BCGA Bulk Cryogen Storage CP36

BCGA CODE OF PRACTICE CP 36

BULK CRYOGENIC LIQUID STORAGE

AT

USERS’ PREMISES

2006

BCGA CODE OF PRACTICE CP 36

BULK CRYOGENIC LIQUID STORAGE AT

USERS’ PREMISES

2006

Copyright © 2006 by British Compressed Gases Association. First printed 2006. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, without permission from the publisher:

BRITISH COMPRESSED GASES ASSOCIATION

1 Gleneagles House Vernon Gate South Street

Derby DE1 1UP

Website: www.bcga.co.uk

ISSN 0260-4809

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BCGA CP36 © 2006

PREFACE

The various publications issued by the British Compressed Gases Association have the objective of establishing consistency in design, construction practices and user operational and maintenance procedures, in order to establish high standards of reliability and safety in the interests of employers, employees and the general public. The Association endeavours to compile these documents using the best sources of information known at the date of issue. The information is used in good faith and belief in its accuracy. The publications are intended for use by technically competent persons and their application does not, therefore, remove the need for technical and managerial judgement in practical situations and with due regard to local circumstances, nor do they confer any immunity or exemption from relevant legal requirements, including by-laws. The onus of responsibility for their application lies with the user. The Association, its officers, its members and individual members of any Working Parties can accept no legal liability or responsibility whatsoever, howsoever arising, for the consequences of the use or misuse of the publications. For the assistance of users, references are given, either in the text or Appendices, to publications such as British, European and International Standards and Codes of Practice, and current legislation that may be applicable. The intention of BCGA is that this document should be read and used in the context of these references where the subjects have a bearing on the local application of the processes or operations carried out by the user. BCGA’s publications are reviewed, and revised if necessary, at three-yearly intervals. Readers are advised to check the list of publications on the Association’s website www.bcga.co.uk to ensure that the copy in their possession is the current version.

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BCGA CP36 © 2006

http://www.bcga.co.uk/

C O N T E N T S

Section Page Terminology and Definitions 6 Introduction 7 Scope 8

1. GENERAL DESIGN CONSIDERATIONS 8 1.1 General 8 1.2 Properties of Nitrogen, Argon and Oxygen 8 1.3 Precautions 9 1.4 Oxygen Deficiency or Enrichment of the Atmosphere 9 1.5 Cryogenic Burns 9 1.6 Air Condensation 9 1.7 Oil, Grease, Combustible Material and other Foreign Matter 10 1.8 Cleaning for Oxygen Service 10 1.9 Embrittlement of Materials 11 1.10 Fire Fighting System 11 1.11 Hot Work 11 1.12 Ignition Sources 11 1.13 Insulation Materials 11 1.14 Regulation and Codes 11 2. LAYOUT AND DESIGN FEATURES 12 2.1 General 12 2.2 Design and Manufacture of the Tank 12 2.3 Safety Distances 12

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BCGA CP36 © 2006

Section Page 2.4 Location of Installation 13 2.4.1 Protection against Electrical Hazards 14 2.4.2 Installation Level and Slope 14 2.4.3 Position of Gas Vents 14 2.4.4 Vapour Clouds 14 2.4.5 Liquid Transfer Area 15 2.4.6 Ventilation of Pump Enclosure 16 2.4.7 Equipment Layout 16 2.4.8 Pressure Relief Devices 16 2.4.9 Isolation Valves 17 2.4.10 Secondary Isolation Valves 17 2.4.11 Couplings 17 2.4.12 Non-return valve 17 2.4.13 Fencing 17 2.4.14 Vaporisers 18 2.4.15 Foundations 18 2.4.16 Bolting Down 19 2.4.17 Other requirements 19 3. ACCESS TO THE INSTALLATION 19 3.1 Means of Escape 19 3.2 Personnel 19 3.3 Access to Installation Controls 19 3.4 Notices and Instructions 20 3.4.1 General Precautions 20 3.4.2 Identification of Contents 21 3.4.3 Legibility of Notices 21 3.4.4 Operating and Emergency Instructions 21 4. TESTING AND COMMISSIONING 21 4.1 Testing of Installation 21 4.1.1 Pressure Test 21 4.1.2 Pressure Relief Devices 22 4.2 Adjustment of Process Control Devices 22 4.3 Posting of Notices 22 4.4 Commissioning 22

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BCGA CP36 © 2006

Section Page 5. OPERATION AND MAINTENANCE 23 5.1 Operation of the Installation 23 5.1.1 Operating Personnel and Procedures 23 5.1.2 Operating Difficulty or Emergency 23 5.2 In Service Inspection and Maintenance 24

5.2.1 General 24 5.2.2 Site 24 5.2.3 Tank Installation 24 5.2.4 Tank 24 5.2.5 Vaporisers 24 5.2.6 Pressure Relief Devices 25 5.2.7 Ancillary Equipment 25 5.2.8 Isolation Valves 25 6. PERMIT TO WORK 25 7. MODIFICATION OF SYSTEM 25 8. TRAINING AND DOCUMENTATION 25 8.1 Documentation 25 8.2 Training of Personnel 26 8.3 Emergency Procedures 27 9. REFERENCES 28 APPENDIX 1 HAZARDS FROM OXYGEN ENRICHMENT 31 APPENDIX 2 SAFETY DISTANCES 32 APPENDIX 3 PLAN VIEW OF LIQUID TRANSFER AREA, ACCESS APRON AND TANKER STANDING AREA 33 APPENDIX 4 RELIEF DEVICE INSPECTION, TESTING AND 38 EXAMINATION APPENDIX 5 “BURNS” DUE TO VERY COLD LIQUEFIED GASES 39 HISTORY AND OBJECTIVES OF BCGA 41

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BCGA CP36 © 2006

BULK CRYOGENIC LIQUID STORAGE AT USERS’ PREMISES Terminology & Definitions

1. Shall: Indicates a mandatory requirement for compliance with this Code of Practice. 2. Should: Indicates a preferred requirement but is not mandatory for compliance with

this Code of Practice. 3. May: Indicates an option available to the user of this Code of Practice. 4. Tank: Indicates an assembly, complete with a piping system, of an inner vessel and an

outer jacket to contain insulation. The insulation space will normally be subject to a vacuum.

5. Vessel: Indicates a pressure vessel, which may or may not be insulated. 6. System 7. Relevant Fluid 8. Danger These terms are defined in the 9. Examination Pressure Systems Safety Regulations 10. User 2000 (18) 11. Protective Device 12. Owner 13. Access Apron: Indicates an area between the tank and a tanker where the process

operating controls on both tank and tanker are accessible to the operator during filling/discharging. This area will normally have provision for containing or diverting a liquid spillage.

14. Liquid Transfer Area: Indicates an area adjacent to the tank which surrounds the

tanker, when the latter is in the filling/discharging position, and which includes the access apron.

15. Competent Person: The competent person should have such practical and theoretical

knowledge and actual experience of the type of plant which he has to examine as will enable him to detect defects or weaknesses, which it is the purpose of the examination to discover, and to assess their importance in relation to the strength and function of the plant. Equivalent levels of knowledge and experience are also required for competent persons engaged in the writing or certifying of Written Schemes of Examination.

