Transfer of Dry Chlorine by Piping

Systems

GEST 73/25
13th Edition
April 2023

EURO CHLOR PUBLICATION

This document can be obtained from:

EURO CHLOR – Rue Belliard 40, Box 15 - B-1040 BRUSSELS
E-mail: eurochlor@cefic.be Internet: http//www.eurochlor.org
 GEST 73/25
13th Edition

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.

April 2023 Page 2 of 31

 GEST 73/25
13th Edition

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.

April 2023 Page 3 of 31

 GEST 73/25
13th Edition

TABLE OF CONTENTS
SUMMARY OF THE MAIN MODIFICATIONS ............................................................ 5
1 INTRODUCTION................................................................................................... 5
2 SCOPE AND DEFINITIONS ................................................................................. 5
3 GENERAL STATEMENTS ................................................................................... 6
3.1 LIQUID PHASE ...................................................................................... 6
3.2 GASEOUS PHASE ................................................................................ 6
4 BASIC DESIGN AND INSTALLATION ................................................................ 7
5 DESIGN AND CONSTRUCTION .......................................................................... 8
5.1 DOUBLE WALL PIPING SYSTEM ......................................................... 8
5.2 BRANCHES AND ANCILLARY EQUIPMENT ....................................... 9
5.3 END CONNECTION AND END OF PIPE VALVES ............................... 9
5.4 INTERMEDIATE ISOLATION VALVES ................................................. 9
5.5 FLANGES, NUTS AND BOLTS ........................................................... 10
5.6 APPLIED LOAD AND STRESSES ...................................................... 10
5.7 DESIGN PRESSURE........................................................................... 11
5.8 DESIGN TEMPERATURE ................................................................... 11
5.9 FLUID VELOCITIES ............................................................................ 11
5.10 PIPE AND BRANCHES DIAMETER .................................................... 12
5.11 CORROSION ALLOWANCE AND PROTECTION .............................. 12
5.12 RADIUS OF CURVATURE .................................................................. 12
5.13 THERMAL INSULATION ..................................................................... 13
5.14 HEAT TRACING OF CHLORINE GAS PIPING SYSTEM.................... 13
5.15 EMPTYING, VENTING AND PURGING .............................................. 14
5.16 TRANSFER EQUIPMENT ................................................................... 15
5.17 PROTECTION AGAINST OVERPRESSURE AND THERMAL
EXPANSION ........................................................................................ 15
5.18 MONITORING THE PIPING SYSTEM CONDITIONS ......................... 16
5.19 MATERIALS OF CONSTRUCTION ..................................................... 17
5.20 SUPPORTS ......................................................................................... 18
5.21 PIPE INSPECTION AND TESTING ..................................................... 19
6 OPERATION ....................................................................................................... 19
6.1 CLEANING AND DRYING BEFORE PUTTING INTO SERVICE ......... 19
6.2 LEAK TESTING ................................................................................... 19
6.3 COMMISSIONING AND TESTING BEFORE PUTTING INTO SERVICE
............................................................................................................. 20
6.4 PUTTING THE PIPING SYSTEM INTO SERVICE .............................. 20
6.5 RUNNING A CHLORINE PIPING SYSTEM......................................... 20
6.6 PERIODICAL INSPECTION AND TESTING OF LONG DISTANCE
PIPING SYSTEM ................................................................................. 20
6.7 MANAGEMENT OF CHANGES ........................................................... 21
6.8 TAKING THE PIPING SYSTEM OUT OF SERVICE ........................... 21
6.9 INTERVENTION IN CASE OF INGRESS OF MOISTURE .................. 22
6.10 INTERVENTION IN THE EVENT OF FAILURE OF THE HEAT
TRACING (FOR GAS PIPING SYSTEM)............................................. 22
6.11 EMERGENCY PROCEDURES AND TRAINING ................................. 22
7 REFERENCES.................................................................................................... 23

April 2023 Page 4 of 31

 GEST 73/25
13th Edition

SUMMARY OF THE MAIN MODIFICATIONS

• Creating alignment of the allowed velocity of liquid chlorine in pipelines. Up
to 7 m/s no erosion but due to practical reasons (e.g., pressure drop and
turbulence etc) the velocity is limited to 2-3 m/s.
• Change in radius of bends and elbows to 3D (radius 1.5D) instead of a radius
of 3D.
• Mentioned that torque calculations should be done with the friction
coefficient of the chlorine compatible grease.
• Changed in chapter 6.6 the minimum period of 5 years for periodic
inspections into a timeperiod that is inline with the requirements of the
relevant competent body.
• Updating standards and some small textual improvements

1 INTRODUCTION
In Europe and other industrialized regions there are many years’ experiences in
operation of piping systems for dry gaseous and liquid chlorine. Design and
maintenance to operate safely those piping systems are well understood. Basic
principles in terms of design, operation and maintenance are summarized in this
recommendation.
Various considerations and basic principles of design and construction are outlined
and should be followed when designing this type of system.
Experience has shown that each installation requires individual consideration.
Accordingly, this document must only be taken as a guide; it is not a comprehensive
design code and in no way should it interfere with competent engineering
judgement. It is recommended, however, that any proposed deviations are discussed
with an experienced chlorine producer.

2 SCOPE AND DEFINITIONS

This recommendation covers piping systems inside and outside production units. It
excludes the following:
• Near atmospheric pressure gaseous chlorine, e.g., cells to compression, low
pressure vents etc.
• instrument piping system downstream of a process isolation valve
• Installations with very low flow using drums and cylinders.
The term piping system is used to cover all elements of a line between two pieces of
equipment and will be a combination of fabricated pipes, fittings, flanges, valves
and supports, etc. The term pipe is used when we only speak of the pipe itself.
NOTE: The definition of dry chlorine is described in GEST 10/362 – Corrosion
Behaviour of Carbon Steel in Wet and Dry Chlorine.

