AMMONIA COMPRESSORS AND REFRIGERATION Entomb From Jakarta Utara
INTRODUCTION
1 A certain circular gives advice on the precautions to be taken across the toxic, fire and explosion hazards presented by refrigeration systems containing ammonia. These are almost likely to be do by LA enforcement officers at clinical stores and food delivery warehouses. It applies to the entire system not simply the compressor house. It provides brief advice on matters of angst to enforcement officers pending review of BS 4434:1980.
2 Appendix 1 outlines the present principles of refrigeration, Appendix 2 gives encouragement on the results of the programme of particular visits carried out in 1983 by Branch Inspectorate (F1) to contemplate present standards in the cooking industry and Appendix 3 gives authentic 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 ammunition that is very soluble in h2o and is much lighter than facet (vapour density 0.59 of a well known of air). Cold vapour (e.g. from leaks) may ever be denser than air. Although there have been incidents of emergency to harmful concentrations of ammonia in the UK near have been few alarming accidents. Ammonia is characterised by a usual pungent odour and is clear by most people at levels of almost 50 ppm in the atmosphere. Although workers become tolerant to that effect and in the yesterday have been able to field without distress at levels up to 70 ppm, currently the recommended exposure breadth for ammonia is 25 ppm, 8 hour TWA (0.0025%) and the cross term exposure limit is 35 ppm, 10 dwarf TWA. At 400 ppm, around people experience immediate nose and throat irritation, still suffer no permanent ill-effects later 30-60 minute exposure. A classification of 700 ppm causes actual irritation to the eyes, and a classification of 1,700 ppm (0.17%) resolve give rise to existing coughing and can be critical after about 30 minutes exposure.
Exposure to concentrations superior 5,000 ppm (0.5%) after all quite short periods container result in death. Consequence to the effects of ammonia varies widely betwixt individuals, and the dose-response effects described raised are likely to be those adept by the more accessible members of the population.
Fire and explosion
4 Ammonia forms a flammable concoction with air at concentrations 'tween 16 and 25% v/v. Attendant have however been literally few incentive explosions involving ammonia compressor houses in the UK and everybody of the reported incidents interested ammonia leakage from plant under maintenance.
Existing guidance
5 Current guidance on the precautions which should be taken amidst ammonia refrigeration plant may be commence in: British Standard 4434: 1980 "Requirements by reason of 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. Ever a' full revision of BS 4434 is taking place.
Precautions
6 Beneath normal circumstances people firmness not be able to allow ammonia concentrations at constant 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 vigor work, including in detailed filling and oil draining. Precautions against fire and explosion firmness be appropriate however, in unoccupied areas aforesaid as compressor houses and solo plant such as scientific stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Con TOXIC RISK
Respiratory protective equipment
7 All person entering an area in which ammonia vapour is expected to be present at a historic level (eg for recoup or fault-finding purposes) prerequisite wear self-contained or airline breathing apparatus. This does not carry routine visits to deposit rooms etc. A adequate and properly maintained team should be conveniently sited close to, but outside, any area in which raised levels of .ammonia vapour efficacy arise. In no conclusion should anyone enter an range where a flammable concentration of gas may be present. Terms of suitable apparatus are contained in Arrange 2501 "Certificate of Consent (Breathing Apparatus)," published annually by HSE. See likewise Guidance Note GS 5 respecting entry into confined spaces.
8 Abundant respiratory protective equipment prerequisite be worn by every body carrying out engineering care work on any construction where there is a liability of release of ammonia. Infinite face canister respirators alongside type A (blue) canisters according good protection in atmospheres up to 2% consolidation or 20,000 ppm, by reason of one hour. Work in such a concentration is fair to lead to burn quickly due to coat irritation as ammonia dissolves in perspiration. A list of suitable appliance is given in form 2502 "Certificate of Consent (Canister Gas Respirators)". After all substantial jobs impervious suits may be elemental if the gas cannot be cleared.
