in the exhaled breath, removes the carbon dioxide

and provides oxygen for breathing. It can be used in any gaseous

atmosphere containing carbon monoxide. Phosgene, Hydrogen

Sulphide, Chlorine, Ammonia, etc. where normal breathing is

restricted.



Limitations:

1. It has got the service life of maximum one hour.

2. It can be used only at a temp. above 32°F, provided hard

work is not to be performed.

3. It can not be used in the explosive atmosphere where the

auto-ignition temp. is 600°F.

4. This equipment cannot be used under water and in open

fires.

Preparation for use:

Install canister into apparatus before wearing the apparatus.

i) Installing Standard Type Canister:

Be sure that the copper foil seal must be fully exposed before

inserting Canister. Lift up on tip of plastic cap until seal is broken

completely. Remove the remaining of the cap exposing the air

tight copper foil canister seal. With the hand wheel screwed

down far enough for the bail to be swung outward, and insert

canister fully into canister holder with the smooth side to the

front.

It is to be inserted in a way so that the copper foil seal is

punctured and the rubber gasket fits against the V-shaped

recess in the plunger casting. Screw the hand wheel clockwise

until it is tight against the canister.

ii) Remove candle cover by rotating swivel plate 180° Pull swivel

plate down, push cover towards centre of canister and let the

cover dangle. DO NOT PULL LANYARD UNTIL READY FOR

USE.

iii) The canister will produce more oxygen than needed and hence

the breathing bags will become over inflated and resist

exhalation. The excess volume can be vented out by depressing

the button valve on the face piece, but do not over vent.

iv) There are two indications in addition to the timer that the

canister is becoming expended.

a) Fogging of the lenses on inhalation and

b) Increased resistance of exhalation.



If either of these two indications appear, return to fresh air.

The following are the important steps in putting on the apparatus

before entering a toxic atmosphere. It must be put on in fresh air

only.

i) Unfasten and straighten all harness straps.

ii) Hold the apparatus by the plunger casting with one hand. Let

the face piece drop over the hand, holding the apparatus.

iii) With other hand the D-ring assembly where the two large web

straps join and place the breast plate of the canister holder on

the chest. Pass the head through V-shaped opening, formed by

two web straps.

iv) With one hand, continue to hold the apparatus on the chest and

with other hand grasp the free end of the web strap. Bring the

end of the strap under the arm & join with D-ring located on

the top side of the breast plate. Repeat the same for other

strap.

v) Adjust the position of the apparatus on the body in such a way

with the help of metal straps so that when the face piece is put

on, the breathing tubes will permit free head movement.

vi) Join waist strap to the small D-ring, located on the lower comer

of the breast plate and pull up to a "Smart fit".

vii) Grip face piece between thumb and fingers, after pulling out all

the head band straps ends towards buckles. Insert chin welt

into the lower part of the face piece and pull the head-bands,

extreme back over the head and get properly fitted.

viii) This must be done in fresh air.

(a) Pull lanyard straight out away from the body. Removal of

cotter pin fires candle, inflating breathing bag with oxygen

within 15 seconds.

Note : If candle fails to fire, insert new canister.

(b) Starting of the candle may be accompanied by a slight

amount of harmless smoke. The breathing bag will be

inflated with oxygen.

Note: Do not attempt to restart and reuse of any type of

canisters.



The apparatus must always be put on in trash air.

i) Check every part before use.

ii) Use only if you are a trained personnel.

iii) Do not enter any explosive atmosphere where the auto-ignition

temp. is lower than 600° F.

iv) Never allow any substance to enter the neck of the canister,

especially oil, water & gasoline, grease etc.

v) Do not use it in atmosphere where gases and vapours can effect

by skin absorption.

vi) When not in use the apparatus should be kept in the carrying

case provided and canisters should be stored in a dry place.

After Use:

Remove the canister by turning the hand wheel down. Swing bail

outward and remove the canister with the hand suitably protected by a

gloves or other covering since the canister may be hot.

