AMMONIA COMPRESSORS AND REFRIGERATION Entomb From Jakarta Timur
INTRODUCTION
1 A certain circular gives advice on the precautions to be taken across the toxic, fire and barrage hazards presented by refrigeration systems containing ammonia. These are almost likely to be begin by LA enforcement officers at scientific stores and food shipment warehouses. It applies to the exhaustive system not simply the compressor house. It provides temporary advice on matters of concern to enforcement officers pending check of BS 4434:1980.
2 Appendix 1 outlines the current principles of refrigeration, Appendix 2 gives aid on the results of the programme of appropriate visits carried out in 1983 by Firm Inspectorate (F1) to acknowledge present standards in the food industry and Appendix 3 gives accurate guidance on electrical standards. Enforcement officers should not overemphasise the hazards of ammonia compared along other refrigerants.
HAZARDS
Toxicity
3 Ammonia is a chemically reactive fuel that is very soluble in h2o and is much lighter than attitude (vapour density 0.59 of a well known of air). Cold vapour (e.g. from leaks) may ever be denser than air. Albeit there have been incidents of danger to harmful concentrations of ammonia in the UK there have been few alarming accidents. Ammonia is characterised by a usual pungent odour and is detectable by most people at levels of almost 50 ppm in the atmosphere. Although workers become tolerant to a well known effect and in the yesterday 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 little TWA. At 400 ppm, around people experience immediate beak and throat irritation, however suffer no permanent ill-effects after 30-60 minute exposure. A category of 700 ppm causes urgent irritation to the eyes, and a class of 1,700 ppm (0.17%) firmness give rise to existing coughing and can be critical after about 30 minutes exposure.
Exposure to concentrations exceptional 5,000 ppm (0.5%) since quite short periods bowl result in death. Consequence to the effects of ammonia varies widely betwixt individuals, and the dose-response effects described above are likely to be those deft by the more clear members of the population.
Fire and explosion
4 Ammonia forms a flammable batter with air at concentrations betwixt 16 and 25% v/v. Ready have however been absolutely few incentive explosions involving ammonia compressor houses in the UK and anybody of the reported incidents interested ammonia leakage from plant under maintenance.
Existing guidance
5 Contemporary guidance on the precautions which should be taken alongside ammonia refrigeration plant may be commence in: British Standard 4434: 1980 "Requirements since Refrigeration Safety: Part 1, General". The requirements (particularly from the f ire and barrage standpoint) are similar to those in the forward (1 969) version. Ever a' full revision of BS 4434 is taking place.
Precautions
6 Beneath normal circumstances people boldness not be able to allow ammonia concentrations at balanced a fraction of the flammable limit. The appropriate precautions are mainly those apt against toxic effects in occupied areas and to employment where sudden exposures are foreseeable, akin as maintenance and health work, including in concrete filling and oil draining. Precautions con fire and explosion resolve be appropriate however, in unoccupied areas aforesaid as compressor houses and alone plant such as clinical stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Adjacent TOXIC RISK
Respiratory protective equipment
7 All person entering an operation in which ammonia vapour is expected to be present at a famous level (eg for recover or fault-finding purposes) requisite wear self-contained or airline breathing apparatus. This does not build routine visits to bury rooms etc. A abundant and properly maintained set should be conveniently sited adjacent to, but outside, all area in which raised levels of .ammonia vapour valor arise. In no circumstances should anyone enter an field where a flammable consolidation of gas may be present. Circumstances of suitable apparatus are contained in File 2501 "Certificate of Approval (Breathing Apparatus)," published annually by HSE. See likewise Guidance Note GS 5 regarding entry into confined spaces.
8 Abundant respiratory protective equipment must be worn by every character carrying out engineering care work on any manufacture where there is a disclosure of release of ammonia. Infinite face canister respirators alongside type A (blue) canisters confer good protection in atmospheres up to 2% consolidation or 20,000 ppm, since one hour. Work in alike a concentration is expected to lead to pain quickly due to leather irritation as ammonia dissolves in perspiration. A list of suitable accessory is given in file 2502 "Certificate of Blessing (Canister Gas Respirators)". As substantial jobs impervious suits may be elemental if the gas cannot be cleared.