9 Everybody who is likely to engagement to use respiratory protective apparatus must be properly trained in its use and prerequisite be fully aware of its limitations. The device must be maintained, kept clean and examined at gutter once a month. Appropriate records should be kept. If canister respirators are hand-me-down there must be an effective system for deciding at the canisters should be renewed.
Evacuation and crisis procedures
10 lt is key that a clear danger procedure is drawn up which charge the precise duties of everybody staff and the arrangements since evacuation, rescue, first aid, plant isolation etc. It is mostly important that evacuation procedures are certainly set out and ever practised where refrigeration systems are in unavailable areas. A common control which may be adequate is to use the fire alarm provided that actuating points are directly available at working areas. Personnel should be warned not to entry any vapour clouds. (Clouds may constantly look like steam as of the cooling of the released gas).
11 Adept exits should be maintained from entomb rooms at, all times. Crew seriously affected by an ammonia bypass suffer streaming eyes and violent coughing and rapidly grow into disorientated. They therefore lack clear prior knowledge of a secure exit route.
Training in bury operation and maintenance
12 Everybody personnel involved in the force and maintenance of the entomb must be adequately trained. The coaching should cover not alone general principles of refrigeration nonetheless also specific points comparable to the particular plant. A well known applies as much to conservation contractors as to an employer's acquiesce staff.
PLANT LOCATION
Plant not designed after all outdoor location
13 In the case of standard refrigeration plant (ie plant not chiefly designed for outdoor location) exposure to excessively low condition temperatures may cause liquefaction of ammonia in reach the compressor leading to compressor damage, which could be hazardous. That type of plant should therefore be sited in a compressor architecture using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, locus reasonably practicable, be fitted with 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 law to facilitate the provision of ventilation and boom relief, compressor-houses should associate at least one external wall. The siting of compressors in ailing areas, basements, etc should be avoided everywhere practicable. Doors between deposit rooms or compressor-houses and further parts of the architecture should be self-closing and well-fitting.
Plant designed after all outdoor location
15 Only deposit specifically designed for the temperature should be installed outdoors. Akin installations should be sited in a protected 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 bottom 50% of the budget wall area.
Plant in workrooms
16 As a ongoing principle the amount of bury containing ammonia situated in workrooms and additional populated areas should be minimised. Ancillary plant such as current drums and liquid pumps should all over possible be sited away from working areas. Compressors are constantly noisy and this is substitute reason for not having diehards in working areas.
Ventilation
17 Compress or houses should be provided amidst adequate and suitable ventilation to defy the following requirements:
(1) Mundane Ventilation Sufficient permanent ventilation should be provided to bar build up of toxic concentrations of ammonia from operational leakage (eg from seals, glands etc). It is possible that the redrafted British Simple will insist on industrial car ventilation rather than rely on rather uncertain animal ventilation.
(2) Emergency ventilation Provision should be made since sufficient mechanical ventilation to prevent flammable ammonia/air mixtures expanding in the event of moderately foreseeable plant or operational downturn (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 since a particular installation courage depend on the type, capacity, alive conditions and location of the plant and may require creature assessment by a ventilation architect with appropriate expertise. However, the back general points apply:
(1) long-lasting natural or mechanical ventilation, or a alliance of both, may be hand-me-down for normal or emergency ventilation. Mechanical ventilation initiated by ammunition detectors or manually (in the event of continuously manned plants) may further be used for emergency ventilation (see para 26); and Appendix 3 after all electrical safety of the system;
(2) the ventilation should radiation to a safe job in the open air;
(3) in by reason of the ventilation to be provided, the likely effects of cold on bury should be taken into history (see para 12);
(4) leakage of air through cracks viable windows, doors etc, or the access of windows or doors should not be relied on since ventilation;
(5) the formulae in BS4434 as quantifying ventilation requirements are rules of ring finger based on unstated assumptions (eg they obtain no account of gallery size or leak rates). Inspectors should caution that the formulae may be hand-me-down as a basic attend but discretion in their correct application to a objective plant should be stressed. That is particularly important along very large systems at the ventilation required by the formulae becomes impracticable; and
(6) it should be dominant that the standard of ventilation addicted by the formulae in BS 4434: 1980 is not intended to force with prolonged releases from central plant failure. However, the closing is very unlikely to continue in properly designed, constructed and maintained plant. Agency of sources of ignition and entomb shutdown (see paras 22-26) should also provide protection in aforesaid circumstances. Manually operated controls as emergency ventilation should be located in a safe, definitely accessible place along with the control or reversal for turning off the compressor.
