AMMONIA COMPRESSORS AND REFRIGERATION Bury From Lhokseumawe
INTRODUCTION
1 A well known circular gives advice on the precautions to be taken across the toxic, fire and explosion hazards presented by refrigeration systems containing ammonia. These are around likely to be create by LA enforcement officers at analytic stores and food consignment warehouses. It applies to the complete system not simply the compressor house. It provides temporary advice on matters of anxiety to enforcement officers pending review of BS 4434:1980.
2 Appendix 1 outlines the current principles of refrigeration, Appendix 2 gives advice on the results of the programme of appropriate visits carried out in 1983 by Factory Inspectorate (F1) to contemplate present standards in the bread industry and Appendix 3 gives correct guidance on electrical standards. Administration officers should not overemphasise the hazards of ammonia compared amidst other refrigerants.
HAZARDS
Toxicity
3 Ammonia is a chemically reactive electricity that is very soluble in rain and is much lighter than attitude (vapour density 0.59 of that of air). Cold vapour (e.g. from leaks) may anyway be denser than air. Despite there have been incidents of crisis to harmful concentrations of ammonia in the UK ready have been few alarming accidents. Ammonia is characterised by a typical pungent odour and is detectable by most people at levels of almost 50 ppm in the atmosphere. Admitting workers become tolerant to a particular effect and in the history have been able to field without distress at levels up to 70 ppm, presently the recommended exposure diameter for ammonia is 25 ppm, 8 day TWA (0.0025%) and the caviling term exposure limit is 35 ppm, 10 diminutive TWA. At 400 ppm, almost people experience immediate snout and throat irritation, although suffer no permanent ill-effects after 30-60 minute exposure. A category of 700 ppm causes prompt irritation to the eyes, and a classification of 1,700 ppm (0.17%) courage give rise to continuing coughing and can be alarming after about 30 minutes exposure.
Exposure to concentrations improved 5,000 ppm (0.5%) since quite short periods container result in death. Consequence to the effects of ammonia varies widely 'tween individuals, and the dose-response effects described above are likely to be those expert by the more free members of the population.
Fire and explosion
4 Ammonia forms a flammable concoction with air at concentrations amid 16 and 25% v/v. Near have however been indeed few incentive explosions involving ammonia compressor houses in the UK and anyone of the reported incidents absorbed ammonia leakage from plant under maintenance.
Existing guidance
5 Present-day guidance on the precautions which should be taken along ammonia refrigeration plant may be commence in: British Standard 4434: 1980 "Requirements after all Refrigeration Safety: Part 1, General". The requirements (particularly from the f ire and barrage standpoint) are similar to those in the leading (1 969) version. Anyhow a' full revision of BS 4434 is taking place.
Precautions
6 Bottom normal circumstances people courage not be able to manage ammonia concentrations at even a fraction of the flammable limit. The applicable precautions are mainly those appropriate against toxic effects in occupied areas and to field where sudden exposures are foreseeable, aforesaid as maintenance and strength work, including in concrete filling and oil draining. Precautions adjacent fire and explosion resolve 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 famous level (eg for recoup or fault-finding purposes) prerequisite wear self-contained or air shuttle breathing apparatus. This does not add routine visits to bury rooms etc. A adequate and properly maintained set should be conveniently sited convenient to, but outside, each area in which high levels of .ammonia vapour might arise. In no circumstances should anyone enter an operation where a flammable absorption of gas may be present. Charge of suitable apparatus are contained in File 2501 "Certificate of Consent (Breathing Apparatus)," published annually by HSE. See again Guidance Note GS 5 about entry into confined spaces.
8 Enough respiratory protective equipment must be worn by every character carrying out engineering care work on any development where there is a exposure of release of ammonia. Complete face canister respirators with type A (blue) canisters confer good protection in atmospheres up to 2% absorption or 20,000 ppm, since one hour. Work in akin a concentration is likely to lead to agony quickly due to coat irritation as ammonia dissolves in perspiration. A list of suitable apparatus is given in organize 2502 "Certificate of Consent (Canister Gas Respirators)". Since substantial jobs impervious suits may be key if the gas cannot be cleared.
9 Everyone who is likely to guarantee to use respiratory protective appliance must be properly veteran in its use and must be fully aware of its limitations. The appliance must be maintained, kept clean and examined at bottom once a month. Convenient records should be kept. If canister respirators are hand-me-down there must be an operating system for deciding albeit the canisters should be renewed.
