Cryogenics Safety Manual. A Guide to Good Practice PDF
Preview Cryogenics Safety Manual. A Guide to Good Practice
Cryogenics Safety Manual A guide to good practice Third edition Safety Panel British Cryogenics Council KllJ T T E R W O R TH Η Ε I Ν Ε Μ Α Ν Ν Butterworth-Heinemann Ltd Linacre House, Jordan Hill, Oxford OX2 8DP PART OF REED INTERNATIONAL BOOKS OXFORD LONDON BOSTON MUNICH NEW DELHI SINGAPORE SYDNEY TOKYO TORONTO WELLINGTON First published by The British Cryogenics Council 1970 Second edition 1982 Third edition published by Butterworth-Heinemann 1991 © British Cryogenics Council 1991 All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 9HE. Applications for the copyright holder's written permission to reproduce any part of this publication should be addressed to the publishers. British Library Cataloguing in Publication Data Cryogenics safety manual. I. British Cryogenics Council Safety Panel 536.028 ISBN 0 7506 0225 2 Library of Congress Cataloguing in Publication Data Cryogenics safety manual: a guide to good practice/Safety Panel, British Cryogenics Council. - 3rd ed. p. cm. Includes bibliographical references and index. ISBN 0 7506 0225 2 1. Low temperature engineering—Safety measure. I. British Cryogenics Council. Safety Panel. TP482.C79 1991 621.59'028'9^dc 20 91-24934 CIP Typeset by MS Filmsetting Limited, Frome, Somerset Printed and bound in Great Britain Tables and illustrations Tables 1 Thermophysical properties of various cryogens 2 2 Coefficient of expansion for various materials 12 3 Thermophysical properties of methane, ethane and ethylene 53 Figures 1 Asphyxiation hazard warning sign 6 2 Fire triangle 8 3 Toughness (impact energy) as a function of temperature for various materials 10 4 Brittle failure of pipeline 10 5 Cryogenic liquid road tanker 16 6 Cryogenic liquid rail tanker 17 7 Selection of portable cryogenic containers 18 8 Typical permit to work 20-23 9 Schematic of air separation process 31 10 LNG storage tank and bund wall 59 11 Ethylene storage tank 67 12 Liquid hydrogen storage tank 92 13 Typical liquid storage Dewar vessel and transfer tube 97 14 Phase diagram for helium 99 Preface The main objective of the British Cryogenics Council is to promote and support the development and safe application of low temperature engineer- ing and cryogenics in the UK. The Cryogenics Safety Manual was first published by the British Cryo- genics Council in 1970, and was revised in 1982. This second revision brings the manual up to date, and incorporates new material, which reflects the growth in use of cryogenic fluids and the continued importance of high standards of safety. It is intended to be a ready source of reference and provide guidance to all persons engaged in the handling of cryogenic fluids at temperatures of 188K or below, whether on a large scale in industry or research establishments, or on a small scale in laboratories. The revision of the Cryogenics Safety Manual has been undertaken by a group of experts within the field of cryogenic safety which comprises the British Cryogenics Council's Safety Panel. Thanks are due to all members of the Panel for their considerable efforts, and in particular to Dr J. Currie, the Panel's Chairman. Thanks are also due to BOC Ltd, Air Products pic, British Gas pic, ICI pic, and the Institute of Cryogenics at Southampton University for making possible the formation of this team, and for providing the facilities to enable it to carry out its work. Dr D.R. Roe British Gas pic Chairman, British Cryogenics Council (1988-91) As the new Chairman of the British Cryogenics Council, I fully endorse the above remarks by Dr Roe and add my own thanks to the members of the Safety Panel. Further, I should like to mention that Dr R.N. Richardson took over as Chairman of the Safety Panel when Dr Currie moved to the USA and has been largely responsible for arranging publication of the Cryogenics Safety Manual. Since cryogenics is constantly changing, the British Cryogenics Council would welcome any suggestions for inclusion in future revisions of the manual. Professor R.G. Scurlock University of Southampton Chairman, British Cryogenics Council (1991- ) Membership of Safety Panel Dr J.L. Currie (Chairman) BOC Limited Mr P. Cook Air Products pic Mr W. Freeman British Gas pic Dr R.N. Richardson (Chairman 1991- ) Institute of Cryogenics, University of Southampton Mr R.W. Sunley ICI pic Notice This manual has been produced for the guidance of all who are concerned with the operation, maintenance and supervision of plant for producing, storing, and handling industrial gases at relatively low temperatures. While