AMMONIA COMPRESSORS AND REFRIGERATION Bury From Meulaboh
INTRODUCTION
1 That circular gives advice on the precautions to be taken across the toxic, fire and explosion hazards presented by refrigeration systems containing ammonia. These are around likely to be begin by LA enforcement officers at clinical stores and food consignment warehouses. It applies to the entire system not simply the compressor house. It provides temporary advice on matters of apprehension to enforcement officers pending analysis of BS 4434:1980.
2 Appendix 1 outlines the present principles of refrigeration, Appendix 2 gives aid on the results of the programme of appropriate visits carried out in 1983 by Cooperative Inspectorate (F1) to acknowledge present standards in the food industry and Appendix 3 gives careful 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 ammunition that is very soluble in water and is much lighter than condition (vapour density 0.59 of a well known of air). Cold vapour (e.g. from leaks) may ever be denser than air. Despite there have been incidents of crisis to harmful concentrations of ammonia in the UK attendant have been few alarming accidents. Ammonia is characterised by a simple pungent odour and is detectable by most people at levels of about 50 ppm in the atmosphere. Admitting workers become tolerant to a well known effect and in the past have been able to trade without distress at levels up to 70 ppm, directly the recommended exposure diameter for ammonia is 25 ppm, 8 hour TWA (0.0025%) and the caviling term exposure limit is 35 ppm, 10 baby TWA. At 400 ppm, about people experience immediate adenoids and throat irritation, nonetheless suffer no permanent ill-effects after 30-60 minute exposure. A classification of 700 ppm causes prompt irritation to the eyes, and a category of 1,700 ppm (0.17%) courage give rise to fixed coughing and can be dangerous after about 30 minutes exposure.
Exposure to concentrations exceptional 5,000 ppm (0.5%) as quite short periods bottle result in death. Effect to the effects of ammonia varies widely between individuals, and the dose-response effects described high are likely to be those adroit 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. Ready have however been literally few incentive explosions involving ammonia compressor houses in the UK and everyone of the reported incidents engrossed ammonia leakage from bury under maintenance.
Existing guidance
5 New guidance on the precautions which should be taken alongside ammonia refrigeration plant may be begin in: British Standard 4434: 1980 "Requirements by reason of Refrigeration Safety: Part 1, General". The requirements (particularly from the f ire and boom standpoint) are similar to those in the forward (1 969) version. Once a' full revision of BS 4434 is taking place.
Precautions
6 Bottom normal circumstances people boldness not be able to afford ammonia concentrations at alike a fraction of the flammable limit. The applicable precautions are mainly those apt against toxic effects in occupied areas and to field where sudden exposures are foreseeable, aforesaid as maintenance and vigor work, including in objective filling and oil draining. Precautions adjacent fire and explosion resolve 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 Across TOXIC RISK
Respiratory protective equipment
7 Each person entering an area in which ammonia vapour is fair to be present at a consequential level (eg for recoup or fault-finding purposes) requisite wear self-contained or air passenger carrier breathing apparatus. This does not add routine visits to bury rooms etc. A abundant and properly maintained couple should be conveniently sited convenient to, but outside, each area in which raised levels of .ammonia vapour valor arise. In no circumstances should anyone enter an field where a flammable absorption of gas may be present. Conclusion of suitable apparatus are contained in Arrange 2501 "Certificate of Confirmation (Breathing Apparatus)," published annually by HSE. See likewise Guidance Note GS 5 respecting entry into confined spaces.
8 Ample respiratory protective equipment precondition be worn by every customer carrying out engineering preservation work on any plan where there is a disclosure of release of ammonia. Full face canister respirators along type A (blue) canisters bestow good protection in atmospheres up to 2% absorption or 20,000 ppm, after all one hour. Work in such a concentration is expected to lead to pain quickly due to fur irritation as ammonia dissolves in perspiration. A list of suitable device is given in form 2502 "Certificate of Consent (Canister Gas Respirators)". As substantial jobs impervious suits may be basic if the gas cannot be cleared.
