AMMONIA COMPRESSORS AND REFRIGERATION Deposit From Sabang
INTRODUCTION
1 That circular gives advice on the precautions to be taken across the toxic, fire and bang hazards presented by refrigeration systems containing ammonia. These are almost likely to be do by LA enforcement officers at impersonal stores and food consignment warehouses. It applies to the entire system not simply the compressor house. It provides brief advice on matters of anxiety to enforcement officers pending review of BS 4434:1980.
2 Appendix 1 outlines the present principles of refrigeration, Appendix 2 gives advice on the results of the programme of peculiar visits carried out in 1983 by Firm Inspectorate (F1) to contemplate present standards in the cuisine industry and Appendix 3 gives careful guidance on electrical standards. Imposition officers should not overemphasise the hazards of ammonia compared amidst other refrigerants.
HAZARDS
Toxicity
3 Ammonia is a chemically reactive fuel that is very soluble in h2o and is much lighter than condition (vapour density 0.59 of that of air). Cold vapour (e.g. from leaks) may anyhow be denser than air. Albeit there have been incidents of emergency to harmful concentrations of ammonia in the UK ready have been few bad accidents. Ammonia is characterised by a typical pungent odour and is conspicuous by most people at levels of almost 50 ppm in the atmosphere. Admitting workers become tolerant to a particular effect and in the yesterday have been able to business without distress at levels up to 70 ppm, at present the recommended exposure length for ammonia is 25 ppm, 8 age TWA (0.0025%) and the annoyed term exposure limit is 35 ppm, 10 little TWA. At 400 ppm, about people experience immediate snout and throat irritation, nonetheless suffer no permanent ill-effects afterwards 30-60 minute exposure. A classification of 700 ppm causes urgent irritation to the eyes, and a category of 1,700 ppm (0.17%) resolve give rise to existing coughing and can be bad after about 30 minutes exposure.
Exposure to concentrations improved 5,000 ppm (0.5%) since quite short periods bowl result in death. Impression to the effects of ammonia varies widely 'tween individuals, and the dose-response effects described high are likely to be those adept by the more free members of the population.
Fire and explosion
4 Ammonia forms a flammable mixture with air at concentrations amid 16 and 25% v/v. Attendant have however been literally few incentive explosions involving ammonia compressor houses in the UK and everyone of the reported incidents absorbed ammonia leakage from bury under maintenance.
Existing guidance
5 New guidance on the precautions which should be taken alongside ammonia refrigeration plant may be begin in: British Standard 4434: 1980 "Requirements as Refrigeration Safety: Part 1, General". The requirements (particularly from the f ire and bang standpoint) are similar to those in the forward (1 969) version. Anyway a' full revision of BS 4434 is taking place.
Precautions
6 Bottom normal circumstances people resolve not be able to manage ammonia concentrations at alike a fraction of the flammable limit. The applicable precautions are mainly those apt against toxic effects in occupied areas and to employment where sudden exposures are foreseeable, akin as maintenance and fitness work, including in objective filling and oil draining. Precautions against fire and explosion firmness be appropriate however, in unoccupied areas such as compressor houses and alone plant such as analytic stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Across TOXIC RISK
Respiratory protective equipment
7 Any person entering an field in which ammonia vapour is acceptable to be present at a consequential level (eg for recover or fault-finding purposes) precondition wear self-contained or air passenger carrier breathing apparatus. This does not build routine visits to entomb rooms etc. A ample and properly maintained set should be conveniently sited adjacent to, but outside, all area in which above levels of .ammonia vapour efficacy arise. In no conclusion should anyone enter an range where a flammable absorption of gas may be present. Circumstances of suitable apparatus are contained in Organize 2501 "Certificate of Confirmation (Breathing Apparatus)," published annually by HSE. See also Guidance Note GS 5 regarding entry into confined spaces.
8 Ample respiratory protective equipment precondition be worn by every body carrying out engineering conservation work on any manufacture where there is a hazard of release of ammonia. Infinite face canister respirators with type A (blue) canisters give good protection in atmospheres up to 2% consolidation or 20,000 ppm, since one hour. Work in akin a concentration is likely to lead to ache quickly due to fur irritation as ammonia dissolves in perspiration. A list of suitable device is given in arrange 2502 "Certificate of Confirmation (Canister Gas Respirators)". Since substantial jobs impervious suits may be essential if the gas cannot be cleared.
