AMMONIA COMPRESSORS AND REFRIGERATION Deposit From Cilegon
INTRODUCTION
1 A certain circular gives advice on the precautions to be taken adjacent the toxic, fire and boom hazards presented by refrigeration systems containing ammonia. These are approximately likely to be commence by LA enforcement officers at analytic stores and food consignment warehouses. It applies to the entire 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 present principles of refrigeration, Appendix 2 gives encouragement on the results of the programme of distinct visits carried out in 1983 by Firm Inspectorate (F1) to acknowledge present standards in the bread industry and Appendix 3 gives accurate guidance on electrical standards. Administration officers should not overemphasise the hazards of ammonia compared alongside other refrigerants.
HAZARDS
Toxicity
3 Ammonia is a chemically reactive fuel that is very soluble in h2o and is much lighter than facet (vapour density 0.59 of a certain of air). Cold vapour (e.g. from leaks) may anyhow be denser than air. Despite there have been incidents of exposure to harmful concentrations of ammonia in the UK attendant have been few dangerous accidents. Ammonia is characterised by a classic pungent odour and is conspicuous by most people at levels of about 50 ppm in the atmosphere. Albeit workers become tolerant to a particular effect and in the past have been able to field without distress at levels up to 70 ppm, currently the recommended exposure length for ammonia is 25 ppm, 8 day TWA (0.0025%) and the annoyed term exposure limit is 35 ppm, 10 diminutive TWA. At 400 ppm, about people experience immediate snout and throat irritation, nonetheless suffer no permanent ill-effects after 30-60 minute exposure. A category of 700 ppm causes immediate irritation to the eyes, and a category of 1,700 ppm (0.17%) resolve give rise to existing coughing and can be critical after about 30 minutes exposure.
Exposure to concentrations improved 5,000 ppm (0.5%) as quite short periods bottle result in death. Consequence to the effects of ammonia varies widely 'tween individuals, and the dose-response effects described over are likely to be those deft by the more accessible members of the population.
Fire and explosion
4 Ammonia forms a flammable blend 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 attentive ammonia leakage from deposit under maintenance.
Existing guidance
5 New guidance on the precautions which should be taken with ammonia refrigeration plant may be begin in: British Standard 4434: 1980 "Requirements since Refrigeration Safety: Part 1, General". The requirements (particularly from the f ire and explosion standpoint) are similar to those in the advance (1 969) version. Anyhow a' full revision of BS 4434 is taking place.
Precautions
6 Concealed by normal circumstances people boldness not be able to manage ammonia concentrations at even a fraction of the flammable limit. The apt precautions are mainly those applicable against toxic effects in occupied areas and to business where sudden exposures are foreseeable, akin as maintenance and health work, including in detailed filling and oil draining. Precautions con fire and explosion resolve be appropriate however, in unoccupied areas alike as compressor houses and unattended plant such as clinical stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Across TOXIC RISK
Respiratory protective equipment
7 Each person entering an range in which ammonia vapour is acceptable to be present at a famous level (eg for recover or fault-finding purposes) requisite wear self-contained or air passenger carrier breathing apparatus. This does not include routine visits to entomb rooms etc. A abundant and properly maintained brace should be conveniently sited warm to, but outside, each area in which raised levels of .ammonia vapour valor arise. In no conclusion should anyone enter an operation where a flammable concentration of gas may be present. Circumstances of suitable apparatus are contained in Arrange 2501 "Certificate of Confirmation (Breathing Apparatus)," published annually by HSE. See again Guidance Note GS 5 regarding entry into confined spaces.
8 Abundant respiratory protective equipment must be worn by every customer carrying out engineering preservation work on any plan where there is a disclosure of release of ammonia. Infinite face canister respirators alongside type A (blue) canisters confer good protection in atmospheres up to 2% concentration or 20,000 ppm, by reason of one hour. Work in such a concentration is acceptable to lead to pain quickly due to fur irritation as ammonia dissolves in perspiration. A list of suitable device is given in arrange 2502 "Certificate of Consent (Canister Gas Respirators)". As substantial jobs impervious suits may be elemental if the gas cannot be cleared.
9 Anybody who is likely to guarantee to use respiratory protective device must be properly skilled in its use and must be fully aware of its limitations. The accessory must be maintained, kept clear and examined at bottom once a month. Convenient records should be kept. If canister respirators are hand-me-down there must be an operating system for deciding although the canisters should be renewed.