April 2023 Page 5 of 31

 GEST 73/25
13th Edition

3 GENERAL STATEMENTS
Chlorine can be transferred safely by piping systems either in the gas or liquid
phase, provided the appropriate design and operating conditions are satisfied,
avoiding two phase flow, which is a source of corrosion by erosion. All precautions
should be taken such that:
• inpiping systems designed to transport only liquid chlorine, vaporisation
cannot occur,
• in piping systems designed for the transfer 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.
Remark: in some exceptional circumstances, gaseous chlorine piping systems have
been designed to allow some partial liquefaction; in this case the construction and
the operation procedures have to take all necessary precautions to cope with the
phenomena, after a specific risk assessment.
This very specific case is not further considered in this recommendation.
3.1 LIQUID PHASE
The design and operation of liquid phase piping system 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
piping system to ensure continuity of the liquid phase.
• The minimum temperature which can occur when depressurizing and purging
the piping system for maintenance or emergency emptying.
• The potential pressure increases by thermal expansion of trapped chlorine
and the protection measures.
• A maximum linear velocity.
• The total pressure drop.
• The safety protection against surge (liquid hammer).
• The quantity of chlorine contained in the piping system which may conflict
with individual and societal risk contours.
• The surrounding of the piping system that could affect its integrity (high
temperature, mechanical damage …).
The above will limit the length and throughput of a particular piping system, as
pumping stations outside the premises of a chlorine-producing or consuming factory
are not recommended. In Europe, there are many years’ experience of liquid phase
piping systems over several km and pressure up to 30-40 bara.
3.2 GASEOUS PHASE
The design and operation of gas phase piping 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 heat tracing system in all circumstances,
particularly in the event of zero flow.

April 2023 Page 6 of 31

 GEST 73/25
13th Edition

• The total pressure drop.

• The quantity of chlorine contained in the system.
In Europe, there are many years’ experiences with gas phase piping systems over
several km and pressure up to 10 bara and sometimes for shorter distances even
higher pressures.

4 BASIC DESIGN AND INSTALLATION

The route for chlorine pipework should:
• Provide the shortest and least complicated design, minimising the chlorine
inventory in the line, while maintaining the ability to satisfactorily
accommodate thermal expansion.
• Provide the maximum protection to the line from all risk of external damage
(mechanical, corrosive, fire or explosion), whether such risk exists at the
time of installation of the piping system or is brought about by subsequent
installations; potential risks created by the proximity of other piping system
or high voltage electric cables should be controlled.
• Avoid, whenever possible, any risk of the normal line temperature being
affected by an external source of high heat output, such as adjacent steam
mains, piping systems containing flammable gases or liquids, etc. If a high
temperature risk exists the chlorine line should be protected (physical
isolation, fire resistant barrier, fire resistant insulation, etc.)
• Allow sufficient access for inspection even though permanent facilities are
not necessary.
• Consider potential risks from natural disasters like earthquake, flooding,
storm etc.
• Minimise the length of low points in the case of liquid chlorine piping systems
to prevent NCl3 accumulation during residual chlorine vaporisation after
emptying the pipe.
Labelling visible at distance or colour-coding of piping system is recommended,
particularly on pipe racks or pipe bridges where immediate access is not possible.
If the piping system is above ground, it should be protected from any risk of
mechanical damage such as falling objects, collisions etc.
If the piping system is laid in a pipe trench, it must be provided with sufficient
support, together with drain provisions to remove water or possible corrosive liquids
from the trench. The trench should also permit access for inspection of the piping
system.
For liquid chlorine, the use of buried piping systems can be the most reliable
depending upon local circumstances and in many cases, this will be the preferred
solution, especially outside plant boundaries.
For gaseous chlorine, a buried piping system should be considered where operating
conditions do not necessitate either heat tracing or thermal insulation to avoid risk
of liquefaction; this means only in circumstances where the piping system is
operated at a sufficiently low pressure.
Where the piping system is buried, the route of the piping system 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 coloured plastic

April 2023 Page 7 of 31

 GEST 73/25
13th Edition

sheets or warning tapes, concrete slabs marked "buried piping system" etc., as
commonly used with gas and electricity utilities).
Dividing a liquid chlorine piping system into smaller segments with automatic
isolation valves, to improve safety, is not recommended (see paragraph 5.4 below).
For gaseous chlorine, the need/number of automatic or remotely controlled
isolation valves along the piping system is defined by the safety study.
In both cases, such valves and flanges represent a weak point in the construction of
the piping system, adding a supplementary risk (e.g., flange leak). Liquid chlorine,
if trapped between two closed valves might cause a pressure increase due to
possible thermal expansion. This would require installing special protection/relief
with connection to an absorption system for each section. Therefore, it is
recommended to avoid such isolation valves, especially outside the confines of
industrial premises.
The inlet and outlet of the piping system should be equipped with isolation valves
(see 5.3). Degassing capabilities to a chlorine absorption facility and/or a
dump/escape tank to catch liquid chlorine is considered necessary for an adequate
response in case of emergency.

