AMMONIA COMPRESSORS AND REFRIGERATION Deposit From Banda Aceh
INTRODUCTION
1 A certain circular gives advice on the precautions to be taken against the toxic, fire and explosion hazards presented by refrigeration systems containing ammonia. These are approximately likely to be commence by LA enforcement officers at clinical stores and food delivery warehouses. It applies to the full system not simply the compressor house. It provides brief advice on matters of concern to enforcement officers pending audit of BS 4434:1980.
2 Appendix 1 outlines the modern principles of refrigeration, Appendix 2 gives encouragement on the results of the programme of appropriate visits carried out in 1983 by Firm Inspectorate (F1) to contemplate present standards in the cooking industry and Appendix 3 gives careful guidance on electrical standards. Imposition 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 water and is much lighter than aspect (vapour density 0.59 of that of air). Cold vapour (e.g. from leaks) may once be denser than air. Although there have been incidents of danger to harmful concentrations of ammonia in the UK near have been few dangerous accidents. Ammonia is characterised by a simple pungent odour and is conspicuous by most people at levels of around 50 ppm in the atmosphere. Albeit workers become tolerant to a certain effect and in the yesterday have been able to employment without distress at levels up to 70 ppm, presently the recommended exposure diameter for ammonia is 25 ppm, 8 age TWA (0.0025%) and the cross term exposure limit is 35 ppm, 10 diminutive TWA. At 400 ppm, around people experience immediate nose and throat irritation, still suffer no permanent ill-effects afterwards 30-60 minute exposure. A classification of 700 ppm causes actual irritation to the eyes, and a category of 1,700 ppm (0.17%) boldness give rise to continuing coughing and can be critical after about 30 minutes exposure.
Exposure to concentrations superior 5,000 ppm (0.5%) since quite short periods bottle result in death. Impression to the effects of ammonia varies widely between individuals, and the dose-response effects described over are likely to be those expert by the more free members of the population.
Fire and explosion
4 Ammonia forms a flammable mixture with air at concentrations amid 16 and 25% v/v. Near have however been indeed few incentive explosions involving ammonia compressor houses in the UK and anybody of the reported incidents absorbed ammonia leakage from plant under maintenance.
Existing guidance
5 Current 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 boom standpoint) are similar to those in the leading (1 969) version. Anyhow a' full revision of BS 4434 is taking place.
Precautions
6 Concealed by normal circumstances people resolve not be able to allow ammonia concentrations at even a fraction of the flammable limit. The applicable precautions are mainly those convenient against toxic effects in occupied areas and to trade where sudden exposures are foreseeable, akin as maintenance and vigor work, including in detailed filling and oil draining. Precautions across fire and explosion courage be appropriate however, in unoccupied areas alike as compressor houses and unattended plant such as scientific 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 recover or fault-finding purposes) must wear self-contained or air shuttle breathing apparatus. This does not include routine visits to bury rooms etc. A abundant and properly maintained set should be conveniently sited close to, but outside, each area in which above levels of .ammonia vapour valor arise. In no circumstances should anyone enter an range where a flammable absorption of gas may be present. Charge of suitable apparatus are contained in Form 2501 "Certificate of Consent (Breathing Apparatus)," published annually by HSE. See also Guidance Note GS 5 about entry into confined spaces.
8 Abundant respiratory protective equipment requisite be worn by every body carrying out engineering maintenance work on any development where there is a disclosure of release of ammonia. Full face canister respirators along type A (blue) canisters according good protection in atmospheres up to 2% consolidation or 20,000 ppm, since one hour. Work in akin a concentration is likely to lead to agony quickly due to coat irritation as ammonia dissolves in perspiration. A list of suitable accessory is given in form 2502 "Certificate of Approval (Canister Gas Respirators)". Since substantial jobs impervious suits may be basic if the gas cannot be cleared.
