AMMONIA COMPRESSORS AND REFRIGERATION Deposit From Pangkalpinang
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 around likely to be commence by LA enforcement officers at analytic stores and food consignment warehouses. It applies to the full system not simply the compressor house. It provides temporary advice on matters of anxiety to enforcement officers pending audit of BS 4434:1980.
2 Appendix 1 outlines the current principles of refrigeration, Appendix 2 gives consultation on the results of the programme of peculiar visits carried out in 1983 by Cooperative Inspectorate (F1) to acknowledge present standards in the cuisine industry and Appendix 3 gives accurate guidance on electrical standards. Administration officers should not overemphasise the hazards of ammonia compared with other refrigerants.
HAZARDS
Toxicity
3 Ammonia is a chemically reactive ammunition that is very soluble in drink and is much lighter than facet (vapour density 0.59 of that of air). Cold vapour (e.g. from leaks) may anyway be denser than air. Although there have been incidents of emergency to harmful concentrations of ammonia in the UK attendant have been few alarming accidents. Ammonia is characterised by a simple pungent odour and is visible by most people at levels of about 50 ppm in the atmosphere. Admitting workers become tolerant to a well known effect and in the history have been able to trade without distress at levels up to 70 ppm, at present the recommended exposure breadth for ammonia is 25 ppm, 8 day TWA (0.0025%) and the faultfinding term exposure limit is 35 ppm, 10 dwarf TWA. At 400 ppm, almost people experience immediate nose and throat irritation, although suffer no permanent ill-effects subsequently 30-60 minute exposure. A grade of 700 ppm causes immediate irritation to the eyes, and a category of 1,700 ppm (0.17%) firmness give rise to continuing coughing and can be dangerous after about 30 minutes exposure.
Exposure to concentrations exceptional 5,000 ppm (0.5%) after all quite short periods bowl result in death. Impression to the effects of ammonia varies widely between individuals, and the dose-response effects described high are likely to be those adroit by the more free members of the population.
Fire and explosion
4 Ammonia forms a flammable mixture with air at concentrations betwixt 16 and 25% v/v. There have however been absolutely few incentive explosions involving ammonia compressor houses in the UK and everybody of the reported incidents interested ammonia leakage from bury under maintenance.
Existing guidance
5 Current guidance on the precautions which should be taken alongside ammonia refrigeration plant may be do in: British Standard 4434: 1980 "Requirements as Refrigeration Safety: Part 1, General". The requirements (particularly from the f ire and explosion standpoint) are similar to those in the first (1 969) version. Anyhow a' full revision of BS 4434 is taking place.
Precautions
6 Bottom normal circumstances people boldness not be able to allow ammonia concentrations at even a fraction of the flammable limit. The appropriate precautions are mainly those applicable against toxic effects in occupied areas and to trade where sudden exposures are foreseeable, alike as maintenance and fitness work, including in detailed filling and oil draining. Precautions adjacent fire and explosion boldness be appropriate however, in unoccupied areas akin as compressor houses and alone plant such as analytic stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Con TOXIC RISK
Respiratory protective equipment
7 Each person entering an field in which ammonia vapour is acceptable to be present at a extraordinary level (eg for get back or fault-finding purposes) must wear self-contained or air service breathing apparatus. This does not build routine visits to entomb rooms etc. A adequate and properly maintained team should be conveniently sited adjacent to, but outside, any area in which high levels of .ammonia vapour might arise. In no charge should anyone enter an operation where a flammable consolidation of gas may be present. Conclusion of suitable apparatus are contained in Form 2501 "Certificate of Confirmation (Breathing Apparatus)," published annually by HSE. See likewise Guidance Note GS 5 about entry into confined spaces.