9 Everybody who is likely to commitment to use respiratory protective device must be properly veteran in its use and must be fully aware of its limitations. The accessory must be maintained, kept blank and examined at least once a month. Convenient records should be kept. If canister respirators are worn there must be an effective system for deciding at the canisters should be renewed.
Evacuation and emergency procedures
10 lt is elemental that a clear crisis procedure is drawn up which conclusion the precise duties of everybody staff and the arrangements as evacuation, rescue, first aid, entomb isolation etc. It is mostly important that evacuation procedures are definitely set out and constantly practised where refrigeration systems are in unavailable areas. A common control which may be abundant is to use the bonfire alarm provided that actuating points are immediately available at working areas. Cadre should be warned not to approach any vapour clouds. (Clouds may constantly look like steam as of the cooling of the released gas).
11 Able exits should be maintained from deposit rooms at, all times. Cadre seriously affected by an ammonia bypass suffer streaming eyes and cruel coughing and rapidly become disorientated. They therefore lack clear prior knowledge of a protected exit route.
Training in bury operation and maintenance
12 Anybody personnel involved in the force and maintenance of the deposit must be adequately trained. The coaching should cover not only general principles of refrigeration nonetheless also specific points related to the particular plant. A well known applies as much to preservation contractors as to an employer's grant staff.
PLANT LOCATION
Plant not designed after all outdoor location
13 In the employment of standard refrigeration bury (ie plant not especially designed for outdoor location) emergency to excessively low aspect temperatures may cause liquefaction of ammonia in the compressor leading to compressor damage, which could be hazardous. A particular type of plant should then be sited in a compressor architecture using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, location reasonably practicable, be fitted amidst explosion relief (eg by using cipher fragile roof). Where loosely held panels are recycled as explosion relief, they should be suitably hushed (eg by chains) to avert them becoming dangerous missiles in the employment of an explosion.
14 ln command to facilitate the accouterment of ventilation and bang relief, compressor-houses should blend at least one extraneous wall. The siting of compressors in debilitated areas, basements, etc should be avoided anyplace practicable. Doors between plant rooms or compressor-houses and additional parts of the building should be self-closing and well-fitting.
Plant designed since outdoor location
15 Only bury specifically designed for the humidity should be installed outdoors. Akin installations should be sited in a safe position in the bring to light air with, if necessary, weather preservation using a Dutch parking space type structure which has an evenly distributed first open area equivalent to at least 50% of the account wall area.
Plant in workrooms
16 As a present principle the amount of deposit containing ammonia situated in workrooms and added populated areas should be minimised. Additional plant such as flood drums and liquid pumps should anyplace possible be sited overseas from working areas. Compressors are constantly noisy and this is alternative reason for not having diehards in working areas.
Ventilation
17 Compress or houses should be provided with adequate and suitable ventilation to encounter the following requirements:
(1) Frequent Ventilation Sufficient permanent ventilation should be provided to bar build up of toxic concentrations of ammonia from operational flow (eg from seals, glands etc). It is possible that the redrafted British Usual will insist on industrial car ventilation rather than bet on rather uncertain natural ventilation.
(2) Emergency ventilation Provision should be made as sufficient mechanical ventilation to bar flammable ammonia/air mixtures developing in the event of kind of foreseeable plant or operational deterioration (eg valve failure). In akin circumstances the aim should be to carry concentrations below 25% of the junior explosive limit (ie 4%).
18 The ventilation requirements as a particular installation courage depend on the type, capacity, effective conditions and location of the deposit and may require creature assessment by a ventilation artist with appropriate expertise. However, the backward general points apply:
(1) permanent natural or mechanical ventilation, or a coalition of both, may be hand-me-down for normal or crisis ventilation. Mechanical ventilation initiated by electricity detectors or manually (in the employment of continuously manned plants) may likewise be used for crisis ventilation (see para 26); and Appendix 3 since electrical safety of the system;
(2) the ventilation should emission to a safe place in the open air;
(3) in by reason of the ventilation to be provided, the possible effects of cold on deposit should be taken into account (see para 12);
(4) leakage of air through cracks viable windows, doors etc, or the access of windows or doors should not be relied on after all ventilation;
(5) the formulae in BS4434 since quantifying ventilation requirements are rules of hook based on unstated assumptions (eg they accept no account of gallery size or leak rates). Inspectors should advise that the formulae may be hand-me-down as a basic escort but discretion in their accurate application to a material plant should be stressed. A certain is particularly important alongside very large systems although the ventilation required by the formulae becomes impracticable; and
(6) it should be best that the standard of ventilation addicted by the formulae in BS 4434: 1980 is not intended to force with prolonged releases from main plant failure. However, the closing is very unlikely to exist in properly designed, constructed and maintained plant. Agency of sources of ignition and bury shutdown (see paras 22-26) should further provide protection in alike circumstances. Manually operated controls after all emergency ventilation should be located in a safe, definitely accessible place along along the control or about-face for turning off the compressor.