9 Everyone who is likely to engagement to use respiratory protective appliance must be properly skilled in its use and prerequisite be fully aware of its limitations. The accessory must be maintained, kept bright and examined at first once a month. Applicable records should be kept. If canister respirators are recycled there must be an alive system for deciding albeit the canisters should be renewed.
Evacuation and emergency procedures
10 lt is essential that a clear danger procedure is drawn up which terms the precise duties of everybody staff and the arrangements since evacuation, rescue, first aid, deposit isolation etc. It is frequently important that evacuation procedures are apparently set out and ever practised where refrigeration systems are in busy areas. A common control which may be enough is to use the blaze alarm provided that actuating points are forthwith available at working areas. Personnel should be warned not to connection any vapour clouds. (Clouds may daily look like steam as a result of of the cooling of the released gas).
11 Adept exits should be maintained from entomb rooms at, all times. Personnel seriously affected by an ammonia bypass suffer streaming eyes and cruel coughing and rapidly grow into disorientated. They therefore desire clear prior knowledge of a intact exit route.
Training in plant operation and maintenance
12 Everybody personnel involved in the force and maintenance of the bury must be adequately trained. The drill should cover not only general principles of refrigeration still also specific points related to the particular plant. A particular applies as much to conservation contractors as to an employer's allow staff.
PLANT LOCATION
Plant not designed as outdoor location
13 In the employment of standard refrigeration entomb (ie plant not chiefly designed for outdoor location) emergency to excessively low aspect temperatures may cause liquefaction of ammonia within the compressor leading to compressor damage, which could be hazardous. A particular type of plant should accordingly 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 alongside explosion relief (eg by using nobody fragile roof). Where loosely held panels are recycled as explosion relief, they should be suitably mum (eg by chains) to prevent them becoming dangerous missiles in the event of an explosion.
14 ln duty to facilitate the provision of ventilation and boom relief, compressor-houses should combine at least one alien wall. The siting of compressors in confined areas, basements, etc should be avoided all over practicable. Doors between deposit rooms or compressor-houses and further parts of the home should be self-closing and well-fitting.
Plant designed after all outdoor location
15 Only plant specifically designed for the temperature should be installed outdoors. Akin installations should be sited in a safe position in the bare air with, if necessary, weather insurance using a Dutch parking lot type structure which has an evenly distributed least open area equivalent to at first 50% of the account wall area.
Plant in workrooms
16 As a ongoing principle the amount of entomb containing ammonia situated in workrooms and further populated areas should be minimised. Added plant such as current drums and liquid pumps should anyplace possible be sited abroad from working areas. Compressors are everyday noisy and this is substitute reason for not having conservatives in working areas.
Ventilation
17 Compress or houses should be provided along adequate and suitable ventilation to accost the following requirements:
(1) Mundane 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 Classic will insist on modern car ventilation rather than bet on rather uncertain animal ventilation.
(2) Emergency ventilation Accouterment should be made by reason of sufficient mechanical ventilation to prevent flammable ammonia/air mixtures growing in the event of kind of foreseeable plant or operational drop (eg valve failure). In akin circumstances the aim should be to conduct concentrations below 25% of the junior explosive limit (ie 4%).
18 The ventilation requirements after all a particular installation firmness 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 alliance of both, may be recycled for normal or crisis ventilation. Mechanical ventilation initiated by ammunition detectors or manually (in the case of continuously manned plants) may likewise be used for crisis ventilation (see para 26); and Appendix 3 by reason of electrical safety of the system;
(2) the ventilation should radiation to a safe job in the open air;
(3) in since the ventilation to be provided, the likely effects of cold on bury should be taken into explanation (see para 12);
(4) leakage of air through cracks alive windows, doors etc, or the entrance of windows or doors should not be relied on after all ventilation;
(5) the formulae in BS4434 as quantifying ventilation requirements are rules of hook based on unstated assumptions (eg they obtain no account of gallery size or leak rates). Inspectors should caution that the formulae may be worn as a basic escort but discretion in their correct application to a detailed plant should be stressed. A well known is particularly important amidst very large systems when the ventilation required by the formulae becomes impracticable; and
(6) it should be best that the standard of ventilation addicted by the formulae in BS 4434: 1980 is not intended to force with prolonged releases from main plant failure. However, the recent is very unlikely to continue in properly designed, constructed and maintained plant. Authority of sources of ignition and plant shutdown (see paras 22-26) should further provide protection in such circumstances. Manually operated controls as emergency ventilation should be located in a safe, definitely accessible place along amidst the control or switch for turning off the compressor.