16. Outer Jacket: The insulation container.

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BCGA CP36 © 2006

BULK CRYOGENIC LIQUID STORAGE AT USERS’ PREMISES Introduction

In 2004, the Industrial Gases Committee (IGC) of the Commission Permanente Internationale (CPI) published a Document 115/04 (1) entitled “Storage of Cryogenic air gases at Users’ Premises”. The objective of the BCGA Code of Practice is to make reference where applicable to UK legislation and British Standards where these apply to cryogenic air gas systems and to take into account the specific practices of the UK industrial gas companies particularly in relation to safety distances. This Code of Practice is based generally on the IGC Document but in some instances gives more detailed requirements for the UK. The BCGA is grateful for the active help and co-operation of the Health and Safety Executive. With the permission of the IGC, sections of the IGC Document have also been duplicated. The BCGA wishes to acknowledge the work done by the IGC committee which prepared Document 115/04. The storage of cryogenic gases in the liquid state under pressure at users' premises not only provides an efficient way of storing gas, but improves safety when used in conjunction with a distribution system by eliminating the need for cylinder handling. However, the particular properties of cryogenic gases necessitate certain precautions to be taken and certain rules to be followed. As part of the continuing effort to promote a high standard of safety the former BCGA documents CP19 & 21 have been reviewed and this new document incorporates the results of that review plus recent information and experience in connection with the safety and reliability of liquid cryogenic storage systems. This BCGA document is intended for the guidance of those persons directly associated with the design, operation and maintenance of bulk liquid storage installations. It does not claim to cover the subject completely but gives advice and should be used with sound engineering judgment. All new storage installations shall comply with this document.

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BCGA CP36 © 2006

SCOPE

A cryogenic air gas system installation on a users’ premises is defined for the purposes of this Code of Practice as the installed static liquid storage tank together with the control equipment and safety devices, vaporising equipment, the storage enclosure and the liquid transfer area. This document covers tanks with an individual water capacity between 1,000 and 125,000 litres. Installations with individual tanks below 1,000 litres are covered in BCGA Code of Practice CP 28 (31). For installations in excess of 125,000 litres including multiple tanks operating as a single tank, this document may also be used as a guidance; applicable regulation may impose different safety distances and legal requirements e.g. COMAH (The Control of Major Accident Hazards Regulations) (33). Transportable cryogenic liquid storage tanks (such as “liquid cylinders”, cryogenic receptacles, containerised tanks and road tankers) are specifically excluded from this Code of Practice. For cylinder filling depots operated by gas suppliers, individual tank storage capacity is normally less than 125,000 litres. In such cases the BCGA Code of Practice on Cryogenic Storage at Production Sites, Reference CP 37 (2) should only apply to these systems when the tank is connected to a manufacturing plant. However the safety distances, the provision for periodic inspection, testing and examination and the liquid transfer area as specified in this Users’ Premises Code of Practice may be applied.

1. GENERAL DESIGN CONSIDERATIONS 1.1 General

Gaseous oxygen, nitrogen and argon are colourless, odourless and tasteless. Nitrogen and argon are non-toxic but asphyxiant. Oxygen is not toxic; it is slightly denser than air. It is not a flammable gas but vigorously supports combustion. Breathing pure oxygen at atmospheric pressure is not dangerous although exposure for several hours may cause temporary functional disorders to the lungs. The following documents should be taken into consideration: BCGA GN11 Use of gases in the workplace. The management of risks associated with reduced oxygen atmospheres (34) IGC Doc. 4/00 Fire hazards of oxygen and oxygen enriched atmospheres (32) IGC Doc. 44/00 Hazards of inert gases (35)

1.2 Properties of nitrogen, argon and oxygen

The physical properties of nitrogen, argon and oxygen are:

Nitrogen Argon Oxygen

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BCGA CP36 © 2006

Content in air Vol % 78.1 0.9 21 Gas density at 1.013 bar, 15 °C kg/m 3 1.19 1.69 1.36 Boiling temperature at 1.013 bar °C -196 -186 -183 Liquid density at 1.013 bar and boiling temperature kg/l 0.8 1.39 1.14 Gas volume of the liquid at ambient conditions l(gas) per l(liquid) 680 810 840 Cold oxygen, nitrogen and argon vapours are heavier than air and may accumulate in pits and trenches.

1.3 Precautions

The properties of oxygen, nitrogen and argon justify the special precautions detailed in 1.4 to1.13

1.4 Oxygen deficiency or enrichment of the atmosphere

The atmosphere normally contains 21% by volume of oxygen. Enrichment may give rise to a significant increase in the rate of combustion. Many materials including some common metals which are not flammable in air, may burn in oxygen, when ignited. Detailed information on this subject is contained in IGC Document 04/00 (32). Nitrogen and argon will act as asphyxiants by displacing the oxygen from the atmosphere. The hazards from oxygen enrichment or deficiency are explained in the BCGA/IGC documents detailed in 1.1. Good ventilation shall always be provided in places where liquid cryogenic gases are stored and/or transferred.

1.5 Cryogenic burns

Severe damage to the skin may be caused by contact with liquid cryogenic gases, and their cold gases or with uninsulated pipes or receptacles containing liquid cryogenic gases. For this reason, gloves and eye protection shall be worn when handling equipment in liquid cryogenic gases service. All the safety aspects of handling cryogenic liquid oxygen cannot be covered adequately in this Code of Practice. The reader is therefore referred to the British Cryoengineering Society, ‘Cryogenic Safety Manual’ (6), for further information.

1.6 Air condensation

Ambient air will condense on uninsulated pipes and vessels containing liquid nitrogen causing local oxygen enrichment of the atmosphere. Insulating materials should be chosen bearing in mind that oxygen enrichment may occur.

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BCGA CP36 © 2006

1.7 Oil, grease, combustible material and other foreign matter

Most oils, grease and organic materials constitute a fire or explosion hazard in oxygen enriched atmospheres and must on no account be used on equipment which is intended for oxygen service. Only materials acceptable for the particular oxygen service application may be used. All equipment for oxygen service shall be specifically designed and prepared.

1.8 Cleaning for Oxygen Service

Before putting equipment into service with oxygen, either for the first time or following maintenance, it is essential that all surfaces which may come into contact with an oxygen enriched environment are "clean for oxygen service", which means: dry and free from any loose or virtually loose constituents, such as slag, rust, weld residues, blasting materials and entirely free from hydrocarbons or other materials incompatible with oxygen. The maintenance and assembly of equipment for oxygen shall be carried out under clean, oil free conditions. All tools and protective clothing (such as overalls, gloves and footwear) shall be clean and free of grease and oil; where gloves are not used, clean hands are essential. Degreasing of an installation or parts of it demands the use of a degreasing agent which satisfies the following requirements • no or slow reaction with oxygen • no or low toxicity (low vapour pressure to keep vapour concentration below

threshold limit) • material compatible with oxygen

It is important that all traces of degreasing agents are removed from the system prior to commissioning with oxygen. Some agents, such as halogenated solvents, may be non-flammable in air, but can explode in oxygen enriched atmospheres or in liquid oxygen. Good housekeeping is necessary to prevent contamination by loose debris or combustibles. Neither nitrogen nor argon reacts with oil or grease, but it is good practice to apply a good standard of cleanliness, although not as stringent as that required for oxygen installation. Advice on the cleaning of oxygen systems is given in the following documents: IGC Doc 33/06 Cleaning of equipment for Oxygen Service - Guidelines (3) gives practical guidance on how to prepare equipment for oxygen service. BS IEC 60877 Code of Practice for procedures for ensuring the cleanliness of industrial process, measurement and control equipment for oxygen service (27).