8 Abundant respiratory protective equipment requisite be worn by every body carrying out engineering care work on any plan where there is a hazard of release of ammonia. Complete face canister respirators along type A (blue) canisters according good protection in atmospheres up to 2% combination or 20,000 ppm, as one hour. Work in akin a concentration is acceptable to lead to burn quickly due to skin irritation as ammonia dissolves in perspiration. A list of suitable device is given in file 2502 "Certificate of Consent (Canister Gas Respirators)". By reason of substantial jobs impervious suits may be essential if the gas cannot be cleared.
9 Anyone who is likely to guarantee to use respiratory protective apparatus must be properly old-time in its use and prerequisite be fully aware of its limitations. The device must be maintained, kept blank and examined at first once a month. Convenient 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 danger procedures
10 lt is essential that a clear danger procedure is drawn up which circumstances the precise duties of anybody staff and the arrangements by reason of evacuation, rescue, first aid, entomb isolation etc. It is frequently important that evacuation procedures are apparently set out and consistently practised where refrigeration systems are in unavailable areas. A common education which may be ample is to use the fire alarm provided that actuating points are forthwith available at working areas. Cadre should be warned not to entry any vapour clouds. (Clouds may everyday look like steam as of the cooling of the released gas).
11 Apt exits should be maintained from plant rooms at, all times. Cadre seriously affected by an ammonia avert suffer streaming eyes and crazy coughing and rapidly come disorientated. They therefore desire clear prior knowledge of a secure exit route.
Training in entomb operation and maintenance
12 Anyone personnel involved in the deal and maintenance of the entomb must be adequately trained. The discipline should cover not solo general principles of refrigeration however also specific points alike to the particular plant. A well known applies as much to preservation contractors as to an employer's allow staff.
PLANT LOCATION
Plant not designed since outdoor location
13 In the employment of standard refrigeration bury (ie plant not notably designed for outdoor location) danger to excessively low facet temperatures may cause liquefaction of ammonia within the compressor leading to compressor damage, which could be hazardous. A well known type of plant should so be sited in a compressor construction 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 hand-me-down as explosion relief, they should be suitably mute (eg by chains) to bar them becoming dangerous missiles in the employment of an explosion.
14 ln law to facilitate the arrangement of ventilation and explosion relief, compressor-houses should associate at least one external wall. The siting of compressors in sick areas, basements, etc should be avoided anywhere practicable. Doors between entomb rooms or compressor-houses and further parts of the home should be self-closing and well-fitting.
Plant designed by reason of outdoor location
15 Only plant specifically designed for the humidity should be installed outdoors. Akin installations should be sited in a secure position in the bare air with, if necessary, weather preservation using a Dutch parking lot type structure which has an evenly distributed gutter open area equivalent to at gutter 50% of the budget wall area.
Plant in workrooms
16 As a current principle the amount of deposit containing ammonia situated in workrooms and further populated areas should be minimised. Added plant such as stream drums and liquid pumps should anyplace possible be sited abroad from working areas. Compressors are constantly noisy and this is substitute reason for not having conservatives in working areas.
Ventilation
17 Compress or houses should be provided amidst adequate and suitable ventilation to confront the following requirements:
(1) Mundane Ventilation Sufficient permanent ventilation should be provided to avoid build up of toxic concentrations of ammonia from operational flood (eg from seals, glands etc). It is possible that the redrafted British Typical will insist on industrial car ventilation rather than await on rather uncertain brute ventilation.
(2) Emergency ventilation Provision should be made as sufficient mechanical ventilation to prevent flammable ammonia/air mixtures increasing in the event of moderately foreseeable plant or operational deterioration (eg valve failure). In alike circumstances the aim should be to conduct concentrations below 25% of the second-string explosive limit (ie 4%).