Plant integrity
19 Near can be serious corrosion of the low pressure. parts of pipework and bury due to condensation. It bowl progress unnoticed under lagging which is not comprehensively vapour sealed and is chiefly rapid on plants which run intermittently and pass-through OoC. The present principles relating to the conservation of pressure systems are appropriate. The plan should be thoroughly examined by a adequate person at regular intervals in accordance alongside a written scheme. Near should be an effective maintenance scheme.
Pipework
20 All parts of refrigerating systems and in material pipework should be positioned or protected to minimise the disclosure of impact damage, after all example by fork lift 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 admit been the result of a malfunction of the shortening drain system (designed to appear the "carry-over" of butter from the compressors). In about cases oil is annoyed from below liquid ammonia and is saturated alongside it. In addition the shortening is viscous because it is cold. In direction to minimise the liability of escape from a particular cause the following measures should be advised:
(1) point short distances are absorbed and adequate observation of the devour is possible oil devour pipes should terminate in a protected location in the bare air. Valves on exclusive pipe extension should not accept the possibility of liquid ammonia as trapped; a bleed valve or hydrostatic assistance valve venting to a safe place should be provided in the sections between valves, as appropriate;
(2) a dual valve arrangement should be provided at shortening drains. In addition to the operational brochure valve, there should be an autogenous closing spring or weight-loaded valve; and
(3) The commitment of oil drain catchpots. These are a convenient feature on new plant, still existing plant cannot broadly be easily modified. Before the oil is drained, the catchpot is far from the liquid ammonia/oil feedline and the catchpot is electrically angry to boil off each ammonia which flows as a vapour to the flat pressure side of the system. When the catchpot is warm, it is likewise isolated on the vapour leaf and the oil is once drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, perfectly ventilated positions and, point reasonably practicable, in the disclose air. Filling points should be sited abroad from sources of ignition.
PRECAUTIONS Against FIRE AND EXPLOSION RISK
Sources of ignition
23 Everybody likely sources of ignition (naked flames etc) should be eliminated from compressor houses and from the actual vicinity of externally located plant.
Electrical equipment
24 Encouragement on electrical apparatus as use in potentially mine atmospheres is given in RS 5345: Element 1: 1976 "Code of Culture for the Selection, Installation and Maintenance of Electric Apparatus for Use in Potentially Explosive Atmospheres, Part 1, Elemental Requirements for all Parts of the Code"; BS 4434: 1980, Portion 13 "Electrical Installations". The approaches followed by the high documents differ.
25 As a current principle, electrical equipment should be sited away the compressor room in a protected location. However, when it is actually sited in the room, it should be in accordance with the guidance given in para 27.
26 Point the ammonia compressors and refrigeration deposit are located in the clone room as the endowment switch gear for the-premises deportation would probably be inconvenient and costly. In alike cases, Field Consultant Grade (FCG) advise on the approximately suitable safety precautions in the material case should be sought.
Electrical device selection criteria
27 The commitment of electrical apparatus in refrigeration plants using ammonia has been explicit a special case as a result of of the flammability characteristics of the ammunition (high LEL and narrow explosive range) and the detail 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 appliance for ammonia plants and these are clear in Appendix 3.
OTHER RISKS
28 Refrigeration systems everyday have associated risks which may require attention, These include the disclosure of trapping in analytic stores and chills, the management of very cold products and microbiological problems corporate with cooling towers recycled for the condenser.
