AMMONIA COMPRESSORS AND REFRIGERATION Bury From Sungai Penuh
INTRODUCTION
1 A well known circular gives advice on the precautions to be taken con the toxic, fire and bang hazards presented by refrigeration systems containing ammonia. These are approximately likely to be create by LA enforcement officers at analytic stores and food shipment warehouses. It applies to the entire system not simply the compressor house. It provides interim 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 aid on the results of the programme of appropriate visits carried out in 1983 by Factory Inspectorate (F1) to acknowledge present standards in the cooking industry and Appendix 3 gives correct guidance on electrical standards. Imposition officers should not overemphasise the hazards of ammonia compared alongside other refrigerants.
HAZARDS
Toxicity
3 Ammonia is a chemically reactive ammunition that is very soluble in h2o 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. Albeit there have been incidents of exposure to harmful concentrations of ammonia in the UK ready have been few alarming accidents. Ammonia is characterised by a simple pungent odour and is conspicuous by most people at levels of about 50 ppm in the atmosphere. Although workers become tolerant to a certain effect and in the history have been able to employment without distress at levels up to 70 ppm, presently the recommended exposure length for ammonia is 25 ppm, 8 date TWA (0.0025%) and the annoyed term exposure limit is 35 ppm, 10 dwarf TWA. At 400 ppm, approximately people experience immediate adenoids and throat irritation, still suffer no permanent ill-effects subsequently 30-60 minute exposure. A grade of 700 ppm causes actual irritation to the eyes, and a category of 1,700 ppm (0.17%) resolve give rise to fixed coughing and can be dangerous after about 30 minutes exposure.
Exposure to concentrations superior 5,000 ppm (0.5%) since quite short periods bottle result in death. Effect to the effects of ammonia varies widely amid individuals, and the dose-response effects described over are likely to be those adept by the more clear members of the population.
Fire and explosion
4 Ammonia forms a flammable mixture with air at concentrations 'tween 16 and 25% v/v. There have however been actually few incentive explosions involving ammonia compressor houses in the UK and anybody of the reported incidents absorbed ammonia leakage from bury under maintenance.
Existing guidance
5 Current guidance on the precautions which should be taken with ammonia refrigeration plant may be begin in: British Standard 4434: 1980 "Requirements as Refrigeration Safety: Part 1, General". The requirements (particularly from the f ire and bang standpoint) are similar to those in the forward (1 969) version. Once a' full revision of BS 4434 is taking place.
Precautions
6 Bottom normal circumstances people firmness not be able to bear 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, such as maintenance and health work, including in objective filling and oil draining. Precautions across fire and explosion resolve be appropriate however, in unoccupied areas akin as compressor houses and only plant such as impersonal stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Adjacent TOXIC RISK
Respiratory protective equipment
7 Each person entering an operation in which ammonia vapour is likely to be present at a consequential level (eg for recoup or fault-finding purposes) requisite wear self-contained or air service breathing apparatus. This does not add routine visits to entomb rooms etc. A enough and properly maintained brace should be conveniently sited close to, but outside, all area in which above levels of .ammonia vapour efficacy arise. In no terms should anyone enter an operation where a flammable concentration of gas may be present. Charge of suitable apparatus are contained in Form 2501 "Certificate of Consent (Breathing Apparatus)," published annually by HSE. See likewise Guidance Note GS 5 about entry into confined spaces.
8 Enough respiratory protective equipment prerequisite be worn by every customer carrying out engineering preservation work on any development where there is a hazard of release of ammonia. Absolute face canister respirators alongside type A (blue) canisters confer good protection in atmospheres up to 2% absorption or 20,000 ppm, as one hour. Work in such a concentration is likely to lead to ache quickly due to coat irritation as ammonia dissolves in perspiration. A list of suitable appliance is given in organize 2502 "Certificate of Approval (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 apparatus must be properly trained in its use and precondition be fully aware of its limitations. The accessory must be maintained, kept blank and examined at first once a month. Apt records should be kept. If canister respirators are used there must be an operating system for deciding at the canisters should be renewed.
Evacuation and danger procedures
10 lt is key that a clear danger procedure is drawn up which conclusion the precise duties of anybody staff and the arrangements by reason of evacuation, rescue, first aid, deposit isolation etc. It is frequently important that evacuation procedures are certainly set out and consistently practised where refrigeration systems are in active areas. A common education which may be adequate is to use the heat alarm provided that actuating points are directly available at working areas. Crew 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 Adequate exits should be maintained from deposit rooms at, all times. Crew 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 protected exit route.
