AMMONIA COMPRESSORS AND REFRIGERATION Plant From Bandung
INTRODUCTION
1 A particular circular gives advice on the precautions to be taken adjacent the toxic, fire and bang hazards presented by refrigeration systems containing ammonia. These are around likely to be begin by LA enforcement officers at scientific stores and food shipment warehouses. It applies to the full system not simply the compressor house. It provides limited advice on matters of angst to enforcement officers pending audit of BS 4434:1980.
2 Appendix 1 outlines the present principles of refrigeration, Appendix 2 gives advice on the results of the programme of appropriate visits carried out in 1983 by Factory Inspectorate (F1) to deal with present standards in the cuisine industry and Appendix 3 gives correct guidance on electrical standards. Enforcement 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 water and is much lighter than condition (vapour density 0.59 of a particular of air). Cold vapour (e.g. from leaks) may once be denser than air. Despite there have been incidents of danger to harmful concentrations of ammonia in the UK attendant have been few alarming accidents. Ammonia is characterised by a simple pungent odour and is conspicuous by most people at levels of almost 50 ppm in the atmosphere. Although workers become tolerant to that effect and in the history have been able to trade 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 caviling term exposure limit is 35 ppm, 10 diminutive TWA. At 400 ppm, almost people experience immediate snout and throat irritation, however suffer no permanent ill-effects later 30-60 minute exposure. A grade of 700 ppm causes immediate irritation to the eyes, and a classification of 1,700 ppm (0.17%) courage give rise to existing coughing and can be critical after about 30 minutes exposure.
Exposure to concentrations exceptional 5,000 ppm (0.5%) since quite short periods container result in death. Effect to the effects of ammonia varies widely betwixt individuals, and the dose-response effects described over are likely to be those deft by the more open members of the population.
Fire and explosion
4 Ammonia forms a flammable mixture with air at concentrations amid 16 and 25% v/v. Attendant have however been absolutely few incentive explosions involving ammonia compressor houses in the UK and anyone of the reported incidents attentive ammonia leakage from entomb under maintenance.
Existing guidance
5 Present-day 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 leading (1 969) version. Once a' full revision of BS 4434 is taking place.
Precautions
6 Beneath normal circumstances people resolve not be able to afford ammonia concentrations at alike a fraction of the flammable limit. The appropriate precautions are mainly those appropriate against toxic effects in occupied areas and to trade where sudden exposures are foreseeable, akin as maintenance and fitness work, including in objective filling and oil draining. Precautions against fire and explosion courage be appropriate however, in unoccupied areas such as compressor houses and solo plant such as clinical stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Across TOXIC RISK
Respiratory protective equipment
7 Any person entering an range in which ammonia vapour is fair to be present at a famous level (eg for recoup or fault-finding purposes) requisite wear self-contained or air shuttle breathing apparatus. This does not build routine visits to deposit rooms etc. A adequate and properly maintained couple should be conveniently sited adjacent to, but outside, each area in which high levels of .ammonia vapour efficacy arise. In no terms should anyone enter an range where a flammable combination of gas may be present. Conclusion of suitable apparatus are contained in Organize 2501 "Certificate of Confirmation (Breathing Apparatus)," published annually by HSE. See also Guidance Note GS 5 about entry into confined spaces.
8 Adequate respiratory protective equipment precondition be worn by every character carrying out engineering conservation work on any manufacture where there is a disclosure of release of ammonia. Full face canister respirators along type A (blue) canisters confer good protection in atmospheres up to 2% combination or 20,000 ppm, as one hour. Work in aforesaid a concentration is likely to lead to ache quickly due to skin irritation as ammonia dissolves in perspiration. A list of suitable appliance is given in file 2502 "Certificate of Blessing (Canister Gas Respirators)". As substantial jobs impervious suits may be basic if the gas cannot be cleared.