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BCGA CP36 © 2006

BCGA Technical Report TR3 (4) gives information about cleaning oxygen system components without the use of chemical solvents.

1.9 Embrittlement of materials

Many materials, such as some carbon steels and plastics, are brittle at very low temperatures and the use of an appropriate material for the service conditions prevailing is essential. Metals suitable for cryogenic service include 9% nickel steel, 18/8 stainless steel and other austenitic stainless steels, copper and its alloys and aluminium alloys. PTFE (polytetrafluoroethylene) is the most widely used plastic material for sealing purposes in cryogenic service but other reinforced plastics are also used. For further information on materials see BS 5429 (5). Sealing materials should be kept out of the product flow.

1.10 Fire Fighting System

First aid fire fighting equipment comprising water hose reels and/or dry powder extinguisher shall be available near a liquid oxygen storage installation. The type and quantity of the fire fighting equipment depends on the size of the installation and should be discussed with the fire authorities.

1.11 Hot Work

No hot work shall be performed in the vicinity of the installation without a Permit to Work. (See 6).

1.12 Ignition Sources

Smoking and open fires shall be prohibited within the minimum distances specified in Section 2.3 of this Code of Practice For electrical equipment, see the safety distance diagram for oxygen storage in Appendix 3.

1.13 Insulation materials

The components used in insulating materials shall be such that the finished insulation is suitable for oxygen service.

1.14 Regulation and codes

This BCGA Code of Practice describes minimum requirements. All relevant statutory regulations shall be applied and relevant Codes of Practice, standards and specifications shall be taken into account in the designs and installations covered by this Code of Practice (see reference list in Section 9).

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BCGA CP36 © 2006

Liquid oxygen falls within the scope of DSEAR (The Dangerous Substances and Explosive Atmospheres Regulations) (36) therefore a risk assessment shall be carried out to ensure that all equipment is in compliance with these regulations.

2 LAYOUT AND DESIGN FEATURES 2.1 General

The installation shall be sited to minimise risk to personnel, local population and property. Consideration should be given to the location of any potentially hazardous processes in the vicinity, which could jeopardise the integrity of the storage installation. An installation may, because of its size or strategic location, come within the scope of specific planning controls. If so, the siting of any proposed installation shall be discussed and agreed with the local authority and appropriate sections of the Health and Safety Executive.

2.2 Design and Manufacture of the Tank

Tanks and associated equipment shall be designed, manufactured and installed in accordance with recognised pressure vessel, storage tank and piping codes that meet the requirements of the Pressure Equipment Regulations 1999 (28).

Tanks shall be designed to withstand wind loads in accordance with the appropriate

design codes e.g BS 6399 Part 2 (7). 2.3 Safety distances

Safety distances are defined as the distance from the exposure to:

Safety distances are defined as the distance from the exposure to:

a) any point on the storage system where in normal operation leakage or spillage can occur (e.g. hose couplings, including those on extended fill lines, relief valve vents, etc), or

b) the tank outer jacket, or

c) the tank nozzles, whichever gives the greatest safety distance to the cryogenic storage tank.

Safety distances are intended to: a) protect personnel from exposure to oxygen enriched or depleted atmospheres

and to prevent fire enhancement in the event of a release of liquid oxygen

b) protect the installation from the effects of thermal radiation or jet flame impingement from fire hazards.

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The safety distances given in this Code of Practice are based on experience and calculations of minor release. The safety distances given are not intended to protect against catastrophic failure of the liquid storage vessel. Previous operating history, the protective devices fitted, material properties and the mode of vessel construction support this philosophy. The distances given in Appendix 3 are intended to protect the storage installation as well as personnel and the environment. They are considered to give protection against risks involved, according to practical experience, in the normal operation of storage installations covered by this Code of Practice.

These distances correspond to well established practice and are derived from operational experience within Europe and the USA. They relate to over hundreds of thousands of tank years in service. Consideration shall be given for provision to divert any spillage towards the safest available area. The safety distances provided to protect the installation against the effects of thermal radiation and jet flame impingement may be reduced by the provision of impervious fire resisting walls of concrete, masonry, or similar construction, (see BS 476 ‘Fire Tests on Building Materials and Structures’ (8)) to a minimum height of 2.5m. The distance between the installation and the exposure around the ends of the fire walls should be equal to or greater than the separation distance given in Appendix 3. Care must be taken to ensure that good ventilation is retained and a minimum clearance between the barrier or wall and the installation shall be 0.6 metres to allow free access to and escape from the enclosure. It is recommended that walls should not be constructed on more than two sides of the installation. Where this is unavoidable a risk assessment shall be conducted.

2.4 Location of the installation

Storage installations should be situated in the open air in a well-ventilated position and where there is no risk of damage by passing vehicles. Installations shall not be located where natural air ventilation is inhibited, unless they are subjected to a suitable and sufficient risk assessment. Examples of locations where such risk assessments are required are:- • inside structures with two or more sides and a roof • enclosed on three or more sides • below ground level or where there are pits, ditches and other ground depressions.

Storage tanks should be at the same level as the tanker parking area to enable the operator/driver to control the transfer operations.

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2.4.1 Protection against electrical hazards

The location shall be chosen so that damage to the installation by electric arcing from overhead or other cables cannot occur. Protection against lightning is not normally required, but may be necessary to comply with local conditions or site regulations. Any necessary lightning protection should be installed in accordance with BS 6651 (11). Flame proof, explosion proof, or other forms of classified electrical equipment are not necessary for cryogenic liquid systems since the products are not classified as flammable gases according to BS EN 60079 (12). Electrical equipment, which is necessary for the installation shall be to BS EN 60529 (13), protection class IP54 or better. For more severe environmental conditions protection class IP55 (designed to protect against water jets) should be used. Consideration should be given to earth bonding of the installation and pipework. All electrical installation shall comply with current electrical legislation

2.4.2 Installation level and slope

Where liquid cryogenic storage tanks are required to be installed at an elevated level, they shall be supported by purpose designed structures, which should withstand or be protected from damage by cryogenic liquid spillage.

The slope of the ground, shall be such as to allow surface water run off.

Where liquid oxygen storage tanks are required to be installed on a slope, consideration shall be given for the prevention of directing hazardous materials, such as oil, towards the oxygen installation or of directing any oxygen spillage towards locations where people are at risk or towards hazardous materials.