9 Everyone who is likely to engagement to use respiratory protective device must be properly old-time in its use and must be fully aware of its limitations. The accessory must be maintained, kept blank and examined at gutter once a month. Apt records should be kept. If canister respirators are recycled there must be an effective system for deciding albeit the canisters should be renewed.
Evacuation and emergency procedures
10 lt is essential that a clear crisis procedure is drawn up which circumstances the precise duties of anyone staff and the arrangements as evacuation, rescue, first aid, entomb isolation etc. It is chiefly important that evacuation procedures are clearly set out and constantly practised where refrigeration systems are in unavailable areas. A common control which may be abundant is to use the blaze alarm provided that actuating points are directly available at working areas. Crew should be warned not to connection any vapour clouds. (Clouds may constantly look like steam because of the cooling of the released gas).
11 Able exits should be maintained from deposit rooms at, all times. Crew seriously affected by an ammonia avert suffer streaming eyes and cruel coughing and rapidly become disorientated. They therefore lack clear prior knowledge of a safe exit route.
Training in bury operation and maintenance
12 Everyone personnel involved in the action and maintenance of the bury must be adequately trained. The coaching should cover not alone general principles of refrigeration still also specific points alike to the particular plant. A well known applies as much to conservation contractors as to an employer's avow staff.
PLANT LOCATION
Plant not designed since outdoor location
13 In the event of standard refrigeration entomb (ie plant not chiefly designed for outdoor location) danger to excessively low aspect temperatures may cause liquefaction of ammonia in a period the compressor leading to compressor damage, which could be hazardous. A particular type of plant should then be sited in a compressor construction using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, where reasonably practicable, be fitted amidst explosion relief (eg by using nobody fragile roof). Where loosely held panels are used as explosion relief, they should be suitably silent (eg by chains) to avert them becoming dangerous missiles in the affair of an explosion.
14 ln law to facilitate the arrangement of ventilation and explosion relief, compressor-houses should blend at least one alien wall. The siting of compressors in ailing areas, basements, etc should be avoided anyplace practicable. Doors between deposit rooms or compressor-houses and additional parts of the construction should be self-closing and well-fitting.
Plant designed after all outdoor location
15 Only deposit specifically designed for the altitude should be installed outdoors. Such installations should be sited in a intact position in the disclose air with, if necessary, weather insurance using a Dutch barn type structure which has an evenly distributed bottom open area equivalent to at first 50% of the cost wall area.
Plant in workrooms
16 As a modern principle the amount of bury containing ammonia situated in workrooms and added populated areas should be minimised. Additional plant such as flood drums and liquid pumps should all over possible be sited overseas from working areas. Compressors are daily noisy and this is substitute reason for not having diehards in working areas.
Ventilation
17 Compress or houses should be provided with adequate and suitable ventilation to defy the following requirements:
(1) Commonplace Ventilation Sufficient permanent ventilation should be provided to avert build up of toxic concentrations of ammonia from operational flood (eg from seals, glands etc). It is possible that the redrafted British Simple will insist on industrial car ventilation rather than await on rather uncertain animal ventilation.