Evacuation and emergency procedures
10 lt is essential that a clear exposure procedure is drawn up which conclusion the precise duties of anyone staff and the arrangements by reason of evacuation, rescue, first aid, entomb isolation etc. It is essentially important that evacuation procedures are definitely set out and ever practised where refrigeration systems are in busy areas. A common development which may be enough is to use the fire alarm provided that actuating points are forthwith available at working areas. Group should be warned not to approach any vapour clouds. (Clouds may everyday look like steam as a result of of the cooling of the released gas).
11 Adept exits should be maintained from bury rooms at, all times. Group seriously affected by an ammonia avoid suffer streaming eyes and crazy coughing and rapidly grow into disorientated. They therefore require clear prior knowledge of a secure exit route.
Training in deposit operation and maintenance
12 Everybody personnel involved in the activity and maintenance of the plant must be adequately trained. The drill should cover not only general principles of refrigeration nonetheless also specific points alike to the particular plant. A particular applies as much to maintenance contractors as to an employer's acquiesce staff.
PLANT LOCATION
Plant not designed by reason of outdoor location
13 In the affair of standard refrigeration deposit (ie plant not notably designed for outdoor location) crisis to excessively low attitude temperatures may cause liquefaction of ammonia in a period the compressor leading to compressor damage, which could be hazardous. A particular type of plant should so be sited in a compressor building using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, point reasonably practicable, be fitted amidst explosion relief (eg by using nobody fragile roof). Where loosely held panels are hand-me-down as explosion relief, they should be suitably silent (eg by chains) to avoid them becoming dangerous missiles in the employment of an explosion.
14 ln duty to facilitate the plan of ventilation and explosion relief, compressor-houses should couple at least one external wall. The siting of compressors in sick areas, basements, etc should be avoided anywhere practicable. Doors between bury 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 deposit specifically designed for the altitude should be installed outdoors. Akin installations should be sited in a safe position in the bring to light air with, if necessary, weather preservation using a Dutch garage type structure which has an evenly distributed first open area equivalent to at gutter 50% of the budget wall area.
Plant in workrooms
16 As a modern principle the amount of entomb containing ammonia situated in workrooms and increased populated areas should be minimised. Added plant such as flood drums and liquid pumps should everywhere possible be sited elsewhere from working areas. Compressors are day-to-day noisy and this is different reason for not having them in working areas.
Ventilation
17 Compress or houses should be provided alongside adequate and suitable ventilation to encounter the following requirements:
(1) Frequent 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 probable that the redrafted British Typical will insist on mechanical car ventilation rather than bet on rather uncertain bodily ventilation.
(2) Emergency ventilation Accouterment should be made by reason of sufficient mechanical ventilation to avert flammable ammonia/air mixtures increasing in the event of fairly foreseeable plant or operational downturn (eg valve failure). In aforesaid circumstances the aim should be to conduct concentrations below 25% of the junior explosive limit (ie 4%).
18 The ventilation requirements since a particular installation courage depend on the type, capacity, alive conditions and location of the plant and may require animal assessment by a ventilation artist with appropriate expertise. However, the back 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 electricity detectors or manually (in the case of continuously manned plants) may again be used for exposure ventilation (see para 26); and Appendix 3 as electrical safety of the system;
(2) the ventilation should radiation to a safe commission in the open air;
(3) in since the ventilation to be provided, the hidden effects of cold on bury should be taken into detail (see para 12);
(4) discharge of air through cracks viable 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 advise that the formulae may be worn as a basic follow but discretion in their careful application to a concrete plant should be stressed. A certain is particularly important with very large systems when the ventilation required by the formulae becomes impracticable; and
(6) it should be leading that the standard of ventilation accustomed by the formulae in BS 4434: 1980 is not intended to deal with prolonged releases from central plant failure. However, the latter is very unlikely to continue in properly designed, constructed and maintained plant. Agency of sources of ignition and plant shutdown (see paras 22-26) should further provide protection in akin circumstances. Manually operated controls as emergency ventilation should be located in a safe, clearly accessible place along alongside the control or switch for turning off the compressor.
Plant integrity
19 There can be serious corrosion of the empty pressure. parts of pipework and bury due to condensation. It bowl progress unnoticed under lagging which is not absolutely vapour sealed and is essentially rapid on plants which ride intermittently and pass-through OoC. The current principles relating to the insurance of pressure systems are appropriate. The plan should be thoroughly examined by a adequate person at regular intervals in accordance along a written scheme. Attendant should be an operating 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 certainly marked to indicate their contents and function.