"DO NOT RE-USE THE CANISTER"

To dispose off canister remove out side, punch a small hole in front,

back and bottom, and place in bucket of clean water sufficient deep to

cover the canister at least three inches. When bubbling stops, any

residual oxygen will be dissipated and the canister will be expended.

Pour the residual water, which is caustic, in drain or any other suitable

manner and then discard the canister.

This is having a multi-purpose design, i.e. (1) either direct air supply

can be taken from the outside air line by passing the cylinder or (2) air

can be drawn directly from the cylinder by-passing the air supply line.

In both cases there is an automatic provision of one of the supplies

entering into the breathing mask when the other one fails, either due

to pressure reduction or any other mechanical or instrument failure.

10.2.2.3 1/2 HR. MSA 401 - Compressed Air Cylinder

Breathing Apparatus.

MSA 401, compressed air cylinder breathing apparatus is a complete

independent breathing protection. It can be used in any gas such as

Carbon-Monoxide, Phosgene, Hydrogen Sulphide, Chlorine, Ammonia

etc. where normal breathing is restricted. This apparatus can be used



in the full range of temperature endured by man. It can only be used

for the duration of 30 minutes at 2216 psi. pressure.

Limitations :

i) This equipment can not be used in open fires and under water.

ii) At the full pressure, it can last for 30 minutes only but the

service life may vary or may change on wearer's breathing

condition and the nature of job.

Preparation for Use:

Before use check the following for order.

i) Pressure gauge for full air in the cylinder.

ii) The high pressure tube is securely attached to the regulator and

cylinder valve.

iii) Check Audio-Alarm Device before going to Hazardous Area.

Operation and Use

i) Wear the complete apparatus so as the cylinder should be on

the back and cylinder valve should be in downward position.

ii) Close the by-pass valve (if opened), red hand-wheel on the

demand regulator and then open the cylinder valve fully.

iii) Open fully the yellow valve (Main line) and observe the pressure

gauge on the demand regulator. The pressure should read

approximately 20 Atm if fully charged.

iv) Wear the mask and pull the straps, so mask should be tight fit

on the face.

WARNINGS :

i) To warn the user about the scarcity of air in cylinder, an Audio

Alarm is given. Leave the hazardous area immediately after the

alarm.

ii) Never remove the face piece except in a safe and non-

hazardous and non-toxic atmosphere.

iii) Cylinder is pressurized. In case of fall the cylinder may damage

and it may create a hazard.

10.2.2.4 Escape Mask with Compressed Air

There are three types of different escape masks with compressed air

cylinder which are kept in plant areas. They are as follows :



a) Saver Set (Drager Escape Mask)

b) Sabre Set

c) SKA-PAK Set.

All these sets are having face mask assembly with corrugated tube,

pressure demand regulator & compressed air cylinder. The duration of

first two types of escape mask is 6 minutes and the third one is of 5

minutes duration.

Limitation :

i) It can not be used in open fires and under water.

ii) These equipment are especially meant for escape purpose only

and having short duration.

Operation & Use:

i) Check the cylinder pressure, the condition of corrugated tube,

facemask & headband (all rubber components).

ii) Clean the visor of the facemask with wet handkerchief-

preferably with Dettol.

iii) Put the bag on shoulder, wear the facemask & start respiration.

a) Saver Set: 6 minutes duration; Cylinder pressure : 2840

psi

Special feature : Cylinder valve is not provided on

cylinder. Airflow regulates with the help of high pressure

demand regulator.

b) Sabre Set: 6 minutes duration; Cylinder pressure : 2900

psi

Special feature : It has got a provision (which is

optional) to attach the audio alarm device which operates

when pressure in the cylinder is reduced up to certain

extent. It has also got the additional provision to connect

the 'on line air connection."

c) SKA-PAK Set: 5 minutes duration; cylinder pressure :

2216 psi

Special feature : Additional provision of online air

connection is available.



10.2.2.5 Hand operated Blower Hose Mask (Blowman's

Breathing Apparatus)

These masks are designed to provide fresh air to the wearer from

outside the gaseous area by keeping the air intake end in fresh air.