5 DESIGN AND CONSTRUCTION

The design and the quality of construction are the most important safety
considerations.
The recommendations contained in this guide should be considered as
complementary to specific European, national or regional codes and regulations
covering the design of piping system in general and liquid/gaseous chlorine piping
systems in particular. If no other requirements exist, the American Society of
Mechanical Engineers Piping Code (ASME) may be used.
Before design work is started, it is recommended that piping system specification
sheets are produced. These should clearly state the standards to be used for pipe,
fittings, flanges, valves, bolts, gaskets etc., for the stated design conditions.
All reasonable precautions should be taken during the construction of the piping
system to minimise ingress of moisture (for example by keeping the pipe parts
tapped before mounting, tent above the welding area, flushing the pipe in
construction …).
In case greases are used they should be compatible (nonreactive) with chlorine.
5.1 Double Wall Piping System
Double wall piping systems are usually not recommended for chlorine, especially for
liquid chlorine, due to the technical difficulties of construction and monitoring;
nevertheless, if imposed by the local authorities, the following points should be
considered:
• The diameter of the outer wall has to be chosen to allow a sufficient distance
between the inner (chlorine) and the outer wall pipes. In particular, the
elbows need to have a curve large enough to allow easy positioning of the two
pipes. The distance between the two pipes is maintained by spacers along the
pipes.
• Special care must be given to thermal expansion effects with possible
rupture: the chlorine pipe can be at a significantly different temperature

April 2023 Page 8 of 31

 GEST 73/25
13th Edition

than the outer wall while in service, although the temperatures become the
same while the piping system is not in service. This effect can be more severe
when liquid chlorine is cooling down due to depressurisation/partial
vaporisation.
• Inspection requirements have to be considered at the initial design of the
piping system.
• As this outer wall is basically installed to monitor possible small leaks of the
chlorine piping system, it can be at a lower pressure rating (for example PN
10).
• The space inside the double wall should be monitored, e.g., by a permanent
flow of dry air or nitrogen with a chlorine detector at the outlet of the
flushing gas with alarm; alternatively, the space can be kept under dry air or
inert gas with high/low pressure alarm.
• Branches are very difficult to build on a chlorine pipe with a double wall.
5.2 Branches and Ancillary Equipment
The number of branches should be strictly limited to the minimum necessary as they
increase the risk of leak and, are difficult to insulate allowing a location for possible
corrosion to initiate. Their location in parts of the main piping system 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.
Vent and drains should only be located inside the supplier’s or the customer’s site.
Large diameter branches should be fitted with guide bars if the piping system is to
be "pigged".
5.3 End Connection and End of Pipe Valves
Isolation valves should be provided at the end of the piping system; the safety study
should demonstrate if they need to be remotely operable, depending on their
location and the quantity of chlorine contained in the piping system. 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 pipe must withstand the liquid hammer generated by closing the
valves; the speed of closure of these valves can be adapted to reduce this effect.
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 17/492 - Specifications and Approval Procedure for Valves to be Used
in Liquid Chlorine or Dry Chlorine Gas.
Valve operation should be guaranteed at the piping system design temperature
(minus 40°C for liquid chlorine).
If the piping system is to be cleaned or inspected with a "pig", the valves should be
of the full-bore type to permit passage.
5.4 Intermediate Isolation Valves
Intermediate isolation valves, if any are required to separate the pipe in different
sections (not recommended for liquid chlorine because of the risk resulting from

April 2023 Page 9 of 31

 GEST 73/25
13th Edition

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.
5.5 Flanges, Nuts and Bolts
Threaded connections for piping system and instrument connections to the piping
system are not recommended.
The pipes should preferably be welded all along their length with only flanges at the
beginning and the end. Where flanges are needed, they will preferably be of tongue
and groove type or flat flanges with blow-out-proof gaskets in the case of liquid
chlorine.
Note: Tongue and groove joints offer a greater potential integrity, but increased
difficulty when assembling or dismantling the joint.
It is recommended that weld neck flanges are used for all pipe sizes.
It has to be taken into consideration that flanges/gaskets may interfere with the
continuity of the cathodic protection.
Bolts and nuts should conform to Unified inch or ISO metric standards and
recognised national standard and be suitable for the selected temperature
conditions. See GEST 88/134 – Stud Bolts, Hexagon Head Bolts and Nuts for
Liquid Chlorine.
The design temperature of nuts and bolts should be in line with the pipe
requirements (e.g., minus 40°C for liquid chlorine).
5.6 Applied Load and Stresses
The following factors should be taken into account when considering the loads and
stresses applied to piping systems:
• Internal and external pressure
• Thermal expansion and contraction
• Weight of pipe and associated equipment
• Weight of the chlorine in the piping system in case of liquid chlorine (the
density of liquid chlorine is approximately 1500 kg/m³)
• Weight of insulation, including the possible accidental ingress of any moisture
when the vapour seal fails.
• Reaction from lines discharging to lower pressure systems.
• In case of liquid chlorine, effect of surge or “water hammer”
• Wind loads.
• Seismic effects
• Snow and ice (particularly where there is the possibility of ice forming on
unlagged lines)
• Forces arising from valve operation.
• People standing on the piping system.
The dynamic forces arising from two phase flow should be considered in case of
filling/emptying a liquid chlorine piping system.