Plant integrity
19 There can be serious corrosion of the empty pressure. parts of pipework and entomb due to condensation. It container progress unnoticed under lagging which is not altogether vapour sealed and is essentially rapid on plants which ride intermittently and pass-through OoC. The present principles relating to the insurance of pressure systems are appropriate. The construction should be thoroughly examined by a able 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 objective pipework should be positioned or safe to minimise the liability of impact damage, after all example by fork passage trucks. Pipework and valves should be definitely marked to indicate their contents and function.
Oil devour system
21 Many of the reported incidents involving ammonia refrigeration systems believe been the result of a malfunction of the shortening drain system (designed to appear the "carry-over" of butter from the compressors). In about cases oil is annoyed from below liquid ammonia and is saturated alongside it. In addition the butter is viscous because it is cold. In command to minimise the disclosure of escape from a particular cause the following measures should be advised:
(1) locus short distances are attentive and adequate observation of the devour is possible oil consume pipes should terminate in a intact location in the bring to light air. Valves on any pipe extension should not enter the possibility of liquid ammonia as trapped; a bleed valve or hydrostatic comfort valve venting to a secure place should be provided in the sections betwixt valves, as appropriate;
(2) a double valve arrangement should be provided at shortening drains. In addition to the operational booklet valve, there should be an automatic closing spring or weight-loaded valve; and
(3) The obligation of oil drain catchpots. These are a convenient feature on new plant, still existing plant cannot generally be easily modified. Ahead the oil is drained, the catchpot is far from the liquid ammonia/oil feedline and the catchpot is electrically angry to boil off exclusive ammonia which flows as a vapour to the empty pressure side of the system. Although the catchpot is warm, it is also isolated on the vapour page and the oil is already drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, accurately ventilated positions and, point reasonably practicable, in the bring to light 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 actual vicinity of externally located plant.
Electrical equipment
24 Advice on electrical apparatus by reason of use in potentially mine atmospheres is given in RS 5345: Article 1: 1976 "Code of Education for the Selection, Airport and Maintenance of Magnetic Apparatus for Use in Potentially Bomb Atmospheres, Part 1, Elemental Requirements for all Parts of the Code"; BS 4434: 1980, Clause 13 "Electrical Installations". The approaches followed by the high documents differ.
25 As a current principle, electrical equipment should be sited elsewhere the compressor room in a secure location. However, when it is necessarily sited in the room, it should be in accordance with the guidance given in para 27.
26 Locus the ammonia compressors and refrigeration bury are located in the carbon room as the capital switch gear for the-premises relocation would probably be inconvenient and costly. In alike cases, Field Consultant Grade (FCG) advise on the approximately suitable safety precautions in the detailed 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 fuel (high LEL and narrow explosive range) and the design that it can be detected at literally low levels by smell. A well known has resulted in a home of options which may be clear when selecting electrical device for ammonia plants and these are express in Appendix 3.
OTHER RISKS
28 Refrigeration systems daily have associated risks which may require attention, These include the liability of trapping in scientific stores and chills, the charge of very cold products and microbiological problems amalgamated with cooling towers used for the condenser.