2.4.3 Position of gas vents

Vents, including those of safety relief devices, shall vent to a safe place in the open, so as not to impinge on personnel, occupied buildings and structural steelwork.

Oxygen vents shall be so positioned that the flow from them cannot mix with that from flammable gas or liquid vents.

Consideration shall be given to the prevention of accumulation of water, including that from condensation, in vent outlets.

All vent systems shall be adequately supported to cope with loads created during discharge.

2.4.4 Vapour clouds

Vapour clouds may be formed during normal operation of a cryogenic system e.g. from vaporisers, from venting during liquid transfer or from the operation of protective devices. The extent of the visible vapour cloud resulting from

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BCGA CP36 © 2006

product release should not be relied upon to indicate the limit of an enriched or depleted oxygen atmosphere.

Vapour clouds from releases are generally low lying (typically below waist height). Such vapour clouds may be quite extensive depending on weather conditions and persons working below ground or at low level in the vicinity may be at risk.

When siting an installation, due consideration shall be given to the possibility of the movement of vapour clouds, originating from spillage or venting, which could be a hazard from oxygen enrichment/deficiency or decreased visibility e.g crossing roads. The prevailing wind direction and the topography shall be taken into account.

In the case of oxygen refer to BCGA Technical Reports TR1 A Method for Estimating the Off-Site Risks from Bulk Storage of Liquefied Oxygen (10) and TR2 The Probability of Fatality in Oxygen Enriched Atmospheres due to Spillage of Liquid Oxygen (30).

In the case of nitrogen and argon refer to BCGA guidance note GN11 (34)

2.4.5 Liquid transfer area

The liquid transfer area shall be designated a ‘No Parking’ area and should be level.

A road tanker, when in position for filling from or discharging to the

installation, shall be in the open air and not be in a walled enclosure from which the escape of liquid or heavy vapour is restricted. Tankers should have easy access to and from the installation at all times.

Kerbs or barriers or bumper blocks shall be provided to prevent damage to any

part of the installation by the tanker or other vehicles.

The liquid transfer area should normally be located adjacent to the fill coupling of the installation and be positioned in such a way that it facilitates the movement of the tanker in the case of an emergency. Extended fill lines should be avoided if possible. Where there is no alternative then suitable ‘repeater’ gauges and valves should be installed. Extended filling connections should be limited to 10m unobstructed line of sight. Greater distances require special provisions. Transfer of liquid with the tanker standing on public property is not recommended. However, if this cannot be avoided, the hazard area shall be clearly defined, using suitable notices during the transfer period. Access to this area during transfer shall be strictly controlled. The road tanker transfer area shall be made of concrete or any other suitable non porous and for oxygen non combustible material - this also includes any expansion joints. See appendix 4 for diagram.

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2.4.6 Ventilation of pump enclosure

Where pumps and/or vaporising equipment are located in enclosures, these shall be properly ventilated. Openings used for access and/or free or forced ventilation shall lead to a place where there is free escape for cold vapour and in case of oxygen where there will be no accumulation of combustible material liable to form a hazard.

Personnel and equipment should be protected from any oxygen pump fire by

means of barriers or suitable shielding. Openings used for access and/or free or forced ventilation shall lead to a place where there is free escape for cold vapour and where there will be no accumulation of combustible material, liable to form a hazard.

2.4.7 Equipment layout

The equipment shall be installed so as to provide for easy access, operation and maintenance. Consideration should be given to the location of valves pipework and controls etc to ensure these are easily accessible. Equipment, pipework and cables should be installed so as to minimise hazards e.g. tripping and allow safe access and egress to the installation.

2.4.8 Pressure Relief Devices

Pressure relief devices shall be provided to prevent over pressure, where this can occur, including situations where liquid can be trapped.

If a three-way valve is installed to accommodate two pressure relief devices

operating, either simultaneously or alternatively, then the size of the valve, regardless of the position of the actuating device, shall be such that adequate protection is provided. The three-way valve should be provided with a position indicator showing which relief devices are “on-line”.

For sizing the relieving capacity of pressure relief devices all operational

conditions shall be considered including:

• boil off rate (including a safety factor) in case of insufficient insulation due to loss of vacuum

• flash gas from filling operations of road tankers

• malfunction of control valves in pressure raising systems; or

• any other foreseeable source of energy input into the vessel

Consideration shall be given to the provision of secondary relief devices, such as bursting discs, depending on the degree of risk associated with the installation and prevailing climatic or environmental conditions, e.g. icing due to high

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humidity, corrosion etc. Safety relief systems should comply with BS EN 13648 (14). Consideration shall also be given in the design of the installation to facilitate the periodic testing of the pressure relief devices. (See 5.2.6).

2.4.9 Isolation valves

Any primary process isolation valve shall be located as close as practical to the vessel itself and be easily accessible. Protection against over pressure shall be installed between any two isolation valves where liquid or cold vapour can be trapped and the position of isolation valves should be such that they can be afforded adequate protection against damage from external sources.

2.4.10 Secondary isolation valves

A secondary means of isolation shall be provided for those lines greater than 9 mm nominal bore and

• emanating from below the normal liquid level and

• having only one means of isolation between tank and atmosphere (such as liquid filling lines),

to prevent any large spillage of liquid should the primary isolating valve fail. The secondary means of isolation, where provided, may be achieved for example, by the installation of a second valve or a non-return valve. Suitable means shall be provided for preventing the build up of pressure of any trapped liquid.

2.4.11 Couplings

Couplings used for the transfer of liquid oxygen shall be non-interchangeable with those used for other products.

2.4.12 Non-return valve

Consideration shall be given to the need to incorporate a non-return valve after the cryogenic gas vaporiser to avoid backflow into the storage tank system.

2.4.13 Fencing

Fencing is required to prevent access of unauthorised persons, where other means are not provided.

On controlled sites with sufficient supervision fencing is optional.

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Where fencing is provided the minimum clearance between the fence and the installation shall be 0.6 m to allow free access and escape inside the enclosure.

The safety distances given in Appendix 3 will apply regardless of the position of the fence.

The height of the fence shall be approximately 1.8 m.

Timber or other readily combustible materials shall not be used for fencing.

Any gates should be outward opening and wide enough to provide for an easy

access and exit of personnel:

• the main gate should have two wings, each at least 0.6 m wide

• the emergency exit gate should have one wing, at least 0.8 m wide Gates shall be locked during normal operation. Consideration should be given

to the provision of an additional emergency exit where the size of fenced area or equipment location necessitates this.

2.4.14 Vaporisers Vaporisers shall be adequately sized for the off take rate specified by the

customer. Where necessary a device to restrict the flow to the maximum flow capacity of the vaporisers shall be installed.

Measures shall be taken to prevent the system temperature downstream of the

vaporiser, dropping to a value, which could cause damage to pipework, etc. The position of ambient vaporisers can severely affect their performance, as

they rely on the free movement of air. 2.4.15 Foundations

The site chosen shall be capable of supporting the plinth, a full vessel and vaporisers under adverse weather conditions. The tank supplier will provide indicative foundation requirements but it is the responsibility of the user to ensure the tank foundation is designed to safely withstand the weight of the tank and its contents plus other possible loads resulting from wind, snow, earthquake etc.