April 2023 Page 10 of 31

 GEST 73/25
13th Edition

The basis for any calculation on expansion and contraction in the system should be
the maximum and minimum temperatures arising from:
• Normal operation
• Start-up and shut-down, including abnormal conditions arising from
maintenance and commissioning activities.
• Predictable transient conditions, e.g., de-icing and cases where the piping
system can operate alternately above and below ambient temperature.
5.7 Design Pressure
For liquid chlorine, the complete piping system, including flanges and all
components, shall be designed for the maximum possible 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 system layout (static height), the delivery
pressure of the pumping/compression system -including at start-up-, the maximum
pressure in the feed tank, etc. (For protections against thermal expansion and
surge, see 7.6). The minimum design pressure to be used is 25 barg, a design
pressure below 25 barg can only be accepted where the service conditions are fully
known and documented.
For gaseous chlorine, the complete piping system shall be designed for the
maximum operating pressure.
In situations where a vacuum may be applied to dry out the system, the pipework
will be subject to external pressure and must be designed accordingly.
5.8 Design Temperature
The complete system should be designed for the maximum temperature capable of
being attained and for the lowest temperature that can occur.
For liquid chlorine, the minimum design temperature should be minus 40°C or
lower).
5.9 Fluid Velocities
Liquid Chlorine Piping System
The velocity of liquid chlorine in the piping system should be limited to avoid
destruction of the protective film of ferric chloride by erosion in carbon steel pipes,
taking into consideration the higher local velocities due to the presence of valves,
orifice plates, bends and other pipework features. Test by the AkzoNobel Corrosion
Department have not indicated any erosion from liquid chlorine at velocities up to 7
m/sec. For practical reasons such as pressure drop, pressure surge (liquid hammer,
avoiding turbulence in bends, after valves etc. and to create a safety margin the
velocity is normally limited to approx. 2 - 3 m/s.
The prevention of flashing at any point is essential to avoid high two-phase
velocities which can cause serious erosion.
Gaseous Chlorine Piping System
Practical experience from some of our members has shown that gas velocities up to
20 m/s are acceptable without deterioration, provided there is no liquid droplets
entrainment.

April 2023 Page 11 of 31

 GEST 73/25
13th Edition

5.10 Pipe and Branches Diameter

Pipes and branches should be NPS 1½ (DN 40) or above because of their substantially
increased robustness.
When NPS 1 (DN 25) is unavoidable, such as in connection with some flow
measurement devices with flange taps (see GEST 94/210 - Code of Practice for the
Installation of Flow Measuring Devices in Dry Gaseous and Liquid Chlorine
Applications), great care must be taken to protect the branches from external
damage by choice of branch type, the branch and pipework routing, and possibly by
the use of protective steelwork, if necessary. They should be reinforced using
proprietary fittings such as butt-welding tees, weldolets etc. and their stand-out
restricted to a minimum. Forged tees are preferred (being well reinforced and
allowing radiography) with 'welding outlet bosses' (e.g., weldolet) being acceptable
(being well reinforced, but not allowing radiography).
Pipe size is chosen based on the chlorine transfer rate required, whilst observing the
velocity limits given in section 5.9. A larger size should not be chosen just to give a
very low velocity, since this will increase the chlorine inventory of the piping
system. In practice, NPS 4 (DN100) has been found to be sufficient for most liquid
chlorine applications. If a larger size is needed, the total design of the system
should be reconsidered.
NOTE: Standard NPS  Normal Pipe Size in inches
Standard DN  ND  Diameter Nominal in Millimeters
5.11 Corrosion Allowance and Protection
In the case that there is one phase flow regime (for gas or liquid), a corrosion
allowance of 1 mm should be used. If there is a risk of two phase flow a corrosion
allowance of 1.5 mm should be used. This allowance should be added to the
calculated thickness required for the pressure design condition. The resulting value
for the wall thickness will normally not be commercially available so the next higher
available wall thickness has to be chosen resulting in a higher available margin for
corrosion allowance.
All piping systems, whether they are above ground or buried, should be provided
with an effective protection (coating) against external corrosion. This protection
should be periodically inspected, especially where buried lines enter and leave the
ground.
Buried piping systems should be protected cathodically and should receive an
adequate external wrapping/coating. This protection should be carefully repeated
after repair.
For these piping systems the following procedures should be carried out:
• A dielectric test of the state of the external protective surface coating after
laying the piping system and before backfilling the excavation.
• An inspection, by means of an impressed electrical signal, of this protective
coating during the first year following the laying of the piping system.
• A routine periodic check of the satisfactory functioning of the cathodic
protection.
5.12 Radius of Curvature
To reduce the risk of erosion in liquid chlorine piping systems the radius of curvature R
of the elbows and bends should always be at least 1.5*D (corresponding to type 3D),

April 2023 Page 12 of 31

 GEST 73/25
13th Edition

where D is the diameter of the nominal pipe size in DN or NPS. If pigs have to be
used, the use of a larger radius of curvature of 2.5*D (corresponding to type 5D) can
be considered.
5.13 Thermal Insulation
The benefit of insulation should always be considered against increased risk of
undetected external corrosion of the pipe.
When a chlorine piping system is to be insulated, greater safety is obtained by
designing the supports, external protection and insulation together as an integrated
system.
Particular precautions need to be taken to avoid any entrapment of moisture during
the installation of the thermal insulation; the work should be performed during dry
weather.
Liquid Chlorine Piping System
For a single wall liquid chlorine piping system above-ground, thermal insulation can
be employed, if necessary, to avoid external water condensation, frosting, potential
fire radiation or heating by sun radiation which could lead to evaporation and two
phases flow. Special attention should be paid to avoid water ingress in the insulation
which could lead to corrosion which is difficult to detect. It is advised to properly
prepare and paint or coat the bare steel pipe before applying the thermal insulation
to prevent corrosion under insulation (CUI).
In the case of a buried piping system, external thermal insulation is usually not
necessary.
For buried piping systems it could be advisable to heat the liquid chlorine just above
the normal temperature of the surrounding soil to avoid heating-up and pressure
increase when there is no chlorine flow.
Gaseous Chlorine Piping System
For gaseous chlorine, thermal insulation is usually not necessary, but can be used
(with or without heat tracing) to avoid the risk of condensation due to
pressure/temperature conditions.
Other means to avoid accidental liquefaction in the pipe may be low operating
pressures, adequate chlorine delivery temperatures and permanent gas circulation.
It should be noted that, in the event of a prolonged shut down or very small delivery
rate, thermal insulation without heat tracing might not be sufficiently effective to
prevent chlorine liquefaction (depending on the chlorine pressure).
Thermal insulation can also be required to protect personnel from high temperature
pipework.
5.14 Heat Tracing of Chlorine Gas Piping System
According to operating pressures, the length of the piping system and other ambient
conditions, heat tracing and thermal insulation can be used to avoid liquefaction of
the gaseous chlorine. All precautions must then be taken to ensure the permanent
availability of the heating system as long as the pipe is in operation and to avoid any
localised overheating to prevent local corrosion or chlorine/iron fire. Such
overheating can be prevented by applying a heating medium with limited
temperature (e.g., hot water supplied from a vessel at atmospheric pressure) or by