Plant integrity
19 Ready can be serious corrosion of the empty pressure. parts of pipework and plant due to condensation. It bag progress unnoticed under lagging which is not altogether vapour sealed and is essentially rapid on plants which tour intermittently and pass-through OoC. The present principles relating to the protection of pressure systems are appropriate. The manufacture should be thoroughly examined by a apt person at regular intervals in accordance with a written scheme. Near should be an effective maintenance scheme.
Pipework
20 All parts of refrigerating systems and in concrete pipework should be positioned or intact to minimise the exposure of impact damage, by reason of example by fork journey trucks. Pipework and valves should be certainly marked to indicate their contents and function.
Oil absorb system
21 Many of the reported incidents involving ammonia refrigeration systems believe been the result of a malfunction of the butter drain system (designed to attend the "carry-over" of oil from the compressors). In around cases oil is bored from below liquid ammonia and is saturated along it. In addition the oil is viscous because it is cold. In direction to minimise the exposure of escape from a well known cause the following measures should be advised:
(1) locus short distances are attentive and adequate observation of the devour is possible oil consume pipes should terminate in a safe location in the expose air. Valves on any pipe extension should not enter the possibility of liquid ammonia as a result of trapped; a bleed valve or hydrostatic assistance valve venting to a intact place should be provided in the sections between valves, as appropriate;
(2) a dual valve arrangement should be provided at margarine drains. In addition to the operational booklet valve, there should be an automatic closing spring or weight-loaded valve; and
(3) The obligation of oil drain catchpots. These are a useful feature on new plant, still existing plant cannot commonly be easily modified. Along the oil is drained, the catchpot is far-off from the liquid ammonia/oil feedline and the catchpot is electrically enraged to boil off any ammonia which flows as a vapour to the flat pressure side of the system. At the catchpot is warm, it is likewise isolated on the vapour recto and the oil is already drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, accurately ventilated positions and, where reasonably practicable, in the disclose air. Filling points should be sited away from sources of ignition.
PRECAUTIONS Against FIRE AND EXPLOSION RISK
Sources of ignition
23 Everybody likely sources of ignition (naked flames etc) should be eliminated from compressor houses and from the urgent vicinity of externally located plant.
Electrical equipment
24 Encouragement on electrical apparatus by reason of use in potentially device atmospheres is given in RS 5345: Detail 1: 1976 "Code of Background for the Selection, Airstrip and Maintenance of Ac Apparatus for Use in Potentially Mine Atmospheres, Part 1, Key Requirements for all Parts of the Code"; BS 4434: 1980, Portion 13 "Electrical Installations". The approaches followed by the over documents differ.
25 As a current principle, electrical equipment should be sited abroad the compressor room in a secure location. However, when it is actually sited in the room, it should be in accordance along the guidance given in para 27.
26 Locus the ammonia compressors and refrigeration entomb are located in the same room as the endowment switch gear for the-premises relocation would probably be inconvenient and costly. In such cases, Field Consultant Category (FCG) advise on the about suitable safety precautions in the detailed case should be sought.
Electrical appliance selection criteria
27 The demand of electrical apparatus in refrigeration plants using ammonia has been clear a special case as a result of of the flammability characteristics of the ammunition (high LEL and finite explosive range) and the detail that it can be detected at literally low levels by smell. A certain has resulted in a location of options which may be express when selecting electrical appliance for ammonia plants and these are expressed in Appendix 3.
OTHER RISKS
28 Refrigeration systems constantly have associated risks which may desire attention, These include the liability of trapping in clinical stores and chills, the management of very cold products and microbiological problems corporate with cooling towers used for the condenser.
ENFORCEMENT APPROACH
29 Imposition officers should advise a particular ammonia refrigeration plant should adapt with the guidance in BS 4434: 1980 as amended and positive by the information in a particular circular. They should anyhow bear in mind:
(1) ammonia presents a toxic liability at concentrations far below those at which it presents exclusive fire or explosion risk. There have been 2 gassing fatalities 'tween 1977 and 1983 in the UK still only 3 incentive ammonia/air explosions in the basic 20 years;
(2) the possible consequences of an employment in terms of ailment to personnel, and the present public should be assessed;
(3) BS4434 was advance published in 1969 and was not intended to be retrospective, admitting improvements in installations which pre-date the simple should be recommended, where reasonably practicable;
(4) analysis of the l983 visits energetically suggest that where defenseless conditions of the plant are found there is daily inadequate attention to retirement and emergency action; and
(5) locus enforcement officers encounter maintenance contractors they should generate enquiries about their busy practices and training.
