1、BRITISH STANDARD CONFIRMED JULY 1988 BS 5429:1976 Code of practice for Safe operation of small-scale storage facilities for cryogenic liquids UDC 621.564:661.91 404:621.646.036:614.8BS5429:1976 This British Standard, having been prepared under the directionof the Refrigeration, Heating and AirCondit
2、ioning Standards Committee, was published underthe authority ofthe Executive Board on 30 November 1976 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference RHE/21 Draft for comment 75/73230 DC and draft for approval 76/72899 ISBN 0 580 09109 6 Cooperating
3、 organizations The Refrigeration, Heating and Air Conditioning Standards Committee, under whose supervision this British Standard was prepared, consists of representatives of the following Government departments and scientific and industrial organizations: Association of Consulting Engineers Associa
4、tion of Manufacturers of Domestic Electrical Appliances Boiler and Radiator Manufacturers Association Ltd. British Combustion Equipment Manufacturers Association British Gas Corporation* British Mechanical Engineering Confederation British Refrigeration and Air Conditioning Association* Building Ser
5、vices Research and Information Association Department of the Environment Department of Health and Social Security* Electricity Supply Industry in England and Wales Engineering Equipment Users Association Heating and Ventilating Contractors Association HEVAC Association Institute of Fuel Institute of
6、 Refrigeration* Institution of Gas Engineers Institution of Heating and Ventilating Engineers Lloyds Register of Shipping* Manufacturers Association of Radiators and Convectors Ministry of Defence* National Coal Board Society of British Gas Industries Water-tube Boilermakers Association The organiza
7、tions marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Associated Offices Technical Committee British Cryogenics Council Chemical Industries Association Liquefied Petroleum Gas
8、Industry Technical Association (UK) Amendments issued since publication Amd. No. Date of issue CommentsBS5429:1976 BSI 08-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii 0 Introduction 1 Section 1. General 1 Scope 1 2 Physical properties 1 3 Health 2 4 Protective clothi
9、ng 3 5 Materials of construction 3 6 Effects of overloading installations 3 7 Pressure relief devices 3 8 Other hazards 3 Section 2. Liquid oxygen 9 Physical properties 4 10 Health 4 11 Protective clothing 4 12 Materials of construction 4 13 Fire 4 14 Other hazards 5 Section 3. Liquid nitrogen 15 Ph
10、ysical properties 5 16 Health 5 17 Protective clothing 5 18 Materials of construction 5 19 Fire 5 20 Other hazards 5 Section 4. Liquid argon 21 Physical properties 5 22 Health 5 23 Protective clothing 6 24 Materials of construction 6 25 Fire 6 Section 5. Liquefied natural gas 26 Physical properties
11、6 27 Health 6 28 Protective clothing 6 29 Materials of construction 6 30 Fire 6 Table 1 Properties of low temperature liquefiable gases 1 Table 2 Health hazards of low temperature liquefiable gases 2 Table 3 Metals for low temperature service 3BS5429:1976 ii BSI 08-1999 Foreword This British Standar
12、d Code of practice has been prepared under the authority of the Refrigeration, Heating and Air Conditioning Standards Committee. Acknowledgement is made to the work of the British Cryogenics Council in this field and in particular its “Cryogenics Safety Manual”, which assisted the committee in prepa
13、ring this code. This code of practice deals with the safe operation of small-scale storage facilities for cryogenic liquids, and it is emphasized that the code has been written principally for the information of users of such storage facilities. It is considered that design, construction and install
14、ation aspects of such equipment are the responsibility of specialized and experienced organizations, and the code does not therefore deal with these aspects of the storage facilities. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standard
15、s are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to7 and a back cover. This standard has been updated (s
16、ee copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5429:1976 BSI 08-1999 1 0 Introduction Over the last few years there have been major changes in the refrigeration industry. Cryogenic liquids are now being used in l
17、arge quantities by industry in general for the storage of gases in a convenient concentrated form, and there is also a growing use of the cryogenic properties of liquid nitrogen in particular as a refrigerant. A code of practice on the safe operation of storage facilities for cryogenic liquids is co
18、nsidered desirable for the information of users. The object of this code is therefore to provide the users of cryogenic liquids with a basic appreciation of the problems and hazards associated with them. The impossibility of making comprehensive recommendations capable of covering every risk situati