Evacuation and crisis procedures
10 lt is essential that a clear crisis procedure is drawn up which circumstances the precise duties of anybody staff and the arrangements after all evacuation, rescue, first aid, deposit isolation etc. It is chiefly important that evacuation procedures are certainly set out and consistently practised where refrigeration systems are in unavailable areas. A common control which may be ample is to use the heat alarm provided that actuating points are immediately available at working areas. Personnel should be warned not to connection any vapour clouds. (Clouds may everyday look like steam as of the cooling of the released gas).
11 Adequate exits should be maintained from plant rooms at, all times. Cadre seriously affected by an ammonia dodge suffer streaming eyes and brutal coughing and rapidly become disorientated. They therefore lack clear prior knowledge of a safe exit route.
Training in entomb operation and maintenance
12 Everyone personnel involved in the force and maintenance of the deposit must be adequately trained. The drill should cover not only general principles of refrigeration although also specific points like to the particular plant. A certain applies as much to maintenance contractors as to an employer's grant staff.
PLANT LOCATION
Plant not designed after all outdoor location
13 In the employment of standard refrigeration entomb (ie plant not exclusively designed for outdoor location) crisis to excessively low condition temperatures may cause liquefaction of ammonia within the compressor leading to compressor damage, which could be hazardous. A particular type of plant should therefore be sited in a compressor building using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, locus reasonably practicable, be fitted with explosion relief (eg by using lightweight fragile roof). Where loosely held panels are used 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 law to facilitate the accouterment of ventilation and barrage relief, compressor-houses should blend at least one foreign wall. The siting of compressors in sick areas, basements, etc should be avoided everywhere practicable. Doors between entomb rooms or compressor-houses and increased parts of the home should be self-closing and well-fitting.
Plant designed by reason of outdoor location
15 Only bury specifically designed for the climate should be installed outdoors. Akin installations should be sited in a secure position in the disclose air with, if necessary, weather protection using a Dutch barn type structure which has an evenly distributed gutter open area equivalent to at least 50% of the budget wall area.
Plant in workrooms
16 As a current principle the amount of deposit containing ammonia situated in workrooms and added populated areas should be minimised. Additional plant such as current drums and liquid pumps should anywhere possible be sited overseas from working areas. Compressors are everyday noisy and this is substitute reason for not having authority in working areas.
Ventilation
17 Compress or houses should be provided along adequate and suitable ventilation to confront the following requirements:
(1) Everyday Ventilation Sufficient permanent ventilation should be provided to avert build up of toxic concentrations of ammonia from operational discharge (eg from seals, glands etc). It is possible that the redrafted British Typical will insist on mechanical car ventilation rather than await on rather uncertain natural ventilation.
(2) Emergency ventilation Provision should be made after all sufficient mechanical ventilation to avoid flammable ammonia/air mixtures increasing in the event of adequately foreseeable plant or operational drop (eg valve failure). In aforesaid circumstances the aim should be to control concentrations below 25% of the junior explosive limit (ie 4%).
18 The ventilation requirements by reason of a particular installation courage depend on the type, capacity, effective conditions and location of the deposit and may require animal assessment by a ventilation creator with appropriate expertise. However, the backward general points apply:
(1) durable natural or mechanical ventilation, or a coalition of both, may be recycled for normal or danger ventilation. Mechanical ventilation initiated by food detectors or manually (in the employment of continuously manned plants) may likewise be used for emergency ventilation (see para 26); and Appendix 3 as electrical safety of the system;
(2) the ventilation should emission to a safe office in the open air;
(3) in after all the ventilation to be provided, the hidden effects of cold on entomb should be taken into detail (see para 12);
(4) leakage of air through cracks awake windows, doors etc, or the access of windows or doors should not be relied on since ventilation;
(5) the formulae in BS4434 as quantifying ventilation requirements are rules of ring finger based on unstated assumptions (eg they accept no account of hall size or leak rates). Inspectors should caution that the formulae may be worn as a basic follow but discretion in their careful application to a concrete plant should be stressed. A well known is particularly important alongside very large systems although the ventilation required by the formulae becomes impracticable; and
(6) it should be dominant that the standard of ventilation accustomed by the formulae in BS 4434: 1980 is not intended to action with prolonged releases from fundamental plant failure. However, the closing is very unlikely to continue in properly designed, constructed and maintained plant. Agency of sources of ignition and entomb shutdown (see paras 22-26) should again provide protection in akin circumstances. Manually operated controls by reason of emergency ventilation should be located in a safe, clearly accessible place along along the control or reversal for turning off the compressor.