Further advice
30 A particular is a complicated mechanical subject and there are active trade pressure groups. Imposition officers are recommended to go after the advice of HSEs Operation Consultant Group (FCG) via the Civil Enforcement Liaison Officer (ELO), along considering enforcement action.
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Ammonia is worn as a refrigerant as long as of particular thermodynamic properties which enable it to move simmer far more efficiently than added refrigerant gases such as halogenated hydrocarbons. It is essentially suited to working in the area approximately OoC to -30oC and therefore is widely used after all food preservation, the chilling of liquids alike as milk, beer and reticent drinks, and in the chemical industry. New systems extend to be installed.
2. A usual system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In education other components such as margarine separator, intercooler, liquid receiver, flow drum and liquid pumps are constantly found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at empty pressure, and hence horizontal temperature, takes in simmer by vaporising. This vapour is removed by the compressor which, in compressing it, raises the climate from below to above ambient. The hot compressed ammunition gives up the melt by condensing to a liquid in the condenser. The high pressure liquid then passes over the pressure reducing valve to the evaporator. At the valve the liquid is cooled as some vapour flashes off. The pausing liquid is available since use in the evaporator.
4 In a down-to-earth system it is expected there will be additional items of plant. An butter separator removes suspended margarine carried over from the compressor and either returns it to the (pressurised) crank-case or holds it after all draining in some way. Attendant may be a multi-stage compressor along an intercooler. This is cooled by aching high pressure liquid into the empty pressure side.
Downstream of the condenser is generally a liquid receiver. Downstream of the reducing valve is everyday found a surge drum which acts as a lagoon of cold liquid and evens aside demand on the compressor and condenser. The liquid ammonia is drawn from the stream drum by a pump. Butter drains may be do on surge drums, liquid receivers, and elsewhere on large plants. Ready is also likely to be an autogenous control system on everyone but the oldest and smallest plants.
A classic practical refrigeration system
1 The aim was to collect consultation about a cross brick of installations. One hundred and forty eight returns were hand-me-down in the analysis which hand-me-down the Edinburgh FCG microcomputer.
2 Returns covered a open range of processes in the cooking and drinks industries. The better single sector was dairying (chilled drink supply) with substantial returns likewise from frozen food producers and analytic stores. In the drinks district cooling and soft drinks carbonators were the preeminent uses.
There were a free range of other uses reported; approximately parts of the bread industry require controlled temperatures below ambient at some article of their process. A free range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were high 5 tonnes, 40% between 1 and 5 tonnes, 35% amid 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest component reported was pre-war and there was a fairly alike spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a autonomous compressor room. Forty-nine percentage had the system charging extent in the compressor entrance and 38% had it outdoors. Twenty-seven per cent of the case could positively be identified as having doors to the outside of the building only. Thirty-six per cent of the added compressor rooms did not believe self-closing doors and 17% did not admit well-fitting doors. With compressors in a independent room this is a exceptionally large number where balanced the most rudimentary precautions to bar the spread of escaping electricity has not been taken. Fifty-five per cent had condensers mounted high ground level outside - normally on the roof. This raises questions of protected access and also avoid in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were ever product freezers in the frozen cuisine sector and carbonators at the muted drinks plants). This points to the commitment for effective emergency procedures in the case of leakage, particularly if it is in the workroom.
5 Alone 3% of installations were identified as having pipework or entomb capable of being damaged by, as example, fork lift trucks. Partly of the entire opinion however had unmarked pipework. (Notes of abounding proformas suggested that a well known would receive early attention).
6 lt proved impossible to carryout meaningful inquiry of the ventilation provided in compressor rooms. A moderate installation seemed to rely largely on natural ventilation (perhaps assisted by a cramped fan) for normal ventilation. Locus there was provision of ventilation exclusively for emergencies, it tended to be a independent system rather than a 2 speed fan on the frequent ventilating system. Only 23% of the installations had 2 ventilation rates applicable and only half the ventilation systems of all kind could be mathematical from outside the compressor room. Unattended half of these ventilation systems were automatically controlled.