April 2023 Page 13 of 31

 GEST 73/25
13th Edition

suitable calculation of the heat density, so that at any point the metal temperature
should never exceed 120°C, considering the worst possible climatic conditions.
If an electrical heating system is used, it should be equipped with self-limiting/self-
regulating heat tracing cables which shall be attached to, but insulated from, the
chlorine pipes to avoid localised hot spots. The elements should be armoured and
externally protected against corrosion and the ingress of moisture. The heating
power should be calculated as a function of the thermal losses and not as a function
of the heat input required to re-vaporise any chlorine which may have condensed in
the pipework. An independent high temperature safety system will be foreseen;
several temperature sensors could be used along the piping system for alarm.
Heating using the electrical resistance of the pipe itself should not be used.
Heat tracing with a transfer fluid (steam or hot water for example), using tubing
attached to, but insulated from the chlorine piping system can also be used as an
alternative. Steam pressure must be low enough (< 2 bara) and the steam must be
saturated (de-superheating system required if necessary) to ensure that
temperature does not exceed 120°C.
If steam heat tracing is applied, all connections which are not welded should be
outside the insulation to prevent water leaks inside the insulation with risk of pipe
corrosion.
5.15 Emptying, Venting and Purging
Emptying and Venting:
• It is essential that the piping system can be rapidly depressurised.
• To empty a liquid phase piping system, vessels large enough to receive the
entire contents of the piping system should be provided as a minimum at the
producer's side but preferably at both ends for long piping system. If possible,
the piping system will be emptied by gravity. It is also possible to empty the
piping system by gas pressure or using a "pig". The pipe will then be vented.
• The design must be such that chlorine gas can be vented into a suitable
installation (absorption unit or compression and liquefaction plant 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 bara) of adequate quantity
and pressure should be permanently available. All precautions will be taken
to avoid contamination by oils, grease or other contaminants that could react
with chlorine.
• The system will be designed to avoid back flow from chlorine to the dry gas
network; this can be realised by dedicated purging system, if its pressure is at
least 2 bar higher than the maximum piping system pressure, or a backflow
protection.
• Purged gas should be passed through a suitable absorption installation to
remove chlorine, before being vented to atmosphere.

April 2023 Page 14 of 31

 GEST 73/25
13th Edition

5.16 Transfer Equipment

For liquid chlorine, the choice of method for pressurising the chlorine to feed the
piping system 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 piping system is a
function of the characteristics required (throughput, operating pressure, maximum
pressure). A non-return system should be installed on the downstream 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.
5.17 Protection Against Overpressure and Thermal Expansion
Liquid Chlorine Thermal Expansion
Liquid chlorine has a very high coefficient of thermal expansion. Consequently, any
warming of liquid chlorine trapped between closed valves, will lead to a build-up of
pressure, which can rapidly exceed the pressure rating of the piping system. This
warming can be caused by factors such as the surrounding air being warmer than the
pipe, sunlight, warm or radiant items near the pipe, etc. Therefore, the piping
system should be designed, and isolation procedures devised, which avoid the
possibility of trapping chlorine between two points of isolation.
Where isolation valves are nevertheless provided along the length of the piping
system, provision must be made to allow for thermal expansion of any trapped liquid
chlorine. Such provision will complicate the piping system and should preferably be
provided at least at one of the ends of the piping system and situated inside the
premises of an industrial location. This can be achieved by either of the following
methods:
• Closed expansion chamber, separated from the chlorine flow by a bursting
disc; this chamber should be filled with inert gas at ambient pressure and
equipped with pressure measurement and alarm.
• Volume compensator using a nitrogen gas cushion as buffering medium (same
remark as here above); this can also be combined with the previous system.
• Spring loaded expansion chamber.
• Bursting discs, relief valves or a combination of these, discharging into a
vessel or a collection system. The bursting of the disc or the functioning of
the relief valve should be alarmed (see GEST 87/133 – Overpressure Relief
of Chlorine Installations).
• A heated chlorine gas “bubble” may also be used but the design should take
the following into account:
o The possibility of excess pressure from the build-up of inert gasses.