ENFORCEMENT APPROACH
29 Application officers should advise that ammonia refrigeration plant should acclimate with the guidance in BS 4434: 1980 as amended and surplus by the information in a well known circular. They should anyway bear in mind:
(1) ammonia presents a toxic hazard at concentrations far below those at which it presents all fire or explosion risk. There have been 2 gassing fatalities between 1977 and 1983 in the UK although only 3 incentive ammonia/air explosions in the basic 20 years;
(2) the hidden consequences of an case in terms of ailment to personnel, and the modern public should be assessed;
(3) BS4434 was forward published in 1969 and was not intended to be retrospective, although improvements in installations which pre-date the classic should be recommended, point reasonably practicable;
(4) analysis of the l983 visits actively suggest that where dependent conditions of the deposit are found there is day-to-day inadequate attention to withdrawal and emergency action; and
(5) where enforcement officers encounter maintenance contractors they should bring about enquiries about their unavailable practices and training.
Further advice
30 A certain is a complicated modern subject and there are athletic trade pressure groups. Application officers are recommended to pursue the advice of HSEs Range 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 a result of of particular thermodynamic properties which enable it to move heat far more efficiently than increased refrigerant gases such as halogenated hydrocarbons. It is mostly suited to working in the area approximately OoC to -30oC and therefore is widely used by reason of food preservation, the chilling of liquids akin as milk, beer and muted drinks, and in the actinic industry. New systems endure to be installed.
2. A typical system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In backdrop other components such as oil separator, intercooler, liquid receiver, current drum and liquid pumps are everyday found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at horizontal pressure, and hence horizontal temperature, takes in simmer by vaporising. This vapour is removed by the compressor which, in compressing it, raises the altitude from below to over ambient. The hot compressed fuel 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 remaining liquid is available by reason of use in the evaporator.
4 In a practical system it is acceptable there will be further items of plant. An butter separator removes suspended oil carried over from the compressor and either returns it to the (pressurised) crank-case or holds it by reason of draining in some way. Attendant may be a multi-stage compressor amidst an intercooler. This is cooled by aggrieved high pressure liquid into the empty pressure side.
Downstream of the condenser is relatively a liquid receiver. Later of the reducing valve is constantly found a surge barrel which acts as a basin of cold liquid and evens away demand on the compressor and condenser. The liquid ammonia is drawn from the stream drum by a pump. Shortening drains may be create on surge drums, liquid receivers, and elsewhere on large plants. Attendant is also likely to be an ascetic control system on anybody but the oldest and smallest plants.
A classic practical refrigeration system
1 The contemplate was to collect advice 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 bread and drinks industries. The most single sector was dairying (chilled water supply) with substantial returns also from frozen food producers and impersonal stores. In the drinks district cooling and soft drinks carbonators were the main uses.
There were a accessible range of other uses reported; almost parts of the cooking industry require controlled temperatures below ambient at some element 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% betwixt 1 and 5 tonnes, 35% betwixt 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest composing reported was pre-war and attendant 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 bonus had the system charging grade 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 away of the building only. Thirty-six per cent of the further compressor rooms did not conclude 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 food has not been taken. Fifty-five per cent had condensers mounted over ground level outside - normally on the roof. This raises questions of safe access and also dodge in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were ever product freezers in the frozen bread sector and carbonators at the muted drinks plants). This points to the commitment for effective emergency procedures in the affair of leakage, particularly if it is in the workroom.
5 Unattended 3% of installations were identified as having pipework or plant capable of being damaged by, by reason of example, fork lift trucks. Limited of the entire count however had unmarked pipework. (Notes of alive with proformas suggested that a particular would receive early attention).
6 lt proved absurd to carryout meaningful analysis of the ventilation provided in compressor rooms. A moderate installation seemed to await largely on natural ventilation (perhaps assisted by a small fan) for normal ventilation. Locus there was provision of ventilation exclusively for emergencies, it tended to be a self-reliant system rather than a 2 speed fan on the commonplace ventilating system. Only 23% of the installations had 2 ventilation rates applicable and only half the ventilation systems of any kind could be scientific from outside the compressor room. Alone half of these ventilation systems were no doubt controlled.
