GEST 73 25 Edition 10

TRANSPORT OF CHLORINE

BY PIPELINE OUTSIDE SITE BOUNDARIES

GEST 73/25

10th Edition

June 2009

EURO CHLOR PUBLICATION

This document can be obtained from:

EURO CHLOR - Avenue E. Van Nieuwenhuyse 4, Box 2 - B-1160 BRUSSELS Telephone: 32-(0)2-676 72 65 - Telefax: 32-(0)2-676 72 41

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June 2009 Page 2 of 22

Euro Chlor

Euro Chlor is the European federation which represents the producers of chlorine and its primary derivatives.

Euro Chlor is working to:

improve awareness and understanding of the contribution that chlorine chemistry has made to the thousands of products, which have improved our health, nutrition, standard of living and quality of life;

maintain open and timely dialogue with regulators, politicians, scientists, the media and other interested stakeholders in the debate on chlorine;

ensure our industry contributes actively to any public, regulatory or scientific debate and provides balanced and objective science-based information to help answer questions about chlorine and its derivatives;

promote the best safety, health and environmental practices in the manufacture, handling and use of chlor-alkali products in order to assist our members in achieving continuous improvements (Responsible Care).

***********

This document has been produced by the members of Euro Chlor and should not be reproduced in whole or in part without the prior written consent of Euro Chlor.

It is intended to give only guidelines and recommendations. The information is provided in good

faith and was based on the best information available at the time of publication. The information is to be relied upon at the user’s own risk. Euro Chlor and its members make no guarantee and

assume no liability whatsoever for the use and the interpretation of or the reliance on any of the information provided.

This document was originally prepared in English by our technical experts. For our members’ convenience, it may have been translated into other EU languages by translators / Euro Chlor members. Although every effort was made to ensure that the translations were accurate, Euro

Chlor shall not be liable for any losses of accuracy or information due to the translation process.

Prior to 1990, Euro Chlor’s technical activities took place under the name BITC (Bureau International Technique du Chlore). References to BITC documents may be assumed to be to

Euro Chlor documents.

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RESPONSIBLE CARE IN ACTION

Chlorine is essential in the chemical industry and consequently there is a need for chlorine to be produced, stored, transported and used. The chlorine industry has co-operated over many years to ensure the well-being of its employees, local communities and the wider environment. This document is one in a series which the European producers, acting through Euro Chlor, have drawn up to promote continuous improvement in the general standards of health, safety and the environment associated with chlorine manufacture in the spirit of Responsible Care.

The voluntary recommendations, techniques and standards presented in these documents are based on the experiences and best practices adopted by member companies of Euro Chlor at their date of issue. They can be taken into account in full or partly, whenever companies decide it individually,in the operation of existing processes and in the design of new installations. They are in no way intended as a substitute for the relevant national or international regulations which should be fully complied with.

It has been assumed in the preparation of these publications that the users will ensure that the contents are relevant to the application selected and are correctly applied by appropriately qualified and experienced people for whose guidance they have been prepared. The contents are based on the most authoritative information available at the time of writing and on good engineering, medical or technical practice but it is essential to take account of appropriate subsequent developments or legislation. As a result, the text may be modified in the future to incorporate evolution of these and other factors.

This edition of the document has been drawn up by the GEST Working Group to whom all suggestions concerning possible revision should be addressed through the offices of Euro Chlor.

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SUMMARY OF THE MAIN MODIFICATIONS

Section Nature

7.5. Modification of the maximum of hydrogen concentration in chlorne

TABLE OF CONTENTS

1 DEFINITIONS......................................................................................................... 6

2 GENERAL STATEMENTS .................................................................................. 6

2.1 LIQUID PHASE ..................................................................................... 6 2.2 GASEOUS PHASE ................................................................................. 7 2.3 CHOICE OF PHASE .............................................................................. 7

3 BASIC DESIGN AND INSTALLATION ............................................................. 7

4 CONSTRUCTION AND DESIGN ....................................................................... 8

4.1 DESIGN PRESSURE ............................................................................. 8

4.2 DESIGN TEMPERATURE .................................................................... 8 4.3 FLUID VELOCITIES ............................................................................. 9

4.4 CORROSION ALLOWANCE ............................................................... 9 4.5 RADIUS OF CURVATURE .................................................................. 9

4.6 THERMAL INSULATION .................................................................... 9 4.7 TRACE HEATING OF CHLORINE GAS PIPELINE .......................... 9

4.8 MATERIALS OF CONSTRUCTION .................................................. 10

Piping 10

Flanges, nuts and bolts 10

Gaskets 11

Thermal insulation 11 4.9 SUPPORTS ........................................................................................... 11