April 2023 Page 15 of 31

 GEST 73/25
13th Edition

o The ability to reliably detect failure of the heating system (in any case the
temperature may not exceed 120°C).
Drawings of acceptable methods of relieving excess pressure are shown in
Appendices 1A, 1B, 1C and 1D.
The volume of the expansion chamber can be calculated on the basis of the volume
increase of the chlorine (in the piping system) due to a temperature increase from
the minimum possible operating temperature to the maximum design temperature
plus a 10% safety margin; alternatively, a good practice is to give this chamber a
volume of 20% of the piping system section to be protected.
Overpressure of the Gaseous Chlorine
Under most circumstances it is unlikely that gaseous chlorine pipe work will require
a pressure relief system to guard against effects of excess pressure (see GEST
87/133 – Overpressure Relief of Chlorine Installations).
If the compressor is capable of overpressuring the piping system, a pressure
interlock or a relief device must be installed. The pressure relief should be located
directly at the outlet of the compressor. These relief devices (bursting discs, relief
valves or a combination of both) should always be connected to an absorption
system or a point of use in the liquefaction (see GEST 87/133 – Overpressure
Relief of Chlorine Installations).
Protection against Surge for Liquid Chlorine
When the velocity of a fluid in a line is suddenly changed, pressure waves occur due
to the change in momentum. When the amplitude of these pressure waves becomes,
critical this is referred to as “Water Hammer” (or Joukowski effect). There can be
pressure increases as well as negative pressures. The usual initiating event for this
condition is the rapid closure of a valve.
More information on this can be found at the following website:
https://publicwiki.deltares.nl/display/WANDA/Fluid+transient+fundamentals.
A calculation of the maximum pressure reached in these cases will be made together
with the chlorine customer. The system should withstand this maximum pressure
and, if necessary, the valve closure (depending on the characteristic of the valve)
time can be increased to reduce the severity of the surge. Additionally, appropriate
surge protections can be installed at least at one end of the piping system (bursting
disc with exhaust in safety storage connected to chlorine absorption, sealed pots
with inert or chlorine gas …); alternatively, the pipe and accessories can be
designed to withstand this maximum pressure.
A surge wave in a pipe will also generate out-of-balance forces at anchors or other
restraints, and these must be designed for the maximum load. It must be noted that
these are dynamic loads and so an appropriate dynamic load factor should be
applied.
All changes in the chlorine piping system should be agreed between supplier and
customer.
5.18 Monitoring the Piping System Conditions
All precautions should be taken to avoid maloperation by means such as locks, logic
systems, interlocks etc. It should be possible to stop automatically the transfer of
chlorine into the piping system in the event of abnormal conditions such as pressure,
temperature and flow.

April 2023 Page 16 of 31

 GEST 73/25
13th Edition

All long-distance piping system outside a single operational facility should include as
a minimum the following monitoring equipment at least at the inlet of the piping
system:
• Measurement and recording of the pressure and temperature.
• Maximum and minimum pressure (and temperature for chlorine gas) alarms.
If the piping system is completely or partly double walled, a leak detector should be
installed (e.g., pressure alarm or chlorine detector on the purge gas of the double
wall).
Permanent connections by telephone and/or computer connection should be
provided between the two ends of the piping system.
5.19 Materials of Construction
All the materials used have to be compatible with chlorine in the design conditions
(See “GEST 79/82 - Materials of Construction for Use in Contact with Chlorine”).
The materials and equipment should be obtained from approved suppliers with a
documented quality insurance procedure.
Piping System
The steel chosen for the construction of the piping system 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 (see 5.2) 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. Where welded pipe is chosen, the full length of the weld
seam of every tube should be inspected by ultrasonic or electromagnetic methods or
should be 100% X-rayed.
Flanges, Nuts and Bolts
The metal used for flanges, nuts and bolts should possess the same characteristics as
that of the piping system.
Gaskets
The gasket used should be made in a material with positive experience on chlorine
(see “GEST 94/216 - Gaskets selection for the use in Liquid Chlorine and Dry or
Wet Chlorine Gas Service” for further information).
The mounting of the gaskets should be performed by well-trained people; only new
gaskets should be used.
The stress relaxation resistance of some gaskets decreases with increasing thickness.
It is therefore recommended that gaskets be fitted inside the bolt circle and should
have thickness compatible with the flange rating.
Where spirally wound gaskets using metal windings and a chlorine compatible filler
material are used, care should be taken to ensure that the flange faces are
machined to the joint manufacturer’s recommended standard and that the mating
flanges are similar, i.e., of the same material and surface finish.
Under no circumstances should gasket contact surfaces be machined in a manner
that leaves tool marks extending radially across the seating surface.

April 2023 Page 17 of 31

 GEST 73/25
13th Edition

No grease which is not compatible with chlorine may be used and torque
calculations should be done with the friction coefficient of the chlorine compatible
grease.
Jointing compounds are not recommended, and paste should not be used with spiral
wound, or PTFE gaskets under any circumstances. However, when paste is used for
flanged joints which have to be broken and remade frequently for process or
maintenance reasons, care should be taken to ensure that the paste is:
• Compatible with chlorine
• Compatible with the gasket material
• Used sparingly and is not forced into the bore of the pipe.
• Spread evenly over the joint surface.
Thermal Insulation
If the installation of thermal insulation is necessary, the materials to be applied
should meet the following criteria:
• Chemically inert to chlorine
• Not flammable or combustible, or at least auto-extinguishing
For cold liquid chlorine, there is no predominant insulation material, but the
following are satisfactorily used:
• Foam glass
• Mineral wool
Other materials are sometimes used please check the reactivity of the materials
with chlorine.
Except for insulation material with closed cells, vapour barriers must be utilised to
prevent the accumulation of moisture on the insulation of any insulated pipe that
operates at temperatures below ambient temperature.
For the cladding used to protect externally the insulation layer and to prevent as far
as possible ingress of water, several materials can be used, according to the local
environment (aluminium, stainless steel, coated carbon steel, plastic, resin, fibre
reinforced resin …). A sufficient spacing should be foreseen between cladding and
the liquid barrier to avoid damaging this one.
For double wall piping system, no insulation will be installed in the inner space.
5.20 Supports
The supports of the piping system should permit the thermal expansion/contraction
of the piping system due to any likely variations in temperature, taking into account
the maximum and minimum achievable temperatures. They should also deal with
any possible earth movement. For above ground piping system, it is preferable to
use large radius expansion loops.
Expansion bellows should not be used because they may be weak points in the
construction, unless a detailed study proves adequacy. 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.
The support system should be designed to avoid any ingress of moisture under the
thermal insulation, where fitted.

April 2023 Page 18 of 31

 GEST 73/25
13th Edition

Buried Piping System.