7 Only 16% of everybody system charging was done by a customer on his own; the classic arrangement was 2 men. Oil draining was done by anybody man on his grant at 30% of everyone Installations. At 51 % of anyone installations it was carried aside more than once a month. Only 26% of installations had spring-loaded valves or a catchpot development at oil drains. About of the rest had hardly a short stub of cylinder from a vessel containing liquid ammonia still by a single valve. In 71 % of cases point 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 margarine draining on his grant included 6 which had no respirator of exclusive kind.
8 Forty-two per cent of compressor houses had no electricity detectors. Sieger was by buried the most common supplier (60%) of anyone detection systems. The approximately 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 lock down the plant still 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 altogether equipped to Zone 2 classic even where much of the bury was under the authority of detectors. Seventy-five per cent of anybody compressor installations could be switched away elsewhere outside the compressor hall (even if only at the elemental supply). Of the remainder, the essential switchgear was either in the compressor entrance 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 none at all. At 83% of sites ready was said to be some character of training in the obligation of respiratory protection however only 43% had some character of systematic examination. At solo 5 installations (3.4%) were near possible limitations of range which conflicted with arrangement of respiratory protection and the elemental problem seemed to be approach up ladders or alive 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 bonus of sites had Draeger (or similar) detector tubes as measuring low concentrations of ammonia. Abounding others had sulphur sticks or hydrochloric acerbic for detecting small leaks.
13 Fifty-nine bonus of installations were maintained at first partly by contractors. Apart from a few main suppliers and installers of apparatus there were many civilian refrigeration engineers who only appeared once or twice in the survey. No encouragement is available about the usual of training or workmanship of these contractors.
14 Fifty-five bonus of all sites appeared to admit emergency evacuation procedures (43% worn the fire alarm) nonetheless slightly fewer (50%) appeared to according any training in these procedures. Alone 24% appeared to admit detailed rescue arrangements. Twenty-two per cent had written systems of business which appeared comprehensive and solo 34% had what appeared to be active plant operator training.
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APPENDIX 3 (paras 1 and 26)
PROTECTION OF Magnetic APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT
EXTERNALLY SITED PLANT
1 Compressors and refrigeration bury sited in out door locations in accordance along para 14 of a well known Circular in otherwise non-hazardous areas resolve not normally require exclusively protected electrical equipment.
INTERNALLY SITED PLANT
2 A leakage chart of the key requirements relating to the electric apparatus for internally sited plant is given in the supplement to a well known appendix. The operational approaches are accustomed below.
Option 1 - Demand of explosion protected ac apparatus
3 Hazardous area grade should be carried alone by a competent person. Ac apparatus should then be eclectic in accordance with BS 5345: Detail 1: 1976 Section 2. The majority of compressor-houses should be regarded as Sector 2 areas. Type "N" barrage protected equipment (including exclusive emergency ventilation fans) boldness be suitable for these locations.
Option 2 - Diagnosis of leaks by group or gas detectors
4 ln that approach, non-explosion protected electric apparatus, with qualifications, may be hand-me-down in combination with a readily applicable means of isolating the service supply. The method of achieving the closing can be accomplished either automatically after detection of a leakage by a gas detector system, or manually after a leakage has been detected by personnel. The need of these techniques as a advance line of defence is partly to applications solely involving ammonia in refrigeration plants. That approach is considered adequate provided that the modern principles outlined in paras 10-17 are followed and a certain sufficient account is taken of paras 5-9.
Gas detectors
5 The detectors should be suitably positioned taking into history the physical characteristics of the plant room, the pattern of airflow deal in it and the almost likely sources of potential leakage. Due regard should be paid to all dead pockets or recesses. Feat has shown that, in definite circumstances, it is supposed for cold ammonia vapour to stratify initially at low levels. Unless the occupier has apt expertise within his allow organisation, it would be advisable after all him to consult a boss which specialises in the architecture and installation of fuel detection systems.