18 The ventilation requirements by reason of a particular installation boldness depend on the type, capacity, active conditions and location of the plant and may require critter assessment by a ventilation builder with appropriate expertise. However, the final general points apply:
(1) long-lasting natural or mechanical ventilation, or a coalition of both, may be hand-me-down for normal or exposure ventilation. Mechanical ventilation initiated by food detectors or manually (in the case of continuously manned plants) may further be used for crisis ventilation (see para 26); and Appendix 3 since electrical safety of the system;
(2) the ventilation should ejaculation to a safe commission in the open air;
(3) in by reason of the ventilation to be provided, the hidden effects of cold on plant should be taken into account (see para 12);
(4) flood of air through cracks awake windows, doors etc, or the opening of windows or doors should not be relied on by reason of ventilation;
(5) the formulae in BS4434 as quantifying ventilation requirements are rules of claw based on unstated assumptions (eg they get no account of entrance size or leak rates). Inspectors should charge that the formulae may be recycled as a basic attend but discretion in their correct application to a objective plant should be stressed. That is particularly important alongside very large systems when the ventilation required by the formulae becomes impracticable; and
(6) it should be best that the standard of ventilation given by the formulae in BS 4434: 1980 is not intended to deal with prolonged releases from essential plant failure. However, the closing is very unlikely to exist in properly designed, constructed and maintained plant. Authority of sources of ignition and plant shutdown (see paras 22-26) should likewise provide protection in alike circumstances. Manually operated controls as emergency ventilation should be located in a safe, definitely accessible place along with the control or reversal for turning off the compressor.
Plant integrity
19 Ready can be serious corrosion of the empty pressure. parts of pipework and deposit due to condensation. It bowl progress unnoticed under lagging which is not comprehensively vapour sealed and is essentially rapid on plants which drive intermittently and pass-through OoC. The ongoing principles relating to the protection of pressure systems are appropriate. The development should be thoroughly examined by a adequate person at regular intervals in accordance alongside a written scheme. There should be an alive 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, since example by fork drive trucks. Pipework and valves should be certainly marked to indicate their contents and function.
Oil consume system
21 Many of the reported incidents involving ammonia refrigeration systems conclude been the result of a malfunction of the oil drain system (designed to show up the "carry-over" of oil from the compressors). In approximately cases oil is bored from below liquid ammonia and is saturated amidst it. In addition the butter is viscous because it is cold. In duty to minimise the hazard of escape from that cause the following measures should be advised:
(1) where short distances are interested and adequate observation of the absorb is possible oil consume pipes should terminate in a intact location in the expose air. Valves on all pipe extension should not admit the possibility of liquid ammonia because trapped; a bleed valve or hydrostatic assistance valve venting to a secure 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 daily valve, there should be an self closing spring or weight-loaded valve; and
(3) The demand of oil drain catchpots. These are a appropriate feature on new plant, however existing plant cannot commonly be easily modified. Along the oil is drained, the catchpot is far-flung from the liquid ammonia/oil feedline and the catchpot is electrically bitter to boil off exclusive ammonia which flows as a vapour to the low pressure side of the system. At the catchpot is warm, it is again isolated on the vapour page and the oil is once drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, properly ventilated positions and, locus reasonably practicable, in the bring to light air. Filling points should be sited elsewhere from sources of ignition.
PRECAUTIONS Across 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 immediate vicinity of externally located plant.
Electrical equipment
24 Encouragement on electrical apparatus after all use in potentially mine atmospheres is given in RS 5345: Design 1: 1976 "Code of Culture for the Selection, Airfield and Maintenance of Electrical Apparatus for Use in Potentially Device Atmospheres, Part 1, Basic Requirements for all Parts of the Code"; BS 4434: 1980, Passage 13 "Electrical Installations". The approaches followed by the high documents differ.
25 As a ongoing principle, electrical equipment should be sited away the compressor room in a intact location. However, when it is actually sited in the room, it should be in accordance along the guidance given in para 27.
26 Where the ammonia compressors and refrigeration bury are located in the carbon room as the endowment switch gear for the-premises deportation would probably be inconvenient and costly. In aforesaid cases, Field Consultant Category (FCG) advise on the about suitable safety precautions in the objective case should be sought.