Oil absorb system
21 Many of the reported incidents involving ammonia refrigeration systems admit been the result of a malfunction of the oil drain system (designed to appear the "carry-over" of butter from the compressors). In almost cases oil is annoyed from below liquid ammonia and is saturated alongside it. In addition the shortening is viscous because it is cold. In command to minimise the hazard of escape from that cause the following measures should be advised:
(1) location short distances are engrossed and adequate observation of the absorb is possible oil absorb pipes should terminate in a intact location in the expose air. Valves on exclusive pipe extension should not concede the possibility of liquid ammonia as a result of trapped; a bleed valve or hydrostatic relief valve venting to a protected place should be provided in the sections betwixt valves, as appropriate;
(2) a binary valve arrangement should be provided at oil drains. In addition to the operational daily valve, there should be an automatic closing spring or weight-loaded valve; and
(3) The need of oil drain catchpots. These are a appropriate feature on new plant, however existing plant cannot generally be easily modified. Ahead the oil is drained, the catchpot is distant from the liquid ammonia/oil feedline and the catchpot is electrically enraged to boil off any ammonia which flows as a vapour to the low pressure side of the system. Albeit the catchpot is warm, it is further isolated on the vapour folio and the oil is already drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, accurately ventilated positions and, location reasonably practicable, in the bring to light air. Filling points should be sited away from sources of ignition.
PRECAUTIONS Across FIRE AND EXPLOSION RISK
Sources of ignition
23 Everyone likely sources of ignition (naked flames etc) should be eliminated from compressor houses and from the prompt vicinity of externally located plant.
Electrical equipment
24 Consultation on electrical apparatus since use in potentially device atmospheres is given in RS 5345: Detail 1: 1976 "Code of Culture for the Selection, Installation and Maintenance of Ac Apparatus for Use in Potentially Bomb Atmospheres, Part 1, Key Requirements for all Parts of the Code"; BS 4434: 1980, Portion 13 "Electrical Installations". The approaches followed by the above documents differ.
25 As a ongoing principle, electrical equipment should be sited elsewhere the compressor room in a secure location. However, when it is approximately sited in the room, it should be in accordance with the guidance given in para 27.
26 Locus the ammonia compressors and refrigeration entomb are located in the same room as the capital switch gear for the-premises removal would probably be inconvenient and costly. In akin cases, Field Consultant Division (FCG) advise on the around suitable safety precautions in the detailed case should be sought.
Electrical apparatus selection criteria
27 The commitment of electrical apparatus in refrigeration plants using ammonia has been express a special case as a result of of the flammability characteristics of the fuel (high LEL and defined explosive range) and the detail that it can be detected at indeed low levels by smell. A certain has resulted in a location of options which may be express when selecting electrical accessory for ammonia plants and these are explicit in Appendix 3.
OTHER RISKS
28 Refrigeration systems constantly have associated risks which may require attention, These include the disclosure of trapping in impersonal stores and chills, the handling of very cold products and microbiological problems amalgamated with cooling towers recycled for the condenser.
ENFORCEMENT APPROACH
29 Imposition 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 anyway bear in mind:
(1) ammonia presents a toxic liability 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 although only 3 incentive ammonia/air explosions in the base 20 years;
(2) the hidden consequences of an employment in terms of disability to personnel, and the modern public should be assessed;
(3) BS4434 was forward published in 1969 and was not intended to be retrospective, albeit improvements in installations which pre-date the usual should be recommended, locus reasonably practicable;
(4) analysis of the l983 visits firmly suggest that where dependent conditions of the entomb are found there is everyday inadequate attention to pullout and emergency action; and
(5) locus enforcement officers encounter care contractors they should generate enquiries about their busy practices and training.
Further advice
30 A well known is a complicated industrial subject and there are athletic trade pressure groups. Imposition officers are recommended to seek the advice of HSEs Field Consultant Group (FCG) via the Civilian Enforcement Liaison Officer (ELO), advanced considering enforcement action.
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Ammonia is used 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 frequently suited to working in the range approximately OoC to -30oC and therefore is widely used as food preservation, the chilling of liquids alike as milk, beer and peaceful drinks, and in the chemical 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 background other components such as shortening separator, intercooler, liquid receiver, stream drum and liquid pumps are constantly found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at low pressure, and hence empty temperature, takes in bake by vaporising. This vapour is removed by the compressor which, in compressing it, raises the temperature from below to raised ambient. The hot compressed electricity gives up the melt by condensing to a liquid in the condenser. The above 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 halting liquid is available as use in the evaporator.
4 In a constructive system it is expected there will be additional items of plant. An oil separator removes suspended butter carried over from the compressor and either returns it to the (pressurised) crank-case or holds it as draining in some way. Ready may be a multi-stage compressor amidst an intercooler. This is cooled by aching high pressure liquid into the flat pressure side.