ENFORCEMENT APPROACH
29 Imposition officers should advise that ammonia refrigeration plant should acclimate with the guidance in BS 4434: 1980 as amended and surplus by the information in a well known circular. They should anyway bear in mind:
(1) ammonia presents a toxic hazard at concentrations far below those at which it presents each fire or explosion risk. Near have been 2 gassing fatalities betwixt 1977 and 1983 in the UK nonetheless only 3 incentive ammonia/air explosions in the basic 20 years;
(2) the hidden consequences of an event in terms of defect to personnel, and the current public should be assessed;
(3) BS4434 was leading published in 1969 and was not intended to be retrospective, admitting improvements in installations which pre-date the classic should be recommended, locus reasonably practicable;
(4) analysis of the l983 visits strongly suggest that where defenseless conditions of the bury are found there is constantly inadequate attention to withdrawal and emergency action; and
(5) point enforcement officers encounter care contractors they should cause enquiries about their active practices and training.
Further advice
30 A particular is a complicated modern subject and there are active trade pressure groups. Imposition officers are recommended to seek 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 hand-me-down as a refrigerant as long as of particular thermodynamic properties which enable it to move bake far more efficiently than further refrigerant gases such as halogenated hydrocarbons. It is mostly suited to working in the field approximately OoC to -30oC and accordingly 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 extend to be installed.
2. A usual system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In backdrop other components such as margarine separator, intercooler, liquid receiver, current drum and liquid pumps are everyday found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at horizontal pressure, and hence low temperature, takes in simmer by vaporising. This vapour is removed by the compressor which, in compressing it, raises the temperature from below to above ambient. The hot compressed electricity gives up the melt by condensing to a liquid in the condenser. The high pressure liquid then passes through 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 expected there will be added items of plant. An margarine separator removes suspended oil carried over from the compressor and either returns it to the (pressurised) crank-case or holds it by reason of draining in some way. Near may be a multi-stage compressor with an intercooler. This is cooled by aching high pressure liquid into the horizontal 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 aside demand on the compressor and condenser. The liquid ammonia is drawn from the current drum by a pump. Oil drains may be do on surge drums, liquid receivers, and away on large plants. There is also likely to be an ascetic control system on everybody but the oldest and smallest plants.
A classic practical refrigeration system
1 The aim was to collect consultation about a cross block of installations. One hundred and forty eight returns were hand-me-down in the analysis which recycled the Edinburgh FCG microcomputer.
2 Returns covered a accessible range of processes in the cuisine and drinks industries. The most single sector was dairying (chilled rain supply) with substantial returns likewise from frozen food producers and scientific stores. In the drinks sector cooling and soft drinks carbonators were the preeminent uses.
There were a accessible range of other uses reported; almost parts of the cuisine industry require controlled temperatures below ambient at some element of their process. A accessible range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were over 5 tonnes, 40% 'tween 1 and 5 tonnes, 35% 'tween 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest component reported was pre-war and there was a fairly balanced spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a independent compressor room. Forty-nine chunk had the system charging amount in the compressor gallery and 38% had it outdoors. Twenty-seven per cent of the case could positively be identified as having doors to the abroad of the building only. Thirty-six per cent of the further compressor rooms did not admit self-closing doors and 17% did not believe well-fitting doors. With compressors in a autonomous room this is a notably large number where even the most rudimentary precautions to bar the spread of escaping food has not been taken. Fifty-five per cent had condensers mounted high ground level outside - normally on the roof. This raises questions of protected access and also avoid 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 quiet drinks plants). This points to the need for effective emergency procedures in the case of leakage, particularly if it is in the workroom.
5 Alone 3% of installations were identified as having pipework or entomb capable of being damaged by, by reason of example, fork lift trucks. Limited of the entire opinion however had unmarked pipework. (Notes of alive with proformas suggested that a certain would receive early attention).
6 lt proved futile to carryout meaningful inquiry of the ventilation provided in compressor rooms. A mediocre installation seemed to await largely on natural ventilation (perhaps assisted by a limited fan) for normal ventilation. Point there was provision of ventilation notably for emergencies, it tended to be a independent system rather than a 2 momentum fan on the everyday ventilating system. Only 23% of the installations had 2 ventilation rates accessible and only half the ventilation systems of each kind could be scientific from outside the compressor room. Only half of these ventilation systems were automatically controlled.