In case of oxygen: • the foundation on which the equipment is installed shall be made of concrete

or any other suitable, non flammable, and non porous material. • Expansion joint materials shall be acceptable for use with liquid oxygen,

however the design should avoid joints within 1 m of the hose coupling points and any operational discharge points.

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Accumulation of water shall be avoided. 2.4.16 Bolting down

Many factors determine whether a tank needs to be bolted down. The following are some of the main factors that should be considered: • seismic activity • wind speed • topography (nature of surrounding terrain) • ground roughness (open or protection provided) • tank shape factor (L/D ratio, attachments to tank)

• the potential to tip the foundation

The principles of BS 6399 (7) shall be followed to determine bolting down requirements.

2.4.17 Other requirements

The location chosen for the installation shall be acceptable to both the gas supplier and the user and shall be exclusively reserved for the storage of cryogenic liquids.

Any modifications shall be carried out in accordance with the applicable design code and in consultation with the liquid supplier.

3 ACCESS TO THE INSTALLATION 3.1 Means of Escape Installations covered by this Code of Practice storing or having facilities to store greater

than 135 tonnes of liquid oxygen require a Fire Certificate under the provisions of the Fire Certificates (Special Premises) Regulations 1976 (9) which are enforced by HSE. The Fire Certificate deals with means of escape in case of fire, fire warning systems, fire training and similar general fire precautions matters.

3.2 Personnel

The installation shall be so designed that authorised persons shall have easy access to and exit from the operating area of the installation at all times. Access to the installation shall be forbidden to all unauthorised persons. Warning notices shall support this.

3.3 Access to installation controls

Filling connections and equipment controls shall be located in such a way that easy access to them is provided.

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BCGA CP36 © 2006

Filling connections and equipment controls should be located in close proximity to each other and in such a way that tanker controls are visible and easily accessible from the tanker operator’s position.

It shall be kept in mind that the length of the flexible connecting hose is normally 3 m.

3.4 Notices and instructions

3.4.1 General precautions

Notices shall be clearly displayed, to be visible at all times, on or near the tank, particularly at access points, the following should be considered: • LIQUID NITROGEN/ARGON/OXYGEN (as appropriate) • NO SMOKING* • NO NAKED LIGHTS* • NO STORAGE OF OIL, GREASE OR COMBUSTIBLE MATERIALS * • AUTHORISED PERSONS ONLY • EXTREME COLD HAZARD

In addition for argon and nitrogen storage installation • ASPHYXIATION HAZARD In addition for oxygen storage installation • OXIDISING SUBSTANCE * Although nitrogen/argon are inert gases it is recommended that smoking and open flames are prohibited within the immediate area to avoid the possibility of causing fire. Symbols should be used instead of written notices wherever possible, e.g.:

ASPHYXIATION DANGERASPHYXIATION DANGERASPHYXIATION DANGER

Cryogenic

Liquid Oxidising Substance

No naked flames

No Smoking No Unauthorised

Access

These signs shall comply with The Health and Safety (Safety Signs and Signals) Regulations 1996 (15) and with BS 5499 Pt 5 “Safety Signs and Colours” (16).

A sign shall be displayed showing:

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– gas supplier’s name and local address

– gas supplier’s emergency phone number

This information should also be available at a control point. 3.4.2 Identification of contents

The storage tank shall be clearly labelled "LIQUID NITROGEN"; "LIQUID ARGON” or "LIQUID OXYGEN" as appropriate.

The storage tank or compound should be clearly labelled with the appropriate UN product identification numbers.

The connection fittings of multistorage installations or long fill lines shall also be clearly marked with gas name or symbol in order to avoid confusion (see also 2.4.5).

3.4.3 Legibility of notices

All displayed notices shall be kept legible, visible and up-to-date at all times. 3.4.4 Operating and emergency instructions Operating and emergency instructions shall be provided by the product supplier

and shall be available and understood by the user before commissioning the installation. (See also 8.1).

These instructions shall be kept up-to-date.

4. TESTING AND COMMISSIONING 4.1 Testing of the installation

Prior to commissioning the following tests shall be carried out by the supplier or his representative in accordance with established procedures. 4.1.1 Pressure test Works manufactured storage tanks and pressure vessels of the installation will

already have been tested/inspected in compliance with the relevant Pressure Vessel Code in the manufacturer’s workshop prior to the first installation. This should be verified from the name plate on the vessel. Further pressure tests shall not be carried out on the vessel without reference to the vessel design documents and tank history.

In order to ensure the integrity of the installation, a pressure test shall be carried

out on site-erected piping/systems in accordance with design codes and

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appropriate standards. Precautions shall be taken to prevent excessive pressure in the system during the test. Following any hydraulic test, the system/equipment shall be drained, thoroughly dried out and checked for moisture content.

Where a pneumatic pressure test is specified, nitrogen or dry oil free air shall be

used as the test medium. The pressure in the system shall be increased gradually up to the test pressure. Pneumatic pressure testing is potentially hazardous and should be carried out in accordance with HSE Guidance Note GS4 (17).

Any defects found during the testing shall be rectified in an approved manner

and the system then retested A leak and function test shall be carried out in accordance with GS4 and at a

pressure in accordance with the applicable code or regulation. Pressure tests/leak tests shall be witnessed by a competent person and a test

certificate signed and issued. Such certificates shall be kept for future reference.

4.1.2 Pressure relief devices

A check shall be made to ensure that all transport locking devices have been removed from pressure relief devices of inner vessel, outer jacket and piping systems and that the devices are undamaged and in working order. The relief device set pressure (stamped on or attached to each device) shall be checked to see it is in accordance with the maximum permissible operating pressure of the system.

Relief valves must have a valid test certificate or be subjected to a successful functional test the results of which shall be recorded.

Where relief devices are adjustable, tamper proof devices shall be fitted.

4.2 Adjustment of controlling devices

The controlling devices shall be adjusted to the required operating conditions of the system and be subjected to a functional test.

4.3 Posting of notices

Notices (see 3.4) shall be posted before putting the installation into service. 4.4 Commissioning

Prior to first fill checks shall be carried out to ensure the suitability of the installation for commissioning.

Commissioning shall only be carried out by experienced personnel and in accordance with a written procedure which shall address the following significant risks:

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• thermal shock • rapid pressure rise • Contamination in oxygen systems leading to auto ignition. • Noise • Gas release

5 OPERATION AND MAINTENANCE 5.1 Operation of the installation

5.1.1 Operating personnel and procedures

Only authorised persons shall be allowed to operate the installation. Operating instructions shall be supplied to operating personnel.

The instructions shall define the safe operating limits of the system and include

the necessary safety information relating to the product and the installation. In general such instructions should be written and presented in a clear concise

format.

For the convenience of the operator the supplier may colour code or identify by other means the hand wheels of these valves which are to be shut in an emergency. These valves should normally be:

• feed and return valves to and from the pressure build up vaporiser • feed valve to the product vaporiser • user house line isolation valve • any withdrawal valve. The number of valves will vary, depending on the type of the installation.