If the terrain to be crossed is unstable or susceptible to movement, a piping system
should not be buried in the ground.
Piping System Above-Ground or in Trenches
The supports should be fixed on foundations, which provide adequate rigidity (taking
into account surge effects for liquid chlorine). 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).
5.21 Pipe Inspection and Testing
Inspection of Piping System Materials
Piping system 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.
Inspection Procedures during Construction
To guarantee a fault-free construction, the inspection procedures should follow the
required codes rigorously, and as a minimum should encompass the following points:
• Certification of welders and of their methods of welding.
• 100% radiography or ultrasonic examination (if radiography is not possible) of
the welds; dye penetrant testing is also useful as it can sometimes detect
defects not identified by radiographic techniques (thorough cleaning is
required after dye penetrant testing).
• Tests of tensile, bending and impact strength, of reference and welded test
pieces. It is advisable that some production welds are cut out and impact
tested, in addition to the testing completed as part of the procedure and
welder qualifications.
• Thickness control.
• Hydraulic pressure test at least at 1.5 times the design pressure after laying
the piping system.
• Leak test after the piping system has been hydraulically tested and dried.
• Check of the heat tracing system, if present.

6 OPERATION
6.1 Cleaning and Drying before Putting into Service
Before putting the piping system into service, all equipment should be degreased,
cleaned and dried according to the GEST 80/84 - Code of Good Practice for the
Commissioning of Installations for Dry Chlorine Gas and Liquid.
6.2 Leak Testing
The dried piping system should then be tested for possible leaks.
The recommended procedures are described in the GEST 80/84 - Code of Good
Practice for the Commissioning of Installations for Dry Chlorine Gas and Liquid.

April 2023 Page 19 of 31

 GEST 73/25
13th Edition

6.3 Commissioning and Testing before Putting into Service

A certain number of final precautions should be taken before putting the piping
system into service and they are described in the GEST 80/84 - Code of Good
Practice for the Commissioning of Installations for Dry Chlorine Gas and Liquid.
6.4 Putting the Piping System into Service
When putting a chlorine piping system into service, the following attention points
should be taken into account:
• For liquid chlorine, flashing will append at the leading edge of the liquid
phase and the vapour lock can cause flow restrictions.
• For gaseous chlorine, the expansion will cool down the fluid with potential
partial condensation and pressure swings.
• If hot work has been performed on the piping system, correct cooling of the
line will be ensured before introducing chlorine.
6.5 Running a Chlorine Piping System
Quality of the Chlorine Introduced
The chlorine introduced in the piping system should be ascertained to be dry, clean
and exempt of reactive impurities (see GEST 80/84 - Code of Good Practice for
the Commissioning of Installations for Dry Chlorine Gas and Liquid).
The quality of chlorine introduced in the piping system should be monitored and
checked periodically.
Physical Conditions
To avoid possible erosion, flow limitations and pressure swings, it is important to
make sure no change of phase occurs in the piping system.
This could be caused by external temperature variation or by abnormal variation of
the pressure at the inlet of the pipe.
6.6 Periodical Inspection and Testing of Long-Distance Piping System.
Routine Visual Check
• Above Ground Installation:
• A regular visual check (frequency based on a risk assessment) of the piping
system and its surroundings should be carried out to ensure nothing
abnormal happens or has happened. Particular attention should be paid to
the following aspects: Possible external corrosion.
• Damage to the supports.
• Areas of frosting or deterioration of the thermal insulation and its
protection.
• Unforeseen works in the vicinity 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 Piping System:
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 piping system are as specified.

April 2023 Page 20 of 31

 GEST 73/25
13th Edition

• A check that no unauthorised activity (e.g., digging …) is taking place near

the piping system.
• A check that the warning devices (flow - and pressure measurements) and
communication systems are functioning correctly.
Periodic Inspection
The cathodic protection should be checked at least once per year.
Periodic maintenance inspection and testing of the system is required, with an
interval in-line with requirements of the relevant competent body. It should take
into account the following aspects:
• Thickness (ultrasonic) testing of the pipe walls in specific areas as defined
at the time of construction (for example where there is a possible risk of
erosion).
• A check on all equipment, including the expansion chambers. 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 piping system systems.
During the periodic check of the piping system, the personnel should be provided
with checklists covering the principal points to be controlled. These checklists and
additional remarks, if necessary, are collected in a logbook.
6.7 Management of Changes
Due to the possible severe consequence of a leak form a chlorine piping system, the
site management of changes policy should include all working condition and
equipment/accessories modifications for which a safety study (HAZOP or similar)
would be systematically performed.
A careful written recording of all inspections, tests, repairs and modifications to the
piping system will be ensured.
6.8 Taking the Piping System 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 piping
system when it is taken out of service. If the shutdown is to be followed by
emptying, it is 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 leading to very low temperature, however at low
pressure). When the liquid has been removed, one can proceed according to the
gaseous chlorine piping system procedure.
For a few hours’ shutdown of a gaseous chlorine piping system the internal pressure
should be lowered; the pressure may not fall below atmosphere to avoid air ingress
but, whenever possible, stay below the chlorine vapour pressure corresponding to
the piping system 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 piping system, or if the duration of the
shutdown is too long to guarantee a correct continuous surveillance, the thermal
tracing, if any, will be kept off, and the chlorine in the piping system will be
replaced by dry inert gas (dew point lower than minus 40°C) by depressurisation,

