AMMONIA COMPRESSORS AND REFRIGERATION Plant From Langsa

by JABS newsindo-27 June 21, 2023

INTRODUCTION

1 A certain circular gives advice on the precautions to be taken against the toxic, fire and barrage hazards presented by refrigeration systems containing ammonia. These are about likely to be create by LA enforcement officers at impersonal stores and food delivery warehouses. It applies to the full system not simply the compressor house. It provides limited advice on matters of angst to enforcement officers pending analysis of BS 4434:1980.

2 Appendix 1 outlines the ongoing principles of refrigeration, Appendix 2 gives advice 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 correct guidance on electrical standards. Imposition officers should not overemphasise the hazards of ammonia compared alongside other refrigerants.

HAZARDS

Toxicity

3 Ammonia is a chemically reactive food that is very soluble in rain and is much lighter than attitude (vapour density 0.59 of a well known of air). Cold vapour (e.g. from leaks) may anyhow be denser than air. Despite there have been incidents of exposure to harmful concentrations of ammonia in the UK near have been few critical accidents. Ammonia is characterised by a simple pungent odour and is visible by most people at levels of approximately 50 ppm in the atmosphere. Albeit workers become tolerant to a particular effect and in the history have been able to field without distress at levels up to 70 ppm, currently the recommended exposure diameter for ammonia is 25 ppm, 8 hour TWA (0.0025%) and the annoyed term exposure limit is 35 ppm, 10 dwarf TWA. At 400 ppm, about people experience immediate adenoids and throat irritation, nonetheless suffer no permanent ill-effects afterwards 30-60 minute exposure. A category of 700 ppm causes immediate irritation to the eyes, and a grade of 1,700 ppm (0.17%) boldness give rise to standing coughing and can be alarming after about 30 minutes exposure.

Exposure to concentrations superior 5,000 ppm (0.5%) as quite short periods bottle result in death. Impression to the effects of ammonia varies widely amid individuals, and the dose-response effects described over are likely to be those expert by the more open members of the population.

Fire and explosion

4 Ammonia forms a flammable concoction with air at concentrations betwixt 16 and 25% v/v. Near 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 along 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 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 allow ammonia concentrations at constant a fraction of the flammable limit. The appropriate precautions are mainly those applicable against toxic effects in occupied areas and to trade where sudden exposures are foreseeable, alike as maintenance and strength work, including in concrete filling and oil draining. Precautions adjacent fire and explosion firmness be appropriate however, in unoccupied areas aforesaid as compressor houses and solo plant such as clinical stores where accumulations of vapour may go unnoticed.

PRECAUTIONS Adjacent TOXIC RISK

Respiratory protective equipment

7 Each person entering an range in which ammonia vapour is likely to be present at a extraordinary level (eg for recover or fault-finding purposes) requisite wear self-contained or airline breathing apparatus. This does not add routine visits to bury rooms etc. A ample and properly maintained team should be conveniently sited convenient to, but outside, any area in which above levels of .ammonia vapour efficacy arise. In no conclusion should anyone enter an field where a flammable consolidation of gas may be present. Charge of suitable apparatus are contained in Form 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 must be worn by every customer carrying out engineering maintenance work on any development where there is a exposure of release of ammonia. Infinite face canister respirators amidst type A (blue) canisters give good protection in atmospheres up to 2% consolidation or 20,000 ppm, as one hour. Work in alike a concentration is likely to lead to ache quickly due to fur irritation as ammonia dissolves in perspiration. A list of suitable apparatus is given in form 2502 "Certificate of Consent (Canister Gas Respirators)". By reason of substantial jobs impervious suits may be essential if the gas cannot be cleared.

9 Anyone who is likely to need to use respiratory protective accessory must be properly veteran in its use and prerequisite be fully aware of its limitations. The appliance must be maintained, kept clear and examined at bottom once a month. Apt records should be kept. If canister respirators are worn there must be an alive system for deciding at the canisters should be renewed.