7 Only 16% of everyone system charging was done by a body on his own; the typical arrangement was 2 men. Margarine draining was done by all man on his grant at 30% of everyone Installations. At 51 % of everyone installations it was carried aside more than once a month. Solo 26% of installations had spring-loaded valves or a catchpot development at oil drains. Approximately of the rest had barely a short stub of drum from a vessel containing liquid ammonia halcyon by a single valve. In 71 % of cases locus the oil drain was unsatisfactory inspectors explicit that the reasonably practicable arrangement was the fitting of self-closing valves. The 30% of installations point one man did the shortening draining on his allow included 6 which had no respirator of each kind.
8 Forty-two per cent of compressor houses had no electricity detectors. Sieger was by broad the most common supplier (60%) of anybody detection systems. The approximately common service period of twice per year reflects a particular company's normal service contract. Nineteen per cent of detector systems were never checked.
Approximately half of the detector installations unattended had one operating level. Twenty-seven per cent of systems did not shut down the plant nonetheless merely raised the alarm. Ten per cent of the systems had no autonomous alarm.
9 Sixty-six percent of compressor foyer electrical installations were not comprehensively equipped to Zone 2 usual even where much of the bury was under the authority of detectors. Seventy-five per cent of everybody compressor installations could be switched aside elsewhere outside the compressor foyer (even if only at the elemental supply). Of the remainder, the essential switchgear was either in the compressor foyer or access to it was over the compressor room.
10 Eighty-eight percentage of all sites had 2 or likewise sets of respiratory protection of some kind. Six installations (4%) had no one at all. At 83% of sites there was said to be some description of training in the commitment of respiratory protection still only 43% had some description of systematic examination. At unattended 5 installations (3.4%) were there possible limitations of operation which conflicted with accouterment of respiratory protection and the elemental problem seemed to be approach up ladders or viable congested items of plant.
11 Forty-seven per cent of sites had reviving apparatus available usually for ongoing first aid rather than especially because of the ammonia.
12 Twenty-seven fee of sites had Draeger (or similar) detector tubes as measuring low concentrations of ammonia. Bounteous others had sulphur sticks or hydrochloric piquant for detecting small leaks.
13 Fifty-nine chunk of installations were maintained at gutter partly by contractors. Alone from a few fundamental suppliers and installers of apparatus there were many governmental refrigeration engineers who alone appeared once or twice in the survey. No consultation is available about the typical of training or workmanship of these contractors.
14 Fifty-five chunk of all sites appeared to believe emergency evacuation procedures (43% used the fire alarm) nonetheless slightly fewer (50%) appeared to bestow any training in these procedures. Alone 24% appeared to conclude detailed rescue arrangements. Twenty-two per cent had written systems of field which appeared comprehensive and solo 34% had what appeared to be alive plant operator training.
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APPENDIX 3 (paras 1 and 26)
PROTECTION OF Electrical APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT
EXTERNALLY SITED PLANT
1 Compressors and refrigeration bury sited in out gate locations in accordance with para 14 of a certain Circular in otherwise non-hazardous areas resolve not normally require chiefly protected electrical equipment.
INTERNALLY SITED PLANT
2 A flow chart of the key requirements relating to the magnetic apparatus for internally sited deposit is given in the supplement to a particular appendix. The operational approaches are disposed below.
Option 1 - Commitment of explosion protected ac apparatus
3 Hazardous area category should be carried alone by a competent person. Electrical apparatus should then be select in accordance with BS 5345: Design 1: 1976 Section 2. The max of compressor-houses should be regarded as Region 2 areas. Type "N" boom protected equipment (including any emergency ventilation fans) resolve be suitable for these locations.
Option 2 - Detection of leaks by personnel or gas detectors
4 ln that approach, non-explosion protected electrical apparatus, with qualifications, may be recycled in combination with a readily convenient means of isolating the service supply. The method of achieving the latter can be accomplished either necessarily after detection of a discharge by a gas detector system, or manually subsequently a leakage has been detected by personnel. The need of these techniques as a leading line of defence is partly to applications solely involving ammonia in refrigeration plants. A particular approach is considered acceptable provided that the present principles outlined in paras 10-17 are followed and a certain sufficient account is taken of paras 5-9.
Gas detectors
5 The detectors should be suitably positioned taking into history the physical characteristics of the deposit room, the pattern of airflow force in it and the about likely sources of possible leakage. Due regard should be paid to each dead pockets or recesses. Feat has shown that, in physical circumstances, it is possible for cold ammonia vapour to stratify initially at horizontal levels. Unless the occupier has able expertise within his acquiesce organisation, it would be advisable as him to consult a employer which specialises in the composition and installation of food detection systems.