5.1.2 Operating difficulty or emergency

If during the operation of the installation an excursion occurs outside the safe operating limits of the system (e.g. overpressure, rapid temperature change), or mechanical damage, this shall be reported immediately to the product supplier and/or tank owner so that a decision about the continued use of the tank can be made and a programme of inspection drawn up by a competent person and implemented. Any operating difficulty or emergency concerning the installation that does not respond to measures covered by the instructions shall be referred to the product supplier. (See also 8.3).

5.2 In Service inspection and maintenance

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5.2.1 General

The introduction of the Pressure Systems Safety Regulations 2000 (18), which are referred to as “the Regulations” in this Code of Practice, has introduced specific requirements covering design, manufacture, installation, operation, maintenance and examination of pressure systems. BCGA Code of Practice CP 23 (19) details requirements arising from these Regulations, as applied to cryogenic liquid storage systems at user premises. For the purpose of clarification in this document, the terms ‘inspection’, ‘checks’ and ‘regular tests’ are activities associated with the normal operation of the installation. The term ‘examination’ means examination in accordance with the Written Scheme as detailed in the Regulations and CP 23.

5.2.2 Site The site should be inspected regularly to ensure that it is maintained in a proper

condition and that safety distances are maintained. 5.2.3 Tank Installation

Periodic and planned maintenance of the installed equipment shall be carried out. An annual external visual inspection should be carried out to confirm the

satisfactory condition of the outer jacket, pipework, valves, controls and auxiliary equipment. A check on the vacuum shall be made whenever an abnormal pressure increase inside the inner vessel has occurred or excessive ice build up is visible.

When the tank is taken out of service a Competent Person shall endorse the

further use of the tank, taking into account the condition of the tank, the operating history and the degree and results of any previous examination(s).

5.2.4 Tank A Competent Person shall validate the vessel as fit for its purpose for a defined

period prior to its first installation. Guidance on periodic revalidation is given in BCGA Code of Practice CP 25 (20). 5.2.5 Vaporisers In cold weather, the operator should regularly check ambient air vaporisers for

any build-up of excessive ice formation. Any such build-ups should be removed by the use of steam or water.

5.2.6 Pressure Relief Devices

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Periodic visual inspections and examination of the devices shall be carried out in accordance with CP 23. Blockages such as ice or foreign debris shall be removed and care taken to monitor for seat leakage, corrosion or other visual defects.

Bursting disc elements may deteriorate due to aggressive environments resulting

in their relief pressure rating being reduced. It may, therefore, be necessary to replace disc elements in such environments on a planned basis. Overpressure/fill protection

The overpressure/filling protection system should be tested in accordance with the Written Scheme. This test must confirm operability of the entire system including actuation of the shutdown device at the appropriate set point.

5.2.7 Ancillary Equipment

Ancillary equipment (other than previously detailed), e.g. pressure/temperature

gauges, should be maintained in accordance with either manufacturers’ recommendations or national codes, whichever is the more stringent.

5.2.8 Isolation Valves Isolation valves should be periodically checked for correct functional operation.

6. PERMIT TO WORK Before maintenance is carried out on the installation, a written Permit to Work may be

required for the particular type of work (e.g. cold work, hot work, entry of vessel, electrical work).

7. MODIFICATION OF SYSTEM

The supplier's equipment shall not be modified by the customer. Any proposed modification to a customer owned installation, or any attached system, shall be discussed and agreed with the product supplier prior to implementation.

8. TRAINING AND DOCUMENTATION 8.1 Documentation

The supplier of the system shall provide sufficient written information concerning the design, construction, examination, operation and maintenance to ensure compliance with the PSSR Regulations (18). As a minimum, the suppler shall provide the user with:

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a) a manual covering operation, maintenance and the safe operating limits of the system including system flow diagrams.

b) the provision of a contact address and emergency telephone number should the

user have any questions about his installation. c) a Safety Data Sheet, which gives information in accordance with the requirements

of the CHIP Regulations (24) and which deals with the prevention of accidents arising from the uncontrolled escape of product from the system.

Note that a written scheme of examination shall be required for the system. The responsibility for providing and complying with this scheme lies with the user. Where systems are leased or hired the user may transfer his responsibility to the owner by written agreement (in accordance with PSSR Schedule 2 (18)).

8.2 Training of personnel

All personnel directly involved in the commissioning, operation and maintenance of liquid cryogenic storage systems shall be fully informed regarding the hazards associated with cryogenic gases and properly trained as applicable to operate or maintain the equipment. Training shall be arranged to cover those aspects and potential hazards that the particular operator is likely to encounter. It should cover, but not necessarily be confined to, the following subjects for all personnel : • potential hazards of the gases • site safety regulations • emergency procedures • use of protective clothing/ apparatus including breathing sets where appropriate • first aid treatment for cryogenic burns • use of fire fighting equipment

In addition individuals shall receive specific training in the activities for which they are employed.

It is recommended that the training be carried out under a formalised system and that records be kept of the training given and, where possible, some indication of the results obtained, in order to show where further training is required. The training programme should make provision for refresher courses on a periodic basis.

8.3 Emergency procedures

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Emergency procedures shall be prepared to cover the event of a spillage of liquid cryogenic gases so that persons likely to be affected shall know the actions required to minimise the adverse effects of such spillage.

Local emergency services should be party to the preparation of the emergency

procedures. Consideration should be given to the carrying out of practical exercises.

The following are guidelines which may be used for formulating emergency procedures: • raise the alarm • summon help and emergency services • isolate the source of gases, if appropriate, safely - where possible • evacuate all persons from the danger area and seal it off • alert the public to possible dangers from vapour clouds and evacuate when necessary • notify the gas supplier.

After the liquid spillage has been isolated, oxygen enrichment/depletion checks should be

carried out in any enclosed areas where the vapour cloud may have entered. This includes basements, pits and confined spaces.

9. REFERENCES

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(1) IGC Document No. 115/04*

Storage of cryogenic air gases at users’ premises

(2) BCGA Code CP 37

Bulk cryogenic liquid storage at production sites.

(3) IGC Document No. 33/06*

Cleaning of equipment for oxygen service - guidelines.

(4) BCGA Technical Report TR3

Replacement substances for the cleaning of oxygen system components.

(5) BS 5429 Code of Practice for Safe Operation of small-scale storage facilities for cryogenic liquids.

(6) ISBN No 8543 2605 7

British Cryoengineering Society : Cryogenic Safety Manual.

(7) BS 6399 Part 2

Code of Practice for Wind Loads.

(8) BS 476

Fire tests on building materials and structures.

(9) SI 2003 : 1976

Fire Certificates (Special Premises) Regulations 1976.


A Method for Estimating the Off-Site Risks from Bulk Storage of Liquefied Oxygen R1 (LOX).

(11) BS 6651

Code of Practice for Protection of Structures against Lightning.

(12) BS EN 60079

Electrical apparatus for explosive gas atmospheres. Part 14.

(13) BS EN 60529

Degrees of Protection Provided by Enclosures.

(14) BS EN 13648 Cryogenic vessels. Safety devices for protection against excessive pressure.