Training in plant operation and maintenance
12 Anyone personnel involved in the activity and maintenance of the bury must be adequately trained. The coaching should cover not only general principles of refrigeration although also specific points like to the particular plant. That applies as much to care contractors as to an employer's allow staff.
PLANT LOCATION
Plant not designed by reason of outdoor location
13 In the event of standard refrigeration plant (ie plant not exclusively designed for outdoor location) emergency to excessively low attitude temperatures may cause liquefaction of ammonia within the compressor leading to compressor damage, which could be hazardous. A well known type of plant should therefore be sited in a compressor construction using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, point reasonably practicable, be fitted alongside explosion relief (eg by using nobody fragile roof). Where loosely held panels are worn as explosion relief, they should be suitably hushed (eg by chains) to avert them becoming dangerous missiles in the case of an explosion.
14 ln direction to facilitate the provision of ventilation and explosion relief, compressor-houses should couple at least one external 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 architecture should be self-closing and well-fitting.
Plant designed by reason of outdoor location
15 Only entomb specifically designed for the altitude should be installed outdoors. Alike installations should be sited in a intact position in the bare air with, if necessary, weather conservation using a Dutch garage type structure which has an evenly distributed first open area equivalent to at gutter 50% of the allocation wall area.
Plant in workrooms
16 As a present principle the amount of bury containing ammonia situated in workrooms and increased populated areas should be minimised. Extra plant such as flood drums and liquid pumps should everywhere possible be sited abroad from working areas. Compressors are everyday noisy and this is different reason for not having conservatives in working areas.
Ventilation
17 Compress or houses should be provided with adequate and suitable ventilation to confront the following requirements:
(1) Commonplace Ventilation Sufficient permanent ventilation should be provided to avoid build up of toxic concentrations of ammonia from operational leakage (eg from seals, glands etc). It is apparent that the redrafted British Simple will insist on modern car ventilation rather than bank on rather uncertain bodily ventilation.
(2) Emergency ventilation Arrangement should be made after all sufficient mechanical ventilation to prevent flammable ammonia/air mixtures increasing in the event of fairly foreseeable plant or operational deterioration (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 by reason of a particular installation boldness depend on the type, capacity, operating conditions and location of the entomb and may require fellow assessment by a ventilation builder with appropriate expertise. However, the final general points apply:
(1) enduring 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 employment of continuously manned plants) may likewise be used for exposure 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 after all the ventilation to be provided, the hidden effects of cold on deposit should be taken into history (see para 12);
(4) flow of air through cracks alive windows, doors etc, or the access of windows or doors should not be relied on after all ventilation;
(5) the formulae in BS4434 as quantifying ventilation requirements are rules of finger based on unstated assumptions (eg they obtain no account of hall size or leak rates). Inspectors should admonish that the formulae may be recycled as a basic escort but discretion in their correct application to a material plant should be stressed. That is particularly important along very large systems although 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 force with prolonged releases from essential plant failure. However, the closing is very unlikely to endure in properly designed, constructed and maintained plant. Administration of sources of ignition and bury shutdown (see paras 22-26) should further provide protection in akin circumstances. Manually operated controls after all emergency ventilation should be located in a safe, absolutely accessible place along alongside the control or reversal for turning off the compressor.
Plant integrity
19 Attendant can be serious corrosion of the flat pressure. parts of pipework and plant due to condensation. It bowl progress unnoticed under lagging which is not completely vapour sealed and is essentially rapid on plants which drive intermittently and pass-through OoC. The ongoing principles relating to the preservation of pressure systems are appropriate. The plan should be thoroughly examined by a apt person at regular intervals in accordance alongside a written scheme. There should be an active maintenance scheme.
Pipework
20 All parts of refrigerating systems and in material pipework should be positioned or secure to minimise the exposure of impact damage, as example by fork journey 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 oil drain system (designed to appear the "carry-over" of butter from the compressors). In approximately cases oil is distressed from below liquid ammonia and is saturated along it. In addition the oil is viscous because it is cold. In law to minimise the liability of escape from that cause the following measures should be advised:
(1) location short distances are attentive and adequate observation of the devour is possible oil deplete pipes should terminate in a secure location in the disclose air. Valves on exclusive pipe extension should not concede the possibility of liquid ammonia as trapped; a bleed valve or hydrostatic comfort valve venting to a safe place should be provided in the sections between valves, as appropriate;
(2) a binary valve arrangement should be provided at butter drains. In addition to the operational booklet valve, there should be an self closing spring or weight-loaded valve; and
(3) The demand of oil drain catchpots. These are a convenient feature on new plant, however existing plant cannot commonly be easily modified. Before the oil is drained, the catchpot is far-flung from the liquid ammonia/oil feedline and the catchpot is electrically bitter to boil off each ammonia which flows as a vapour to the horizontal pressure side of the system. At the catchpot is warm, it is further isolated on the vapour folio 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 expose air. Filling points should be sited overseas from sources of ignition.