Buried pipeline 11

Pipelines above-ground or in trenches 11

5 INSPECTION AND TESTING ........................................................................... 12

5.1 INSPECTION OF PIPING MATERIALS ............................................ 12 5.2 INSPECTION PROCEDURES DURING CONSTRUCTION ............ 12

6 ACCESSORIES ................................................................................................... 12

6.1 FLANGES, BRANCHES AND ANCILLARY EQUIPMENT ............ 12

6.2 END CONNECTION VALVES ........................................................... 13 6.3 ISOLATION VALVES ......................................................................... 13 6.4 EMPTYING, VENTING AND PURGING .......................................... 13

6.5 TRANSFER EQUIPMENT .................................................................. 14 6.6 PROTECTION AGAINST OVERPRESSURE AND THERMAL

EXPANSION ...................................................................................................... 14 6.7 PROTECTION AGAINST SURGE FOR LIQUID CHLORINE ......... 15

6.8 PROTECTION AGAINST CORROSION ........................................... 15

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6.9 EQUIPMENT FOR MEASUREMENT AND MONITORING THE

CONDITION OF THE PIPELINE ...................................................................... 16 6.10 MALOPERATION MEASURES/PROCEDURES .............................. 16

7 OPERATION ........................................................................................................ 16

7.1 CLEANING AND DRYING BEFORE PUTTING INTO SERVICE.. 16 7.2 LEAK TESTING ................................................................................... 17

7.3 COMMISSIONING AND TESTING BEFORE PUTTING INTO

SERVICE ............................................................................................................ 17 7.4 TAKING THE PIPELINE OUT OF SERVICE ................................... 17 7.5 QUALITY OF THE CHLORINE INTRODUCED .............................. 18 7.6 PRECAUTIONS AGAINST INGRESS OF MOISTURE OR OTHER

REACTIVE MATERIALS ................................................................................. 19 7.7 PRECAUTIONS IN THE EVENT OF FAILURE OF THE TRACE

HEATING (FOR GAS PIPELINE)..................................................................... 19 7.8 PERIODICAL INSPECTION AND TESTING ................................... 19 7.9 EMERGENCY PROCEDURES AND TRAINING ............................. 20

8 REFERENCES .................................................................................................... 21

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1 DEFINITIONS

This code of practice concerns the transfer of dry gaseous or liquid chlorine by “long distance” pipelines. These are defined as pipelines which pass outside of the limits of a chlorine producer or consumer site boundary.

2 GENERAL STATEMENTS

Chlorine can be transported safely by a long pipeline, either in the gas or liquid phase, provided the appropriate design and operating conditions are satisfied. All precautions should be taken such that, in a pipeline designed to carry only liquid chlorine, vaporisation cannot occur, and in a pipeline designed for the transport of only chlorine gas, nothing should lead to the formation of liquid. In each case, specific precautions are required. These are described for both states within this recommendation.

I some exceptional circumstances gaseous chlorine pipelines have been designed to accept some partial liquefaction in function of the physical conditions; in this case the construction and the operation procedures have to take all necessary precautions to cope with the phenomena, and especially:

Minimum design temperature and material of piping,

Thermal expansion of trapped liquid chlorine,

Drain tank for rapid emptying of the chlorine,

Maximum velocity of the fluid.

This very specific case is not considered in this recommendation.

2.1 Liquid phase

The design and operation of liquid phase pipelines must consider at least the following issues:

The maximum transfer pressure which is technically achievable.

The temperature and pressure of the chlorine at the inlet and exit of the pipeline in order to ensure continuity of the liquid phase.

A maximum linear velocity.

Total pressure drop.

Safety protection against surge.

Quantity of chlorine contained in the pipeline may conflict with individual and societal risk contours.

The above will determine the length and throughput of a particular pipeline system, as pumping stations outside the confines of a chlorine-producing or

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consuming factory are not recommended. In Europe, there are many years experience of liquid phase pipelines up to a length of about 8 km with inlet pressures up to about 30 bars (a).

2.2 Gaseous phase

The design and operation of gas phase pipeline systems must consider at least the following issues:

The maximum inlet pressure technically achievable.

The risk of liquefaction associated with either the operating pressure or a fall in temperature.

The maximum temperature of the trace heating system in all circumstances, particularly in the event of zero flow.

The total pressure drop.

The quantity of chlorine contained in the system.

In Europe, there are many years experience with gas phase pipelines up to a length of 4 km and with inlet pressures up to 6 bars absolute.

2.3 Choice of phase

The choice of phase is determined by the requirements of the user plants and by safety considerations.