9 Everybody who is likely to commitment to use respiratory protective accessory must be properly skilled in its use and precondition be fully aware of its limitations. The accessory must be maintained, kept clean and examined at first once a month. Apt records should be kept. If canister respirators are used there must be an alive system for deciding at the canisters should be renewed.
Evacuation and emergency procedures
10 lt is elemental that a clear crisis procedure is drawn up which circumstances the precise duties of anyone staff and the arrangements since evacuation, rescue, first aid, deposit isolation etc. It is mostly 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 blaze alarm provided that actuating points are immediately available at working areas. Group should be warned not to access any vapour clouds. (Clouds may everyday look like steam as of the cooling of the released gas).
11 Adequate exits should be maintained from bury rooms at, all times. Group seriously affected by an ammonia avoid suffer streaming eyes and brutal coughing and rapidly grow into disorientated. They therefore require clear prior knowledge of a safe exit route.
Training in bury operation and maintenance
12 Anyone personnel involved in the force and maintenance of the plant must be adequately trained. The discipline should cover not alone general principles of refrigeration still also specific points related to the particular plant. A well known applies as much to maintenance contractors as to an employer's allow staff.
PLANT LOCATION
Plant not designed as outdoor location
13 In the affair of standard refrigeration plant (ie plant not chiefly designed for outdoor location) emergency 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 then be sited in a compressor building using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, location reasonably practicable, be fitted along explosion relief (eg by using cipher fragile roof). Where loosely held panels are worn as explosion relief, they should be suitably mum (eg by chains) to bar them becoming dangerous missiles in the event of an explosion.
14 ln duty to facilitate the provision of ventilation and barrage relief, compressor-houses should couple at least one external wall. The siting of compressors in sick areas, basements, etc should be avoided anyplace practicable. Doors between plant rooms or compressor-houses and further 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. Aforesaid installations should be sited in a intact position in the bring to light air with, if necessary, weather protection using a Dutch garage type structure which has an evenly distributed least open area equivalent to at first 50% of the allocation wall area.
Plant in workrooms
16 As a modern principle the amount of plant containing ammonia situated in workrooms and further populated areas should be minimised. Extra plant such as stream drums and liquid pumps should everywhere possible be sited elsewhere from working areas. Compressors are daily noisy and this is different reason for not having authority in working areas.
Ventilation
17 Compress or houses should be provided amidst adequate and suitable ventilation to accost the following requirements:
(1) Mundane Ventilation Sufficient permanent ventilation should be provided to prevent build up of toxic concentrations of ammonia from operational leakage (eg from seals, glands etc). It is apparent that the redrafted British Classic will insist on industrialized car ventilation rather than rely on rather uncertain natural ventilation.
(2) Emergency ventilation Arrangement should be made by reason of sufficient mechanical ventilation to bar flammable ammonia/air mixtures growing in the event of fairly foreseeable plant or operational decline (eg valve failure). In alike circumstances the aim should be to keep concentrations below 25% of the inferior explosive limit (ie 4%).
18 The ventilation requirements after all a particular installation courage depend on the type, capacity, alive conditions and location of the bury and may require creature assessment by a ventilation artist with appropriate expertise. However, the back general points apply:
(1) permanent natural or mechanical ventilation, or a amalgam of both, may be used for normal or danger ventilation. Mechanical ventilation initiated by electricity detectors or manually (in the event of continuously manned plants) may again be used for danger ventilation (see para 26); and Appendix 3 by reason of electrical safety of the system;
(2) the ventilation should emission to a safe place in the open air;
(3) in after all the ventilation to be provided, the hidden effects of cold on entomb should be taken into history (see para 12);
(4) flood of air through cracks viable windows, doors etc, or the entry of windows or doors should not be relied on after all ventilation;
(5) the formulae in BS4434 after all quantifying ventilation requirements are rules of ring finger based on unstated assumptions (eg they take no account of gallery size or leak rates). Inspectors should charge that the formulae may be used as a basic escort but discretion in their careful application to a objective plant should be stressed. A well known is particularly important alongside very large systems albeit the ventilation required by the formulae becomes impracticable; and
(6) it should be famous 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. Control of sources of ignition and plant shutdown (see paras 22-26) should further provide protection in akin circumstances. Manually operated controls by reason of emergency ventilation should be located in a safe, definitely accessible place along with the control or switch for turning off the compressor.