PRECAUTIONS Adjacent FIRE AND EXPLOSION RISK
Sources of ignition
23 Anybody likely sources of ignition (naked flames etc) should be eliminated from compressor houses and from the prompt vicinity of externally located plant.
Electrical equipment
24 Aid on electrical apparatus since use in potentially mine atmospheres is given in RS 5345: Article 1: 1976 "Code of Education for the Selection, Installation and Maintenance of Magnetic Apparatus for Use in Potentially Bomb Atmospheres, Part 1, Basic Requirements for all Parts of the Code"; BS 4434: 1980, Paragraph 13 "Electrical Installations". The approaches followed by the above documents differ.
25 As a current principle, electrical equipment should be sited abroad the compressor room in a protected location. However, when it is necessarily sited in the room, it should be in accordance alongside the guidance given in para 27.
26 Location the ammonia compressors and refrigeration deposit are located in the xerox room as the endowment switch gear for the-premises removal would probably be inconvenient and costly. In akin cases, Field Consultant Category (FCG) advise on the almost suitable safety precautions in the concrete case should be sought.
Electrical accessory selection criteria
27 The obligation of electrical apparatus in refrigeration plants using ammonia has been expressed a special case as long as of the flammability characteristics of the food (high LEL and limited explosive range) and the element that it can be detected at literally low levels by smell. A well known has resulted in a location of options which may be explicit when selecting electrical device for ammonia plants and these are express in Appendix 3.
OTHER RISKS
28 Refrigeration systems everyday have associated risks which may desire attention, These include the exposure of trapping in analytic stores and chills, the conduct of very cold products and microbiological problems corporate with cooling towers worn for the condenser.
ENFORCEMENT APPROACH
29 Application officers should advise that ammonia refrigeration plant should adapt with the guidance in BS 4434: 1980 as amended and plus by the information in that circular. They should ever bear in mind:
(1) ammonia presents a toxic hazard at concentrations far below those at which it presents all fire or explosion risk. Near 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 possible consequences of an case in terms of ailment to personnel, and the current public should be assessed;
(3) BS4434 was advance published in 1969 and was not intended to be retrospective, admitting improvements in installations which pre-date the classic should be recommended, location reasonably practicable;
(4) analysis of the l983 visits actively suggest that where dependent conditions of the deposit are found there is everyday inadequate attention to evacuation and emergency action; and
(5) locus enforcement officers encounter care contractors they should bring about enquiries about their active practices and training.
Further advice
30 A particular is a complicated industrialized subject and there are energetic trade pressure groups. Imposition officers are recommended to go after the advice of HSEs Operation Consultant Group (FCG) via the Civilian Enforcement Liaison Officer (ELO), along considering enforcement action.
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Ammonia is recycled as a refrigerant as a result of of particular thermodynamic properties which empower it to move heat far more efficiently than added refrigerant gases such as halogenated hydrocarbons. It is chiefly suited to working in the field approximately OoC to -30oC and therefore is widely used after all food preservation, the chilling of liquids aforesaid as milk, beer and peaceful drinks, and in the synthetic industry. New systems extend to be installed.
2. A classic system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In background other components such as shortening separator, intercooler, liquid receiver, flood 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 altitude from below to high ambient. The hot compressed fuel gives up the bake by condensing to a liquid in the condenser. The over 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 halting liquid is available since use in the evaporator.
4 In a practical system it is acceptable there will be increased items of plant. An butter separator removes suspended margarine carried over from the compressor and either returns it to the (pressurised) crank-case or holds it as draining in some way. Near may be a multi-stage compressor amidst an intercooler. This is cooled by hurt high pressure liquid into the low pressure side.
Downstream of the condenser is relatively a liquid receiver. Later of the reducing valve is day-to-day found a surge drum 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. Oil drains may be create on surge drums, liquid receivers, and abroad on large plants. Ready is also likely to be an ascetic control system on anybody but the oldest and smallest plants.
A classic practical refrigeration system
1 The aim was to collect aid about a cross brick of installations. One hundred and forty eight returns were used in the analysis which used the Edinburgh FCG microcomputer.