3 BASIC DESIGN AND INSTALLATION

The pipeline should be protected from all risks of external fire or explosion, whether such risk exists at the time of installation of the pipeline or is brought about by subsequent installations. All other external risks to the pipeline (corrosion …) should also be avoided, for example due to the proximity of another pipeline or of high-voltage electric cables. If the pipeline is an above-ground installation and capable of inspection, it should be protected from any risk of mechanical damage such as falling objects, traffic etc.

If a pipeline is laid in a pipe trench, it must be provided with sufficient support, together with drain provisions to remove rain- and drainwater, or possible corrosive liquids from the trench. The trench should also permit access for inspection of the pipeline.

For liquid chlorine, the use of buried pipelines can be the most reliable depending upon local circumstances, and in many cases this will be the preferred solution.

For gaseous chlorine, a buried pipeline should be considered where operating conditions do not necessitate either trace heating or thermal insulation to avoid risk of liquefaction; this means only in circumstances where the pipeline is operated at a sufficiently low pressure.

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Where the pipeline is buried, the route of the pipeline should be well indicated at the surface, and it should be protected against any unauthorised excavation, by some form of below ground indicator (for example concrete slabs marked "buried pipeline").

Dividing a liquid chlorine pipeline into smaller segments with automatic isolation valves, in order to improve safety, is not recommended.

For gaseous chlorine, the need for rapidly closing (automatic or remotely controlled) isolation valves along the length of the pipeline is related to its length and to the quantity of chlorine held up in the pipeline. For safety considerations, the maximum quantity of chlorine accepted between two isolation valves should be related to the location of the pipeline (safety study).

In both cases, such valves represent a weak point in the construction of the pipeline, adding the supplementary risk, for liquid chlorine, of trapping liquid between two closed valves with possible thermal expansion thereafter (necessity to install special protection and possibility to connect to absorption system for each section). Therefore, it is recommanded to avoid such isolation valves outside the confines of industrial premises.

The in- and outlet of the pipeline will be equipped with isolation valves (taking into account the risk of surge for liquid chlorine), and at least one of the extremities will be connected, via remotely operated valve, to a degassing system (with surge tank for liquid chlorine) and chlorine absorption facility. This will allow safe depressurisation of the pipeline in case of an incident.

4 CONSTRUCTION AND DESIGN

The quality of construction is the most important safety consideration.

4.1 Design Pressure

For liquid chlorine, the complete pipeline system should be designed for a maximum operating pressure equal to the vapour pressure of chlorine at the maximum operating temperature chosen, plus a safety margin determined by factors such as the magnitude of possible surge effects, the pressure drop, the piping layout, the delivery pressure of the pumping/compression system, the maximum pressure in the feed tank, etc.

For gaseous chlorine, the complete pipeline system should be designed for a minimum pressure of 1.5 times the maximum operating pressure.

4.2 Design Temperature

For liquid chlorine, the design temperatures should be in all cases the most severe temperatures -lowest and highest- expected in service. The selected minimum design temperature should be minus 40°C (purging by inert gas, evaporation can create temperatures as low as minus 40°C).

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For gaseous chlorine, the complete system should be designed for the maximum temperature capable of being attained and for the lowest temperature that can occur.

4.3 Fluid Velocities

The velocity of liquid chlorine in the pipeline should be limited to 2 metres per second, which is the maximum to avoid destruction of the protective film of ferric chloride by erosion. The prevention of flashing at any point is essential to avoid high two-phase velocities which can cause serious erosion.

Practical experience from some of our members has shown that gas velocities up to 20 m/s are acceptable without deterioration (be sure there is no liquid entrainment).

4.4 Corrosion Allowance

A minimum corrosion allowance of 1 mm should be used; for dry liquid chlorine, an additional 0.5 mm for potential erosion should be added. Normally these allowances are included in the choice of the schedule for the pipeline (the allowance should be added to the calculated thickness required for the pressure design condition).

4.5 Radius of Curvature

Even where there is no intention to use a "pig", the radius of curvature of bends should always be at least 3 diameters to reduce the risk of erosion.

4.6 Thermal Insulation

For a liquid chlorine pipeline above-ground, thermal insulation can be employed, if necessary, in order to avoid external water condensation, frosting or possibly fire radiation. In the case of a buried pipeline, external thermal insulation can not be used, to avoid the risk of corrosion brought by reduction of the cathodic protection.

For a gas pipeline, thermal insulation is required when it is heat traced. In other circumstances, it can be provided if it is the only means of avoiding liquefaction. Other means include low operating pressures, adequate chlorine delivery temperatures and permanent gas circulation. It should be noted that in the event of a prolonged shut down, the thermal insulation becomes ineffective.