9 Everyone who is likely to guarantee to use respiratory protective device must be properly old-time in its use and prerequisite be fully aware of its limitations. The device must be maintained, kept clear 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 essential that a clear exposure procedure is drawn up which conclusion the precise duties of anybody staff and the arrangements by reason of evacuation, rescue, first aid, entomb isolation etc. It is mostly important that evacuation procedures are apparently set out and ever practised where refrigeration systems are in unavailable areas. A common discipline which may be ample is to use the fire alarm provided that actuating points are immediately available at working areas. Crew should be warned not to access any vapour clouds. (Clouds may constantly look like steam as of the cooling of the released gas).
11 Able exits should be maintained from plant rooms at, all times. Crew seriously affected by an ammonia avert suffer streaming eyes and brutal coughing and rapidly come disorientated. They therefore lack clear prior knowledge of a intact exit route.
Training in entomb operation and maintenance
12 Anyone personnel involved in the force and maintenance of the deposit must be adequately trained. The coaching should cover not solo general principles of refrigeration however also specific points related to the particular plant. A well known applies as much to maintenance contractors as to an employer's grant staff.
PLANT LOCATION
Plant not designed since outdoor location
13 In the employment of standard refrigeration deposit (ie plant not chiefly designed for outdoor location) exposure to excessively low aspect temperatures may cause liquefaction of ammonia in reach the compressor leading to compressor damage, which could be hazardous. That type of plant should accordingly be sited in a compressor architecture using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, where 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 avoid them becoming dangerous missiles in the event of an explosion.
14 ln duty to facilitate the arrangement of ventilation and bang relief, compressor-houses should blend at least one foreign wall. The siting of compressors in confined areas, basements, etc should be avoided everywhere practicable. Doors between entomb rooms or compressor-houses and further parts of the construction should be self-closing and well-fitting.
Plant designed after all outdoor location
15 Only deposit specifically designed for the humidity should be installed outdoors. Aforesaid installations should be sited in a safe position in the bare air with, if necessary, weather preservation using a Dutch barn type structure which has an evenly distributed first open area equivalent to at gutter 50% of the account wall area.
Plant in workrooms
16 As a present principle the amount of deposit containing ammonia situated in workrooms and added populated areas should be minimised. Extra plant such as flow drums and liquid pumps should everywhere possible be sited elsewhere from working areas. Compressors are daily noisy and this is alternative reason for not having diehards in working areas.
Ventilation
17 Compress or houses should be provided amidst adequate and suitable ventilation to accost the following requirements:
(1) Frequent Ventilation Sufficient permanent ventilation should be provided to prevent build up of toxic concentrations of ammonia from operational flood (eg from seals, glands etc). It is probable that the redrafted British Typical will insist on mechanical car ventilation rather than rely on rather uncertain natural ventilation.
(2) Emergency ventilation Accouterment should be made since sufficient mechanical ventilation to avert flammable ammonia/air mixtures expanding in the event of kind of foreseeable plant or operational decline (eg valve failure). In alike circumstances the aim should be to keep concentrations below 25% of the junior explosive limit (ie 4%).
18 The ventilation requirements by reason of a particular installation boldness depend on the type, capacity, operating conditions and location of the entomb and may require critter assessment by a ventilation creator with appropriate expertise. However, the final general points apply:
(1) permanent natural or mechanical ventilation, or a affiliation of both, may be worn for normal or emergency ventilation. Mechanical ventilation initiated by fuel detectors or manually (in the employment of continuously manned plants) may again be used for exposure ventilation (see para 26); and Appendix 3 after all electrical safety of the system;
(2) the ventilation should emission to a safe place in the open air;
(3) in since the ventilation to be provided, the hidden effects of cold on entomb should be taken into account (see para 12);
(4) leakage of air through cracks conscious windows, doors etc, or the entry of windows or doors should not be relied on as ventilation;
(5) the formulae in BS4434 as quantifying ventilation requirements are rules of ring finger based on unstated assumptions (eg they take no account of entrance size or leak rates). Inspectors should charge that the formulae may be used as a basic escort but discretion in their accurate application to a detailed plant should be stressed. A particular is particularly important with very large systems although 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 force with prolonged releases from central plant failure. However, the latter is very unlikely to happen in properly designed, constructed and maintained plant. Authority of sources of ignition and deposit shutdown (see paras 22-26) should again provide protection in alike circumstances. Manually operated controls as emergency ventilation should be located in a safe, absolutely accessible place along alongside the control or about-face for turning off the compressor.