Electrical device selection criteria
27 The need of electrical apparatus in refrigeration plants using ammonia has been clear a special case because of the flammability characteristics of the ammunition (high LEL and finite explosive range) and the design that it can be detected at absolutely low levels by smell. A well known has resulted in a address of options which may be express when selecting electrical apparatus for ammonia plants and these are expressed in Appendix 3.
OTHER RISKS
28 Refrigeration systems everyday have associated risks which may lack attention, These include the exposure of trapping in clinical stores and chills, the management of very cold products and microbiological problems joint with cooling towers recycled for the condenser.
ENFORCEMENT APPROACH
29 Application officers should advise a particular ammonia refrigeration plant should accommodate with the guidance in BS 4434: 1980 as amended and additional by the information in that circular. They should anyhow bear in mind:
(1) ammonia presents a toxic disclosure at concentrations far below those at which it presents exclusive fire or explosion risk. There have been 2 gassing fatalities betwixt 1977 and 1983 in the UK still only 3 incentive ammonia/air explosions in the bottom 20 years;
(2) the hidden consequences of an event in terms of ailment to personnel, and the current public should be assessed;
(3) BS4434 was forward published in 1969 and was not intended to be retrospective, admitting improvements in installations which pre-date the typical should be recommended, locus reasonably practicable;
(4) analysis of the l983 visits strongly suggest that where defenseless conditions of the entomb are found there is daily inadequate attention to retirement and emergency action; and
(5) point enforcement officers encounter conservation contractors they should achieve enquiries about their busy practices and training.
Further advice
30 A certain is a complicated industrial subject and there are energetic trade pressure groups. Application officers are recommended to pursue the advice of HSEs Area Consultant Group (FCG) via the Domestic Enforcement Liaison Officer (ELO), along considering enforcement action.
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Ammonia is used as a refrigerant as long as of particular thermodynamic properties which enable it to move bake far more efficiently than further refrigerant gases such as halogenated hydrocarbons. It is chiefly suited to working in the area approximately OoC to -30oC and so is widely used by reason of food preservation, the chilling of liquids aforesaid as milk, beer and reticent drinks, and in the synthetic industry. New systems continue to be installed.
2. A typical 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, stream drum and liquid pumps are constantly found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at empty pressure, and hence low temperature, takes in heat by vaporising. This vapour is removed by the compressor which, in compressing it, raises the temperature from below to raised ambient. The hot compressed food gives up the bake by condensing to a liquid in the condenser. The over pressure liquid then passes buttoned up the pressure reducing valve to the evaporator. At the valve the liquid is cooled as some vapour flashes off. The pausing liquid is available by reason of use in the evaporator.
4 In a constructive system it is acceptable there will be further items of plant. An shortening separator removes suspended oil carried over from the compressor and either returns it to the (pressurised) crank-case or holds it after all draining in some way. Near 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 relatively a liquid receiver. Downstream of the reducing valve is constantly found a surge cask which acts as a basin of cold liquid and evens away demand on the compressor and condenser. The liquid ammonia is drawn from the flow drum by a pump. Shortening 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 everybody but the oldest and smallest plants.
A usual practical refrigeration system
1 The contemplate was to collect advice about a cross brick of installations. One hundred and forty eight returns were recycled in the analysis which recycled the Edinburgh FCG microcomputer.
2 Returns covered a free range of processes in the cuisine and drinks industries. The biggest single sector was dairying (chilled rain supply) with substantial returns further from frozen food producers and analytic stores. In the drinks sector cooling and soft drinks carbonators were the leading uses.
There were a accessible 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% 'tween 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest basic 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 self-reliant compressor room. Forty-nine percentage had the system charging amount in the compressor gallery and 38% had it outdoors. Twenty-seven per cent of the sample could positively be identified as having doors to the abroad of the building only. Thirty-six per cent of the increased compressor rooms did not believe 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 above ground level outside - commonly on the roof. This raises questions of intact access and also avert in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were continually product freezers in the frozen cooking sector and carbonators at the quiet drinks plants). This points to the engagement for effective emergency procedures in the affair of leakage, particularly if it is in the workroom.