4.7 Trace heating of chlorine gas pipeline

According to operating pressures, the length of the pipeline and other ambient conditions, tracing can be used to avoid liquefaction of the chlorine. All precautions must then be taken to ensure the permanent availability of the

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heating system and to avoid any localised overheating to prevent local corrosion or chlorine/iron fire. Such overheating can be prevented on the basis of suitable calculation of the heating density, so that at no point the metal temperature should not exceed 120°C.

Electrical trace heating by means of quality resistance elements (self limiting in temperature) attached to, the chlorine pipeline is preferred,

The resistance elements should preferably be armoured externally and protected against corrosion and the ingress of moisture.

The capacity should be calculated as a function of the thermal losses, and not as a function of the heat input required for the revaporisation of the liquid chlorine.

Spirally wound trace heating should be avoided except over short distances.

Resistance heating using the pipe itself shall not be used.

Trace heating with steam, using tubing attached to the chlorine pipeline can also be used as an alternative. Steam can be replaced by any other heating fluid (i.e. hot water). Steam pressure must be low enough to ensure that temperature does not exceed 120°C. Desuperheating devices may be required if the steam is not saturated.

If steam trace heating is applied all connections should be outside the insulation to prevent corrosion (water in insulation resulting from possible leaks).

4.8 Materials of Construction

All the materials used have to be compatible with chlorine (see “GEST 79/82 - Materials of construction for use in contact with chlorine” and GEST 79/82A - Choice of Materials of Construction for Use in Contact with Chlorine (Spreadsheet))

Piping

The steel chosen for the construction of the pipework should be of a certified quality, fine grain steel and readily weldable.

For liquid chlorine, it will have a satisfactory impact strength, according to the standards being used, at minus 40°C after welding.

The metal used in branches and other pieces welded to the pipe should be of a quality compatible with the base metal chosen for the pipe itself. It is advisable to choose a quality of steel which avoids the need for stress relief after welding. Seamless pipe is preferred.

Flanges, nuts and bolts

The pipeline should be completely welded with only flanges at the beginning and the end. The metal used for flanges, nuts and bolts should possess the same characteristics as that of the piping. Weld neck flanges should be used for all

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flange connections. The flanges should be designed to avoid a possible expulsion of the gasket (e.g. male/female or tongue and groove type), and taking into consideration the continuity of the cathodic protection (if present).

Gaskets

The gasket used should be made in a material with positive experience on chlorine, see “GEST 94/216 - Experience of Non-Asbestos Gaskets on Liquid and Dry Chlorine Gas Service” for further information.

Thermal insulation

If the installation of thermal insulation is necessary, the materials to be applied should meet the following criteria:

- Non-flammability

- Chemically inert to chlorine

- Totally sealed against the ingress of moisture

- Protected against mechanical damage.

The most appropriate materials corresponding to these criteria are, for example, foam glass and vapour seal polyurethane (non-flammable or auto-extinguishing) ... Preventing the ingress of atmospheric moisture necessitates the choice of a closed pore structure material, or provision of a high quality external gas-tight wrapping.

Note: the bare pipeline (carbon steel) should be coated before the insulation is applied, to prevent corrosion by moist air.

Aluminum shall not be used for insulation cladding due to reactivity concerns.

4.9 Supports

Buried pipeline

If the terrain to be crossed is unstable or susceptible to movement, a pipeline should not be buried in the ground.

Pipelines above-ground or in trenches

The supports should be fixed on foundations, which provide adequate rigidity (taking account surge effects for liquid chlorine). If necessary, they should be insulated from the pipe with a mechanically robust material, which also provides adequate thermal insulation to avoid frosting on the support (leading to external corrosion). The supports should permit the thermal expansion of the pipeline due to any likely variations in temperature, and should also deal with any possible earth movement. The support system should be designed to avoid any ingress of moisture under the thermal insulation.

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5 INSPECTION AND TESTING

5.1 Inspection of Piping Materials

Piping materials, nuts and bolts should be tested to ensure conformity with the requirements of national and international codes.

The tests are particularly important where they relate to the impact strength of the metal before and after welding.

5.2 Inspection Procedures during Construction

In order to guarantee a fault-free construction, the inspection procedures should follow the required codes rigorously, and as a minimum should encompass the following points:

100% radiography or ultrasonic examination (if radiography is not possible) of the welds

Tests of tensile, bending and impact strength, of reference and welded test pieces.

Thickness control.

Certification of welders and of their methods of welding.

Hydraulic pressure test at least at 1.5 times the design pressure after laying the pipeline.

Leak test after the pipeline has been hydraulically tested and dried.

Check of the trace heating system, if present.