every attempt has been made to deal with all foreseeable hazards, the final responsibility for safety must remain with those designing, maintaining, and operating the equipment. The British Cryogenics Council accepts no liability for any errors in, or omissions from, the manual. Membership of Safety Panel Dr J.L. Currie (Chairman) BOC Limited Mr P. Cook Air Products pic Mr W. Freeman British Gas pic Dr R.N. Richardson (Chairman 1991- ) Institute of Cryogenics, University of Southampton Mr R.W. Sunley ICI pic Notice This manual has been produced for the guidance of all who are concerned with the operation, maintenance and supervision of plant for producing, storing, and handling industrial gases at relatively low temperatures. While every attempt has been made to deal with all foreseeable hazards, the final responsibility for safety must remain with those designing, maintaining, and operating the equipment. The British Cryogenics Council accepts no liability for any errors in, or omissions from, the manual. Introduction The underlying principle behind all operations is to perform them safely. This is not achieved by chance but depends on detailed assessment of all the hazards. The Cryogenics Safety Manual provides the operator, designer and handler of cryogenic fluids and equipment with the basic safety principles that must be considered before performing any operation with cryogenic fluids. The manual is primarily aimed at operators and managers engaged in the production, handling and use of cryogenic fluids but is recommended reading for all personnel who may become involved with cryogenic fluids. The manual attempts to cover the safety aspects of all areas of cryogenic fluid applications from large-scale industrial production to small-scale research usage. For the purposes of the manual a cryogenic fluid is defined as one which is normally manufactured, stored, handled or processed at a temperature at or below -85°C(188K). The manual consists of five chapters. Chapter 1 describes the general safety requirements applicable to all cryogenic fluids covered in the manual. The remaining four parts look specifically at the particular hazards of defined categories of cryogenic fluids. Chapter 2 covers the atmospheric gases - nitrogen, oxygen, and argon - and deals in detail with the hazards of production and large-scale storage. Chapter 3 covers the flammable gases - liquefied natural gas (LNG), ethylene, and ethane - and again describes the safety issues in production and large-scale storage. Chapter 4 is concerned with the particular problems of handling liquid hydrogen, and how to prevent fires/explosions with this unique cryogen. Chapter 5 looks at small- scale uses of the rare gases helium, neon, krypton and xenon. Chapter 1, 'General safety requirements', is intended to be read in conjunction with any of the remaining four parts of the manual. This edition of the Cryogenics Safety Manual includes new regulations which have come into force since the previous edition and cover large-scale storage/handling of certain cryogenic fluids. The bibliography sections have also been significantly revised to include references to the latest literature. Chapter 1 has been revised to improve the definition of those safety issues that are common to all the specific hazards of particular cryogenic fluids covered in Chapters 2-5. Chapter 3 has been restructured to reflect a similar format to the other sections. Chapter 4 has been revised to reflect modern safety thinking on the handling of liquid hydrogen. Chapter 5, on the rare gases, has been expanded to include krypton and xenon. 1 General safety requirements A cryogen is the liquid, or under appropriate conditions solid, phase of one of the so called permanent gases; that is a gas which cannot be liquefied by the application of pressure alone at ambient temperature. In terms of thermodynamic properties this means that the critical temperature of the substance is below ambient. For the purposes of this manual a cryogenic fluid (cryogen) is defined as one which is normally manufactured, stored, handled or processed at a temperature at or below — 85°C (188K). The properties of various cryogens are given in Table 1. 