Downstream of the condenser is approximately a liquid receiver. Ensuing of the reducing valve is everyday found a surge drum which acts as a pond of cold liquid and evens away demand on the compressor and condenser. The liquid ammonia is drawn from the flow drum by a pump. Margarine drains may be begin on surge drums, liquid receivers, and overseas on large plants. There is also likely to be an automatic control system on anyone but the oldest and smallest plants.
A typical practical refrigeration system
1 The intend was to collect advice about a cross bar of installations. One hundred and forty eight returns were used in the analysis which recycled the Edinburgh FCG microcomputer.
2 Returns covered a clear range of processes in the cooking and drinks industries. The better single sector was dairying (chilled drink supply) with substantial returns again from frozen food producers and scientific stores. In the drinks district cooling and soft drinks carbonators were the main uses.
There were a clear range of other uses reported; approximately parts of the food industry require controlled temperatures below ambient at some detail of their process. A open range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were over 5 tonnes, 40% between 1 and 5 tonnes, 35% amid 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest basic 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 nonpartisan compressor room. Forty-nine fee had the system charging grade in the compressor foyer and 38% had it outdoors. Twenty-seven per cent of the case 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 believe self-closing doors and 17% did not believe well-fitting doors. With compressors in a nonpartisan room this is a especially large number where even the most rudimentary precautions to prevent the spread of escaping food has not been taken. Fifty-five per cent had condensers mounted raised ground level outside - ordinarily on the roof. This raises questions of intact access and also dodge in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were constantly product freezers in the frozen bread sector and carbonators at the quiet drinks plants). This points to the guarantee 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 plant capable of being damaged by, since example, fork lift trucks. Moderate of the entire poll however had unmarked pipework. (Notes of alive with proformas suggested that a certain would receive early attention).
6 lt proved futile to carryout meaningful investigation of the ventilation provided in compressor rooms. A moderate installation seemed to bet largely on natural ventilation (perhaps assisted by a cramped fan) for normal ventilation. Location there was provision of ventilation notably for emergencies, it tended to be a independent system rather than a 2 momentum fan on the mundane ventilating system. Only 23% of the installations had 2 ventilation rates convenient and only half the ventilation systems of exclusive kind could be scientific from outside the compressor room. Alone half of these ventilation systems were necessarily controlled.
7 Only 16% of anyone system charging was done by a customer on his own; the simple arrangement was 2 men. Oil draining was done by anyone man on his acquiesce at 30% of anybody Installations. At 51 % of everyone installations it was carried down more than once a month. Unattended 26% of installations had spring-loaded valves or a catchpot construction at oil drains. Around of the rest had barely a short stub of cylinder from a vessel containing liquid ammonia closed by a single valve. In 71 % of cases point the oil drain was unsatisfactory inspectors explicit that the reasonably practicable alteration was the fitting of self-closing valves. The 30% of installations point one man did the shortening draining on his avow included 6 which had no respirator of all 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 forget it checked.
Approximately half of the detector installations solo had one operating level. Twenty-seven per cent of systems did not lock down the plant nonetheless merely raised the alarm. Ten per cent of the systems had no nonpartisan alarm.
9 Sixty-six percent of compressor hall electrical installations were not completely equipped to Zone 2 simple even where much of the bury was under the agency of detectors. Seventy-five per cent of everybody compressor installations could be switched abroad elsewhere outside the compressor foyer (even if only at the essential supply). Of the remainder, the key switchgear was either in the compressor foyer or access to it was through the compressor room.
10 Eighty-eight bonus of all sites had 2 or further sets of respiratory conservation of some kind. Six installations (4%) had no one 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 sort of systematic examination. At alone 5 installations (3.4%) were attendant possible limitations of area which conflicted with arrangement of respiratory protection and the key problem seemed to be connection up ladders or alive congested items of plant.
11 Forty-seven per cent of sites had reviving accessory available usually for current first aid rather than especially because of the ammonia.
12 Twenty-seven bonus of sites had Draeger (or similar) detector tubes after all measuring low concentrations of ammonia. Alive with others had sulphur sticks or hydrochloric piquant for detecting small leaks.
13 Fifty-nine bonus of installations were maintained at bottom partly by contractors. Apart from a few central suppliers and installers of appliance there were many governmental refrigeration engineers who only appeared once or twice in the survey. No advice is available about the usual of training or workmanship of these contractors.
14 Fifty-five chunk of all sites appeared to believe emergency evacuation procedures (43% used the fire alarm) however slightly fewer (50%) appeared to confer any training in these procedures. Alone 24% appeared to accept detailed rescue arrangements. Twenty-two per cent had written systems of field which appeared comprehensive and solo 34% had what appeared to be effective plant operator training.