7 Only 16% of anybody system charging was done by a person on his own; the classic arrangement was 2 men. Oil draining was done by everybody man on his avow at 30% of anyone Installations. At 51 % of everyone installations it was carried alone more than once a month. Unattended 26% of installations had spring-loaded valves or a catchpot development at oil drains. Almost of the rest had barely a short stub of cask from a vessel containing liquid ammonia closed by a single valve. In 71 % of cases locus the oil drain was unsatisfactory inspectors expressed that the reasonably practicable adjustment was the fitting of self-closing valves. The 30% of installations locus one man did the oil draining on his acquiesce included 6 which had no respirator of any kind.
8 Forty-two per cent of compressor houses had no ammunition detectors. Sieger was by deep the most common supplier (60%) of everyone detection systems. The almost common service period of twice per year reflects a particular company's normal service contract. Nineteen per cent of detector systems were never 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 altogether equipped to Zone 2 simple even where much of the plant was under the agency of detectors. Seventy-five per cent of anybody compressor installations could be switched absent elsewhere outside the compressor foyer (even if only at the elemental supply). Of the remainder, the elemental switchgear was either in the compressor hall or access to it was complete the compressor room.
10 Eighty-eight bonus of all sites had 2 or likewise sets of respiratory insurance of some kind. Six installations (4%) had nobody at all. At 83% of sites near was said to be some character of training in the demand of respiratory protection although only 43% had some array of systematic examination. At unattended 5 installations (3.4%) were ready possible limitations of field which conflicted with plan of respiratory protection and the basic problem seemed to be connection up ladders or conscious congested items of plant.
11 Forty-seven per cent of sites had reviving device available usually for current first aid rather than notably because of the ammonia.
12 Twenty-seven fee of sites had Draeger (or similar) detector tubes as measuring low concentrations of ammonia. Alive with others had sulphur sticks or hydrochloric piquant for detecting small leaks.
13 Fifty-nine fee of installations were maintained at gutter partly by contractors. Aside from a few central suppliers and installers of apparatus there were many domestic refrigeration engineers who alone appeared once or twice in the survey. No aid is available about the classic of training or workmanship of these contractors.
14 Fifty-five chunk of all sites appeared to admit emergency evacuation procedures (43% worn the fire alarm) nonetheless slightly fewer (50%) appeared to bestow any training in these procedures. Solo 24% appeared to admit detailed rescue arrangements. Twenty-two per cent had written systems of employment which appeared comprehensive and solo 34% had what appeared to be active plant operator training.
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APPENDIX 3 (paras 1 and 26)
PROTECTION OF Electric APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT
EXTERNALLY SITED PLANT
1 Compressors and refrigeration deposit sited in out gate locations in accordance amidst para 14 of a certain Circular in otherwise non-hazardous areas boldness not normally require chiefly protected electrical equipment.
INTERNALLY SITED PLANT
2 A flow chart of the elemental requirements relating to the electric apparatus for internally sited entomb is given in the supplement to a certain appendix. The operational approaches are accustomed below.
Option 1 - Obligation of explosion protected ac apparatus
3 Hazardous area classification should be carried away by a competent person. Electric apparatus should then be select in accordance with BS 5345: Detail 1: 1976 Section 2. The bulk of compressor-houses should be regarded as District 2 areas. Type "N" explosion protected equipment (including any emergency ventilation fans) firmness be suitable for these locations.
Option 2 - Discovery of leaks by cadre or gas detectors
4 ln a particular approach, non-explosion protected electric apparatus, with qualifications, may be recycled in combination with a readily applicable means of isolating the heat supply. The method of achieving the final can be accomplished either automatically after detection of a discharge by a gas detector system, or manually afterwards a leakage has been detected by personnel. The need of these techniques as a advance line of defence is half to applications solely involving ammonia in refrigeration plants. A well known approach is considered adequate provided that the modern 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 account the physical characteristics of the entomb room, the pattern of airflow activity in it and the about likely sources of possible leakage. Due regard should be paid to all dead pockets or recesses. Exploit has shown that, in actual circumstances, it is possible for cold ammonia vapour to stratify initially at empty levels. Unless the occupier has apt expertise within his avow organisation, it would be advisable by reason of him to consult a employer 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 classification where one detector per 36M2 of plaster area would probably be sufficient, although more may be elemental if there are broad beams creating recesses. The detailed is to ensure a certain the ammonia is detected and the apparatus rendered safe before flammable concentrations enter a source of ignition. (This objective, which is likewise applicable to "detection" of a leak by personnel, is chiefly critical with regard to electric apparatus which is not notably designed to be non-sparking, non explosion-protected electrical apparatus and electrical device with temperatures above 630'C).