(15) SI 341 : 1996

The Health & Safety (Safety Signs and Signals) Regulations 1996.

(16) BS 5499

Part 5 Graphical symbols and signs. Safety signs including fire safety signs. Signs with specific safety meanings.

(17) HSE GS 4

Safety in Pressure Testing 1998.

(18) SI 128 : 2000

The Pressure Systems Safety Regulations 2000.

(19) BCGA Code CP 23

Application of the Pressure Systems Safety Regulations 2000 to Industrial and Medical Pressure Systems Installed at User Premises.

(20)

BCGA Code CP 25

Revalidation of Bulk Liquid Oxygen, Nitrogen, Argon and Hydrogen Cryogenic Storage Tanks.

(21) IGC Document

No 24/02 *

Cryogenic pressure vessels - pressure protection devices.

(22) HS (G) 191

Emergency Planning for COMAH Regulations 1999.

(23) BCGA Guidance Note GN1

Guidance Notes on the Preparation of Major Emergency Procedures.

(24) SI 1689 : 2002 The Chemicals (Hazard Information and Packaging for Supply) Regulations

(25) LPGA COP 1

Bulk LPG storage at fixed installations

(26) BCGA Code CP 6

The Safe Use of Acetylene in the Pressure Range 0-1.5 bar (0-22 lb/in2).

(27) BS IEC 60877

Procedures for ensuring the cleanliness of industrial process- measurement and control equipment in oxygen service.

(28) SI 2001 : 1999

The Pressure Equipment Regulations 1999.

(29) IGC Document 59/98*

The prevention of excessive pressure in cryogenic tanks during filling.


The Probability of Fatality in Oxygen Enriched Atmospheres due to spillage of Liquid Oxygen.

(31) BCGA Code CP28

Vacuum Insulated Tanks of not more than 1000 litres Volume which are Static Installations at User Premises.


Fire hazards of oxygen and oxygen enriched atmospheres

(33) SI 743 : 1999 The Control of Major Accident Hazards 1999

(34) BCGA Guidance Note GN11

Use of gases in the workplace. The management of risks associated with reduced oxygen atmospheres


Hazards of inert gases

(36) SI 2776 : 2002 The Dangerous Substances and Explosive Atmospheres Regulations

Legislation generally applicable to storage of cryogenic gases at User’s Premises:

- Housing and Planning Act 1986 Part iv - Hazardous Substances

- The Health and Safety at Work etc Act 1974

- The Factories Act 1961

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- The Offices Shops and Railways Premises Act 1963

- The Consumer Protection Act

* A European Industrial Gases Association (EIGA) publication obtainable from:

Website: www.eiga.be

e-mail: [email protected]

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http://www.eiga.be/

mailto:[email protected]

APPENDIX 1

Sheet 1 of 1 Asphyxiation

Nitrogen and argon may produce local oxygen-deficient atmospheres, which will produce asphyxia if breathed. This is especially true in confined spaces.

Atmospheres containing less than 18% oxygen are potentially dangerous and

entry into atmospheres containing less than 19.5% is not recommended. Atmospheres containing less than 10% oxygen can cause brain damage and

death. Asphyxia due to oxygen deficiency is often rapid with no prior warning to the

victim. A general indication of what is liable to happen in oxygen deficient atmospheres is given in the table below, but it should be appreciated that the reactions of some individuals can be very different from those shown.

.

Oxygen Content (Vol %)

Effects and Symptoms

(at atmospheric pressure)

11-14

Diminution of physical and intellectual performance without person’s knowledge.

8-11

Possibility of fainting after a short period without prior warning.

6-8

Fainting within a few minutes; resuscitation possible if carried out immediately.

0-6

Fainting almost immediate; death ensues; brain damage even if rescued.

The victim may well not be aware of the asphyxia. If any of the following

symptoms appear in situations where asphyxia is possible and breathing apparatus is not in use, immediately move the affected person to the open air, following up with artificial respiration if necessary.

(i) Rapid and gasping breathing (ii) Rapid fatigue (iii) Nausea (iv) Vomiting (v) Collapse or incapacity to move (vi) Unusual behaviour Attempts to rescue affected persons from confined spaces or where oxygen

deficient atmospheres may be present should only be made by persons trained in the use of breathing apparatus and confined space entry procedures.

Further details of the hazards of asphyxiation can be found in BCGA GN11 (25)

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APPENDIX 2

Sheet 1 of 1

HAZARDS FROM OXYGEN ENRICHMENT Fire Hazards from Oxygen Enrichment Oxygen reacts with most elements. The initiation, speed, vigour and extent of these reactions depend in particular upon: - the concentration, temperature and pressure of the reactants - ignition energy and mode of ignition Reaction Mechanism The mechanism of these reactions is complicated and depends, among other things, upon the nature of the substances concerned, their physical state, geometric configuration, concentration and manner of ignition. This too influences the speed of reaction, which can vary from slow combustion to an explosion. Combustibility of Materials Oxygen enrichment of the atmosphere, even by a few percent, considerably increases the risk of fire. Materials which do not burn in air, including fireproofing materials, may burn vigorously or even spontaneously in enriched air. Combustion Characteristics Oxygen enrichment alters considerably the characteristics of combustion. Materials ignite more easily and sparks which would normally be regarded as harmless can cause fire. The resulting flames are much hotter and are propagated at much greater speed. Hydrocarbon Oils and Grease Oil and grease are particularly hazardous in the presence of oxygen as they ignite spontaneously and burn with explosive violence. They should NEVER be used to lubricate oxygen or enriched air equipment. Special lubricants with which oxygen can be used under certain conditions are available. Smoking Burning accidents, which occur, are often triggered off by the lighting of a cigarette. Therefore it is impossible to over-emphasise the danger of smoking in oxygen-enriched atmospheres or where oxygen enrichment can occur. In such areas smoking shall be forbidden.

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APPENDIX 3 Sheet 1 of 5

SAFETY DISTANCES IN METRES Distance between oxygen storage tanks from 1000 up to 175,000 litres water capacity and typical hazards.

NOTE (1) The safety distances are measured from the exposure to whichever is the lesser of:

a) Any point on the storage system where, in normal operation, leakage or spillage can occur. b) The tank outer jacket. c) The vessel nozzles.

NOTE (2) Assumed maximum liquid phase pipework diameter 42mm (1.5″ nominal bore).

NOTE (3) For buildings the distances are measured to the nearest opening: ie door, window, vent etc.

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TABLE 1: SEPARATION DISTANCES: LIQUEFIED FLAMMABLE GASES,

FLAMMABLE LIQUIDS AND OXYGEN STORAGE a) LPG Storage

Size of Storage

LPG Vessels

Liquid Oxygen

Vessel (tonnes)

Weight Capacity

(tonnes)

Equivalent Liquid

Capacity (m³) 15ºC

Separation Distance

(metres)

Up to 200

0 - 1.1 1.1 - 4.0 4.0 - 60.0 60.0 - 150 150.0 and above

0 - 2.2 2.2 - 7.8 7.8 - 117.0 117.0 - 124.0 294.0 and above

6.0 7.5 15.0 22.5 30.0

LPG cylinders and other liquefied flammable gas(*) cylinders above 50 kg total capacity.