The use is restricted for a maximum of two hose lines, each originating

at the blower and not exceeding 30 feet length.

Limitation:

There should not be any entanglement of the hose which restricts the

movement of the person.

Points to remember.

i) Blower should be kept in the open atmosphere where

contamination of any dangerous vapours are not present.

ii) Blower must be operated continuously during use of the mask

and the man who operates should not leave the place.

iii) Life line should be provided.

iv) The face piece should be properly adjusted and tested before

using it.

v) The use of this apparatus is restricted for a maximum of two

hose lines, each originating from the blower and not exceeding

30" length.

vi) The proper functioning of the blower to discharge the air is to be

ensured.

vii) Safety harness & belt should be properly fastened to provide

comfortable movement of personnel.

10.2.2.6 On Line Air Hose Mask:

Normally a breathing airline connection from the compressor to the

plant area will be provided. The header pressure of the compressor is

8 to 9 kg/cm3g and at the plant battery limit is normally 1.5 kg/cm3g.

Tapping is taken to concern plant areas. At the end of the service air

line, an assembly known as the norozen filter along with pressure

indicator is provided. To this assembly, a provision of two ½" dia.

tappings is made with quick fix / release coupling 'Female end'.

In the plant areas where these facilities are provided, the following

assemblies are available:



i) Face mask with headbands and a corrugated tube with

couplings.

ii) An air line regulator along with leather belt & the upstream

of the regulator is fitted with the coupling & corrugated

tube & the downstream with a rubber tubing of 3/8" dia.

The length of the rubber tubing is generally 15 to 30 Mts.

and the end of the tubing is provided with a 'Male end' of

the quick fix / release coupling.

Use:

i) Push the 'Male end' of quick fix coupling into the

'Female end'.

ii) Open the isolation valve.

iii) Wear the mask.

Limitation :

This is not a completely dependent system.

10.2.2.7 Resuscitator:

To restore normal breathing when accidents or illness interferes with

respiration, two different devices / equipments are used. They are as

follows:

a) LA-IF resuscitator.

b) Pneolator.

a) LA - IF resuscitator :

This is a bellow type hand operated equipment used for giving artificial

respiration. It has also got a provision at one end of the aspirator bulb,

to connect extra 02 cylinder so that pure oxygen can also be

administered.

Limitation :

i) Limited quantity of air-blow can be achieved.

ii) Continuous manual administering of compressed air is

required without any interruption.

Operation and use:

i) Before use, remove the air from the aspirator bulb by

squeezing it. Repeat the same 2 to 3 times.



ii) Squeeze the aspirator bulb, by holding the mouth piece on

victim's mouth. Remove it for victim's exhalation. Repeat

the procedure.

Precaution :

The aspirator bulb should be checked and cleaned prior to use of

equipment.

b) Pneolator:

Introduction:

Pneolator is an instrument that automatically performs artificial

respiration with a gentle predetermined pressure on inhalation and

without suction on exhalation. When the victim is breathing, this

instrument is very much effective for applying Oxygen by a simple

adjustment. If the air passage is obstructed by mucous or any foreign

material, immediately a warning is given by a chattering sound from

the valve. This obstruction can be removed by using the ejector

provided with the Pneolator.

Operating instructions (for the non-breathing victim) :

i) Open the lid of the case and turn on cylinder valve

fully.

ii) Remove cycling valve assembly from holder and

select and attach the proper size of mask.

iii) Turn the pressure adjusting knob, so that the low

pressure gauge needle is set (at Infant, Child or

Adult) as required. The pressure increases as the

knob is turned anti-clockwise.

iv) Place the mask on the victim's face holding it

secured, so that air tight seal is obtained. The

exhalation valve cover murt be hand tight for the

purpose of cycling valve.

Caution:

i) The use of Aspirator and Airways by laymen is

subject to a difference of opinion medically.

Therefore the Aspirator of the airways should be



used only with approval of a physician and subject

to his instructions.

ii) Replace the mask on victim and continue the

artificial respiration until breathing is re-established.

