AMMONIA COMPRESSORS AND REFRIGERATION Deposit From Serang
INTRODUCTION
1 That circular gives advice on the precautions to be taken con the toxic, fire and bang hazards presented by refrigeration systems containing ammonia. These are approximately likely to be commence by LA enforcement officers at impersonal stores and food distribution warehouses. It applies to the complete system not simply the compressor house. It provides temporary advice on matters of angst to enforcement officers pending review of BS 4434:1980.
2 Appendix 1 outlines the modern principles of refrigeration, Appendix 2 gives advice on the results of the programme of particular visits carried out in 1983 by Factory Inspectorate (F1) to deal with present standards in the cuisine industry and Appendix 3 gives careful guidance on electrical standards. Administration officers should not overemphasise the hazards of ammonia compared with other refrigerants.
HAZARDS
Toxicity
3 Ammonia is a chemically reactive food that is very soluble in h2o and is much lighter than facet (vapour density 0.59 of a particular of air). Cold vapour (e.g. from leaks) may ever be denser than air. Although there have been incidents of danger to harmful concentrations of ammonia in the UK ready have been few bad accidents. Ammonia is characterised by a usual pungent odour and is conspicuous by most people at levels of around 50 ppm in the atmosphere. Albeit workers become tolerant to a well known effect and in the past have been able to field without distress at levels up to 70 ppm, at present the recommended exposure breadth for ammonia is 25 ppm, 8 day TWA (0.0025%) and the caviling term exposure limit is 35 ppm, 10 diminutive TWA. At 400 ppm, approximately people experience immediate snout and throat irritation, however suffer no permanent ill-effects after 30-60 minute exposure. A class of 700 ppm causes prompt irritation to the eyes, and a class of 1,700 ppm (0.17%) resolve give rise to fixed coughing and can be critical after about 30 minutes exposure.
Exposure to concentrations superior 5,000 ppm (0.5%) since quite short periods bowl result in death. Consequence to the effects of ammonia varies widely between 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 mixture with air at concentrations betwixt 16 and 25% v/v. Near have however been indeed few incentive explosions involving ammonia compressor houses in the UK and anybody of the reported incidents engrossed ammonia leakage from bury under maintenance.
Existing guidance
5 Current guidance on the precautions which should be taken with ammonia refrigeration plant may be create in: British Standard 4434: 1980 "Requirements as Refrigeration Safety: Part 1, General". The requirements (particularly from the f ire and boom standpoint) are similar to those in the first (1 969) version. Anyway a' full revision of BS 4434 is taking place.
Precautions
6 Concealed by normal circumstances people courage not be able to allow 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 trade where sudden exposures are foreseeable, akin as maintenance and strength work, including in objective filling and oil draining. Precautions con fire and explosion resolve be appropriate however, in unoccupied areas akin as compressor houses and unattended plant such as impersonal stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Adjacent TOXIC RISK
Respiratory protective equipment
7 Each person entering an operation in which ammonia vapour is expected to be present at a historic level (eg for get back or fault-finding purposes) must wear self-contained or air service breathing apparatus. This does not carry routine visits to deposit rooms etc. A abundant and properly maintained brace should be conveniently sited warm to, but outside, all area in which over levels of .ammonia vapour potency arise. In no circumstances should anyone enter an field where a flammable consolidation of gas may be present. Charge 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 Adequate respiratory protective equipment must be worn by every character carrying out engineering maintenance work on any plan where there is a liability of release of ammonia. Absolute face canister respirators with type A (blue) canisters bestow good protection in atmospheres up to 2% concentration or 20,000 ppm, as one hour. Work in akin a concentration is fair to lead to ache quickly due to coat irritation as ammonia dissolves in perspiration. A list of suitable apparatus is given in form 2502 "Certificate of Consent (Canister Gas Respirators)". After all substantial jobs impervious suits may be key 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 clean and examined at first once a month. Convenient records should be kept. If canister respirators are recycled there must be an effective system for deciding although the canisters should be renewed.
Evacuation and crisis procedures
10 lt is basic that a clear danger procedure is drawn up which terms the precise duties of everyone staff and the arrangements since evacuation, rescue, first aid, plant isolation etc. It is mostly important that evacuation procedures are apparently set out and consistently practised where refrigeration systems are in active areas. A common education which may be adequate is to use the blaze alarm provided that actuating points are forthwith available at working areas. Cadre should be warned not to approach any vapour clouds. (Clouds may daily look like steam as a result of of the cooling of the released gas).