Evacuation and danger procedures

10 lt is basic that a clear emergency procedure is drawn up which charge the precise duties of anyone staff and the arrangements as evacuation, rescue, first aid, plant isolation etc. It is chiefly important that evacuation procedures are apparently set out and always practised where refrigeration systems are in working areas. A common development which may be ample is to use the fire alarm provided that actuating points are directly available at working areas. Cadre should be warned not to access any vapour clouds. (Clouds may daily look like steam as long as of the cooling of the released gas).

11 Apt exits should be maintained from plant rooms at, all times. Cadre seriously affected by an ammonia avoid suffer streaming eyes and cruel coughing and rapidly develop into disorientated. They therefore desire clear prior knowledge of a protected exit route.

Training in entomb operation and maintenance

12 Anybody personnel involved in the activity and maintenance of the deposit must be adequately trained. The training should cover not unattended general principles of refrigeration although also specific points related to the particular plant. A well known applies as much to preservation contractors as to an employer's avow staff.

PLANT LOCATION

Plant not designed after all outdoor location

13 In the event of standard refrigeration bury (ie plant not exclusively designed for outdoor location) crisis to excessively low aspect temperatures may cause liquefaction of ammonia in reach the compressor leading to compressor damage, which could be hazardous. A particular 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, location reasonably practicable, be fitted alongside explosion relief (eg by using nothing fragile roof). Where loosely held panels are recycled as explosion relief, they should be suitably mum (eg by chains) to avoid them becoming dangerous missiles in the affair of an explosion.

14 ln law to facilitate the provision of ventilation and bang relief, compressor-houses should blend at least one foreign wall. The siting of compressors in sick areas, basements, etc should be avoided anywhere practicable. Doors between bury rooms or compressor-houses and increased parts of the home should be self-closing and well-fitting.

Plant designed as outdoor location

15 Only bury specifically designed for the climate should be installed outdoors. Aforesaid installations should be sited in a intact position in the bare air with, if necessary, weather protection using a Dutch parking lot type structure which has an evenly distributed least open area equivalent to at first 50% of the budget wall area.

Plant in workrooms

16 As a current principle the amount of bury containing ammonia situated in workrooms and increased populated areas should be minimised. Extra plant such as flood drums and liquid pumps should anywhere possible be sited abroad from working areas. Compressors are day-to-day noisy and this is alternative reason for not having diehards in working areas.

Ventilation

17 Compress or houses should be provided alongside adequate and suitable ventilation to encounter the following requirements:

(1) Frequent Ventilation Sufficient permanent ventilation should be provided to bar 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 modern car ventilation rather than bank on rather uncertain brute ventilation.

(2) Emergency ventilation Plan should be made after all sufficient mechanical ventilation to avert flammable ammonia/air mixtures developing 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 since a particular installation firmness depend on the type, capacity, effective conditions and location of the plant and may require creature assessment by a ventilation creator 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 danger ventilation. Mechanical ventilation initiated by fuel detectors or manually (in the case of continuously manned plants) may likewise be used for danger ventilation (see para 26); and Appendix 3 since electrical safety of the system;

(2) the ventilation should emission to a safe job in the open air;

(3) in as the ventilation to be provided, the likely effects of cold on deposit should be taken into history (see para 12);

(4) flood of air through cracks conscious windows, doors etc, or the entrance of windows or doors should not be relied on as ventilation;

(5) the formulae in BS4434 by reason of quantifying ventilation requirements are rules of ring finger based on unstated assumptions (eg they get no account of entrance size or leak rates). Inspectors should caution that the formulae may be recycled as a basic accompany but discretion in their careful application to a concrete plant should be stressed. A well known is particularly important amidst very large systems at the ventilation required by the formulae becomes impracticable; and

(6) it should be dominant that the standard of ventilation given by the formulae in BS 4434: 1980 is not intended to force with prolonged releases from central plant failure. However, the recent is very unlikely to exist in properly designed, constructed and maintained plant. Agency of sources of ignition and plant shutdown (see paras 22-26) should again provide protection in aforesaid circumstances. Manually operated controls since emergency ventilation should be located in a safe, definitely accessible place along along the control or about-face for turning off the compressor.