Operating Instructions ( for the breathing victim ) :

If the victim is breathing when the Pneolator arrives after the

restoration of breathing on a non-breathing victim, Oxygen should be

administered for therapeutic support until a physician decides it is no

longer necessary. Turn the pressure adjusting knob so that low

pressure gauge needle is set at "ASSISTER" position. This provides a

small constant flow of Oxygen at a slight positive pressure so that

easier breathing results. Whenever more Oxygen than the constant

flow is delivered, he automatically obtains all the desired Oxygen by

actuating the inhalator valve.

10.2.2.8 Pressurised Head-to-Toe Suits :

Special pressurised head-to-toe suits are provided in plant areas,

which can protect the external body parts as well as internal

respiratory system. These are commonly used during the maintenance

and repair jobs for the acids, caustic, chemical vapour service. Mainly

two types of chemical resistance air pressurised head-to-toe suits are

used, namely "Class C Suit" and "Class D Suit".

Class C Suit:

This is a gralite mode synthetic rubber air pressure suit made for

corrosive acids and hydrocarbon services.

Class D Suit:

Two types of Class D type suits are available :

a) It is complete air fed PVC suit made of double coated thick and

flexible PVC to resist hydrofluoric acid. The suit comprises of

jacket, combined with hood and pant having air line regulator

connection.

b) It is a complete air fed suit made up from Butyl coated nylon

fabric to be impervious to liquids and vapours. It covers neck-to-

toe and has got a separate provision of chemical resistance hood.


__________________________________________________Gas Detection Devices 1

11.0 GAS TESTING / DETECTION DEVICES

General

Besides the fixed installations for identifying, monitoring and

controlling hazards such as flammability, toxicity and Oxygen

deficiency, portable and robust instruments are needed during the

commissioning period as well.

Various types of portable instruments such as Explosive meter, Toxic

Gas detector are available. They are to periodically checked and

ensured that they are in good working conditions, before being put

into actual use by the commissioning team.

11.1 COMBUSTIBLE / EXPLOSIVE GAS DETECTOR

For detection of combustible gases, the instrument known as the

Explosimeter is used. It is an instrument by means of which an area /

atmosphere can be conveniently and quickly tested for the presence of

combustible gases / vapours within their flammable limits.

For areas of Hydrogen / Hydrocarbon and pure oxygen mixtures, the

instrument should be ordered specific as per the requirement. They

should be weather proof and pertaining to the Hydrogen / Hydrocarbon

ambience requirement.

Few Important Hints:

a) The instrument assembly, sampling line and the aspirator bulb

assembly should be proof and tested before each set of

sampling.

b) Always keep the sampling line combustion chamber free of

choking.

c) Never dip the -sampling tube into a liquid and always use a flash

trap assembly.

d) Check the instrument whether in use or not at least once in a day.

e) Replace the battery cells immediately if found leaky.

f) While in doubt, have the instrument serviced and calibrated.


__________________________________________________Gas Detection Devices 2

Technical Brochure and the operating instruction sheet for the

combustible gas detector available with the safety cell is enclosed here

11.2 TOXIC GAS DETECTORS

Accurate measurement of toxic gases and vapours present at very low

concentrations (ppm) is necessary for monitoring of plant / work areas

and confined spaces before jobs are taken up. The toxic gas detectors

helps us in knowing the concentrations of the given chemical, which

can be matched against the Threshold Limit Value of that chemical,

based on which we can judge whether it is safe for routine operations /

work / maintenance requirements etc.

Each detector tube packet comes with an instructions sheet and

readings and interpretations done exactly as per the same.

11.3 OXYGEN DEFICIENCY INSTRUMENTS

Prior oxygen measurement in areas suspected to be deficient in

oxygen, like process vessels, pits, tanks and other confined areas

which are to be worked on is a mandatory safety requirement before

authorizing the work. Even after commencement of jobs this should be

repeated at regular intervals to ensure oxygen content is a minimum

of 18% by volume in the areas where work is going on. Before the

usage of the instrument, it should be checked for the calibration.

Technical Brochure and the operating instruction sheet for the oxygen

level monitor available with the safety cell is enclosed here.

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