5 Only 3% of installations were identified as having pipework or deposit capable of being damaged by, after all example, fork lift trucks. Half of the entire poll however had unmarked pipework. (Notes of bounteous proformas suggested that a certain would receive early attention).
6 lt proved futile 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 limited fan) for normal ventilation. Where there was provision of ventilation exclusively for emergencies, it tended to be a independent system rather than a 2 agility fan on the commonplace ventilating system. Only 23% of the installations had 2 ventilation rates convenient and only half the ventilation systems of all kind could be experimental from outside the compressor room. Solo half of these ventilation systems were automatically controlled.
7 Only 16% of anybody system charging was done by a body on his own; the classic arrangement was 2 men. Shortening draining was done by anyone man on his acquiesce at 30% of anybody Installations. At 51 % of anyone installations it was carried aside more than once a month. Alone 26% of installations had spring-loaded valves or a catchpot manufacture at oil drains. Almost of the rest had practically a short stub of cylinder from a vessel containing liquid ammonia fixed by a single valve. In 71 % of cases location the oil drain was unsatisfactory inspectors expressed that the reasonably practicable adjustment was the fitting of self-closing valves. The 30% of installations location one man did the butter draining on his avow included 6 which had no respirator of each kind.
8 Forty-two per cent of compressor houses had no ammunition detectors. Sieger was by buried the most common supplier (60%) of everyone detection systems. The around common service period of twice per year reflects a certain 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 push down the plant still merely raised the alarm. Ten per cent of the systems had no independent alarm.
9 Sixty-six percent of compressor entrance electrical installations were not completely equipped to Zone 2 simple even where much of the plant was under the control of detectors. Seventy-five per cent of anyone compressor installations could be switched aside elsewhere outside the compressor gallery (even if only at the elemental supply). Of the remainder, the key switchgear was either in the compressor hall or access to it was through the compressor room.
10 Eighty-eight fee of all sites had 2 or also sets of respiratory insurance 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 description of systematic examination. At unattended 5 installations (3.4%) were attendant possible limitations of range which conflicted with provision of respiratory protection and the essential problem seemed to be entry up ladders or awake congested items of plant.
11 Forty-seven per cent of sites had reviving accessory available usually for modern first aid rather than notably because of the ammonia.
12 Twenty-seven bonus of sites had Draeger (or similar) detector tubes after all measuring low concentrations of ammonia. Abounding others had sulphur sticks or hydrochloric biting for detecting small leaks.
13 Fifty-nine fee of installations were maintained at least partly by contractors. Afar from a few central suppliers and installers of device there were many civilian refrigeration engineers who only appeared once or twice in the survey. No consultation is available about the usual of training or workmanship of these contractors.
14 Fifty-five percentage of all sites appeared to accept emergency evacuation procedures (43% worn the fire alarm) although slightly fewer (50%) appeared to according any training in these procedures. Solo 24% appeared to admit detailed rescue arrangements. Twenty-two per cent had written systems of field which appeared comprehensive and only 34% had what appeared to be effective plant operator training.
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APPENDIX 3 (paras 1 and 26)
PROTECTION OF Electric APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT
EXTERNALLY SITED PLANT
1 Compressors and refrigeration entomb sited in out gate locations in accordance along para 14 of a well known Circular in otherwise non-hazardous areas resolve not normally require chiefly protected electrical equipment.
INTERNALLY SITED PLANT
2 A discharge chart of the elemental requirements relating to the ac apparatus for internally sited bury is given in the supplement to a well known appendix. The operational approaches are addicted below.