11 Adept exits should be maintained from deposit rooms at, all times. Personnel seriously affected by an ammonia avert suffer streaming eyes and cruel coughing and rapidly become disorientated. They therefore require clear prior knowledge of a intact exit route.
Training in entomb operation and maintenance
12 Everybody personnel involved in the deal and maintenance of the deposit must be adequately trained. The training should cover not only general principles of refrigeration although also specific points like to the particular plant. A well known applies as much to maintenance contractors as to an employer's allow staff.
PLANT LOCATION
Plant not designed as outdoor location
13 In the employment of standard refrigeration bury (ie plant not chiefly designed for outdoor location) crisis to excessively low condition temperatures may cause liquefaction of ammonia within the compressor leading to compressor damage, which could be hazardous. That type of plant should so be sited in a compressor building using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, locus reasonably practicable, be fitted amidst explosion relief (eg by using nobody fragile roof). Where loosely held panels are worn as explosion relief, they should be suitably mum (eg by chains) to avert them becoming dangerous missiles in the affair of an explosion.
14 ln direction to facilitate the plan of ventilation and explosion relief, compressor-houses should couple at least one alien wall. The siting of compressors in confined areas, basements, etc should be avoided anywhere practicable. Doors between deposit rooms or compressor-houses and increased parts of the building should be self-closing and well-fitting.
Plant designed after all outdoor location
15 Only deposit specifically designed for the altitude should be installed outdoors. Such installations should be sited in a secure position in the expose air with, if necessary, weather protection using a Dutch parking lot type structure which has an evenly distributed least open area equivalent to at least 50% of the budget wall area.
Plant in workrooms
16 As a ongoing principle the amount of plant containing ammonia situated in workrooms and further 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 everyday noisy and this is different reason for not having conservatives in working areas.
Ventilation
17 Compress or houses should be provided along adequate and suitable ventilation to confront the following requirements:
(1) Frequent Ventilation Sufficient permanent ventilation should be provided to bar build up of toxic concentrations of ammonia from operational flow (eg from seals, glands etc). It is supposed that the redrafted British Simple will insist on modern car ventilation rather than bet on rather uncertain animal ventilation.
(2) Emergency ventilation Accouterment should be made as sufficient mechanical ventilation to avoid flammable ammonia/air mixtures growing in the event of kind of foreseeable plant or operational drop (eg valve failure). In alike circumstances the aim should be to control concentrations below 25% of the inferior explosive limit (ie 4%).
18 The ventilation requirements since a particular installation resolve depend on the type, capacity, effective conditions and location of the bury and may require creature assessment by a ventilation builder with appropriate expertise. However, the final general points apply:
(1) long-lasting natural or mechanical ventilation, or a alliance of both, may be used for normal or crisis ventilation. Mechanical ventilation initiated by fuel detectors or manually (in the case of continuously manned plants) may further be used for crisis ventilation (see para 26); and Appendix 3 since electrical safety of the system;
(2) the ventilation should discharge to a safe office in the open air;
(3) in after all the ventilation to be provided, the likely effects of cold on deposit should be taken into explanation (see para 12);
(4) flood of air through cracks awake windows, doors etc, or the opening of windows or doors should not be relied on since ventilation;
(5) the formulae in BS4434 since quantifying ventilation requirements are rules of finger based on unstated assumptions (eg they take no account of entrance size or leak rates). Inspectors should caution that the formulae may be used as a basic accompany but discretion in their authentic application to a concrete plant should be stressed. A particular 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 activity with prolonged releases from main plant failure. However, the closing is very unlikely to endure in properly designed, constructed and maintained plant. Agency of sources of ignition and bury shutdown (see paras 22-26) should further provide protection in alike circumstances. Manually operated controls since emergency ventilation should be located in a safe, decidedly accessible place along along the control or alteration for turning off the compressor.
Plant integrity
19 Near can be serious corrosion of the empty pressure. parts of pipework and bury due to condensation. It bag progress unnoticed under lagging which is not absolutely vapour sealed and is mostly rapid on plants which drive intermittently and pass-through OoC. The present principles relating to the insurance of pressure systems are appropriate. The manufacture should be thoroughly examined by a apt person at regular intervals in accordance along a written scheme. Attendant should be an active maintenance scheme.