6 ACCESSORIES

6.1 Flanges, Branches and Ancillary Equipment

The number of flanges and branches should be strictly limited to the minimum necessary. Their location in parts of the main pipeline which are below ground should be avoided. If this cannot be avoided they should be placed in inspection chambers accessible to personnel wearing protective clothing. Large diameter branches should be fitted with guide bars if the pipeline is to be "pigged". Small diameter branches should not be less than 40 mm and of sufficient wall thickness to avoid any possibility of deformation (see “GEST 79/81 – Dry liquid and gaseous chlorine piping systems located inside producer’s or consumer’s plants”).

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6.2 End Connection Valves

Remotely operable isolation valves should be provided at the ends of the pipeline. Consideration should be given to automatically close these valves in the case of upset at any point in the system (for example following an abnormal drop in pressure). In the case of liquid chlorine, the speed of closure should be low enough to avoid hydraulic shock.

The valves may be installed to permit in-service functionality testing.

The material of the valves should be compatible with that of the pipe. They should conform to recommendations of Euro Chlor. Refer to the following documents for further information:

GEST 89/140 - Specification for Flanged Steel Globe Valves- (Bellows Sealed) -for Use with Liquid Chlorine

GEST 90/150 – Specification for Flanged Steel Globe Valves (Packed Gland) for Use on Liquid Chlorine

GEST 93/180 – Specification for Flanged Steel Ball Valves for Use on Liquid Chlorine

GEST 99/252 - Specification for Flanged Steel Ball Valves for Use with Dry Gaseous Chlorine

Valve operation should be guaranteed at the pipeline design temperature (minus 40°C for liquid chlorine).

If the pipeline is to be cleaned or inspected with a "pig", the valves should be of the full bore type in order to permit passage.

6.3 Isolation Valves

Intermediate isolation valves, if any are used to separate the pipe in different sections (not recommended for liquid chlorine because of the risk of additional flanges, and thermal expansion for trapped liquid), should be remotely operated type, applying the same considerations as for the end-of-pipe valves.

As for the end-of-pipe valves, all such valves should be carefully chosen and should be located and protected to prevent unauthorised access.

Consideration has to be given to the sequence of closure of the valves.

6.4 Emptying, Venting and Purging

Emptying and Venting:

- It is essential that the pipeline can be rapidly depressurised.

- In order to empty a liquid phase pipeline, vessels large enough to receive the entire contents of the pipeline should be provided at the producer's side but preferably at both ends of the pipeline for long pipelines. If

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possible, the pipeline will be emptied by gravity. It is also possible to empty the pipeline by gas pressure or by the use of a "pig".

- The design must be such that chlorine gas can be vented into a suitable installation (absorption unit or compression and liquefaction of adequate capacity). In the case of liquid chlorine, it should be noted that this venting will take place at low temperature. All equipment associated with the operation, therefore, should be suitable for the actual temperatures which will arise.

Purging:

- Inert dry gas (dew point less than minus 40°C at 1 bar (a)) of adequate quantity and pressure should be permanently available. Purged gas should be passed through a suitable absorption installation to remove chlorine, before being vented to atmosphere.

6.5 Transfer Equipment

For liquid chlorine, the choice of method for pressurising the chlorine to feed the pipeline is a function of the characteristics of the piping system (throughput, operating pressure, maximum pressure). Three methods are recommended:

Transfer by gravity

Transfer from a vessel padded by chlorine gas, or by a dry inert gas, taking into account the maximum pressure appropriate for all accessories on the container.

Transfer by pumping from a vessel. Equipment should be installed on the discharge of the pump to prevent reverse flow to avoid overfilling of the feed tank,

For gaseous chlorine, the choice of compressor for feeding the pipeline system is a function of the characteristics required (throughput, operating pressure, maximum pressure). A non return system should be installed on the down stream side of the compressor and particular attention must be paid to its reliability (the choice of an automatic valve is recommended).

If the gas supply comes from vaporisation of liquid chlorine, and if the working pressure is high enough, it is possible to work without any additional transfer equipment.

6.6 Protection against Overpressure and Thermal Expansion

Liquid chlorine thermal expansion

Where isolation valves are provided along the length of the pipeline, provision must be made to allow for thermal expansion of any trapped liquid chlorine. Such provision should preferably be provided at least at one of the extremities of the pipeline and situated inside the confines of an industrial location. This can be achieved by either of the following methods:

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- Closed expansion tanks, in which it is necessary to verify the permanent presence of a gaseous phase. This gas phase can be obtained either by vaporised chlorine, or by the use of an inert gas.

- Bursting discs or relief valves discharging into a vessel or a collection system. In controlled circumstances, it should be possible to isolate these relief devices for maintenance. The bursting of the disc or the functioning of the relief valve should be alarmed.