(2) Emergency ventilation Provision should be made since sufficient mechanical ventilation to avoid flammable ammonia/air mixtures increasing in the event of adequately foreseeable plant or operational decline (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 as a particular installation firmness depend on the type, capacity, operating conditions and location of the plant and may require creature assessment by a ventilation builder with appropriate expertise. However, the back general points apply:
(1) long-lasting natural or mechanical ventilation, or a coalition of both, may be recycled for normal or emergency ventilation. Mechanical ventilation initiated by electricity detectors or manually (in the case of continuously manned plants) may also be used for emergency ventilation (see para 26); and Appendix 3 after all electrical safety of the system;
(2) the ventilation should radiation to a safe commission in the open air;
(3) in by reason of the ventilation to be provided, the likely effects of cold on entomb should be taken into detail (see para 12);
(4) flow of air through cracks viable windows, doors etc, or the access of windows or doors should not be relied on by reason of ventilation;
(5) the formulae in BS4434 since quantifying ventilation requirements are rules of hook based on unstated assumptions (eg they get no account of hall size or leak rates). Inspectors should caution that the formulae may be used as a basic accompany but discretion in their correct application to a detailed plant should be stressed. A well known is particularly important along very large systems although the ventilation required by the formulae becomes impracticable; and
(6) it should be leading that the standard of ventilation addicted by the formulae in BS 4434: 1980 is not intended to activity with prolonged releases from central plant failure. However, the recent is very unlikely to happen in properly designed, constructed and maintained plant. Authority of sources of ignition and entomb shutdown (see paras 22-26) should further provide protection in such circumstances. Manually operated controls by reason of emergency ventilation should be located in a safe, decidedly accessible place along amidst the control or alteration for turning off the compressor.
Plant integrity
19 Near can be serious corrosion of the flat pressure. parts of pipework and entomb due to condensation. It container progress unnoticed under lagging which is not comprehensively vapour sealed and is frequently rapid on plants which run intermittently and pass-through OoC. The modern principles relating to the insurance of pressure systems are appropriate. The manufacture should be thoroughly examined by a adequate person at regular intervals in accordance amidst a written scheme. Ready should be an effective maintenance scheme.
Pipework
20 All parts of refrigerating systems and in detailed pipework should be positioned or intact to minimise the hazard of impact damage, as example by fork passage trucks. Pipework and valves should be definitely marked to indicate their contents and function.
Oil consume 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 show up the "carry-over" of shortening from the compressors). In almost cases oil is annoyed from below liquid ammonia and is saturated alongside it. In addition the butter is viscous because it is cold. In command to minimise the hazard of escape from a certain cause the following measures should be advised:
(1) location short distances are engrossed and adequate observation of the deplete is possible oil devour pipes should terminate in a intact location in the bare air. Valves on each pipe extension should not concede the possibility of liquid ammonia as long as trapped; a bleed valve or hydrostatic comfort valve venting to a safe place should be provided in the sections amid valves, as appropriate;
(2) a binary valve arrangement should be provided at margarine drains. In addition to the operational magazine valve, there should be an self closing spring or weight-loaded valve; and
(3) The need of oil drain catchpots. These are a useful feature on new plant, however 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 any ammonia which flows as a vapour to the flat pressure side of the system. When the catchpot is warm, it is also isolated on the vapour leaf and the oil is before drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, properly ventilated positions and, location reasonably practicable, in the bring to light air. Filling points should be sited overseas from sources of ignition.
PRECAUTIONS Across FIRE AND EXPLOSION RISK
Sources of ignition
23 Anyone 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 as use in potentially mine atmospheres is given in RS 5345: Article 1: 1976 "Code of Culture for the Selection, Airfield and Maintenance of Ac Apparatus for Use in Potentially Device Atmospheres, Part 1, Key Requirements for all Parts of the Code"; BS 4434: 1980, Clause 13 "Electrical Installations". The approaches followed by the high documents differ.
25 As a modern principle, electrical equipment should be sited outside the compressor room in a safe location. However, when it is actually sited in the room, it should be in accordance amidst the guidance given in para 27.
26 Locus the ammonia compressors and refrigeration entomb are located in the carbon room as the capital switch gear for the-premises relocation would probably be inconvenient and costly. In such cases, Field Consultant Grade (FCG) advise on the almost suitable safety precautions in the concrete case should be sought.
Electrical accessory selection criteria
27 The need of electrical apparatus in refrigeration plants using ammonia has been clear a special case as a result of of the flammability characteristics of the electricity (high LEL and limited explosive range) and the article that it can be detected at actually low levels by smell. A certain has resulted in a address of options which may be expressed when selecting electrical device for ammonia plants and these are express in Appendix 3.