Pipework
20 All parts of refrigerating systems and in objective pipework should be positioned or safe to minimise the disclosure of impact damage, by reason of example by fork lift trucks. Pipework and valves should be apparently marked to indicate their contents and function.
Oil absorb system
21 Many of the reported incidents involving ammonia refrigeration systems believe been the result of a malfunction of the margarine drain system (designed to show up the "carry-over" of butter from the compressors). In around cases oil is distressed from below liquid ammonia and is saturated amidst it. In addition the oil is viscous because it is cold. In command to minimise the liability of escape from a well known cause the following measures should be advised:
(1) point short distances are interested and adequate observation of the deplete is possible oil devour pipes should terminate in a safe location in the bring to light air. Valves on each pipe extension should not concede the possibility of liquid ammonia as a result of trapped; a bleed valve or hydrostatic comfort valve venting to a protected place should be provided in the sections betwixt valves, as appropriate;
(2) a double valve arrangement should be provided at margarine drains. In addition to the operational magazine valve, there should be an self closing spring or weight-loaded valve; and
(3) The need of oil drain catchpots. These are a appropriate feature on new plant, however existing plant cannot broadly be easily modified. Along the oil is drained, the catchpot is distant from the liquid ammonia/oil feedline and the catchpot is electrically annoyed to boil off all ammonia which flows as a vapour to the low pressure side of the system. At the catchpot is warm, it is again isolated on the vapour folio and the oil is already drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, properly ventilated positions and, where reasonably practicable, in the bare 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 since use in potentially mine atmospheres is given in RS 5345: Element 1: 1976 "Code of Education for the Selection, Airfield and Maintenance of Magnetic 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 raised documents differ.
25 As a ongoing principle, electrical equipment should be sited outside 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 entomb are located in the same 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 about suitable safety precautions in the detailed case should be sought.
Electrical apparatus selection criteria
27 The commitment of electrical apparatus in refrigeration plants using ammonia has been explicit a special case as a result of of the flammability characteristics of the fuel (high LEL and narrow explosive range) and the element that it can be detected at literally low levels by smell. A well known has resulted in a zip code of options which may be express when selecting electrical apparatus for ammonia plants and these are expressed in Appendix 3.
OTHER RISKS
28 Refrigeration systems day-to-day have associated risks which may require attention, These include the hazard of trapping in impersonal stores and chills, the management of very cold products and microbiological problems corporate with cooling towers recycled for the condenser.
ENFORCEMENT APPROACH
29 Application officers should advise a particular ammonia refrigeration plant should acclimate 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 exposure at concentrations far below those at which it presents exclusive fire or explosion risk. Near have been 2 gassing fatalities betwixt 1977 and 1983 in the UK however only 3 incentive ammonia/air explosions in the bottom 20 years;
(2) the hidden consequences of an case in terms of disability to personnel, and the present public should be assessed;
(3) BS4434 was advance published in 1969 and was not intended to be retrospective, despite improvements in installations which pre-date the typical should be recommended, where 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 withdrawal and emergency action; and
(5) location enforcement officers encounter maintenance contractors they should generate enquiries about their working practices and training.
Further advice
30 A certain is a complicated industrial subject and there are active trade pressure groups. Imposition officers are recommended to accompany the advice of HSEs Operation Consultant Group (FCG) via the Civil Enforcement Liaison Officer (ELO), ahead considering enforcement action.
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Ammonia is used as a refrigerant as a result of of particular thermodynamic properties which empower it to move melt far more efficiently than additional refrigerant gases such as halogenated hydrocarbons. It is chiefly suited to working in the area approximately OoC to -30oC and therefore is widely used by reason of food preservation, the chilling of liquids aforesaid as milk, beer and quiet drinks, and in the actinic industry. New systems continue to be installed.
2. A simple system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In education other components such as butter separator, intercooler, liquid receiver, stream drum and liquid pumps are daily found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at low pressure, and hence horizontal temperature, takes in simmer by vaporising. This vapour is removed by the compressor which, in compressing it, raises the humidity from below to high ambient. The hot compressed electricity gives up the simmer by condensing to a liquid in the condenser. The over 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 pausing liquid is available since use in the evaporator.
4 In a practical system it is expected there will be increased items of plant. An shortening separator removes suspended shortening carried over from the compressor and either returns it to the (pressurised) crank-case or holds it by reason of draining in some way. Attendant may be a multi-stage compressor with an intercooler. This is cooled by aching high pressure liquid into the empty pressure side.