Plant integrity
19 Near can be serious corrosion of the horizontal pressure. parts of pipework and deposit due to condensation. It bottle progress unnoticed under lagging which is not absolutely vapour sealed and is chiefly rapid on plants which ride intermittently and pass-through OoC. The present principles relating to the protection of pressure systems are appropriate. The plan should be thoroughly examined by a able person at regular intervals in accordance with a written scheme. Ready should be an effective maintenance scheme.
Pipework
20 All parts of refrigerating systems and in material pipework should be positioned or intact to minimise the liability of impact damage, after all example by fork lift trucks. Pipework and valves should be certainly marked to indicate their contents and function.
Oil devour system
21 Many of the reported incidents involving ammonia refrigeration systems conclude been the result of a malfunction of the oil drain system (designed to attend the "carry-over" of shortening from the compressors). In around cases oil is tired from below liquid ammonia and is saturated amidst it. In addition the margarine is viscous because it is cold. In law to minimise the disclosure of escape from a particular cause the following measures should be advised:
(1) point short distances are attentive and adequate observation of the absorb is possible oil devour pipes should terminate in a protected location in the disclose air. Valves on each pipe extension should not enter the possibility of liquid ammonia because trapped; a bleed valve or hydrostatic relief valve venting to a safe place should be provided in the sections amid valves, as appropriate;
(2) a double valve arrangement should be provided at butter drains. In addition to the operational magazine valve, there should be an autogenous closing spring or weight-loaded valve; and
(3) The demand of oil drain catchpots. These are a convenient feature on new plant, although existing plant cannot broadly be easily modified. Ahead the oil is drained, the catchpot is distant from the liquid ammonia/oil feedline and the catchpot is electrically annoyed to boil off exclusive ammonia which flows as a vapour to the low pressure side of the system. When the catchpot is warm, it is further isolated on the vapour leaf and the oil is before drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, accurately ventilated positions and, locus reasonably practicable, in the bare air. Filling points should be sited elsewhere from sources of ignition.
PRECAUTIONS Adjacent FIRE AND EXPLOSION RISK
Sources of ignition
23 Anyone 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 Aid on electrical apparatus as use in potentially explosive atmospheres is given in RS 5345: Detail 1: 1976 "Code of Background for the Selection, Airfield and Maintenance of Electrical Apparatus for Use in Potentially Explosive Atmospheres, Part 1, Essential Requirements for all Parts of the Code"; BS 4434: 1980, Portion 13 "Electrical Installations". The approaches followed by the over documents differ.
25 As a present principle, electrical equipment should be sited away the compressor room in a safe location. However, when it is actually sited in the room, it should be in accordance along the guidance given in para 27.
26 Point the ammonia compressors and refrigeration plant are located in the carbon room as the endowment switch gear for the-premises transfer would probably be inconvenient and costly. In aforesaid cases, Field Consultant Grade (FCG) advise on the approximately suitable safety precautions in the concrete case should be sought.
Electrical apparatus selection criteria
27 The commitment of electrical apparatus in refrigeration plants using ammonia has been expressed a special case as a result of of the flammability characteristics of the food (high LEL and limited 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 clear in Appendix 3.
OTHER RISKS
28 Refrigeration systems daily have associated risks which may crave attention, These include the liability of trapping in impersonal stores and chills, the conduct of very cold products and microbiological problems corporate with cooling towers used for the condenser.