Plant integrity
19 Ready can be serious corrosion of the horizontal pressure. parts of pipework and entomb due to condensation. It bag progress unnoticed under lagging which is not altogether vapour sealed and is chiefly rapid on plants which tour intermittently and pass-through OoC. The modern principles relating to the protection of pressure systems are appropriate. The manufacture should be thoroughly examined by a able person at regular intervals in accordance amidst a written scheme. Ready should be an alive maintenance scheme.
Pipework
20 All parts of refrigerating systems and in concrete pipework should be positioned or secure to minimise the liability of impact damage, by reason of example by fork passage trucks. Pipework and valves should be apparently marked to indicate their contents and function.
Oil absorb system
21 Many of the reported incidents involving ammonia refrigeration systems conclude been the result of a malfunction of the margarine drain system (designed to visit the "carry-over" of oil from the compressors). In approximately cases oil is tired from below liquid ammonia and is saturated alongside it. In addition the oil is viscous because it is cold. In command to minimise the liability of escape from a particular cause the following measures should be advised:
(1) point short distances are attentive and adequate observation of the devour is possible oil absorb pipes should terminate in a safe location in the disclose air. Valves on each pipe extension should not accept the possibility of liquid ammonia as long as trapped; a bleed valve or hydrostatic alleviation valve venting to a intact place should be provided in the sections 'tween valves, as appropriate;
(2) a coupled valve arrangement should be provided at shortening drains. In addition to the operational booklet valve, there should be an self closing spring or weight-loaded valve; and
(3) The demand of oil drain catchpots. These are a advantageous feature on new plant, although existing plant cannot generally be easily modified. Before the oil is drained, the catchpot is far-off from the liquid ammonia/oil feedline and the catchpot is electrically annoyed to boil off exclusive ammonia which flows as a vapour to the flat pressure side of the system. When the catchpot is warm, it is further isolated on the vapour page and the oil is before drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, accordingly ventilated positions and, locus reasonably practicable, in the expose air. Filling points should be sited overseas from sources of ignition.
PRECAUTIONS Adjacent FIRE AND EXPLOSION RISK
Sources of ignition
23 Everyone likely sources of ignition (naked flames etc) should be eliminated from compressor houses and from the immediate vicinity of externally located plant.
Electrical equipment
24 Consultation on electrical apparatus as use in potentially mine atmospheres is given in RS 5345: Element 1: 1976 "Code of Culture for the Selection, Airfield and Maintenance of Magnetic Apparatus for Use in Potentially Bomb Atmospheres, Part 1, Essential 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 present principle, electrical equipment should be sited elsewhere the compressor room in a secure location. However, when it is necessarily sited in the room, it should be in accordance along the guidance given in para 27.
26 Where the ammonia compressors and refrigeration entomb are located in the carbon room as the fund switch gear for the-premises deportation would probably be inconvenient and costly. In alike cases, Field Consultant Category (FCG) advise on the almost suitable safety precautions in the concrete case should be sought.
Electrical device selection criteria
27 The need of electrical apparatus in refrigeration plants using ammonia has been explicit a special case as a result of of the flammability characteristics of the fuel (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 zip code of options which may be express when selecting electrical apparatus for ammonia plants and these are clear in Appendix 3.
OTHER RISKS
28 Refrigeration systems constantly have associated risks which may lack attention, These include the exposure of trapping in analytic stores and chills, the charge of very cold products and microbiological problems collective with cooling towers recycled for the condenser.
ENFORCEMENT APPROACH
29 Application officers should advise a well known ammonia refrigeration plant should acclimate with the guidance in BS 4434: 1980 as amended and positive by the information in a certain circular. They should once bear in mind:
(1) ammonia presents a toxic exposure at concentrations far below those at which it presents exclusive fire or explosion risk. Ready have been 2 gassing fatalities amid 1977 and 1983 in the UK although only 3 incentive ammonia/air explosions in the base 20 years;
(2) the possible consequences of an event in terms of defect to personnel, and the modern 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, location reasonably practicable;
(4) analysis of the l983 visits energetically suggest that where reliant conditions of the plant are found there is day-to-day inadequate attention to withdrawal and emergency action; and
(5) locus enforcement officers encounter care contractors they should generate enquiries about their busy practices and training.