19、on should be appreciated, but an intelligent application of the principles and recommendations that follow will cover most situations. Since the larger proportion of users depends on the cryogenic industry for the supply of both the liquid and the container, this code does not deal with the requirem
20、ents of the design and manufacture of the equipment. Similarly it does not deal with the installation of the equipment, as advice on this subject is normally given by the supplier to the user. At the present time most installation capacities fall into the range0.5t 1)to135t liquid oxygen, or the liq
21、uid volume equivalent of liquid nitrogen, liquid argon or liquefied natural gas. The minimum figure of0.5t covers the smallest capacity of container used commercially for storage; in the case of liquid oxygen, special planning procedures are necessary for capacities greater than135t. Section 1. Gene
22、ral 1 Scope This code of practice deals with the safe operation of small-scale storage facilities for cryogenic liquids in the capacity range0.5t to135t liquid oxygen, or the liquid volume equivalent of liquid nitrogen, liquid argon or liquefied natural gas. The code is primarily intended to cover i
23、ndustrial storage, but some of the code applies to liquid storage integral with production units. The range0.5t to135t has been chosen since0.5t covers the smallest capacity of container used commercially for storage and135t, in the case of liquid oxygen, is the limit beyond which in the United King
24、dom special planning requirements and procedures apply before such storage can be installed. In some circumstances special regulations will apply (e.g.in mines) and their provisions will have to be observed. 2 Physical properties Some physical properties of the cryogenic liquids are given in Table 1
25、. Table 1 Properties of low temperature liquefiable gases 1) t = tonne Property Oxygen (O 2 ) Nitrogen (N 2 ) Argon (Ar) Natural gas Molecular weight Colour of gas Colour of liquid Taste of gas Odour Normal boiling point at atmospheric pressure ( C) Ratio of volume of gas to volume of liquid, measur
26、ed at15 C and absolute pressure of1atm Liquid density at absolute pressure of1atm(kg/m 3 ) Flammability limits 32 None Light blue None None 183 842 1141 None, but supports combustion vigorously 28 None None None None 196 682 807 None 39 None None None None 186 822 1394 None 16.4 to 16.8 None None No
27、ne None 161 to 163 616 to 621 431 to 439 5 % to 15 %BS5429:1976 2 BSI 08-1999 3 Health 3.1 General health hazards. A brief summary of health hazards of low temperature liquefiable gases is given in Table 2. Table 2 Health hazards of low temperature liquefiable gases 3.2 Cold burns and frostbite 3.2.
28、1 Cold burns. Cryogenic liquids, cold vapours and gases can produce effects on the skin similar to a burn. Naked parts of the body coming into contact with uninsulated cold equipment may also stick fast by virtue of the freezing of available moisture and the flesh may be torn on removal. 3.2.2 Frost
29、bite. Severe or prolonged exposure to cold vapours and gases can cause frostbite. Local pain usually gives warning of freezing but sometimes no pain is experienced. Frozen tissues are painless and appear waxy with a pallid yellowish colour. Thawing of the frozen tissue can cause intense pain. Shock
30、may also occur. 3.2.3 Treatment for cold burns and frostbite. Loosen any clothing that may restrict blood circulation and seek immediate medical attention for all frostbite injuries. Move the casualty to a warm place but do not apply direct heat to the affected parts. Every effort should be made to
31、protect the frozen parts from injury and infection. Dry sterile bulky dressings can be used for this purpose but should not be applied so tightly that the blood circulation is restricted. Alcoholic drinks and smoking may have a harmful effect on injured tissue and are not recommended as part of firs
32、t aid treatment. 3.3 Effects of cold on lungs. Prolonged breathing of extremely cold atmospheres may damage the lungs. 3.4 Hypothermia 3.4.1 General. Low environmental temperatures can cause hypothermia and all persons at risk should have warm clothing. Hypothermia is possible in any environment bel
33、ow10 C but susceptibility depends on length of exposure, temperature and the individual. Older persons are more likely to be affected. 3.4.2 Symptoms. The symptoms of hypothermia are a slowing down of physical and mental responses unreasonable behaviour or irritability difficulty in speech or vision
34、 stumbling cramp and shivers 3.4.3 Treatment. Persons apparently suffering from hypothermia should be wrapped in blankets and moved to a warm place. No external form of heating should be applied except under medical supervision. 3.5 Asphyxia 3.5.1 General. The normal oxygen content of air is20.9% by