OTHER RISKS
28 Refrigeration systems day-to-day have associated risks which may crave attention, These include the liability of trapping in scientific stores and chills, the handling of very cold products and microbiological problems joint with cooling towers worn for the condenser.
ENFORCEMENT APPROACH
29 Application officers should advise a particular ammonia refrigeration plant should acclimate with the guidance in BS 4434: 1980 as amended and additional by the information in a certain circular. They should once bear in mind:
(1) ammonia presents a toxic disclosure at concentrations far below those at which it presents any fire or explosion risk. Ready have been 2 gassing fatalities 'tween 1977 and 1983 in the UK although only 3 incentive ammonia/air explosions in the basic 20 years;
(2) the possible consequences of an case in terms of disability to personnel, and the modern public should be assessed;
(3) BS4434 was advance published in 1969 and was not intended to be retrospective, despite improvements in installations which pre-date the simple should be recommended, location reasonably practicable;
(4) analysis of the l983 visits actively suggest that where defenseless conditions of the entomb are found there is everyday inadequate attention to withdrawal and emergency action; and
(5) locus enforcement officers encounter conservation contractors they should generate enquiries about their working practices and training.
Further advice
30 A particular is a complicated mechanical subject and there are active trade pressure groups. Enforcement officers are recommended to seek the advice of HSEs Field Consultant Group (FCG) via the Domestic Enforcement Liaison Officer (ELO), along considering enforcement action.
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Ammonia is used as a refrigerant because of particular thermodynamic properties which facilitate it to move melt far more efficiently than further refrigerant gases such as halogenated hydrocarbons. It is mostly suited to working in the range approximately OoC to -30oC and accordingly is widely used as food preservation, the chilling of liquids aforesaid as milk, beer and peaceful drinks, and in the synthetic industry. New systems advance to be installed.
2. A usual system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In background other components such as margarine separator, intercooler, liquid receiver, current drum and liquid pumps are daily found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at flat pressure, and hence flat temperature, takes in heat by vaporising. This vapour is removed by the compressor which, in compressing it, raises the altitude from below to high ambient. The hot compressed ammunition gives up the heat by condensing to a liquid in the condenser. The over 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 resting liquid is available as use in the evaporator.
4 In a down-to-earth system it is likely there will be increased items of plant. An oil separator removes suspended oil carried over from the compressor and either returns it to the (pressurised) crank-case or holds it since draining in some way. Near may be a multi-stage compressor alongside an intercooler. This is cooled by aggrieved high pressure liquid into the low pressure side.
Downstream of the condenser is almost a liquid receiver. Ensuing of the reducing valve is day-to-day found a surge cask which acts as a basin of cold liquid and evens down demand on the compressor and condenser. The liquid ammonia is drawn from the flood drum by a pump. Oil drains may be create on surge drums, liquid receivers, and away on large plants. There is also likely to be an automatic control system on anyone but the oldest and smallest plants.
A classic practical refrigeration system
1 The contemplate was to collect aid about a cross block of installations. One hundred and forty eight returns were worn in the analysis which used the Edinburgh FCG microcomputer.
2 Returns covered a accessible range of processes in the cuisine and drinks industries. The biggest single sector was dairying (chilled water supply) with substantial returns further from frozen food producers and impersonal stores. In the drinks district cooling and soft drinks carbonators were the preeminent uses.
There were a clear range of other uses reported; approximately parts of the cuisine industry require controlled temperatures below ambient at some article of their process. A clear range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were over 5 tonnes, 40% 'tween 1 and 5 tonnes, 35% betwixt 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest component reported was pre-war and ready was a fairly balanced spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a autonomous compressor room. Forty-nine chunk had the system charging extent in the compressor hall and 38% had it outdoors. Twenty-seven per cent of the fragment could positively be identified as having doors to the abroad of the building only. Thirty-six per cent of the added compressor rooms did not accept self-closing doors and 17% did not admit well-fitting doors. With compressors in a nonpartisan room this is a particularly large number where alike the most rudimentary precautions to bar the spread of escaping fuel has not been taken. Fifty-five per cent had condensers mounted raised ground level outside - normally on the roof. This raises questions of secure access and also dodge in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were constantly product freezers in the frozen cuisine sector and carbonators at the peaceful drinks plants). This points to the commitment 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 plant capable of being damaged by, by reason of example, fork lift trucks. Moderate of the entire ballot however had unmarked pipework. (Notes of bounteous proformas suggested that that would receive early attention).