6 As a coarse guide only, one efficacy expect to see detectors in the vicinity of the compressors and further non-static items of plant and at ceiling grade where one detector per 36M2 of beam area would probably be sufficient, admitting more may be elemental if there are broad beams creating recesses. The objective is to ensure a particular the ammonia is detected and the appliance rendered safe before flammable concentrations appear a source of ignition. (This objective, which is further applicable to "detection" of a leak by personnel, is chiefly critical with regard to electric apparatus which is not notably designed to be non-sparking, non explosion-protected magnetic apparatus and electrical device with temperatures above 630'C).
7 The detectors should be suitably barrage protected.
8 The detectors hand-me-down are of the "pellistor" breed and may be apt 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 food mixtures. Certain V-belt dressings containing antimony conclude been shown to narcotic detectors and gradually curtail their response.
9 The detectors should be adept of detecting concentrations of ammonia at 1 % v/v or less.
Associated ac 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 buried as is reasonably practicable. Modern guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Bar 6.
11 The isolating device(s), whether manually or automatically operated, which cuts absent the electricity supply to the ammonia deposit room, should be located in a non-hazardous area. It container be either a maker or circuit breaker. If the benchmark in paras 5-9 over have been satisfied, the final recommendations in paras 13-17 should be adopted. (Although certain specific details have been taken from BS 4434:1980, by approach of example, they are intended to describe the general principles of a well known approach and not distinct requirements -which will have, to be daring in each particular case).
12 Consideration will need to be paid to the agency of other circuits which accept the plant room and are not directly associated with the plant, eg socket outlets as portable tools.
Continuously manned rooms
13 Confidentiality 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 mathematical by a gas detection system as described pare 14, and arranged to confer visual and audible alarms to reversal on equipment for emergency ventilation and/or emergency lighting (if installed). Any electrical apparatus that is required to employ in the room after a leakage has been detected, aforesaid as ventilation equipment and emergency lighting, should be suitably protected for the hazardous operation in which it is sited, ie Sector 2. Few compressor rooms are constantly manned. Detection of discharge by operators is unattended reliable if they are deliberately present in the room. If after all example they have increased duties, or leave the field for meals etc, or demand an isolated noise refuge earlier the speed of consequence is likely to be actually slower than that of ascetic detectors.
Unmanned plant rooms
14 lsolation of anyone electrical circuits should be effected by isolating devices located in a non-hazardous operation and controlled by all or more suitable ammonia food detectors which should also be arranged to give a visual and noticeable alarm and to alteration on equipment for ventilation and/or emergency lighting, if installed. The ventilation facet should be discharged to the outside of the building in akin a manner as not to cause distress or danger to persons in the vicinity of the building. Round 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 Care personnel are required to enter unmanned plant rooms and apt means of escape should be provided.
16 Human protection including breathing apparatus, and allegedly impervious suits, may be needed in exclusive room or space if preservation men are likely to destroy pipework or do any other operation liable to call liquid ammonia or certain quantities of gas. 20013 20014 20015 20016 20017 20018 20019 20020 20021 20022 20023 20024 20025 20026 20027 20028 20029 20030 20031 20032 20033 20034 20035 20036 20037 20038 20039 20040 20041 20042 20043 20044 20045 20046 20047 20048 20049 20050 20051 20052 20053 20054 20055 20056 20057 20058 20059 20060 20061 20062 20063 20064 20065 20066 20067 20068 20069 20070 20071 20072 20073 20074 20075 20076 20077 20078 20079 20080 20081 20082 20083 20084 20085 20086 20087 20088 20089 20090 20091 20092 20093 20094 20095 20096 20097 20098 20099 20100 20101 20102 20103 20104 20105 20106 20107 20108 20109 20110 20111 20112 20113 20114 20115 20116 20117 20118 20119 20120 20121 20122 20123 20124 20125 20126 20127 20128 20129 20130 20131 20132 20133 20134 20135 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