6 As a choppy guide only, one might expect to see detectors in the vicinity of the compressors and additional non-static items of entomb and at ceiling category where one detector per 36M2 of roof area would probably be sufficient, despite more may be essential if there are expansive beams creating recesses. The objective is to ensure that the ammonia is detected and the accessory rendered safe before flammable concentrations enter a source of ignition. (This objective, which is likewise applicable to "detection" of a leak by personnel, is chiefly critical with regard to electrical apparatus which is not notably designed to be non-sparking, non explosion-protected electrical apparatus and electrical device with temperatures above 630'C).
7 The detectors should be suitably explosion protected.
8 The detectors recycled are of the "pellistor" type and may be accountable to poisoning by airborne contaminants. They should then be properly installed and maintained and consistently checked. The operation of the detectors should be finite using standard ammonia ammunition mixtures. Certain V-belt dressings containing antimony conclude been shown to narcotic detectors and gradually cut their response.
9 The detectors should be adequate of detecting concentrations of ammonia at 1 % v/v or less.
Associated ac apparatus
10 Account should be taken of the electric control system circuitry and the severe possible degree of downturn to safety should be achieved, so buried as is reasonably practicable. Current guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Block 6.
11 The isolating device(s), whether manually or no doubt operated, which cuts away the electricity supply to the ammonia entomb room, should be located in a non-hazardous area. It container be either a maker or circuit breaker. If the criteria in paras 5-9 above have been satisfied, the behind recommendations in paras 13-17 should be adopted. (Although certain specific details have been taken from BS 4434:1980, by path of example, they are intended to define the general principles of a particular approach and not recognizable requirements -which will have, to be bold in each particular case).
12 Mind will need to be paid to the control of other circuits which concede the plant room and are not presently associated with the plant, eg socket outlets as portable tools.
Continuously manned rooms
13 Privacy of all electrical circuits should be effected by isolating devices located in a non-hazardous area. These devices should be scientific by push buttons instantly outside the plant room, or mathematical by a gas diagnosis system as described pare 14, and arranged to give visual and audible alarms to switch on equipment for crisis ventilation and/or emergency lighting (if installed). Each electrical apparatus that is required to apply in the room later a leakage has been detected, such as ventilation equipment and emergency lighting, should be suitably safe for the hazardous range in which it is sited, ie District 2. Few compressor rooms are gradually manned. Detection of flood by operators is alone reliable if they are gradually present in the room. If after all example they have increased duties, or leave the range for meals etc, or commitment an isolated noise refuge once the speed of effect is likely to be physically slower than that of automatic detectors.
Unmanned plant rooms
14 lsolation of anyone electrical circuits should be effected by isolating devices located in a non-hazardous range and controlled by anyone or more suitable ammonia ammunition detectors which should also be arranged to give a visual and distinct alarm and to reversal on equipment for ventilation and/or danger lighting, if installed. The ventilation attitude should be discharged to the away of the building in aforesaid a manner as not to matter distress or danger to persons in the vicinity of the building. Band isolation should be effected at ammonia concentrations below 25% LEL and an bell setting of 1.5% v/v followed by ring isolation at 3% v/v is suggested.
15 Conservation personnel are required to accept unmanned plant rooms and adequate means of escape should be provided.
16 Animal protection including breathing apparatus, and apparently impervious suits, may be needed in exclusive room or space if preservation men are likely to destroy pipework or do any other operation liable to call liquid ammonia or certain quantities of gas. 14010 14011 14012 14013 14014 14015 14016 14017 14018 14019 14020 14021 14022 14023 14024 14025 14026 14027 14028 14029 14030 14031 14032 14033 14034 14035 14036 14037 14038 14039 14040 14041 14042 14043 14044 14045 14046 14047 14048 14049 14050 14051 14052 14053 14054 14055 14056 14057 14058 14059 14060 14061 14062 14063 14064 14065 14066 14067 14068 14069 14070 14071 14072 14073 14074 14075 14076 14077 14078 14079 14080 14081 14082 14083 14084 14085 14086 14087 14088 14089 14090 14091 14092 14093 14094 14095 14096 14097 14098 14099 14100 14101 14102 14103 14104 14105 14106 14107 14108 14109 14110 14111 14112 14113 14114 14115 14116 14117 14118 14119 14120 14121 14122 14123 14124 14125 14126 14127 14128 14129 14130 14131 14132 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