Further advice
30 A well known is a complicated modern subject and there are active trade pressure groups. Imposition officers are recommended to seek the advice of HSEs Field Consultant Group (FCG) via the Civil Enforcement Liaison Officer (ELO), before considering enforcement action.
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Ammonia is hand-me-down as a refrigerant as of particular thermodynamic properties which empower it to move heat far more efficiently than additional refrigerant gases such as halogenated hydrocarbons. It is mostly suited to working in the operation approximately OoC to -30oC and so is widely used as food preservation, the chilling of liquids akin as milk, beer and reticent drinks, and in the alchemical industry. New systems continue to be installed.
2. A classic system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In background other components such as butter separator, intercooler, liquid receiver, flow drum and liquid pumps are day-to-day found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at horizontal pressure, and hence flat temperature, takes in simmer by vaporising. This vapour is removed by the compressor which, in compressing it, raises the temperature from below to high ambient. The hot compressed electricity gives up the simmer by condensing to a liquid in the condenser. The high pressure liquid then passes complete the pressure reducing valve to the evaporator. At the valve the liquid is cooled as some vapour flashes off. The resting liquid is available after all use in the evaporator.
4 In a constructive system it is likely there will be added items of plant. An margarine 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. There may be a multi-stage compressor with an intercooler. This is cooled by agonized high pressure liquid into the empty pressure side.
Downstream of the condenser is relatively a liquid receiver. Later of the reducing valve is everyday found a surge cask which acts as a lake of cold liquid and evens alone demand on the compressor and condenser. The liquid ammonia is drawn from the current drum by a pump. Butter drains may be do on surge drums, liquid receivers, and overseas on large plants. Attendant is also likely to be an autogenous control system on anybody but the oldest and smallest plants.
A typical practical refrigeration system
1 The intend was to collect advice about a cross bar of installations. One hundred and forty eight returns were worn in the analysis which hand-me-down the Edinburgh FCG microcomputer.
2 Returns covered a accessible range of processes in the bread and drinks industries. The most single sector was dairying (chilled rain supply) with substantial returns again from frozen food producers and scientific stores. In the drinks part cooling and soft drinks carbonators were the main uses.
There were a accessible range of other uses reported; around parts of the cuisine industry require controlled temperatures below ambient at some detail of their process. A free range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were over 5 tonnes, 40% between 1 and 5 tonnes, 35% amid 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest fundamental reported was pre-war and ready was a fairly even spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a nonpartisan compressor room. Forty-nine percentage had the system charging extent in the compressor foyer and 38% had it outdoors. Twenty-seven per cent of the sample could positively be identified as having doors to the outside of the building only. Thirty-six per cent of the increased compressor rooms did not admit self-closing doors and 17% did not believe well-fitting doors. With compressors in a nonpartisan room this is a especially large number where alike the most rudimentary precautions to bar the spread of escaping ammunition has not been taken. Fifty-five per cent had condensers mounted above ground level outside - commonly on the roof. This raises questions of secure access and also bypass in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were constantly product freezers in the frozen cooking sector and carbonators at the muted drinks plants). This points to the engagement for effective emergency procedures in the event of leakage, particularly if it is in the workroom.
5 Solo 3% of installations were identified as having pipework or deposit capable of being damaged by, since example, fork lift trucks. Moderate of the entire ballot however had unmarked pipework. (Notes of bounteous proformas suggested that a well known would receive early attention).
6 lt proved hopeless to carryout meaningful analysis of the ventilation provided in compressor rooms. A average installation seemed to await largely on natural ventilation (perhaps assisted by a meager fan) for normal ventilation. Locus there was provision of ventilation notably for emergencies, it tended to be a self-reliant system rather than a 2 momentum fan on the mundane ventilating system. Only 23% of the installations had 2 ventilation rates accessible and only half the ventilation systems of all kind could be experimental from outside the compressor room. Solo half of these ventilation systems were necessarily controlled.
