Dr. Asit Patra-dmi.cra (1)

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Application of Consequence Analysis

and Risk Assessment in ERDMP

Dr. Asit K Patra

Disaster Management Institute

Bhopal


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What we do in Consequence Analysis

Consequence Analysis --- an analytical approach used

to determ ine the poss ible phys ical effects resulting fromthe release of a hazardous substance.

Source term modelling -- Estimation of the source term --

how much mater ial in what form(gas/liquid/two-phase)is being released

Hazard modelling -- Estimation of the hazard level as a

function of time and at selected receptor locations.

Vulnerability modelling --- Estimation of damage level on

the selected receptor, based on the hazard level at the

receptor location.


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1. Discharge Models: Loss of containment/Release

scenarios.

2. Dispersion Models: Transport and dispersion of

released flammable/Explosive/toxic chemicals.

3. Consequence/Effect models: Effect on people,

property and environment.

What we do in Consequence Analysis*****Contd.


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(A) Liquid Discharges

* Hole in atmospheric storage tank or other atmospheric

storage vessel or pipe under liquid head.

* Hole in vessel or pipe containing pressurized liquid

below its normal boiling point.

(B) Gas Discharges

* Hole in equipment (pipe, vessel) containing gas under

pressure

* Relief valve discharge (of vapour only)

Contd..

Typical Release Scenarios


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*Evaporation from liquid pool (e.g., naptha, heavy cut

etc.)

*Relief valve discharge from top of pressurized storagetank

* Generation of toxic combustion products as a result of

fire

(C) Two-Phase Discharges

*Hole inpressurized storage tank or pipe containing a

liquid above its normal boiling point.

* Relief valve discharge (e.g., due to a runaway reaction or

foaming liquid)


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.... .. .

++++++++++++++++

+++++++++++++++++++++++

++++++++++++++++

Leak

Aerosol

TBOILING POINT< T AMBIENT

Pool Spread

BoilingPool

Flash

Example: Super-heated release (Release of Liquid Chlorine)

Tank with

liquid


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EXAMPLERELEASE OF PRESSURISED

GAS

Release

Jet fire

No ignitionSafe dispersion

Ignition

Delayed

ignition

Immediate

ignition

Open

atmosphere

Congested atmosphere Vapour cloudexplosion

Flash fire


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EXAMPLERELEASE OF A REFRIGERATED

LIQUEFIED GAS

Release

Pool fire


Ignition

Delayed

ignition

Immediate

ignition

Open

atmosphere

Congested atmosphere Vapour cloudexplosion

Flash fire


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EXAMPLEEVENT TREE FOR RELEASING OF

LIQUEFIED GAS UNDER PRESSURE

Release


Ignition

Delayed

ignition

Openatmosphere

Congested atmosphereVCE

Flash fire

Immediate

ignition

No cooling

CoolingJet fire

BLEVE


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Atmospheric Dispersion

The process of dilution of a hazardous substance by the

surrounding fluid.Initial Acceleration

& Dilution Internal Negative

Buoyancy

Ambient

Turbulence

Source Emission Transition to Ambient Turbulence


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Wind speed & direction:Dilutes the released chemical and then it

spreads along the wind direction.

Thermal stability: Stable (E - F), Neutral(D) and Unstable (A-C)

Temperature Inversion: Suppress the movement of toxic cloud.

Factors Affecting Transport and Dispersal of toxic chemicals


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Procedures : CA

Two types of analysisthat make up an

Consequence Analysis (CA):

(i) Worst Case Release Scenario Analysis

(WCRSA): how far away -------

the worst possibleaccident release

scenario .

(ii) Alternative Case Release Scenario

Analysis (ACRSA): circumstances that

are more likely to occur accidentally.


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Scenario:Jet Fire Scenario of Natural Gas while being

transported through underground pipeline

Pipe Diameter: 20 inches Pipe Length: 10 Km

Pipe Press: 500 psia Pipe Temperature: 35 C

Wind: 5 meters/second Ground Roughness: Industrial

Air Temperature: 35 C Stability Class: DRelative Humidity: 70%

*******************************************************

THREAT ZONE:

Threat Modeled: Thermal radiation from jet fire

4.5 Kw/m2 (Blue Zone) 168

12.5 Kw/m2 (Orange Zone) 99

37.5 Kw/m2 (Red Zone) 45 meters

Consequence Analysis


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Scenario:Catastrophic rupture of a Naptha storage tank: Pool Fire

Chemical details:* Capacity of tank = 950 m3. * Density at 20OC = 0.93 g/ml.

* Dyke Dimension: 40.5 m x 36.25 m

* Storage Conditions: Atmospheric.

* LFL/LEL = 1% by volume of air.