Plant integrity
19 Attendant can be serious corrosion of the horizontal pressure. parts of pipework and plant due to condensation. It bottle progress unnoticed under lagging which is not comprehensively vapour sealed and is chiefly rapid on plants which drive intermittently and pass-through OoC. The ongoing principles relating to the protection of pressure systems are appropriate. The construction should be thoroughly examined by a adept person at regular intervals in accordance amidst a written scheme. There should be an operating maintenance scheme.
Pipework
20 All parts of refrigerating systems and in concrete pipework should be positioned or intact to minimise the disclosure of impact damage, after all example by fork drive 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 admit been the result of a malfunction of the oil drain system (designed to visit the "carry-over" of margarine from the compressors). In about cases oil is distressed from below liquid ammonia and is saturated with it. In addition the shortening is viscous because it is cold. In law to minimise the exposure of escape from a well known cause the following measures should be advised:
(1) point short distances are engrossed and adequate observation of the deplete is possible oil consume pipes should terminate in a protected location in the bare air. Valves on exclusive pipe extension should not admit the possibility of liquid ammonia because 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 coupled valve arrangement should be provided at oil drains. In addition to the operational booklet valve, there should be an self closing spring or weight-loaded valve; and
(3) The obligation of oil drain catchpots. These are a advantageous feature on new plant, however existing plant cannot commonly be easily modified. Before the oil is drained, the catchpot is distant from the liquid ammonia/oil feedline and the catchpot is electrically angry to boil off any ammonia which flows as a vapour to the flat pressure side of the system. Albeit the catchpot is warm, it is also isolated on the vapour folio and the oil is before drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, perfectly ventilated positions and, point reasonably practicable, in the bare air. Filling points should be sited abroad from sources of ignition.
PRECAUTIONS Adjacent 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 actual vicinity of externally located plant.
Electrical equipment
24 Advice on electrical apparatus since use in potentially explosive atmospheres is given in RS 5345: Detail 1: 1976 "Code of Backdrop for the Selection, Airfield and Maintenance of Magnetic Apparatus for Use in Potentially Bomb Atmospheres, Part 1, Basic Requirements for all Parts of the Code"; BS 4434: 1980, Passage 13 "Electrical Installations". The approaches followed by the over documents differ.
25 As a present principle, electrical equipment should be sited elsewhere the compressor room in a secure location. However, when it is actually 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 clone room as the endowment switch gear for the-premises relocation would probably be inconvenient and costly. In such cases, Field Consultant Grade (FCG) advise on the almost suitable safety precautions in the concrete case should be sought.
Electrical apparatus selection criteria
27 The demand of electrical apparatus in refrigeration plants using ammonia has been explicit a special case because of the flammability characteristics of the ammunition (high LEL and finite explosive range) and the detail that it can be detected at indeed low levels by smell. A well known has resulted in a location of options which may be clear when selecting electrical apparatus for ammonia plants and these are express in Appendix 3.
OTHER RISKS
28 Refrigeration systems constantly have associated risks which may lack attention, These include the hazard of trapping in scientific stores and chills, the handling of very cold products and microbiological problems amalgamated with cooling towers worn for the condenser.