7 The detectors should be suitably barrage protected.
8 The detectors worn are of the "pellistor" category and may be apt to poisoning by airborne contaminants. They should accordingly be properly installed and maintained and consistently checked. The operation of the detectors should be defined using standard ammonia fuel mixtures. Certain V-belt dressings containing antimony believe been shown to drug detectors and gradually curtail their response.
9 The detectors should be adequate of detecting concentrations of ammonia at 1 % v/v or less.
Associated electrical apparatus
10 Account should be taken of the electric control system circuitry and the severe possible degree of drop to safety should be achieved, so deep-seated as is reasonably practicable. Current guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Brick 6.
11 The isolating device(s), whether manually or no doubt operated, which cuts absent the electricity supply to the ammonia entomb 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 back 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 identify the general principles of a particular approach and not recognizable requirements -which will have, to be dangerous in each particular case).
12 Mind will need to be paid to the administration of other circuits which accept the plant room and are not directly associated with the plant, eg socket outlets after all portable tools.
Continuously manned rooms
13 Concealment of all electrical circuits should be effected by isolating devices located in a non-hazardous area. These devices should be experimental by push buttons forthwith outside the plant room, or experimental by a gas diagnosis system as described pare 14, and arranged to according visual and audible alarms to alteration on equipment for exposure ventilation and/or emergency lighting (if installed). Exclusive electrical apparatus that is required to engage in the room later a leakage has been detected, alike as ventilation equipment and emergency lighting, should be suitably secure for the hazardous field in which it is sited, ie District 2. Few compressor rooms are continuously manned. Detection of discharge by operators is unattended reliable if they are continuously present in the room. If since example they have added duties, or leave the field for meals etc, or obligation an isolated noise refuge earlier the speed of consequence is likely to be palpably slower than that of ascetic detectors.
Unmanned plant rooms
14 lsolation of everyone electrical circuits should be effected by isolating devices located in a non-hazardous operation and controlled by anyone or more suitable ammonia electricity detectors which should again be arranged to bestow a visual and noticeable alarm and to switch on equipment for ventilation and/or crisis lighting, if installed. The ventilation attitude should be discharged to the away of the building in alike a manner as not to explanation distress or danger to persons in the vicinity of the building. Band isolation should be effected at ammonia concentrations below 25% LEL and an buzz 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 adept means of escape should be provided.
16 Personal protection including breathing apparatus, and ostensibly impervious suits, may be needed in each room or space if maintenance men are likely to damage pipework or do exclusive other operation liable to disclose liquid ammonia or actual quantities of gas. 18008 18009 18010 18011 18012 18013 18014 18015 18016 18017 18018 18019 18020 18021 18022 18023 18024 18025 18026 18027 18028 18029 18030 18031 18032 18033 18034 18035 18036 18037 18038 18039 18040 18041 18042 18043 18044 18045 18046 18047 18048 18049 18050 18051 18052 18053 18054 18055 18056 18057 18058 18059 18060 18061 18062 18063 18064 18065 18066 18067 18068 18069 18070 18071 18072 18073 18074 18075 18076 18077 18078 18079 18080 18081 18082 18083 18084 18085 18086 18087 18088 18089 18090 18091 18092 18093 18094 18095 18096 18097 18098 18099 18100 18101 18102 18103 18104 18105 18106 18107 18108 18109 18110 18111 18112 18113 18114 18115 18116 18117 18118 18119 18120 18121 18122 18123 18124 18125 18126 18127 18128 18129 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