ENFORCEMENT APPROACH
29 Imposition officers should advise a well known ammonia refrigeration plant should adapt with the guidance in BS 4434: 1980 as amended and positive by the information in that circular. They should ever bear in mind:
(1) ammonia presents a toxic liability at concentrations far below those at which it presents exclusive fire or explosion risk. Near have been 2 gassing fatalities between 1977 and 1983 in the UK although only 3 incentive ammonia/air explosions in the basement 20 years;
(2) the potential consequences of an event in terms of defect to personnel, and the present public should be assessed;
(3) BS4434 was leading published in 1969 and was not intended to be retrospective, although improvements in installations which pre-date the usual should be recommended, locus reasonably practicable;
(4) analysis of the l983 visits actively suggest that where reliant conditions of the plant are found there is constantly inadequate attention to evacuation and emergency action; and
(5) location enforcement officers encounter preservation contractors they should cause enquiries about their working practices and training.
Further advice
30 A well known is a complicated industrialized subject and there are athletic trade pressure groups. Imposition officers are recommended to go after the advice of HSEs Area Consultant Group (FCG) via the Domestic Enforcement Liaison Officer (ELO), ahead considering enforcement action.
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Ammonia is recycled as a refrigerant as of particular thermodynamic properties which enable it to move heat far more efficiently than further refrigerant gases such as halogenated hydrocarbons. It is chiefly suited to working in the operation approximately OoC to -30oC and so is widely used since food preservation, the chilling of liquids alike as milk, beer and quiet drinks, and in the synthetic industry. New systems endure to be installed.
2. A usual system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In culture 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 flat pressure, and hence low temperature, takes in melt by vaporising. This vapour is removed by the compressor which, in compressing it, raises the altitude from below to over ambient. The hot compressed electricity gives up the simmer by condensing to a liquid in the condenser. The above 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 down-to-earth system it is fair there will be further items of plant. An shortening 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. Ready may be a multi-stage compressor alongside an intercooler. This is cooled by aching high pressure liquid into the horizontal pressure side.
Downstream of the condenser is generally a liquid receiver. Later of the reducing valve is everyday found a surge barrel which acts as a basin of cold liquid and evens down demand on the compressor and condenser. The liquid ammonia is drawn from the current drum by a pump. Margarine drains may be do on surge drums, liquid receivers, and overseas on large plants. Ready is also likely to be an ascetic control system on anyone but the oldest and smallest plants.
A classic practical refrigeration system
1 The contemplate was to collect consultation about a cross bar of installations. One hundred and forty eight returns were worn in the analysis which worn the Edinburgh FCG microcomputer.
2 Returns covered a accessible range of processes in the cooking and drinks industries. The better single sector was dairying (chilled h2o supply) with substantial returns likewise from frozen food producers and analytic stores. In the drinks sector cooling and soft drinks carbonators were the leading uses.
There were a accessible range of other uses reported; around parts of the bread 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 above 5 tonnes, 40% between 1 and 5 tonnes, 35% 'tween 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest fundamental reported was pre-war and ready was a fairly constant spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a nonpartisan compressor room. Forty-nine chunk had the system charging extent in the compressor gallery 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 increased compressor rooms did not admit self-closing doors and 17% did not accept well-fitting doors. With compressors in a autonomous room this is a particularly large number where even the most rudimentary precautions to prevent the spread of escaping fuel has not been taken. Fifty-five per cent had condensers mounted above ground level outside - regularly on the roof. This raises questions of safe access and also avoid in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were consistently 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 employment of leakage, particularly if it is in the workroom.
5 Solo 3% of installations were identified as having pipework or deposit capable of being damaged by, as example, fork lift trucks. Half of the entire poll however had unmarked pipework. (Notes of many proformas suggested that that would receive early attention).
6 lt proved futile to carryout meaningful reasoning of the ventilation provided in compressor rooms. A moderate installation seemed to bank largely on natural ventilation (perhaps assisted by a small fan) for normal ventilation. Point there was provision of ventilation notably for emergencies, it tended to be a self-reliant system rather than a 2 agility fan on the frequent ventilating system. Only 23% of the installations had 2 ventilation rates available and only half the ventilation systems of any kind could be mathematical from outside the compressor room. Solo half of these ventilation systems were necessarily controlled.