ENFORCEMENT APPROACH
29 Enforcement officers should advise a certain ammonia refrigeration plant should acclimate with the guidance in BS 4434: 1980 as amended and surplus by the information in a certain circular. They should once bear in mind:
(1) ammonia presents a toxic hazard at concentrations far below those at which it presents any fire or explosion risk. There have been 2 gassing fatalities betwixt 1977 and 1983 in the UK nonetheless only 3 incentive ammonia/air explosions in the bottom 20 years;
(2) the likely consequences of an event in terms of impairment to personnel, and the ongoing public should be assessed;
(3) BS4434 was first published in 1969 and was not intended to be retrospective, despite improvements in installations which pre-date the usual should be recommended, location reasonably practicable;
(4) analysis of the l983 visits energetically suggest that where defenseless conditions of the bury are found there is daily inadequate attention to evacuation and emergency action; and
(5) point enforcement officers encounter care contractors they should generate enquiries about their unavailable practices and training.
Further advice
30 That is a complicated mechanical subject and there are active trade pressure groups. Imposition officers are recommended to seek the advice of HSEs Range Consultant Group (FCG) via the Civil Enforcement Liaison Officer (ELO), ahead considering enforcement action.
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Ammonia is hand-me-down as a refrigerant as a result of of particular thermodynamic properties which facilitate it to move bake far more efficiently than further refrigerant gases such as halogenated hydrocarbons. It is chiefly suited to working in the field approximately OoC to -30oC and so is widely used by reason of food preservation, the chilling of liquids alike as milk, beer and quiet drinks, and in the actinic industry. New systems endure 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 daily found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at low pressure, and hence empty temperature, takes in heat by vaporising. This vapour is removed by the compressor which, in compressing it, raises the climate from below to raised ambient. The hot compressed ammunition gives up the heat 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 resting liquid is available as use in the evaporator.
4 In a practical system it is likely there will be increased items of plant. An oil separator removes suspended oil carried over from the compressor and either returns it to the (pressurised) crank-case or holds it as draining in some way. Attendant may be a multi-stage compressor with an intercooler. This is cooled by aching high pressure liquid into the low pressure side.
Downstream of the condenser is relatively a liquid receiver. Downstream of the reducing valve is day-to-day found a surge cylinder which acts as a pond of cold liquid and evens aside demand on the compressor and condenser. The liquid ammonia is drawn from the flood drum by a pump. Shortening drains may be begin on surge drums, liquid receivers, and elsewhere on large plants. Near is also likely to be an ascetic control system on anyone but the oldest and smallest plants.
A classic practical refrigeration system
1 The design was to collect encouragement about a cross chunk of installations. One hundred and forty eight returns were used in the analysis which used the Edinburgh FCG microcomputer.
2 Returns covered a clear range of processes in the cooking and drinks industries. The biggest single sector was dairying (chilled rain supply) with substantial returns likewise from frozen food producers and scientific stores. In the drinks region cooling and soft drinks carbonators were the leading uses.
There were a free 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 raised 5 tonnes, 40% between 1 and 5 tonnes, 35% between 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest composing reported was pre-war and near was a fairly alike spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a nonpartisan compressor room. Forty-nine bonus had the system charging extent in the compressor hall and 38% had it outdoors. Twenty-seven per cent of the pattern 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 admit well-fitting doors. With compressors in a self-reliant room this is a notably large number where constant the most rudimentary precautions to bar the spread of escaping fuel has not been taken. Fifty-five per cent had condensers mounted above ground level outside - ordinarily on the roof. This raises questions of safe access and also avert in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were ever product freezers in the frozen cuisine sector and carbonators at the reticent drinks plants). This points to the commitment for effective emergency procedures in the event of leakage, particularly if it is in the workroom.
5 Solo 3% of installations were identified as having pipework or plant capable of being damaged by, after all example, fork lift trucks. Moderate of the entire opinion however had unmarked pipework. (Notes of many proformas suggested that a certain would receive early attention).
6 lt proved impossible to carryout meaningful analysis of the ventilation provided in compressor rooms. A average installation seemed to await largely on natural ventilation (perhaps assisted by a limited fan) for normal ventilation. Point there was provision of ventilation especially for emergencies, it tended to be a nonpartisan system rather than a 2 agility fan on the commonplace ventilating system. Only 23% of the installations had 2 ventilation rates applicable and only half the ventilation systems of each kind could be experimental from outside the compressor room. Only half of these ventilation systems were no doubt controlled.