2 Returns covered a accessible range of processes in the bread and drinks industries. The better single sector was dairying (chilled h2o supply) with substantial returns also from frozen food producers and analytic stores. In the drinks region cooling and soft drinks carbonators were the preeminent uses.
There were a accessible range of other uses reported; about parts of the bread industry require controlled temperatures below ambient at some design of their process. A free range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were raised 5 tonnes, 40% 'tween 1 and 5 tonnes, 35% betwixt 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest fundamental reported was pre-war and near was a fairly constant spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a independent compressor room. Forty-nine bonus had the system charging degree in the compressor entrance and 38% had it outdoors. Twenty-seven per cent of the case could positively be identified as having doors to the elsewhere of the building only. Thirty-six per cent of the additional compressor rooms did not admit self-closing doors and 17% did not accept well-fitting doors. With compressors in a nonpartisan room this is a exceptionally large number where constant the most rudimentary precautions to bar the spread of escaping ammunition has not been taken. Fifty-five per cent had condensers mounted high ground level outside - regularly on the roof. This raises questions of protected access and also bypass 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 guarantee for effective emergency procedures in the event of leakage, particularly if it is in the workroom.
5 Unattended 3% of installations were identified as having pipework or deposit capable of being damaged by, since example, fork lift trucks. Limited of the entire opinion however had unmarked pipework. (Notes of bounteous proformas suggested that a particular would receive early attention).
6 lt proved futile to carryout meaningful investigation of the ventilation provided in compressor rooms. A ordinary installation seemed to bet largely on natural ventilation (perhaps assisted by a meager fan) for normal ventilation. Locus there was provision of ventilation especially for emergencies, it tended to be a independent system rather than a 2 momentum fan on the frequent ventilating system. Only 23% of the installations had 2 ventilation rates convenient and only half the ventilation systems of exclusive kind could be experimental from outside the compressor room. Alone half of these ventilation systems were no doubt controlled.
7 Only 16% of anyone system charging was done by a character on his own; the classic arrangement was 2 men. Margarine draining was done by anybody man on his avow at 30% of anybody Installations. At 51 % of everyone installations it was carried aside more than once a month. Only 26% of installations had spring-loaded valves or a catchpot manufacture at oil drains. Approximately of the rest had barely a short stub of barrel from a vessel containing liquid ammonia closed by a single valve. In 71 % of cases locus the oil drain was unsatisfactory inspectors explicit that the reasonably practicable arrangement was the fitting of self-closing valves. The 30% of installations point one man did the butter draining on his allow included 6 which had no respirator of each kind.
8 Forty-two per cent of compressor houses had no fuel detectors. Sieger was by buried the most common supplier (60%) of anybody 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 only had one operating level. Twenty-seven per cent of systems did not bar 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 usual even where much of the entomb was under the agency of detectors. Seventy-five per cent of everybody compressor installations could be switched abroad elsewhere outside the compressor gallery (even if only at the essential supply). Of the remainder, the essential switchgear was either in the compressor foyer or access to it was over the compressor room.
10 Eighty-eight bonus of all sites had 2 or also sets of respiratory preservation of some kind. Six installations (4%) had none at all. At 83% of sites near was said to be some sort of training in the demand of respiratory protection however only 43% had some character of systematic examination. At solo 5 installations (3.4%) were ready possible limitations of area which conflicted with arrangement of respiratory protection and the essential problem seemed to be approach up ladders or alive congested items of plant.
11 Forty-seven per cent of sites had reviving accessory available usually for modern first aid rather than chiefly because of the ammonia.
12 Twenty-seven fee of sites had Draeger (or similar) detector tubes by reason of measuring low concentrations of ammonia. Abounding others had sulphur sticks or hydrochloric piquant for detecting small leaks.
13 Fifty-nine chunk of installations were maintained at least partly by contractors. Afar from a few central suppliers and installers of appliance there were many civil refrigeration engineers who solo appeared once or twice in the survey. No consultation is available about the simple of training or workmanship of these contractors.
14 Fifty-five chunk of all sites appeared to conclude emergency evacuation procedures (43% used the fire alarm) although slightly fewer (50%) appeared to give any training in these procedures. Alone 24% appeared to conclude detailed rescue arrangements. Twenty-two per cent had written systems of employment which appeared comprehensive and solo 34% had what appeared to be alive plant operator training.
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APPENDIX 3 (paras 1 and 26)
PROTECTION OF Magnetic APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT
EXTERNALLY SITED PLANT
1 Compressors and refrigeration plant sited in out aperture locations in accordance alongside para 14 of that Circular in otherwise non-hazardous areas firmness not normally require chiefly protected electrical equipment.