6 lt proved absurd to carryout meaningful inquiry of the ventilation provided in compressor rooms. A mediocre installation seemed to await largely on natural ventilation (perhaps assisted by a small 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 frequent ventilating system. Only 23% of the installations had 2 ventilation rates accessible and only half the ventilation systems of all kind could be mathematical from outside the compressor room. Alone half of these ventilation systems were naturally controlled.
7 Only 16% of anyone system charging was done by a customer on his own; the simple arrangement was 2 men. Butter draining was done by anybody man on his grant at 30% of everyone Installations. At 51 % of everybody installations it was carried down more than once a month. Alone 26% of installations had spring-loaded valves or a catchpot development at oil drains. Approximately of the rest had comparatively a short stub of barrel from a vessel containing liquid ammonia halcyon by a single valve. In 71 % of cases location the oil drain was unsatisfactory inspectors clear that the reasonably practicable alteration was the fitting of self-closing valves. The 30% of installations locus one man did the butter draining on his acquiesce included 6 which had no respirator of exclusive kind.
8 Forty-two per cent of compressor houses had no ammunition detectors. Sieger was by deep-seated the most common supplier (60%) of everyone detection systems. The about common service period of twice per year reflects that company's normal service contract. Nineteen per cent of detector systems were forget it checked.
Approximately half of the detector installations solo had one operating level. Twenty-seven per cent of systems did not lock 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 absolutely equipped to Zone 2 simple even where much of the bury was under the authority of detectors. Seventy-five per cent of anyone 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 foyer or access to it was over the compressor room.
10 Eighty-eight fee of all sites had 2 or likewise sets of respiratory protection of some kind. Six installations (4%) had nobody at all. At 83% of sites there was said to be some sort of training in the commitment of respiratory protection nonetheless only 43% had some sort of systematic examination. At alone 5 installations (3.4%) were there possible limitations of operation which conflicted with arrangement of respiratory protection and the elemental problem seemed to be approach up ladders or awake congested items of plant.
11 Forty-seven per cent of sites had reviving accessory available usually for present first aid rather than exclusively because of the ammonia.
12 Twenty-seven bonus of sites had Draeger (or similar) detector tubes by reason of measuring low concentrations of ammonia. Bounteous others had sulphur sticks or hydrochloric acid for detecting small leaks.
13 Fifty-nine bonus of installations were maintained at first partly by contractors. Afar from a few essential suppliers and installers of apparatus there were many civil refrigeration engineers who solo appeared once or twice in the survey. No consultation is available about the usual of training or workmanship of these contractors.
14 Fifty-five bonus of all sites appeared to believe emergency evacuation procedures (43% used the fire alarm) although slightly fewer (50%) appeared to according 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 alone 34% had what appeared to be active 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 entomb sited in out door locations in accordance amidst para 14 of a well known Circular in otherwise non-hazardous areas boldness not normally require notably protected electrical equipment.
INTERNALLY SITED PLANT
2 A flow chart of the elemental requirements relating to the magnetic apparatus for internally sited bury is given in the supplement to that appendix. The operational approaches are addicted below.
Option 1 - Obligation of explosion protected ac apparatus
3 Hazardous area classification should be carried aside by a competent person. Electrical apparatus should then be exclusive in accordance with BS 5345: Element 1: 1976 Section 2. The max of compressor-houses should be regarded as Sector 2 areas. Type "N" explosion protected equipment (including each emergency ventilation fans) boldness be suitable for these locations.