7 Only 16% of anybody system charging was done by a customer on his own; the typical arrangement was 2 men. Oil draining was done by anybody man on his avow at 30% of everybody Installations. At 51 % of everybody installations it was carried down more than once a month. Unattended 26% of installations had spring-loaded valves or a catchpot development at oil drains. Approximately of the rest had practically a short stub of cask from a vessel containing liquid ammonia closed by a single valve. In 71 % of cases location the oil drain was unsatisfactory inspectors express that the reasonably practicable alteration was the fitting of self-closing valves. The 30% of installations where one man did the shortening draining on his avow included 6 which had no respirator of any kind.
8 Forty-two per cent of compressor houses had no ammunition detectors. Sieger was by broad the most common supplier (60%) of anyone detection systems. The approximately common service period of twice per year reflects a particular company's normal service contract. Nineteen per cent of detector systems were don't hold your breath checked.
Approximately half of the detector installations solo had one operating level. Twenty-seven per cent of systems did not shut down the plant still merely raised the alarm. Ten per cent of the systems had no nonpartisan alarm.
9 Sixty-six percent of compressor entrance electrical installations were not comprehensively equipped to Zone 2 typical even where much of the entomb was under the administration of detectors. Seventy-five per cent of anyone compressor installations could be switched absent elsewhere outside the compressor entrance (even if only at the elemental supply). Of the remainder, the essential switchgear was either in the compressor entrance or access to it was complete the compressor room.
10 Eighty-eight percentage of all sites had 2 or again sets of respiratory protection of some kind. Six installations (4%) had none at all. At 83% of sites there was said to be some sort of training in the demand of respiratory protection still only 43% had some array of systematic examination. At unattended 5 installations (3.4%) were there possible limitations of field which conflicted with arrangement of respiratory protection and the basic 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 current first aid rather than notably because of the ammonia.
12 Twenty-seven chunk of sites had Draeger (or similar) detector tubes by reason of measuring low concentrations of ammonia. Bounteous others had sulphur sticks or hydrochloric acid for detecting small leaks.
13 Fifty-nine fee of installations were maintained at first partly by contractors. Alone from a few main suppliers and installers of appliance there were many governmental 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 bonus of all sites appeared to admit emergency evacuation procedures (43% recycled the fire alarm) nonetheless slightly fewer (50%) appeared to bestow any training in these procedures. Unattended 24% appeared to admit detailed rescue arrangements. Twenty-two per cent had written systems of field which appeared comprehensive and unattended 34% had what appeared to be operating 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 aperture locations in accordance with para 14 of that Circular in otherwise non-hazardous areas resolve not normally require especially protected electrical equipment.
INTERNALLY SITED PLANT
2 A discharge chart of the basic requirements relating to the electrical apparatus for internally sited entomb is given in the supplement to a particular appendix. The operational approaches are disposed below.
Option 1 - Need of explosion protected electric apparatus
3 Hazardous area grade should be carried alone by a competent person. Electric apparatus should then be select in accordance with BS 5345: Design 1: 1976 Section 2. The mass of compressor-houses should be regarded as District 2 areas. Type "N" barrage protected equipment (including any emergency ventilation fans) resolve be suitable for these locations.
Option 2 - Diagnosis of leaks by group or gas detectors
4 ln a certain approach, non-explosion protected magnetic apparatus, with qualifications, may be worn in combination with a readily accessible means of isolating the electricity supply. The method of achieving the latter can be accomplished either necessarily after detection of a flood by a gas detector system, or manually after a leakage has been detected by personnel. The need of these techniques as a first line of defence is moderate to applications solely involving ammonia in refrigeration plants. A well known approach is considered capable 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 detail the physical characteristics of the entomb room, the pattern of airflow deal in it and the around likely sources of potential leakage. Due regard should be paid to exclusive dead pockets or recesses. Experience has shown that, in actual circumstances, it is possible for cold ammonia vapour to stratify initially at horizontal levels. Unless the occupier has apt expertise within his allow organisation, it would be advisable by reason of him to consult a corporation which specialises in the composition and installation of fuel detection systems.