Table 1: Maximum affected distances (in meter) for Pool fire

scenarios under D class with wind speed of 5.0 m/s

Thermal radiation Affected Distance in Metre from Poollevels for Fire

4.5 Kw/m2 (Blue Zone) 69

12.5 Kw/m2 (Orange Zone) 24

37.5 Kw/m2 (Red Zone) Not Reached

Consequence Analysis using SAFETI Micro


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Case Study: Consequence and Risk Analysis of

Natural Gas Release scenarios (TransportationMode: Underground Pipeline)


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Analysis identifies release of NG due to two events(i) Rupture of pipeline.

(ii) Hole in the pipeline.

Consequences

1. Jet FireMost Credible release Scenario

2. Vapour cloud ExplosionCredible Scenarios

3. Flash fire - Credible Scenarios

4. FireballNot possible

5. Pool FireNot possible

Identification of Hazards

FMEA M d C d C


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FMEA: Mode, Causes and Consequences.


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** Normally Fire ball scenario is not expected. Its

frequency of occurrence is low.

** Jet fireand flash fireare the credible scenarios with

sufficient frequencies of occurrences.

** VCE chances are considered as only 10% and

remaining 90% cases results in flash fire incidents.

Failure Frequency Assessment: Pipeline and Scenarios


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Probability of Ignition

Leak Size Ignition Probability

10 mm20 mm (Small Leak) -------- 0.01 0.03

~ 50 mm (Medium Leak) --------------- 0.07

Full Bore Rupture ------------------------ 0.3

E t t f h d i id t t f NG i li


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Event tree for hazardous incident outcomes of NG pipeline

SELECTION OF MAXIMUM CREDIBLE LOSS


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SCENARIOS

Maximum pipeline length in between twosectionalizing valves = 32 km with 20 inches diameter.

Worst-case Scenario: Full bore rupture

Alternative-case Scenario: Release through Leak sizes

of 20 mm (small hole) and 40 mm (medium hole).

Operating Pressure = 37 kgf/cm2

Volume pack in the line= 232736 m3= 180131 kg.



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SCENARIOS

Other Input Parameters

Average temperature = 30OC

Average relative humidity = 70%

Wind speeds = 1.5 m/s to 5 m/s

Atmospheric Stability = B, D and F

Angles of release for jet fire scenario: 45Oand 90Oto

the pipeline.


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CONSEQUENCE ANALYSIS RESULTS:FIRE


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Radiation radii of jet fire for rupture of pipeline when

the angle of release is 90 degree with the pipeline.


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Overpressure radii of vapour cloud explosion of NG for

rupture of pipeline when the angle of release is 90 degree

with the pipeline.


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Pipeline Risk = Linear Risk

Risk contours for a pipeline = Risk transects = Risk at

given transverse distances from the pipeline.

Pipeline Risk

POPULATION DENSITY USED IN RISK


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POPULATION DENSITY USED IN RISK

CALCULATION


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FATALITY RISK TRANSECT OF PIPELINE

Outcome of Consequence &


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Outcome of Consequence &

Risk Analysis

(a) Maximum loss scenarios

(b) Consequences in terms of Heat radiation, Over

pressure and intoxication.

Identification of vulnerable zones and

classification of unitswhich have the potential forcreating an off-site emergency.

(d)Identification of important facilities which are

coming into the vulnerable zones.

DMI


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Concern for man himself and his

safetymust always form the chief

interest of all technical endeavours.

Never forget this in the midst of your

diagrams and equations.

------ Einstein.

DMI


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For Further Information, Please contact:

[email protected]

Thanks

DMIInfrastructures required


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. Complete Inventoryof hazardous processes, chemicals,

details of storage (T, P, type of vessel etc.) etc.

. Expert professionalshaving thorough understanding of

the process thermodynamics and atmospheric dispersion.

. Meteorological data and knowledge of stability classes.

. Relevant Softwareto predict vulnerable zones

DMIInfrastructures requiredfor Consequence/Risk

Analysis


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Part I: Baseline Information

Consequence Analysis --- an analytical approach used todetermine the possible physical effects resulting from the

release of a hazardous substance.

The credibility of any given modelling result depends upon the

credibility of the release scenario (hazardous event) chosen,

the supporting assumptions made in the analysis and the

technical merits of the model itself.

A good understanding of the underlying physics of the

scenario is essential to the success of model selection.


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MAJOR INDUSTRIAL ESTATES IN MADHYA

PRADESH

Hazard modelling ---Estimation of the hazard level as a function of

time and at selected receptor locations.