Option 1 - Demand of explosion protected electrical apparatus
3 Hazardous area classification should be carried alone by a competent person. Electrical apparatus should then be exclusive in accordance with BS 5345: Detail 1: 1976 Section 2. The max of compressor-houses should be regarded as District 2 areas. Type "N" barrage protected equipment (including all emergency ventilation fans) firmness 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 worn in combination with a readily convenient means of isolating the heat supply. The method of achieving the final can be accomplished either no doubt after detection of a flow by a gas detector system, or manually subsequently a leakage has been detected by personnel. The need of these techniques as a forward line of defence is moderate to applications solely involving ammonia in refrigeration plants. A certain approach is considered competent provided that the present 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 explanation the physical characteristics of the plant room, the pattern of airflow action in it and the approximately likely sources of possible leakage. Due regard should be paid to all dead pockets or recesses. Adventure has shown that, in certain circumstances, it is apparent for cold ammonia vapour to stratify initially at low levels. Unless the occupier has adept expertise within his acquiesce organisation, it would be advisable as him to consult a company which specialises in the composition and installation of electricity detection systems.
6 As a rough guide only, one valor expect to see detectors in the vicinity of the compressors and additional non-static items of bury and at ceiling classification where one detector per 36M2 of ceiling area would probably be sufficient, albeit more may be key if there are expansive beams creating recesses. The detailed is to ensure a certain the ammonia is detected and the apparatus rendered safe before flammable concentrations enter a source of ignition. (This objective, which is further applicable to "detection" of a leak by personnel, is mostly critical with regard to electrical apparatus which is not especially designed to be non-sparking, non explosion-protected electrical apparatus and electrical accessory with temperatures above 630'C).
7 The detectors should be suitably bang protected.
8 The detectors worn are of the "pellistor" type and may be subject to poisoning by airborne contaminants. They should then be properly installed and maintained and always checked. The operation of the detectors should be limited using standard ammonia electricity mixtures. Certain V-belt dressings containing antimony accept 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 electrical apparatus
10 Account should be taken of the electric control system circuitry and the extreme possible degree of downturn to safety should be achieved, so buried as is reasonably practicable. Ongoing guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Brick 6.
11 The isolating device(s), whether manually or necessarily operated, which cuts absent the electricity supply to the ammonia bury room, should be located in a non-hazardous area. It bag be either a maker or circuit breaker. If the norm in paras 5-9 over have been satisfied, the backward recommendations in paras 13-17 should be adopted. (Although physical specific details have been taken from BS 4434:1980, by path of example, they are intended to identify the general principles of a well known approach and not definite requirements -which will have, to be desperate in each particular case).
12 Consideration will need to be paid to the authority of other circuits which enter the plant room and are not currently associated with the plant, eg socket outlets as 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 instantly outside the plant room, or experimental 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). Each electrical apparatus that is required to engage in the room afterwards a leakage has been detected, such as ventilation equipment and emergency lighting, should be suitably secure for the hazardous field in which it is sited, ie District 2. Few compressor rooms are continuously manned. Detection of discharge by operators is only reliable if they are gradually present in the room. If as example they have increased duties, or leave the operation for meals etc, or need an isolated noise refuge already the speed of effect is likely to be actually slower than that of autogenous 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 all or more suitable ammonia fuel detectors which should again be arranged to give a visual and distinct alarm and to reversal on equipment for ventilation and/or crisis lighting, if installed. The ventilation attitude should be discharged to the outside of the building in such a manner as not to explanation distress or danger to persons in the vicinity of the building. Round isolation should be effected at ammonia concentrations below 25% LEL and an buzz setting of 1.5% v/v followed by round isolation at 3% v/v is suggested.
15 Care personnel are required to concede unmanned plant rooms and able means of escape should be provided.
16 Personal protection including breathing apparatus, and apparently impervious suits, may be needed in exclusive room or space if conservation men are likely to consume pipework or do any other operation liable to announce liquid ammonia or actual quantities of gas. 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 14133 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