Plant integrity

19 Attendant can be serious corrosion of the empty pressure. parts of pipework and plant due to condensation. It container progress unnoticed under lagging which is not completely vapour sealed and is mostly rapid on plants which ride intermittently and pass-through OoC. The ongoing principles relating to the preservation of pressure systems are appropriate. The construction should be thoroughly examined by a adept person at regular intervals in accordance along a written scheme. Attendant should be an effective maintenance scheme.

Pipework

20 All parts of refrigerating systems and in concrete pipework should be positioned or secure to minimise the liability of impact damage, after all example by fork lift trucks. Pipework and valves should be clearly marked to indicate their contents and function.

Oil devour system

21 Many of the reported incidents involving ammonia refrigeration systems accept been the result of a malfunction of the oil drain system (designed to attend the "carry-over" of oil from the compressors). In approximately cases oil is tired from below liquid ammonia and is saturated alongside it. In addition the butter is viscous because it is cold. In direction to minimise the hazard of escape from a certain cause the following measures should be advised:

(1) where short distances are interested and adequate observation of the devour is possible oil deplete pipes should terminate in a protected location in the disclose air. Valves on any pipe extension should not enter the possibility of liquid ammonia as a result of trapped; a bleed valve or hydrostatic relief valve venting to a safe place should be provided in the sections betwixt valves, as appropriate;

(2) a coupled valve arrangement should be provided at butter drains. In addition to the operational brochure valve, there should be an autogenous closing spring or weight-loaded valve; and

(3) The obligation of oil drain catchpots. These are a advantageous feature on new plant, still existing plant cannot customarily be easily modified. Before the oil is drained, the catchpot is distant from the liquid ammonia/oil feedline and the catchpot is electrically bitter to boil off exclusive ammonia which flows as a vapour to the low pressure side of the system. At the catchpot is warm, it is further isolated on the vapour leaf and the oil is once drained from it.

Ammonia filling point

22 Ammonia filling points should be located in safe, accurately ventilated positions and, location reasonably practicable, in the bring to light air. Filling points should be sited elsewhere from sources of ignition.

PRECAUTIONS Against 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 Consultation on electrical apparatus after all use in potentially bomb atmospheres is given in RS 5345: Element 1: 1976 "Code of Culture for the Selection, Airfield and Maintenance of Magnetic Apparatus for Use in Potentially Mine Atmospheres, Part 1, Basic Requirements for all Parts of the Code"; BS 4434: 1980, Passage 13 "Electrical Installations". The approaches followed by the above documents differ.

25 As a modern principle, electrical equipment should be sited elsewhere the compressor room in a intact location. However, when it is necessarily sited in the room, it should be in accordance amidst the guidance given in para 27.

26 Locus the ammonia compressors and refrigeration entomb are located in the xerox room as the foundation switch gear for the-premises relocation would probably be inconvenient and costly. In such cases, Field Consultant Grade (FCG) advise on the around suitable safety precautions in the detailed case should be sought.

Electrical device selection criteria

27 The obligation of electrical apparatus in refrigeration plants using ammonia has been express a special case as long as of the flammability characteristics of the electricity (high LEL and narrow explosive range) and the design that it can be detected at literally low levels by smell. A certain has resulted in a address of options which may be explicit when selecting electrical accessory for ammonia plants and these are clear in Appendix 3.

OTHER RISKS

28 Refrigeration systems constantly have associated risks which may crave attention, These include the hazard of trapping in impersonal stores and chills, the handling of very cold products and microbiological problems joint with cooling towers worn for the condenser.

ENFORCEMENT APPROACH

29 Administration officers should advise a certain ammonia refrigeration plant should accommodate with the guidance in BS 4434: 1980 as amended and additional by the information in a certain circular. They should once bear in mind:

(1) ammonia presents a toxic liability at concentrations far below those at which it presents exclusive fire or explosion risk. Attendant have been 2 gassing fatalities betwixt 1977 and 1983 in the UK still only 3 incentive ammonia/air explosions in the basement 20 years;

(2) the hidden consequences of an employment in terms of ailment to personnel, and the ongoing public should be assessed;

(3) BS4434 was forward published in 1969 and was not intended to be retrospective, although improvements in installations which pre-date the typical should be recommended, where reasonably practicable;

(4) analysis of the l983 visits energetically suggest that where defenseless conditions of the entomb are found there is daily inadequate attention to evacuation and emergency action; and

(5) locus enforcement officers encounter preservation contractors they should achieve enquiries about their unavailable practices and training.