7 Only 16% of everyone system charging was done by a person on his own; the typical arrangement was 2 men. Oil draining was done by anyone man on his allow at 30% of anyone Installations. At 51 % of anyone installations it was carried aside more than once a month. Solo 26% of installations had spring-loaded valves or a catchpot development at oil drains. Almost of the rest had comparatively a short stub of cylinder from a vessel containing liquid ammonia still by a single valve. In 71 % of cases where the oil drain was unsatisfactory inspectors expressed that the reasonably practicable alteration was the fitting of self-closing valves. The 30% of installations location one man did the shortening draining on his grant included 6 which had no respirator of any kind.
8 Forty-two per cent of compressor houses had no electricity detectors. Sieger was by deep the most common supplier (60%) of anyone detection systems. The almost common service period of twice per year reflects a certain company's normal service contract. Nineteen per cent of detector systems were don't hold your breath checked.
Approximately half of the detector installations solo had one operating level. Twenty-seven per cent of systems did not lock down the plant however merely raised the alarm. Ten per cent of the systems had no nonpartisan alarm.
9 Sixty-six percent of compressor foyer electrical installations were not altogether equipped to Zone 2 typical even where much of the entomb was under the agency of detectors. Seventy-five per cent of everybody compressor installations could be switched aside elsewhere outside the compressor hall (even if only at the elemental supply). Of the remainder, the essential switchgear was either in the compressor foyer or access to it was buttoned up the compressor room.
10 Eighty-eight fee of all sites had 2 or further sets of respiratory protection of some kind. Six installations (4%) had no one at all. At 83% of sites attendant was said to be some array of training in the commitment of respiratory protection nonetheless only 43% had some array of systematic examination. At alone 5 installations (3.4%) were ready possible limitations of area which conflicted with arrangement of respiratory protection and the elemental problem seemed to be approach up ladders or alive congested items of plant.
11 Forty-seven per cent of sites had reviving appliance available usually for ongoing first aid rather than exclusively because of the ammonia.
12 Twenty-seven bonus of sites had Draeger (or similar) detector tubes as measuring low concentrations of ammonia. Alive with others had sulphur sticks or hydrochloric biting for detecting small leaks.
13 Fifty-nine fee of installations were maintained at least partly by contractors. Afar from a few essential suppliers and installers of appliance there were many civilian refrigeration engineers who alone appeared once or twice in the survey. No aid is available about the usual of training or workmanship of these contractors.
14 Fifty-five percentage of all sites appeared to conclude emergency evacuation procedures (43% recycled the fire alarm) still slightly fewer (50%) appeared to give any training in these procedures. Alone 24% appeared to accept detailed rescue arrangements. Twenty-two per cent had written systems of employment which appeared comprehensive and alone 34% had what appeared to be active 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 entomb sited in out aperture locations in accordance along para 14 of that Circular in otherwise non-hazardous areas firmness not normally require chiefly protected electrical equipment.
INTERNALLY SITED PLANT
2 A leakage chart of the basic requirements relating to the magnetic apparatus for internally sited plant is given in the supplement to that appendix. The operational approaches are given below.
Option 1 - Need of explosion protected electric apparatus
3 Hazardous area grade should be carried alone by a competent person. Ac apparatus should then be exclusive in accordance with BS 5345: Design 1: 1976 Section 2. The mass of compressor-houses should be regarded as Sector 2 areas. Type "N" bang protected equipment (including each emergency ventilation fans) resolve be suitable for these locations.
Option 2 - Detection of leaks by personnel or gas detectors
4 ln a particular approach, non-explosion protected electric apparatus, with qualifications, may be hand-me-down in combination with a readily accessible means of isolating the heat supply. The method of achieving the latter can be accomplished either naturally after detection of a flow by a gas detector system, or manually subsequently a leakage has been detected by personnel. The need of these techniques as a forward line of defence is partly to applications solely involving ammonia in refrigeration plants. A well known approach is considered acceptable provided that the ongoing principles outlined in paras 10-17 are followed and that sufficient account is taken of paras 5-9.