6 As a rough guide only, one might expect to see detectors in the vicinity of the compressors and increased non-static items of plant and at ceiling category where one detector per 36M2 of roof area would probably be sufficient, albeit more may be essential if there are extensive beams creating recesses. The material is to ensure that the ammonia is detected and the device 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 especially designed to be non-sparking, non explosion-protected magnetic apparatus and electrical apparatus with temperatures above 630'C).
7 The detectors should be suitably boom protected.
8 The detectors worn are of the "pellistor" type and may be conditional to poisoning by airborne contaminants. They should so be properly installed and maintained and consistently checked. The operation of the detectors should be defined using standard ammonia food mixtures. Certain V-belt dressings containing antimony admit been shown to cure detectors and gradually cut down their response.
9 The detectors should be adequate of detecting concentrations of ammonia at 1 % v/v or less.
Associated electrical apparatus
10 Account should be taken of the electric control system circuitry and the acute possible degree of downturn to safety should be achieved, so deep-seated as is reasonably practicable. Present guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Brick 6.
11 The isolating device(s), whether manually or automatically operated, which cuts abroad the electricity supply to the ammonia plant room, should be located in a non-hazardous area. It bowl be either a producer or circuit breaker. If the benchmark 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 approach of example, they are intended to define the general principles of a well known approach and not distinct requirements -which will have, to be bold 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 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 instantly outside the plant room, or objective by a gas discovery system as described pare 14, and arranged to bestow visual and audible alarms to reversal on equipment for exposure ventilation and/or emergency lighting (if installed). Any electrical apparatus that is required to exploit in the room afterwards a leakage has been detected, akin as ventilation equipment and crisis lighting, should be suitably safe for the hazardous operation in which it is sited, ie District 2. Few compressor rooms are gradually manned. Detection of flow by operators is unattended reliable if they are gradually present in the room. If after all example they have further duties, or leave the area for meals etc, or need an isolated noise refuge once the speed of impression is likely to be palpably slower than that of autogenous detectors.
Unmanned plant rooms
14 lsolation of anyone electrical circuits should be effected by isolating devices located in a non-hazardous area and controlled by anyone or more suitable ammonia food detectors which should further be arranged to bestow a visual and noticeable alarm and to switch on equipment for ventilation and/or crisis lighting, if installed. The ventilation condition 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. Band isolation should be effected at ammonia concentrations below 25% LEL and an bell setting of 1.5% v/v followed by arena isolation at 3% v/v is suggested.
15 Preservation personnel are required to accept unmanned plant rooms and able 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 maintenance men are likely to crush pipework or do exclusive other operation liable to announce liquid ammonia or actual quantities of gas. 12010 12011 12012 12013 12014 12015 12016 12017 12018 12019 12020 12021 12022 12023 12024 12025 12026 12027 12028 12029 12030 12031 12032 12033 12034 12035 12036 12037 12038 12039 12040 12041 12042 12043 12044 12045 12046 12047 12048 12049 12050 12051 12052 12053 12054 12055 12056 12057 12058 12059 12060 12061 12062 12063 12064 12065 12066 12067 12068 12069 12070 12071 12072 12073 12074 12075 12076 12077 12078 12079 12080 12081 12082 12083 12084 12085 12086 12087 12088 12089 12090 12091 12092 12093 12094 12095 12096 12097 12098 12099 12100 12101 12102 12103 12104 12105 12106 12107 12108 12109 12110 12111 12112 12113 12114 12115 12116 12117 12118 12119 12120 12121 12122 12123 12124 12125 12126 12127 12128 12129 12130 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