April 2023 Page 21 of 31

 GEST 73/25
13th Edition

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 piping system shall be isolated upstream and
downstream by the installation of blind flanges, or the removal of a spool piece
provided for this purpose. However, the piping system should not be left open to
moist atmosphere to prevent corrosion (the FeCl3 layer will attract moisture and
become corrosive liquid: see GEST 10/362 – Corrosion Behaviour of Carbon Steel
in Wet and Dry Chlorine).
Additional information on disconnecting the equipment can be found in the GEST
80/84 - Code of Good Practice for the Commissioning of Installations for Dry
Chlorine Gas and Liquid.
No welding intervention will be allowed until it has been ascertained that the piping
system is fully free of chlorine.
6.9 Intervention in Case of Ingress of Moisture
All necessary precautions must be taken to avoid the entry of moisture or reactive
materials into the piping system.
If any moisture ingress occurs accidentally, with formation of large amount of ferric
chloride hydrate on the internal wall, the first action will be to flush the piping
system with nitrogen to remove possible hydrogen formation.
If possible, a first mechanical removal of the ferric chloride deposit can be done,
followed by cleaning of the piping system by pigging.
If necessary, the remaining hydrates could be eliminated by one of the following:
• 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) after
having replaced all gaskets.
• 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).
• Drying with hot inert gas flow until a dew point lower than minus 40 °C is
reached and maintained for several hours (at least 24 hours).
6.10 Intervention in the Event of Failure of the HEAT Tracing (for Gas Piping
system)
In the event of a failure leading to the shut-down of the heat tracing system, which
should be alarmed, it is preferable to reduce the pressure in the piping system and
to vent it down to avoid chlorine condensation. If anyway accidental liquefaction
has taken place, the piping system should be taken out of service (see GEST 80/84 –
Commissioning and Decommissioning of Installations for Dry Chlorine gas and
Liquid).
6.11 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 and parties (producers and users) involved, including external
emergency services.

April 2023 Page 22 of 31

 GEST 73/25
13th Edition

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 or the effects of chlorine-iron fire. Periodic
exercises and re-training shall be organised to ensure maintaining sufficient
knowledge and skills.
Whenever possible, common routing of the piping system with electric cables or
flammable fluids should be avoided.
Self-contained breathing equipment and protective clothing suitable for dealing with
a chlorine leak should be available in lockers located at least near to the ends of the
piping system and accessible at any time in case of emergency.
A means of indicating the wind direction should be installed to inform the operators
of the direction of gaseous dispersion that might occur in the event of a leak. The
persons involved in a chlorine leak should escape perpendicularly to the wind
direction.

7 REFERENCES
GEST 73/17 - Storage of Liquid Chlorine
GEST 76/55 - Maximum Levels of Nitrogen Trichloride in Liquid Chlorine
GEST 78/73 - Design Principles and Operational Procedures for Loading/Off
Loading Liquid Chlorine Road and Rail Tankers and ISO-Containers
GEST 79/82 - Materials of Construction for Use in Contact with Chlorine
GEST 80/84 - Code of Good Practice for the Commissioning of Installations for
Dry Chlorine Gas and Liquid
GEST 87/133 – Overpressure Relief of Chlorine Installations
GEST 94/216 – Gaskets Selection for the Use in Liquid Chlorine and Dry or Wet
Chlorine Gas Service
GEST 10/362 – Corrosion Behaviour of Carbon Steel in Wet and Dry Chlorine
GEST 17/492 - Specifications and Approval Procedure for Valves to be used in
Liquid Chlorine or Dry Chlorine Gas.

April 2023 Page 23 of 31

 GEST 73/25
13th Edition

Appendix 1A – Pressure Relief System for Liquid Chlorine Piping

System – Expansion Vessel

NOTE: Instrumentation symbols in accordance with ANSI/ISA5.1-1984

April 2023 Page 24 of 31

 GEST 73/25
13th Edition

Possible alternative solution using a nitrogen gas cushion.

Drawing from Pamphlet 60, by courtesy of the Chlorine Institute.

April 2023 Page 25 of 31

 GEST 73/25
13th Edition

Appendix 1B – Pressure Relief for Liquid Chlorine Piping System –

Bursting Disc
NOTE: Instrumentation symbols in accordance with ANSI/ISA5.1-1984 (R1992)

April 2023 Page 26 of 31

 GEST 73/25
13th Edition

Appendix 1C – Example of Volume Compensator for Liquid Chlorine

Piping System

April 2023 Page 27 of 31

 GEST 73/25
13th Edition

Appendix 1D – Pressure Relief for Liquid Chlorine Piping System –

Gaseous Chlorine Expansion Tank
NOTE: Instrumentation symbols in accordance with ANSI/ISA5.1-1984 (R1992).
This system might not give protection for pressure surge. The pressure surge will
result in a liquid spray into the gaseous chlorine. The liquid spray is colder than the
chlorine gas resulting in condensation and pressure drop which might increase the
effects of the pressure surge.

TIAS
+/-

isolation

expansion tank
self-regulating electrical heating

gaseous sheet

perforated metal plate

space
liquid

Cl2 - pipeline

April 2023 Page 28 of 31

 GEST 73/25
13th Edition

Appendix 2A – Sliding Support Resting on Structural Steel – Typical

Arrangement for Sub-Zero Operation.
Note: for systems operating at ambient temperature, the same arrangement may be
used but with the slide clamped directly to the pipework.

Clamping collar

Pipe supports

Pipe

Slides

April 2023 Page 29 of 31

 GEST 73/25
13th Edition

Appendix 2B – Hanger Assembly Used with Limit Stop – Typical

Arrangement for Sub-Zero Operation.
Notes:
1. The manufacture of hangers needs to be carefully controlled to ensure that
no weakness is created as a result of threading or welding. A minimum
diameter of 12 mm is recommended.
2. For non-insulated systems operating at ambient temperature the same
arrangement may be used but with the clamp fitted directly to the pipework.

April 2023 Page 30 of 31

 GEST 73/25
13th Edition

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 Partners.

Details and fees are available from:

Euro Chlor
Rue Belliard 40
Box 15
B-1040 Brussels
Belgium

Email: eurochlor@cefic.be
Internet: http://www.eurochlor.org

April 2023 Page 31 of 31