Further advice

30 That is a complicated modern subject and there are active trade pressure groups. Enforcement officers are recommended to pursue the advice of HSEs Range 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 facilitate it to move bake far more efficiently than increased refrigerant gases such as halogenated hydrocarbons. It is chiefly suited to working in the operation approximately OoC to -30oC and accordingly is widely used by reason of food preservation, the chilling of liquids alike as milk, beer and muted drinks, and in the alchemical industry. New systems continue to be installed.

2. A classic system theoretically needs 4 components:

(1) evaporator;

(2) compressor;

(3) condenser; and

(4) reducing valve

In culture other components such as butter 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 low temperature, takes in heat by vaporising. This vapour is removed by the compressor which, in compressing it, raises the humidity from below to over ambient. The hot compressed fuel gives up the heat by condensing to a liquid in the condenser. The above pressure liquid then passes over the pressure reducing valve to the evaporator. At the valve the liquid is cooled as some vapour flashes off. The resting liquid is available after all use in the evaporator.

4 In a constructive system it is likely there will be further items of plant. An oil separator removes suspended margarine carried over from the compressor and either returns it to the (pressurised) crank-case or holds it after all draining in some way. Ready may be a multi-stage compressor with an intercooler. This is cooled by hurt high pressure liquid into the low pressure side.

Downstream of the condenser is relatively a liquid receiver. Ensuing of the reducing valve is everyday found a surge cylinder which acts as a lagoon of cold liquid and evens away demand on the compressor and condenser. The liquid ammonia is drawn from the flood drum by a pump. Oil drains may be do on surge drums, liquid receivers, and away on large plants. Attendant is also likely to be an ascetic control system on anybody 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 recycled in the analysis which recycled the Edinburgh FCG microcomputer.

2 Returns covered a clear range of processes in the cooking and drinks industries. The most single sector was dairying (chilled h2o supply) with substantial returns likewise from frozen food producers and clinical stores. In the drinks region cooling and soft drinks carbonators were the main uses.

There were a open range of other uses reported; around parts of the cuisine industry require controlled temperatures below ambient at some design of their process. A free range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were high 5 tonnes, 40% 'tween 1 and 5 tonnes, 35% amid 100kg and 1 tonne and 12% 1 00 kg or below.

The oldest fundamental reported was pre-war and near was a fairly constant spread of age from 1960 to the present.

3 Eighty-nine per cent of installations had a autonomous compressor room. Forty-nine chunk had the system charging grade in the compressor foyer and 38% had it outdoors. Twenty-seven per cent of the case could positively be identified as having doors to the abroad of the building only. Thirty-six per cent of the additional compressor rooms did not believe self-closing doors and 17% did not believe well-fitting doors. With compressors in a autonomous room this is a notably large number where balanced the most rudimentary precautions to avert the spread of escaping electricity has not been taken. Fifty-five per cent had condensers mounted high ground level outside - commonly on the roof. This raises questions of safe access and also dodge 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 muted drinks plants). This points to the guarantee for effective emergency procedures in the event of leakage, particularly if it is in the workroom.

5 Only 3% of installations were identified as having pipework or plant capable of being damaged by, since example, fork lift trucks. Limited of the entire ballot however had unmarked pipework. (Notes of bounteous proformas suggested that a particular would receive early attention).

6 lt proved impossible to carryout meaningful reasoning of the ventilation provided in compressor rooms. A average installation seemed to rely largely on natural ventilation (perhaps assisted by a meager fan) for normal ventilation. Point there was provision of ventilation exclusively for emergencies, it tended to be a self-reliant system rather than a 2 agility fan on the commonplace ventilating system. Only 23% of the installations had 2 ventilation rates convenient and only half the ventilation systems of exclusive kind could be objective from outside the compressor room. Alone half of these ventilation systems were automatically controlled.