Overpressure of the gaseous chlorine

If the compressor is capable of overpressuring the pipeline, a relief device must be installed at the outlet of the compressor. These relief devices should always be connected to an absorption system or a point of use in the liquefaction. They should be capable of being isolated from the pipeline for maintenance.

Steel pipe thermal expansion

- The thermal expansion and contraction of the pipe should be carefully studied and all precautions should be taken to avoid any unacceptable consequences. The design basis for thermal expansion of the pipeline should take into account the maximum and minimum achievable temperatures. In case of liquid chlorine, the minimum temperature to consider should be minus 40°C. For above ground pipelines, it is preferable to use large radius expansion loops. Expansion bellows must not be used because they are weak points in the construction. For straight lines, where free expansion cannot take place, account must be taken of the longitudinal stresses which will result from the maximum variation in temperature.

6.7 Protection against Surge for Liquid Chlorine

A calculation of the maximum pressure reached when closing a valve will be made and, if necessary, appropriate surge protections will be installed at least at one end of the pipeline (bursting disc with exhaust in safety storage connected to chlorine absorption, sealed pots with inert or chlorine gas …).

6.8 Protection against Corrosion

All pipelines, whether they are above ground or buried, should be provided with an effective protection against external corrosion.

Buried pipelines should be protected cathodically, and receive an adequate external coating. For these pipelines the following procedures should be carried out:

A dielectric test of the state of the external protective surface coating before laying the pipeline.

An inspection, by means of an impressed electrical signal, of this protective coating during the first year following the laying of the pipeline.

A routine periodic check of the satisfactory functioning of the cathodic protection.

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6.9 Equipment for Measurement and Monitoring the Condition of the Pipeline

All pipelines should include as a minimum the following equipment:

Measurement and recording of the pressure and temperature at the inlet and outlet.

Maximum and minimum pressure (and temperature for chlorine gas) alarms and, if appropriate, means for relaying their signals to both ends of the pipeline.

Flow measurement at both ends with differential alarms or, for liquid chlorine, .measurement of the weight of the feed or discharge tanks,

The personnel at both ends of the pipeline should be provided with appropriate methods for monitoring the functioning and status of the safety measures indicated above, i.e.:

Remotely operated isolation valves at the two ends.

Remotely operated isolation valves along the length of the pipeline, if any.

Bursting discs and relief devices (if presents).

Connections to the venting system (and drain tank for liquid chlorine).

If the pipeline is completely or partly double walled for a specific reason, a leak detector should be installed (e.g. pressure alarm or chlorine detector on the purge gas of the dubble wall).

Permanent connections by telephone and/or computer connection between the two ends of the pipeline shall be provided.

6.10 Maloperation Measures/Procedures

All precautions should be taken to avoid maloperation by means such as locks, logic systems, interlocks etc. The transfer of chlorine into the pipeline should be stopped automatically in the event of overpressure (for liquid chlorine), abnormal temperature (for gaseous chlorine) or abnormal pressure drop in the system.

7 OPERATION

7.1 Cleaning and Drying before Putting into Service

Before putting into service the pipeline all equipment should be degreased, cleaned and dried (see also GEST 80/84 - Code of Good Practice for the Commissioning of Installations for Dry Chlorine Gas and Liquid. If a hydraulic pressure test is done, it is necessary to replace the gaskets after the test, as otherwise the system is difficult to dry out. Hydraulic testing, cleaning and drying should be carried out before the installation of valves and other accessories.

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Drying should be carried out with the aid of a dry inert gas to obtain a stable dew point of less than minus 40°C at 1bar (a) at the exit of the pipeline. Drying by the use of methanol or hydrocarbons, which could cause a risk of explosion in the presence of chlorine, should be done only in well controlled circumstances where perfect draining of the pipe can be ensured with additional purging with nitrogen, not forgetting the branches. If possible, vacuum drying may be used.

For greasing internal equipment which can possibly come into contact with the chlorine, only greases compatible with chorine can be used (chlorofluorinated grease).

7.2 Leak Testing

In addition to the test procedures laid down in sections 5.2. and 7.1, and before putting the pipeline into service, the entire system, including all valves and other accessories should be tested in order to guarantee their perfect leak tightness under all conditions of service. The following test methods may be used:

Tests with a mixture of chlorine and dry air at a overpressure (e.g. 2 bars (g)), the gasketting systems being checked with the aid of ammonia.

Air pressure test at an overpressure (e.g. 2 bars (g)), and detection of leaks by the use of water containing a frothing aid.