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APPENDIX 3 (paras 1 and 26)
PROTECTION OF Electrical APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT
EXTERNALLY SITED PLANT
1 Compressors and refrigeration plant sited in out gate locations in accordance along para 14 of a well known Circular in otherwise non-hazardous areas courage not normally require notably protected electrical equipment.
INTERNALLY SITED PLANT
2 A flow chart of the elemental requirements relating to the magnetic apparatus for internally sited plant is given in the supplement to a certain appendix. The operational approaches are disposed below.
Option 1 - Demand of explosion protected magnetic apparatus
3 Hazardous area classification should be carried down by a competent person. Magnetic apparatus should then be preferred in accordance with BS 5345: Element 1: 1976 Section 2. The mass of compressor-houses should be regarded as Region 2 areas. Type "N" boom protected equipment (including all emergency ventilation fans) courage be suitable for these locations.
Option 2 - Analysis of leaks by crew or gas detectors
4 ln a certain approach, non-explosion protected magnetic apparatus, with qualifications, may be used in combination with a readily convenient means of isolating the heat supply. The method of achieving the closing can be accomplished either naturally after detection of a flow by a gas detector system, or manually after a leakage has been detected by personnel. The demand of these techniques as a advance line of defence is partly to applications solely involving ammonia in refrigeration plants. A particular approach is considered competent provided that the ongoing principles outlined in paras 10-17 are followed and a well known 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 activity 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 actual circumstances, it is probable for cold ammonia vapour to stratify initially at low levels. Unless the occupier has able expertise within his allow 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 bumpy guide only, one might expect to see detectors in the vicinity of the compressors and further non-static items of entomb and at ceiling category where one detector per 36M2 of plaster area would probably be sufficient, albeit more may be key if there are broad beams creating recesses. The material is to ensure a particular the ammonia is detected and the accessory rendered safe before flammable concentrations land a source of ignition. (This objective, which is again applicable to "detection" of a leak by personnel, is mostly critical with regard to ac apparatus which is not notably designed to be non-sparking, non explosion-protected ac apparatus and electrical apparatus with temperatures above 630'C).
7 The detectors should be suitably explosion protected.
8 The detectors recycled are of the "pellistor" type and may be subject to poisoning by airborne contaminants. They should so be properly installed and maintained and ever checked. The operation of the detectors should be narrow using standard ammonia fuel mixtures. Certain V-belt dressings containing antimony accept been shown to cure 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 electrical control system circuitry and the acute possible degree of drop to safety should be achieved, so broad as is reasonably practicable. Modern guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Block 6.
11 The isolating device(s), whether manually or naturally operated, which cuts away the electricity supply to the ammonia deposit room, should be located in a non-hazardous area. It bottle be either a producer or circuit breaker. If the precedent in paras 5-9 over have been satisfied, the backward recommendations in paras 13-17 should be adopted. (Although certain specific details have been taken from BS 4434:1980, by access of example, they are intended to describe the general principles of a certain approach and not definite requirements -which will have, to be dangerous in each particular case).
12 Attention will need to be paid to the control of other circuits which accept the plant room and are not directly associated with the plant, eg socket outlets since 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 mathematical by push buttons directly outside the plant room, or experimental by a gas analysis system as described pare 14, and arranged to bestow visual and audible alarms to alteration on equipment for exposure ventilation and/or emergency lighting (if installed). All electrical apparatus that is required to exploit in the room later a leakage has been detected, aforesaid as ventilation equipment and exposure lighting, should be suitably protected for the hazardous operation in which it is sited, ie District 2. Few compressor rooms are constantly manned. Detection of leakage by operators is solo reliable if they are deliberately present in the room. If since example they have further duties, or leave the operation for meals etc, or demand an isolated noise refuge earlier the speed of effect is likely to be physically 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 area and controlled by anybody or more suitable ammonia fuel detectors which should again be arranged to bestow a visual and definite alarm and to about-face on equipment for ventilation and/or crisis lighting, if installed. The ventilation condition should be discharged to the elsewhere 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 alarm setting of 1.5% v/v followed by band isolation at 3% v/v is suggested.
15 Preservation personnel are required to admit unmanned plant rooms and apt means of escape should be provided.
16 Personal protection including breathing apparatus, and possibly impervious suits, may be needed in each room or space if conservation men are likely to damage pipework or do any other operation liable to declare liquid ammonia or physical quantities of gas. 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 20136 20137 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