7 Only 16% of anybody system charging was done by a character on his own; the classic arrangement was 2 men. Margarine draining was done by anyone man on his allow at 30% of anybody Installations. At 51 % of everyone installations it was carried away more than once a month. Only 26% of installations had spring-loaded valves or a catchpot plan at oil drains. Approximately of the rest had comparatively a short stub of drum from a vessel containing liquid ammonia closed by a single valve. In 71 % of cases point the oil drain was unsatisfactory inspectors clear that the reasonably practicable alteration was the fitting of self-closing valves. The 30% of installations location one man did the margarine draining on his avow included 6 which had no respirator of all kind.

8 Forty-two per cent of compressor houses had no ammunition detectors. Sieger was by deep-seated the most common supplier (60%) of everybody detection systems. The approximately common service period of twice per year reflects a certain company's normal service contract. Nineteen per cent of detector systems were never checked.

Approximately half of the detector installations unattended had one operating level. Twenty-seven per cent of systems did not shut down the plant however merely raised the alarm. Ten per cent of the systems had no self-reliant alarm.

9 Sixty-six percent of compressor foyer electrical installations were not comprehensively equipped to Zone 2 typical even where much of the deposit was under the authority of detectors. Seventy-five per cent of everyone compressor installations could be switched absent elsewhere outside the compressor foyer (even if only at the basic supply). Of the remainder, the basic switchgear was either in the compressor foyer or access to it was buttoned up the compressor room.

10 Eighty-eight percentage of all sites had 2 or also sets of respiratory protection of some kind. Six installations (4%) had none at all. At 83% of sites attendant was said to be some character of training in the need of respiratory protection still only 43% had some array of systematic examination. At solo 5 installations (3.4%) were attendant possible limitations of range which conflicted with provision of respiratory protection and the elemental problem seemed to be connection up ladders or awake congested items of plant.

11 Forty-seven per cent of sites had reviving apparatus available usually for present first aid rather than especially 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 chunk of installations were maintained at bottom partly by contractors. Alone from a few main suppliers and installers of device there were many domestic refrigeration engineers who solo appeared once or twice in the survey. No aid is available about the usual of training or workmanship of these contractors.

14 Fifty-five fee of all sites appeared to admit emergency evacuation procedures (43% worn the fire alarm) still slightly fewer (50%) appeared to confer any training in these procedures. Only 24% appeared to conclude detailed rescue arrangements. Twenty-two per cent had written systems of business which appeared comprehensive and alone 34% had what appeared to be operating plant operator training.

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APPENDIX 3 (paras 1 and 26)

PROTECTION OF Magnetic APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT

EXTERNALLY SITED PLANT

1 Compressors and refrigeration plant sited in out exit locations in accordance alongside para 14 of a certain Circular in otherwise non-hazardous areas boldness not normally require especially protected electrical equipment.

INTERNALLY SITED PLANT

2 A flow chart of the key requirements relating to the electric apparatus for internally sited plant is given in the supplement to a well known appendix. The operational approaches are disposed below.

Option 1 - Need of explosion protected electric apparatus

3 Hazardous area category should be carried away by a competent person. Electrical apparatus should then be eclectic in accordance with BS 5345: Element 1: 1976 Section 2. The max of compressor-houses should be regarded as Part 2 areas. Type "N" bang protected equipment (including any emergency ventilation fans) resolve be suitable for these locations.

Option 2 - Detection of leaks by crew or gas detectors

4 ln that approach, non-explosion protected ac apparatus, with qualifications, may be recycled in combination with a readily convenient means of isolating the electricity supply. The method of achieving the closing can be accomplished either no doubt after detection of a flow by a gas detector system, or manually afterwards a leakage has been detected by personnel. The need of these techniques as a forward line of defence is limited to applications solely involving ammonia in refrigeration plants. A well known approach is considered competent provided that the modern 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 account the physical characteristics of the plant room, the pattern of airflow force in it and the approximately likely sources of hidden leakage. Due regard should be paid to all dead pockets or recesses. Experience has shown that, in definite circumstances, it is probable for cold ammonia vapour to stratify initially at horizontal levels. Unless the occupier has able expertise within his avow organisation, it would be advisable since him to consult a employer which specialises in the beauty and installation of electricity detection systems.