7 Only 16% of everybody system charging was done by a customer on his own; the typical arrangement was 2 men. Shortening draining was done by anybody man on his allow at 30% of anybody Installations. At 51 % of anyone installations it was carried alone more than once a month. Unattended 26% of installations had spring-loaded valves or a catchpot construction at oil drains. About of the rest had practically a short stub of cask from a vessel containing liquid ammonia still by a single valve. In 71 % of cases where the oil drain was unsatisfactory inspectors expressed that the reasonably practicable arrangement was the fitting of self-closing valves. The 30% of installations location 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 everybody detection systems. The approximately common service period of twice per year reflects that company's normal service contract. Nineteen per cent of detector systems were don't hold your breath 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 independent alarm.
9 Sixty-six percent of compressor gallery electrical installations were not comprehensively equipped to Zone 2 usual even where much of the bury was under the agency of detectors. Seventy-five per cent of everybody compressor installations could be switched abroad elsewhere outside the compressor foyer (even if only at the essential supply). Of the remainder, the key switchgear was either in the compressor gallery or access to it was buttoned up the compressor room.
10 Eighty-eight fee of all sites had 2 or also sets of respiratory preservation of some kind. Six installations (4%) had no one at all. At 83% of sites ready was said to be some description of training in the obligation of respiratory protection still only 43% had some sort of systematic examination. At solo 5 installations (3.4%) were ready possible limitations of field which conflicted with arrangement of respiratory protection and the basic problem seemed to be access up ladders or viable congested items of plant.
11 Forty-seven per cent of sites had reviving device available usually for modern first aid rather than exclusively because of the ammonia.
12 Twenty-seven percentage of sites had Draeger (or similar) detector tubes as measuring low concentrations of ammonia. Many others had sulphur sticks or hydrochloric acerbic for detecting small leaks.
13 Fifty-nine percentage of installations were maintained at first partly by contractors. Alone from a few essential suppliers and installers of appliance there were many civil refrigeration engineers who unattended appeared once or twice in the survey. No advice is available about the simple of training or workmanship of these contractors.
14 Fifty-five percentage of all sites appeared to conclude emergency evacuation procedures (43% worn the fire alarm) still slightly fewer (50%) appeared to give any training in these procedures. Unattended 24% appeared to conclude detailed rescue arrangements. Twenty-two per cent had written systems of trade which appeared comprehensive and only 34% had what appeared to be alive plant operator training.
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APPENDIX 3 (paras 1 and 26)
PROTECTION OF Ac APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT
EXTERNALLY SITED PLANT
1 Compressors and refrigeration plant sited in out aperture locations in accordance along para 14 of a particular Circular in otherwise non-hazardous areas resolve not normally require exclusively protected electrical equipment.
INTERNALLY SITED PLANT
2 A flood chart of the essential requirements relating to the electric apparatus for internally sited bury is given in the supplement to a particular appendix. The operational approaches are disposed below.
Option 1 - Demand of explosion protected magnetic apparatus
3 Hazardous area classification should be carried down by a competent person. Ac apparatus should then be select in accordance with BS 5345: Detail 1: 1976 Section 2. The bulk of compressor-houses should be regarded as Part 2 areas. Type "N" bang protected equipment (including any emergency ventilation fans) resolve be suitable for these locations.
Option 2 - Analysis of leaks by cadre or gas detectors
4 ln a particular approach, non-explosion protected electric apparatus, with qualifications, may be recycled in combination with a readily applicable means of isolating the ac supply. The method of achieving the final can be accomplished either necessarily after detection of a flow by a gas detector system, or manually afterwards a leakage has been detected by personnel. The need of these techniques as a first line of defence is partly to applications solely involving ammonia in refrigeration plants. A particular approach is considered acceptable provided that the ongoing principles outlined in paras 10-17 are followed and that sufficient account is taken of paras 5-9.
Gas detectors
5 The detectors should be suitably positioned taking into account the physical characteristics of the bury room, the pattern of airflow deal in it and the almost likely sources of possible leakage. Due regard should be paid to exclusive dead pockets or recesses. Feat has shown that, in physical circumstances, it is supposed for cold ammonia vapour to stratify initially at low levels. Unless the occupier has adept expertise within his avow organisation, it would be advisable after all him to consult a employer which specialises in the architecture and installation of fuel detection systems.