INTERNALLY SITED PLANT
2 A discharge chart of the elemental requirements relating to the electric apparatus for internally sited bury is given in the supplement to a well known appendix. The operational approaches are accustomed below.
Option 1 - Obligation of explosion protected electrical apparatus
3 Hazardous area grade should be carried down by a competent person. Ac apparatus should then be exclusive in accordance with BS 5345: Design 1: 1976 Section 2. The majority of compressor-houses should be regarded as Part 2 areas. Type "N" boom protected equipment (including all emergency ventilation fans) courage be suitable for these locations.
Option 2 - Detection of leaks by cadre or gas detectors
4 ln a certain approach, non-explosion protected electric apparatus, with qualifications, may be used in combination with a readily accessible means of isolating the electricity supply. The method of achieving the final can be accomplished either naturally after detection of a leakage by a gas detector system, or manually subsequently a leakage has been detected by personnel. The demand of these techniques as a forward line of defence is limited to applications solely involving ammonia in refrigeration plants. A particular approach is considered capable provided that the present 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 explanation the physical characteristics of the bury room, the pattern of airflow force in it and the about likely sources of hidden leakage. Due regard should be paid to any dead pockets or recesses. Exploit has shown that, in certain circumstances, it is apparent for cold ammonia vapour to stratify initially at horizontal levels. Unless the occupier has able expertise within his grant organisation, it would be advisable by reason of him to consult a company which specialises in the balance and installation of food detection systems.
6 As a bumpy guide only, one efficacy expect to see detectors in the vicinity of the compressors and increased non-static items of bury and at ceiling grade where one detector per 36M2 of plaster area would probably be sufficient, although more may be key if there are expansive beams creating recesses. The concrete is to ensure a certain the ammonia is detected and the accessory rendered safe before flammable concentrations appear a source of ignition. (This objective, which is also applicable to "detection" of a leak by personnel, is mostly critical with regard to electric apparatus which is not especially designed to be non-sparking, non explosion-protected electric apparatus and electrical apparatus with temperatures above 630'C).
7 The detectors should be suitably boom protected.
8 The detectors hand-me-down are of the "pellistor" type and may be subject to poisoning by airborne contaminants. They should so be properly installed and maintained and constantly checked. The operation of the detectors should be narrow using standard ammonia ammunition mixtures. Certain V-belt dressings containing antimony admit been shown to narcotic detectors and gradually curtail their response.
9 The detectors should be apt of detecting concentrations of ammonia at 1 % v/v or less.
Associated electric apparatus
10 Account should be taken of the electric control system circuitry and the intense possible degree of deterioration to safety should be achieved, so deep 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 automatically operated, which cuts aside the electricity supply to the ammonia bury room, should be located in a non-hazardous area. It container be either a contractor or circuit breaker. If the benchmark in paras 5-9 above have been satisfied, the back recommendations in paras 13-17 should be adopted. (Although physical specific details have been taken from BS 4434:1980, by way of example, they are intended to define the general principles of that approach and not distinct requirements -which will have, to be daring in each particular case).
12 Attention will need to be paid to the agency of other circuits which admit the plant room and are not currently associated with the plant, eg socket outlets after all 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 mathematical by push buttons immediately outside the plant room, or scientific by a gas detection system as described pare 14, and arranged to according visual and audible alarms to about-face on equipment for danger ventilation and/or emergency lighting (if installed). All electrical apparatus that is required to apply in the room subsequently a leakage has been detected, alike as ventilation equipment and exposure lighting, should be suitably intact for the hazardous field in which it is sited, ie Region 2. Few compressor rooms are continuously manned. Detection of flow by operators is solo reliable if they are continuously present in the room. If as example they have further duties, or leave the field for meals etc, or need an isolated noise refuge earlier the speed of impression is likely to be substantially slower than that of self detectors.
Unmanned plant rooms
14 lsolation of anybody electrical circuits should be effected by isolating devices located in a non-hazardous range and controlled by anybody or more suitable ammonia ammunition detectors which should also be arranged to give a visual and definite alarm and to switch on equipment for ventilation and/or danger lighting, if installed. The ventilation condition should be discharged to the abroad of the building in such a manner as not to element distress or danger to persons in the vicinity of the building. Ring 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 Preservation personnel are required to enter unmanned plant rooms and adept means of escape should be provided.
16 Personal protection including breathing apparatus, and ostensibly impervious suits, may be needed in exclusive room or space if conservation men are likely to consume pipework or do all other operation liable to declare liquid ammonia or definite 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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