6 As a choppy guide only, one potency expect to see detectors in the vicinity of the compressors and increased non-static items of deposit and at ceiling category where one detector per 36M2 of ceiling area would probably be sufficient, despite more may be basic if there are extensive beams creating recesses. The objective is to ensure a particular the ammonia is detected and the device rendered safe before flammable concentrations arrive a source of ignition. (This objective, which is further applicable to "detection" of a leak by personnel, is essentially critical with regard to electric apparatus which is not chiefly designed to be non-sparking, non explosion-protected electrical apparatus and electrical accessory with temperatures above 630'C).

7 The detectors should be suitably barrage protected.

8 The detectors used are of the "pellistor" type and may be subject to poisoning by airborne contaminants. They should then be properly installed and maintained and consistently checked. The operation of the detectors should be narrow using standard ammonia ammunition mixtures. Certain V-belt dressings containing antimony accept been shown to medicine detectors and gradually reduce their response.

9 The detectors should be able of detecting concentrations of ammonia at 1 % v/v or less.

Associated electric apparatus

10 Account should be taken of the electrical control system circuitry and the severe possible degree of decline to safety should be achieved, so deep as is reasonably practicable. Current guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Block 6.

11 The isolating device(s), whether manually or naturally operated, which cuts aside the electricity supply to the ammonia plant room, should be located in a non-hazardous area. It bowl be either a maker 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 way of example, they are intended to identify the general principles of a well known approach and not noticeable requirements -which will have, to be dangerous in each particular case).

12 Debate will need to be paid to the control 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 Privacy of all electrical circuits should be effected by isolating devices located in a non-hazardous area. These devices should be scientific by push buttons forthwith outside the plant room, or objective by a gas analysis 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 engage in the room afterwards a leakage has been detected, akin as ventilation equipment and emergency lighting, should be suitably safe for the hazardous field in which it is sited, ie Region 2. Few compressor rooms are continuously manned. Detection of leakage by operators is alone reliable if they are gradually present in the room. If as example they have increased duties, or leave the area for meals etc, or commitment an isolated noise refuge before the speed of effect is likely to be substantially slower than that of automatic detectors.

Unmanned plant rooms

14 lsolation of everybody electrical circuits should be effected by isolating devices located in a non-hazardous field and controlled by anybody or more suitable ammonia fuel detectors which should further be arranged to bestow a visual and recognizable alarm and to switch on equipment for ventilation and/or exposure lighting, if installed. The ventilation aspect should be discharged to the abroad of the building in aforesaid a manner as not to matter distress or danger to persons in the vicinity of the building. Band isolation should be effected at ammonia concentrations below 25% LEL and an vesper setting of 1.5% v/v followed by band isolation at 3% v/v is suggested.

15 Maintenance personnel are required to accept unmanned plant rooms and adept means of escape should be provided.

16 Personal protection including breathing apparatus, and apparently impervious suits, may be needed in any room or space if maintenance men are likely to damage pipework or do all other operation liable to call liquid ammonia or actual quantities of gas. 19013 19014 19015 19016 19017 19018 19019 19020 19021 19022 19023 19024 19025 19026 19027 19028 19029 19030 19031 19032 19033 19034 19035 19036 19037 19038 19039 19040 19041 19042 19043 19044 19045 19046 19047 19048 19049 19050 19051 19052 19053 19054 19055 19056 19057 19058 19059 19060 19061 19062 19063 19064 19065 19066 19067 19068 19069 19070 19071 19072 19073 19074 19075 19076 19077 19078 19079 19080 19081 19082 19083 19084 19085 19086 19087 19088 19089 19090 19091 19092 19093 19094 19095 19096 19097 19098 19099 19100 19101 19102 19103 19104 19105 19106 19107 19108 19109 19110 19111 19112 19113 19114 19115 19116 19117 19118 19119 19120 19121 19122 19123 19124 19125 19126 19127 19128 19129 19130 19131 19132 19133 19134 19135 19136 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