35、 volume. Atmospheres containing less than18% oxygen are potentially dangerous. Permanent brain damage and death can arise from breathing atmospheres containing less than10% oxygen. Immediate unconsciousness and death will follow breathing of atmospheres free of oxygen. For this reason the oxygen con
36、tent of atmospheres has to be measured with a purpose-made instrument that has been calibrated immediately before use. In certain circumstances consideration should be given to provision of personal oxygen deficiency meters fitted with alarms. NOTEEven when the oxygen content is shown to be adequate
37、, a flammability test should be made before entry if a flammable gas is involved, using a purpose-made instrument. 3.5.2 Symptoms of asphyxia. If any of the following symptoms appear in situations where a breathing apparatus is not in use, the affected person should immediately move to open air or i
38、mmediate rescue should be made followed by resuscitation (see3.5.3): Health hazard Oxygen Nitrogen Argon Natural gas Local effects Cold contact burns Frostbite Hypothermia General effects Respiratory difficulty due to vapour inhalation Suffocation Toxic Supports life Yes Yes Yes Yes No No Yes Yes Ye
39、s Yes Yes Yes No No Yes Yes Yes Yes Yes No No Yes Yes Yes Yes Yes No No poor breathing nausea abnormal pulse vomiting rapid fatigue inability to move faulty judgement convulsive movements insensitivity to pain collapse abnormal emotionsBS5429:1976 BSI 08-1999 3 3.5.3 Rescue and resuscitation. If som
40、eone has been exposed to an oxygen-deficient atmosphere, rescuers should not attempt to enter the same atmosphere without appropriate breathing apparatus, otherwise they themselves may be overcome. (Many fatal accidents have occurred in industry where would-be rescuers, not equipped with breathing a
41、pparatus, have attempted to rescue colleagues overcome by oxygen-deficient atmospheres.) 3.6 Toxicity. The gases listed in Table 1 have negligible toxicity at atmospheric pressure. 4 Protective clothing All protective clothing should be dry and oil-free before use. Protective clothing is intended to
42、 protect the user when handling cold equipment and against accidental contact with cryogenic liquid. Leather gloves should always be worn when handling anything that is, or may have been recently, in contact with cryogenic liquids. Gloves should be a loose fit so that they may be readily removed sho
43、uld liquid splash onto or into them. Care should also be taken with woven clothing and gloves so that saturation with liquid does not occur. When spraying or splashing is likely to occur, eyes should be protected with a face shield or goggles. Overalls or similar type clothing should be worn, prefer
44、ably without pockets or turn-ups where liquid could be trapped. Trousers should be worn outside boots. Clothing that has been contaminated with spilled liquid or cold vapour should be ventilated before the wearer goes into a confined space or near a source of ignition. The wearer should walk about i
45、n the open air with his coat open for a minimum ventilation period of5min. 5 Materials of construction 5.1 General. The properties of materials change at low temperature but the danger of “brittle fracture” is the most significant consideration when selecting materials. Also, many materials regarded
46、 as non-flammable in air are readily combustible in oxygen and oxygen-enriched atmospheres. It should be noted that oxygen-enriched atmospheres can exist on nitrogen equipment due to air condensation on the cold surfaces. 5.2 Metals for low temperature service. Metals used should satisfy the impact
47、test requirements of the design code. A broad guide to the application of the various commonly used metals is given in Table 3. Carbon steel is extremely brittle at cryogenic temperatures and should not be used for cryogenic liquid containers, but it may be used for jacketing double-skin containers
48、where thermal insulation separates the inner and outer vessels, provided that adequate precautions are taken at pipework penetrations. Table 3 Metals for low temperature service 6 Effects of overloading installations Careful consideration should be given to any proposal to change the service or incr
49、ease the throughput of an installation above that for which it was designed, as this introduces the risk of cold fluids entering parts of the equipment not designed for low temperatures. 7 Pressure relief devices Cryogenic liquids have low latent heats of evaporation. The volume of vapour or gas produced is several hundred times the original volume of liquid and for this reason it is essential that an adequately sized pressure relief device suitably vented to a safe place should be provided on each section of an installation in which cryogenic liqui
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