Helium test at overpressure (e.g. 2 bars (g)) in a calm and non-ventilated atmosphere.

7.3 Commissioning and Testing before Putting into Service

A certain number of precautions should be taken before putting the pipeline into service:

Check on the quality of chlorine introduced (see section 7.5).

Purge of the pipeline with chlorine gas to eliminate all inerts before putting it under pressure.

Further check on the leak-tightness and good operation of all the accessories.

For liquid chlorine, introduction of liquid chlorine while the system remains under pressure of chlorine gas; for gaseous chlorine, progressive putting into operation up to the desired throughput and pressure

Continuously increasing flow rate up to the desired throughput.

Final visual check on the system.

7.4 Taking the Pipeline out of Service

Special attention is requested during transient phases and shut down operations.

For liquid chlorine, care must be taken to avoid trapping liquid within the pipeline when it is taken out of service. If the shutdown is to be followed by emptying, it is

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possible to remove the liquid chlorine with the aid of nitrogen, dry compressed air or with a “pig”. In the case of removal by inert gas, care must be taken to remove first as much liquid chlorine as possible before injecting the inert gas (chlorine vaporisation could then lead to a quite low temperature).

For a few hours shutdown of a gaseous chlorine pipeline the thermal tracing, if any, will be turned off to avoid the risk of hot spots, and the pressure lowered; the pressure may not fall below atmosphere to avoid air ingress but, whenever possible, stay below the chlorine vapour pressure corresponding to the pipeline temperature, to prevent the risk of liquefaction; before restart, all efforts must be made to confirm the absence of any liquid phase chlorine.

If works have to be performed on the pipeline, or if the duration of the shut down is too long to guarantee a correct continuous surveillance, the thermal tracing, if any, will be kept off, and the chlorine in the pipeline will be replaced by dry inert gas (dew point lower than minus 40 °C) by depressurisation, venting and purging towards an appropriate installation (liquefaction, absorption, etc). This operation should be continued until the residual chlorine content within the system permits its opening or dismantling without risk of corrosion or gassing of personnel.

For all maintenance operations the pipeline shall be isolated upstream and downstream by the installation of blank flanges, or the removal of a spool piece provided for this purpose.

7.5 Quality of the Chlorine Introduced

The chlorine should be dry (< 20 mg water per kg) and clean; it must contain no organic material which is capable of reacting with chlorine

For liquid chlorine, the NCl3 content will be in accordance with GEST 76/55 - Maximum Levels of Nitrogen Trichloride in Liquid Chlorine.

The gaseous chlorine can form an explosive mixture with hydrogen. The current information relating to the flammable limits of hydrogen in gaseous chlorine is presented in the table below, with the effect of the initial temperature.

Temp (°C) H2-Air (vol % H2) H2-Oxygen (vol % H2) H2-Chlorine (vol % H2)

-60 4.0 - 69 4.0 - 96 5.0 - 90

-40 4.0 - 71 4.0 - 96 4.0 - 90.5

-20 4.0 - 72 4.0 - 96 4.0 - 91.5

0 4.0 - 73 4.0 - 96 3.5 - 92

20 - 25 4.0 - 75 4.0 - 96 3 - 92.5

50 3.7 - 76 4.0 - 96 3 - 93

100 3.0 - 80 4.0 - 97 3 - 93

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The influence of the initial pressure is relatively small between 0.25 and 11.5 bara. It is recommended that experimental measurements are undertaken if operating at higher pressure.

The practical operating conditions in the production lines and equipments will be chosen to work with a suitable safety margin with respect to these limits, taking into account the fact that pressure increase widens the flammability zone and that the concentration will increase either as a result of condensation in a pipeline operating under high pressure in cold weather.

In-line analysers will be used to check that one always remains below the low limit of the table.

The quality of chlorine introduced in the pipeline should be checked periodically.

7.6 Precautions against Ingress of Moisture or other Reactive Materials

All necessary precautions must be taken to avoid the entry of moisture or reactive materials into the pipeline. If an inert gas is used for purging the pipeline, it should have a dew point of less than minus 40°C at 1 bar (a). The pressure of this gas should be at least 2 bars greater than the maximum pipeline pressure, and all precautions must be taken to ensure that this difference is permanently maintained, and that the gas cannot be contaminated by any other material.

Action in case of moisture ingress: all precautions will be taken to avoid ingress of moisture in the pipeline; if any occurs accidentally, with formation of large amount of ferric chloride on the internal wall, the corresponding hydrates will be eliminated by one of the following:

o washing with a slightly alkaline solution (20 - 30 g/l), rinsing with water wash, and then drying with inert gas (dew point lower than minus 40 °C),

o mechanical cleaning with dry sand jet (dew point lower than minus 40 °C), and then dried with inert gas (dew point lower than minus 40 °C),

o drying with hot inert gas until a dew point lower than minus 40 °C is reached and maintained for several hours (at least 24 hours).