7.5

See also LPGA COP 1 Bulk LPG storage at fixed installations(25). b) Other Bulk Flammable Liquids and Liquefied Flammable Gases The separation distances listed above for LPG should be applied to the same stored

volumes (m3) of other bulk liquefied flammable gases and may be used for the same stored volumes (m3) of bulk flammable liquids (#). These distances may be reduced depending on the nature of the flammable liquid and any protective measure and in these cases an individual assessment of the proposed location shall be carried out.

* Common examples of liquefied flammable gases supplied in cylinders include: ammonia,

hydrogen sulphide and ethylene oxide. # Common examples of bulk flammable liquids include: acetone, methanol, diesel, petrol.

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APPENDIX 3

Sheet 3 of 5 TABLE 2: SEPARATION DISTANCES: COMPRESSED FLAMMABLE GASES

AND OXYGEN STORAGE

Compressed Flammable

Gas Cylinders (m³) (Gas volume measured at 1013 mbar and 15°C)

Liquid Oxygen Storage

up to 200 tonnes Separation Distance (metres)

Up to 70 Above 70

5.0 8.0

Notes: 1) For liquefied flammable gas cylinders, see Table 1. 2) Distances in Table 2 are based on hydrogen cylinders. 3) For separation distance for Acetylene, see BCGA CP 6 (26).

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TABLE 3: SEPARATION DISTANCES: FLAMMABLE LIQUID OR GAS LINES

WITH UNION FLANGES ETC AND OXYGEN STORAGE

Flammable Liquid or Gas Line Size

(nominal)

Liquid Oxygen Storage up to 200

Tonnes Separation Distance (metres)

mm

Bore inches Bore

Metres

Up to Up to Above

25 50 50

1 2 2

6.0 10.0 15.0

Notes: 1. The above separation distances are intended to provide protection for the LOX storage

tank against jet flame impingement from an ignited release from the flammable liquid/gas line.

2. The distances are based on LPG as the contents of the flammable liquid/gas line and are

given as a ‘worst case’. 3. For flammable liquids or gases other than LPG in the line, the above distances should be

used, unless it can be shown that smaller distances are adequate to avoid jet flame impingement.

4. If some means of protection from jet flame impingement (such as shielding of the joint

by fire resistive material) can be provided between the union/flange on the flammable liquid/gas line and the LOX storage and this can be shown to provide an equal or greater degree of protection than the separation distances shown, the separation distances may be reduced.

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Appendix 3

SAFETY DISTANCES Sheet 5 of 5 Distance between nitrogen or argon storage and typical exposures for individual storage tanks from 1000 litres up to 250,000 litres net liquid capacity (distance in metres).

NOTES: (1) The safety distances are measured from the exposure to: (a) any point on the storage system where in normal operation leakage or spillage

can occur, or: (b) the tank outer jacket, or: (c) the vessel nozzles, whichever gives the greatest safety distance to the

nitrogen/argon storage tank. (2) Assumed maximum liquid phase pipework diameter 50 mm (2") nominal bore. (3) For offices, canteens, etc. the distances are measured to the nearest opening in the

building, eg doors and windows. Ventilator air intakes should be at least 1.0 metre above ground level, if within 10 metres of the installation.

(4) Any door within 3 metres of the installation should be of the self closing type.

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* For acetylene refer to BCGA CP 6 (26)

Appendix 5 Sheet 1 of 2

“BURNS” DUE TO VERY COLD LIQUEFIED GASES

The temperature of liquefied gases varies. The boiling points, i.e. the temperatures at which the liquefied gas vaporises, are as follows: Nitrogen -196oC Argon -186oC Oxygen -183oC General Effect on Tissue The effect of extreme cold on tissue is to destroy it, a similar end result to that of heat exposure, and in like fashion the amount of cold and the duration of contact is crucial. The destruction of tissue is not so immediately obvious as in the case of burns, since pain is absent in the frozen stage, and the tissue, although rigid, keeps its normal shape and is not obviously destroyed. Pain and destruction becomes more apparent as thawing occurs. Those who have had mild frostbite of fingers or toes will have some idea of the pain on re-warming. Prevention of contact with very cold liquids is quite vital and those who work in this field must be aware of the hazard. Skin Effects Liquid, vapour, or low-temperature gas can produce effects on the skin, which will vary in severity with temperature and the length of exposure. Naked or insufficiently protected parts of the body coming into contact with uninsulated pipes or vessels may stick fast by virtue of the freezing of moisture and flesh may be torn in removal. The wearing of wet clothing should be avoided. Continued exposure of naked flesh to cold atmospheres can result in frostbite. There usually is sufficient warning by local pain whilst the freezing action is taking place. Re-warming with lukewarm water at 42oC to 44oC (107 oF to 111oF) is generally sufficient safeguard against injury. Effect of Cold on Lungs Whilst transient and short exposure produces discomfort in breathing, prolonged inhalation of vapour or cold gas, whether respirable or not, can produce serious effects on the lungs.

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Appendix 5 Sheet 2 of 2

FIRST AID TREATMENT OF COLD CONTACT BURNS

Flush the affected areas of skin with copious quantities of tepid water, but do not apply any form of direct heat, e.g. hot water, room heaters, etc. Move casualty to a warm place (about 22°C; 295K). If medical attention is not immediately available, arrange for the casualty to be transported to hospital without delay. While waiting for transport:

• Loosen any restrictive clothing.

• Continue to flush the affected areas of skin with copious quantities of tepid water.

• Protect frozen parts with bulky, dry, sterile dressings. Do not apply too tightly so as to cause restriction of blood circulation.

• Keep the patient warm and at rest.

• Ensure ambulance crew or hospital is advised of details of accident and first aid treatment already administered.

• Smoking and alcoholic beverages reduce the blood supply to the affected part and should be avoided.

The above text has been reproduced with the permission of the British Cryoengineering Society from its “Cryogenics Safety Manual”, Reference No. ISBN 08543 26057 (6).

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HISTORY AND OBJECTIVES OF BCGA

The British Compressed Gases Association was established in August 1971, as the successor to the British Acetylene Association, formed in 1901. Its members consist of producers, suppliers of gases equipment and container manufacturers and users operating in the compressed gases field. The main objective of the Association is the advancement of technology and safe practice in the manufacture, handling and use of all gases and the design and manufacture of all containers, apparatus, appliances, plant, etc. BCGA also provides advice and makes representations, insofar as these relate to particular problems of the compressed gases industry, on behalf of its members to all regulatory bodies, including the UK Government, concerning legislation both existing and proposed. Policy is determined by a Council elected from member firms, with detailed technical studies being undertaken by a Technical Committee and its specialist Sub-Groups appointed for this purpose.

Further details of the Association may be obtained from:

BRITISH COMPRESSED GASES ASSOCIATION

1 Gleneagles House Vernon Gate South Street

Derby DE1 1UP

Website: www.bcga.co.uk

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www.bcga.co.uk

BCGA Bulk Cryogen Storage CP36

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