Estimation of:

Thermal radiation flux for fires (for a jet fire, pool fire, or fireball)

Overpressure for explosions (for a confined explosion, boiling

liquid expanding vapour explosion [BLEVE], or vapour cloud

explosion (VCE)

* Ambient concentrations for a toxic or flammable gas release (for

modelling the effects of a toxic cloud or flash fire),


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MAJOR INDUSTRIAL ESTATES IN MADHYA

PRADESH

Vulnerability modelling --- Estimation of damage

level on the selected receptor, based on the hazard

level at the receptor location.

L i Di f C /Ri k A l i

DMI


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Logic Diagram for Consequence /Risk Analysis

Release of Hazardous Substance

Discharge & Dispersion Models

Explosion & Fire Models

Consequence Models

Risk Calculation

Flammable Release

Toxic Release

Mitigation

Factors

B i f D i ti f ABCD i li


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Brief Description of ABCD pipeline

MODE:ABCD receives natural gas from Oil India Ltd.

through a 200 km underground pipelinestarting from A to D.

The pipelines are of level PSL 2 as per API 5L.

OPERATING CONDITIONS: The maximum operating

pressure and temperature at the pipeline is 45 kgf/cm2and

60OC respectively with the design pressure of 92 kgf/cm2.

PIPELINE ROUTE DESCRIPTION WITH FACILITIES:

(i) ABCD starts at the A dispatch station located near Oil India

Ltd. well No. 50 .


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Brief Description of ABCD

(ii) From dispatch section, the ABCD goes to 22 km with 20

pipeline. One sectionalizing valve station (SV1) is installed inthis section. The river R1 with a width of 517 m is situated at a

distance of 9.0 km from dispatch section.

(iii) From SV1, ABCD goes on to a distance of 31 km with 20pipeline. One sectionalizing valve station (SV2)is installed.

(iv) From SV2, the pipeline system goes on to a distance of 23

km with 20pipeline. One sectionalizing valve station (SV3) isinstalled.There are two rivers river R2 with width of 90 m

and R3 with width of 120 m - located at the distances of 6 km

and 12 km respectively from SV2.


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(v) From SV3, ABCD goes on to a distance of 25 km with 20

pipeline. One intermediate pigging station (IP1) is installed.

The river R4 with width of 65 m is situated at a distance of 12.5

km in this section from SV3.

(vi) From IP1, the pipeline system, goes on to a distance of 24

km with 20pipeline. One sectionalizing valve station (SV4) is

installed.

(vii) From SV4, ABCD goes on to a distance of 23 km with 20

pipeline. One sectionalizing valve station (SV5) is installed. The

river R5 with width of 60 m is situated at a distance of 2.5 km

in this section from SV5.


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(viii) From SV5, ABCD goes on to a distance of 32 km with 20

pipeline. One intermediate pigging station (IP2) is installed.

This is the longest stretch in between two sectionalizing valves.

(ix) From IP2, the pipeline system, goes on to a distance of 14

km with 16pipeline. The receiving station at D is installed in

this section.The river R6 with width of 160 m is situated at a

distance of 10 km in this section.

(x) The receiving station of D refinery is the end point of

ABCD.



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(i) Manufacture, Storage and Import of Hazardous

Chemicals (MS& IHC) Rules of 1989 as amended in2000 of Environment (Protection) Act of 1986, Govt.

of India.

(ii) Failure Mode and Effect Analysis (FMEA)

Id tifi ti f H d MS&IHC R l


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Identification of Hazards as per MS&IHC Rules

Hazards of NG: The natural gas to be transported by the pipelines

predominantly contains methane (around 92%). Other components

of the gas include ethane, propane and butane. As per the MS&IHC

Rules 1989 as amended in 2000, methane comes under Flammable

gascategory. Its Lower Flammability/Explosivity Level (LFL/LEL)is 5% and upper level range (UFL/UEL) is 15% by volume of air. Its

flash point is -188OC.

The minimum ignition energy for pure Methane at atmospherepressure is 0.29 mJ, which is very low when compared to static

discharge of 22 mJ (on walking) or ordinary spark plug discharge of

25 mJ. Hence ignition can occur at any time during the gas release.


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References

1. Loss Prevention in Chemical Process Industries. Volume

1, 2 & 3. by F. P. Lees, 1996. Butterworth Publications.

2. Guidelines for Chemical Process Quantitative Risk

Analysis. 2ndEdition, CCPS, AIChE, 2000.


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CONSEQUENCE ANALYSIS RESULTS:VCE


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CONSEQUENCE ANALYSIS RESULTS:VCE


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Pipeline Risk = Linear Risk

Risk follows the entire pipeline length, in contrast to a fixedhazardous facility, where the risk extends only to a

limited distance from the facility.

Risk contours for a pipeline are represented as running parallel

to the pipeline. Risk levels for linear risks are often presented

in the form of risk transects, showing the risk at given

transverse distances from the pipeline

Pipeline Risk

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