7.7 Precautions in the Event of Failure of the Trace Heating (for Gas Pipeline)

In the event of failure of the trace heating system, for which the operating personnel should be aware, it is preferable to reduce the pressure in the pipeline and to vent it down to avoid chlorine liquefaction. If accidental liquefaction does take place, it is essential to reduce the pressure in the pipeline and to allow it to vent down before putting it back into service.

7.8 Periodical Inspection and Testing

Above Ground Installation

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A visual inspection at least once per week of the pipeline and its surroundings should be carried out. Particular attention should be paid to the following aspects:

- Areas of frosting or deterioration of the thermal insulation.

- Circumstances arising in the vicinity of the pipeline which could present any risk to it, e.g. crane activity.

- A check that the warning devices (flow - and pressure measurements) and communication systems are functioning correctly.

Buried pipelines

A visual inspection of the route, from the air and/or on foot, at least once per week, with:

- A check that the confines of the pipeline are as specified.

- A check that the warning devices (flow - and pressure measurements) and communication systems are functioning correctly.

A check on the cathodic protection (At least once per year).

Inspection and test

Periodic inspection and testing of the system is required, with an interval never exceeding 5 years. It should take into account the following aspects:

- Thickness testing of the pipe walls in specific areas as specified at the time of construction (ultrasonic).

- Visual inspection of the protective coating of the buried pipeline.

- A check on all equipment. As a general rule, all accessories should be replaced in a systematic manner before there is any risk of them becoming defective.

- Inspection of the supports for above ground pipeline systems.

Re-testing

If a re-test is required, a pneumatic test is preferred. A hydraulic re-test of the pipeline is not advisable, because of the subsequent risk of internal corrosion to the piping system which could occur in a potentially uncontrolled manner.

7.9 Emergency Procedures and Training

The following precautions should be taken:

A written emergency plan, and precise instructions and communications systems in case of emergency, should be permanently available and brought to the knowledge of all personnel involved, including external emergency services.

All personnel, including those of the public authorities who could be asked to assist in the event of an emergency, should be specifically instructed in the means of dealing with leakages of chlorine. Exercises and re-training shall be organised on a frequency to ensure sufficient knowledge and skill.

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Self-contained breathing equipments and protective clothing suitable for dealing with a chlorine leak (liquid if it is the case) should be available in lockers located near to the ends of the pipeline, and accessible at all times in case of emergency.

A means of indicating the wind direction should be installed in order to inform the operators of the direction of gaseous dispersion that might occur in the event of a leak.

During the periodic check of the pipeline, as indicated above in 3.5.6, the personnel carrying out the inspection should be provided with checklists covering the principal points to be controlled. These checklists and, if necessary, additional remarks, are collected in a logbook.

Bearing in mind the specific hazards associated with chlorine-iron fire, a study should be carried out of the means of dealing with a fire in the vicinity of the pipeline.

Common routing of the pipeline with electric cables or flammable fluids should be avoided.

8 REFERENCES

GEST 72/10 - Pressure Storage of Liquid Chlorine

GEST 76/55 - Maximum Levels of Nitrogen Trichloride in Liquid Chlorine

GEST 79/81 - Dry Liquid and Gaseous Chlorine Piping Systems Located Inside Producer's or Consumer's Plants

GEST 79/82 - Materials of Construction for Use in Contact with Chlorine (General Information)

GEST 79/82A - Choice of Materials of Construction for Use in Contact with Chlorine (Spreadsheet)

GEST 89/140 - Specification for Flanged Steel Globe Valves (Bellows Sealed) for Use with Liquid Chlorine

GEST 90/150 - Specification for Flanged Steel Globe Valves (Packed Gland) for Use with Liquid Chlorine

GEST 93/180 - Specification for Flanged Steel Ball Valves (Packed Gland) for Use with Liquid Chlorine

GEST 99/252 - Specification for Flanged Steel Ball Valves for Use with Dry Gaseous Chlorine

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Industrial consumers of chlorine, engineering and equipment supply companies worldwide and chlorine producers outside Europe may establish a permanent relationship with Euro Chlor by becoming Associate Members or Technical Correspondents.

Details of membership categories and fees are available from:

Euro Chlor

Avenue E Van Nieuwenhuyse 4

Box 2

B-1160 Brussels

Belgium

Tel: +32 2 676 7211

Fax: +32 2 676 7241

e-mail: [email protected]

Internet: http://www.eurochlor.org

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