Gas detectors
5 The detectors should be suitably positioned taking into history the physical characteristics of the plant room, the pattern of airflow force in it and the approximately likely sources of potential leakage. Due regard should be paid to all dead pockets or recesses. Exploit has shown that, in physical circumstances, it is probable for cold ammonia vapour to stratify initially at horizontal levels. Unless the occupier has adequate expertise within his grant organisation, it would be advisable after all him to consult a corporation which specialises in the balance and installation of fuel detection systems.
6 As a choppy guide only, one valor expect to see detectors in the vicinity of the compressors and increased non-static items of entomb and at ceiling category where one detector per 36M2 of ceiling area would probably be sufficient, albeit more may be basic if there are expansive beams creating recesses. The objective is to ensure that the ammonia is detected and the device rendered safe before flammable concentrations enter a source of ignition. (This objective, which is again applicable to "detection" of a leak by personnel, is frequently critical with regard to electric apparatus which is not especially designed to be non-sparking, non explosion-protected electric apparatus and electrical appliance with temperatures above 630'C).
7 The detectors should be suitably boom protected.
8 The detectors recycled are of the "pellistor" category and may be subject to poisoning by airborne contaminants. They should accordingly be properly installed and maintained and constantly checked. The operation of the detectors should be limited using standard ammonia food mixtures. Certain V-belt dressings containing antimony admit been shown to cure detectors and gradually reduce their response.
9 The detectors should be apt of detecting concentrations of ammonia at 1 % v/v or less.
Associated ac apparatus
10 Account should be taken of the electrical control system circuitry and the intense possible degree of drop to safety should be achieved, so deep-seated as is reasonably practicable. Ongoing guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Block 6.
11 The isolating device(s), whether manually or naturally operated, which cuts absent the electricity supply to the ammonia bury room, should be located in a non-hazardous area. It bottle be either a producer or circuit breaker. If the criteria in paras 5-9 above have been satisfied, the behind recommendations in paras 13-17 should be adopted. (Although actual specific details have been taken from BS 4434:1980, by approach of example, they are intended to describe the general principles of a particular approach and not definite requirements -which will have, to be desperate in each particular case).
12 Attention will need to be paid to the agency of other circuits which concede the plant room and are not presently associated with the plant, eg socket outlets as 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 scientific by push buttons immediately outside the plant room, or experimental by a gas discovery system as described pare 14, and arranged to confer visual and audible alarms to about-face on equipment for danger ventilation and/or emergency lighting (if installed). All electrical apparatus that is required to engage in the room subsequently a leakage has been detected, aforesaid as ventilation equipment and danger lighting, should be suitably intact for the hazardous range in which it is sited, ie District 2. Few compressor rooms are gradually manned. Detection of leakage by operators is unattended reliable if they are continuously present in the room. If by reason of example they have additional duties, or leave the range for meals etc, or obligation an isolated noise refuge earlier the speed of feeling is likely to be actually slower than that of autogenous detectors.
Unmanned plant rooms
14 lsolation of everybody electrical circuits should be effected by isolating devices located in a non-hazardous range and controlled by anyone or more suitable ammonia food detectors which should also be arranged to according a visual and distinct alarm and to switch on equipment for ventilation and/or crisis lighting, if installed. The ventilation attitude should be discharged to the elsewhere of the building in such a manner as not to matter distress or danger to persons in the vicinity of the building. Ring isolation should be effected at ammonia concentrations below 25% LEL and an buzz setting of 1.5% v/v followed by ring isolation at 3% v/v is suggested.
15 Maintenance personnel are required to concede unmanned plant rooms and adequate means of escape should be provided.
16 Human protection including breathing apparatus, and allegedly impervious suits, may be needed in exclusive room or space if maintenance men are likely to consume pipework or do each other operation liable to disclose liquid ammonia or physical quantities of gas. 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 18130 18131 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