Option 2 - Analysis of leaks by personnel or gas detectors
4 ln a certain approach, non-explosion protected electric apparatus, with qualifications, may be hand-me-down in combination with a readily available means of isolating the ac supply. The method of achieving the latter can be accomplished either naturally after detection of a flood by a gas detector system, or manually afterwards a leakage has been detected by personnel. The need of these techniques as a leading line of defence is moderate to applications solely involving ammonia in refrigeration plants. A certain approach is considered capable provided that the current principles outlined in paras 10-17 are followed and a particular 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 entomb room, the pattern of airflow action in it and the about likely sources of potential leakage. Due regard should be paid to each dead pockets or recesses. Adventure has shown that, in definite circumstances, it is possible for cold ammonia vapour to stratify initially at flat levels. Unless the occupier has adept expertise within his grant organisation, it would be advisable after all him to consult a boss which specialises in the composition and installation of electricity detection systems.
6 As a bumpy guide only, one might expect to see detectors in the vicinity of the compressors and further non-static items of plant and at ceiling class where one detector per 36M2 of plaster area would probably be sufficient, admitting more may be basic if there are broad beams creating recesses. The detailed is to ensure a certain the ammonia is detected and the appliance rendered safe before flammable concentrations arrive a source of ignition. (This objective, which is further applicable to "detection" of a leak by personnel, is mostly critical with regard to electric apparatus which is not notably designed to be non-sparking, non explosion-protected electrical apparatus and electrical accessory with temperatures above 630'C).
7 The detectors should be suitably explosion protected.
8 The detectors used are of the "pellistor" category and may be subject to poisoning by airborne contaminants. They should therefore be properly installed and maintained and ever checked. The operation of the detectors should be defined using standard ammonia electricity mixtures. Certain V-belt dressings containing antimony admit been shown to medicine detectors and gradually reduce their response.
9 The detectors should be able 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 deterioration to safety should be achieved, so deep as is reasonably practicable. Current guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Bar 6.
11 The isolating device(s), whether manually or necessarily operated, which cuts abroad the electricity supply to the ammonia deposit room, should be located in a non-hazardous area. It container be either a producer or circuit breaker. If the precedent in paras 5-9 high have been satisfied, the backward recommendations in paras 13-17 should be adopted. (Although certain specific details have been taken from BS 4434:1980, by way of example, they are intended to identify the general principles of a certain approach and not noticeable requirements -which will have, to be daring in each particular case).
12 Mind will need to be paid to the authority of other circuits which accept the plant room and are not presently associated with the plant, eg socket outlets since portable tools.
Continuously manned rooms
13 Aloofness of all electrical circuits should be effected by isolating devices located in a non-hazardous area. These devices should be objective by push buttons directly outside the plant room, or objective by a gas diagnosis system as described pare 14, and arranged to bestow visual and audible alarms to reversal on equipment for danger ventilation and/or emergency lighting (if installed). All electrical apparatus that is required to exploit in the room after a leakage has been detected, such as ventilation equipment and danger lighting, should be suitably secure for the hazardous operation in which it is sited, ie District 2. Few compressor rooms are gradually manned. Detection of flow by operators is alone reliable if they are deliberately present in the room. If since example they have further duties, or leave the field for meals etc, or need an isolated noise refuge earlier the speed of effect is likely to be palpably slower than that of automatic detectors.
Unmanned plant rooms
14 lsolation of anybody electrical circuits should be effected by isolating devices located in a non-hazardous area and controlled by all or more suitable ammonia electricity detectors which should likewise be arranged to according a visual and recognizable alarm and to about-face on equipment for ventilation and/or exposure lighting, if installed. The ventilation attitude should be discharged to the away of the building in akin a manner as not to element 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 band isolation at 3% v/v is suggested.
15 Maintenance personnel are required to enter unmanned plant rooms and apt means of escape should be provided.
16 Animal protection including breathing apparatus, and possibly impervious suits, may be needed in any room or space if preservation men are likely to crush pipework or do all other operation liable to disclose liquid ammonia or physical 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 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