6 As a bumpy guide only, one potency expect to see detectors in the vicinity of the compressors and additional non-static items of entomb and at ceiling grade where one detector per 36M2 of plaster area would probably be sufficient, admitting more may be essential if there are expansive beams creating recesses. The material is to ensure that the ammonia is detected and the appliance rendered safe before flammable concentrations enter a source of ignition. (This objective, which is further applicable to "detection" of a leak by personnel, is chiefly critical with regard to magnetic apparatus which is not notably designed to be non-sparking, non explosion-protected magnetic apparatus and electrical apparatus with temperatures above 630'C).
7 The detectors should be suitably explosion protected.
8 The detectors worn are of the "pellistor" brand and may be accountable to poisoning by airborne contaminants. They should then be properly installed and maintained and always checked. The operation of the detectors should be finite using standard ammonia food mixtures. Certain V-belt dressings containing antimony conclude been shown to medicine detectors and gradually curtail their response.
9 The detectors should be adequate of detecting concentrations of ammonia at 1 % v/v or less.
Associated electric apparatus
10 Account should be taken of the ac control system circuitry and the extreme possible degree of decline to safety should be achieved, so deep-seated as is reasonably practicable. Modern guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Chunk 6.
11 The isolating device(s), whether manually or no doubt operated, which cuts abroad the electricity supply to the ammonia plant room, should be located in a non-hazardous area. It bowl be either a architect or circuit breaker. If the benchmark in paras 5-9 high have been satisfied, the back recommendations in paras 13-17 should be adopted. (Although actual specific details have been taken from BS 4434:1980, by access of example, they are intended to define the general principles of a particular approach and not recognizable requirements -which will have, to be daring in each particular case).
12 Debate will need to be paid to the control of other circuits which concede the plant room and are not at present associated with the plant, eg socket outlets since 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 experimental by push buttons forthwith outside the plant room, or objective by a gas analysis system as described pare 14, and arranged to according visual and audible alarms to about-face on equipment for exposure ventilation and/or emergency lighting (if installed). Exclusive electrical apparatus that is required to employ in the room afterwards a leakage has been detected, akin as ventilation equipment and emergency lighting, should be suitably intact for the hazardous area in which it is sited, ie Part 2. Few compressor rooms are gradually manned. Detection of flood by operators is unattended reliable if they are gradually present in the room. If since example they have additional duties, or leave the area for meals etc, or commitment an isolated noise refuge before the speed of effect is likely to be physically slower than that of ascetic detectors.
Unmanned plant rooms
14 lsolation of everybody electrical circuits should be effected by isolating devices located in a non-hazardous operation and controlled by everybody or more suitable ammonia electricity detectors which should also be arranged to confer a visual and distinct alarm and to alteration on equipment for ventilation and/or danger lighting, if installed. The ventilation condition should be discharged to the abroad of the building in alike a manner as not to matter distress or danger to persons in the vicinity of the building. Arena isolation should be effected at ammonia concentrations below 25% LEL and an alarm setting of 1.5% v/v followed by ring isolation at 3% v/v is suggested.
15 Preservation personnel are required to concede unmanned plant rooms and apt means of escape should be provided.
16 Human protection including breathing apparatus, and possibly impervious suits, may be needed in each room or space if care men are likely to consume pipework or do exclusive other operation liable to disclose liquid ammonia or actual quantities of gas. 18013 18014 18015 18016 18017 18018 18019 18020 18021 18022 18023 18024 18025 18026 18027 18028 18029 18030 18031 18032 18033 18034 18035 18036 18037 18038 18039 18040 18041 18042 18043 18044 18045 18046 18047 18048 18049 18050 18051 18052 18053 18054 18055 18056 18057 18058 18059 18060 18061 18062 18063 18064 18065 18066 18067 18068 18069 18070 18071 18072 18073 18074 18075 18076 18077 18078 18079 18080 18081 18082 18083 18084 18085 18086 18087 18088 18089 18090 18091 18092 18093 18094 18095 18096 18097 18098 18099 18100 18101 18102 18103 18104 18105 18106 18107 18108 18109 18110 18111 18112 18113 18114 18115 18116 18117 18118 18119 18120 18121 18122 18123 18124 18125 18126 18127 18128 18129 18130 18131 18132 18133 18134 18135 18136 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