1.1 Health 1.1.1 Cryogenic burns and frostbite Exposure of the skin to low temperature can produce effects on the skin similar to a burn. These will vary in severity with temperature and the time of exposure. Naked or insufficiently protected parts of the body coming into contact with very cold uninsulated pipes or vessels may stick fast by virtue of the freezing of available moisture, and the flesh may be torn on removal. Special care is needed when wearing wet gloves. Prolonged exposure to cold can result in frostbite. There may well be insufficient warning through local pain while the freezing action is taking place. All cold burns should be checked by a first aider or, in extreme circumstances, by a medical expert to confirm extent of damage. Prolonged inhalation of cold vapour or gas can damage the lungs. Cryogenic liquids and vapour can damage the eyes. The low viscosity of cryogenic liquids means that they will penetrate woven or other porous clothing materials much faster than, for example, water. 1.1.1.1 Precautions Protective clothing for handling low-temperature liquefied gases serves mainly to protect against cold burns. Non-absorbent gloves (PVC or leather) should always be worn when handling anything that is or may have been in contact with cold liquids or ι 2 Cryogenics Safety Manual Ethane CH26 30 -89 (184.6) -183 (89.9) +32 (305) 49.7 437 546 1.05 488.3 flammable no Xenon Ethylene Xe CH 24 131 28 -109 -104 (164.1) (169.3) -140 -169 (133.2) (104.2) +17 +10 (290) (283) 60 52.5 556 489 3100 565 4.61 0.97 96.2 483.4 no flammable no no ed non-toxic. Krypton Kr 84 -152 (121.4) -169 (104.2) -63 (210) 56 677 2400 2.93 108.0 no no e consider Methane CH 4 16 -161 (111.7) -183 (90.6) -82 (191) 47 626 424 0.56 512.4 flammable no s. ns listed ar s e Argon Oxygen Ar 0 2 40 32 -186 -183 (87.3) (90.2) -189 -219 (84.0) (54.8) -122 -119 (151) (154) 49.5 51.4 820 843 1390 1142 1.40 1.12 162.7 212.9 no yes no no yogens are colourle effect, all the cryog perties of various cryogens Helium Hydrogen Neon Nitrogen Ne N He H22 4 2 20 28 -269 -253 -246 -196 (4.2) (20.3) (27.1) (77.4) — -259 -249 -210 (14.1) (24.5) (63.3) -268 -240 -229 -147 (5) (33) (44) (126) 2.3 13.4 27.8 34.5 738 826 1417 678 125 70 1200 804 0.14 0.07 0.70 0.98 23.9 451.9 87.0 199.2 no flammable no no yes yes yes yes xygen, which is light blue, all the liquid cr nd CH, which have a slight anaesthetic 26 o o a Table 1 Thermophysical pr Chemical symbol Molecular weight Normal boiling point °C (K) Freezing temperature °C (K) Critical temperature °C (K) Critical pressure, bar Expansion ratio - increase in volume as liquid at 1 bar boils to 1 bar, 15°C gas at Density of saturated liquid at 3) lbar(kgnTRelative gas density (referenced to dry air at 1 bar, 15°C, density 3) 1.21 kgm" Latent heat of vaporisation at 1 bar (cooling potential of phase _1kJkg) change) (hfg Fire/explosion hazard Air liquefaction hazard Note: With the exception of liquid H With the exception of C24 General safety requirements 3 vapours. Gloves should be a loose fit so that they may be readily removed should liquid splash on to them or into them. If severe spraying or splashing is likely to occur eyes should be protected with a face shield or goggles. Trousers should be worn outside boots and have no pockets or turnups. 1.1.1.2 First aid (cryogenic 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: (a) Loosen any restrictive clothing. (b) Continue to flush the affected areas of skin with copious quantities of tepid water. (c) Protect frozen parts with bulky, dry, sterile dressings. Do not apply too tightly so as to cause restriction of blood circulation. (d) Keep the patient warm and at rest. (e) Ensure ambulance crew or hospital is advised of details of accident and first aid treatment already administered. (f) Smoking and alcoholic beverages reduce the blood supply to the affected part and should be avoided. 1.1.2 Oxygen deficiency (anoxia) None of the gases listed in Table 1 have any odour, and therefore they cannot be detected by smell. Apart from oxygen, all the gases are asphyxiants. Carbon monoxide has particularly hazardous toxic properties, which are discussed more fully in Chapter 4. Accounts of the symptoms arising from the sudden and gradual onset of oxygen deficiency in the atmosphere are given below. 1.1.2.1 Sudden asphyxia In sudden and acute asphyxia, such as that from inhalation of a gas containing practically no oxygen, unconsciousness is immediate. The victim falls as if struck down by a blow on the head and may die in a few minutes, unless immediate remedial action is taken. 1.1.2.2 Gradual asphyxia Sudden asphyxia is the most common form encountered in practice but degrees of asphyxia will occur when the atmosphere contains less than 20.9 per cent of oxygen by volume. Alexander and Him wick (1939) recognize four stages. It should be appreciated that the concentrations given are rough guides only, and may vary with individuals and ambient conditions.
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