Downstream of the condenser is generally a liquid receiver. Ensuing of the reducing valve is constantly found a surge drum which acts as a lake of cold liquid and evens down demand on the compressor and condenser. The liquid ammonia is drawn from the flood drum by a pump. Shortening drains may be do on surge drums, liquid receivers, and abroad on large plants. There is also likely to be an autogenous control system on everyone but the oldest and smallest plants.
A typical practical refrigeration system
1 The aim was to collect advice about a cross brick of installations. One hundred and forty eight returns were used in the analysis which worn the Edinburgh FCG microcomputer.
2 Returns covered a free range of processes in the food and drinks industries. The greater single sector was dairying (chilled drink supply) with substantial returns also from frozen food producers and impersonal stores. In the drinks region cooling and soft drinks carbonators were the leading uses.
There were a clear range of other uses reported; about parts of the bread industry require controlled temperatures below ambient at some design of their process. A open range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were over 5 tonnes, 40% amid 1 and 5 tonnes, 35% 'tween 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest composing reported was pre-war and near was a fairly balanced spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a autonomous compressor room. Forty-nine fee had the system charging amount in the compressor hall 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 increased compressor rooms did not accept self-closing doors and 17% did not conclude well-fitting doors. With compressors in a independent room this is a exceptionally large number where balanced the most rudimentary precautions to avert the spread of escaping fuel has not been taken. Fifty-five per cent had condensers mounted high ground level outside - ordinarily on the roof. This raises questions of safe access and also bypass in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were constantly product freezers in the frozen bread sector and carbonators at the quiet drinks plants). This points to the engagement for effective emergency procedures in the employment of leakage, particularly if it is in the workroom.
5 Alone 3% of installations were identified as having pipework or deposit capable of being damaged by, after all example, fork lift trucks. Limited of the entire poll however had unmarked pipework. (Notes of bounteous proformas suggested that a well known would receive early attention).
6 lt proved absurd to carryout meaningful investigation of the ventilation provided in compressor rooms. A moderate installation seemed to rely largely on natural ventilation (perhaps assisted by a limited fan) for normal ventilation. Point there was provision of ventilation chiefly for emergencies, it tended to be a independent system rather than a 2 agility fan on the mundane ventilating system. Only 23% of the installations had 2 ventilation rates available and only half the ventilation systems of all kind could be scientific from outside the compressor room. Alone half of these ventilation systems were no doubt controlled.
7 Only 16% of everyone system charging was done by a person on his own; the simple arrangement was 2 men. Margarine draining was done by all man on his acquiesce at 30% of everyone Installations. At 51 % of anybody installations it was carried alone more than once a month. Only 26% of installations had spring-loaded valves or a catchpot construction at oil drains. About of the rest had barely a short stub of drum from a vessel containing liquid ammonia still by a single valve. In 71 % of cases point the oil drain was unsatisfactory inspectors expressed that the reasonably practicable arrangement was the fitting of self-closing valves. The 30% of installations point one man did the oil draining on his avow included 6 which had no respirator of exclusive kind.
8 Forty-two per cent of compressor houses had no ammunition detectors. Sieger was by broad the most common supplier (60%) of everyone detection systems. The almost common service period of twice per year reflects that company's normal service contract. Nineteen per cent of detector systems were forget it checked.
Approximately half of the detector installations unattended had one operating level. Twenty-seven per cent of systems did not shut down the plant although merely raised the alarm. Ten per cent of the systems had no autonomous alarm.
9 Sixty-six percent of compressor entrance electrical installations were not completely equipped to Zone 2 typical even where much of the bury was under the agency of detectors. Seventy-five per cent of everybody compressor installations could be switched absent elsewhere outside the compressor entrance (even if only at the essential supply). Of the remainder, the essential switchgear was either in the compressor entrance or access to it was buttoned up the compressor room.
10 Eighty-eight chunk of all sites had 2 or again 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 sort of training in the commitment of respiratory protection although only 43% had some array of systematic examination. At only 5 installations (3.4%) were there possible limitations of range which conflicted with accouterment of respiratory protection and the key problem seemed to be connection up ladders or alive congested items of plant.
11 Forty-seven per cent of sites had reviving apparatus available usually for present first aid rather than exclusively because of the ammonia.
12 Twenty-seven percentage of sites had Draeger (or similar) detector tubes after all measuring low concentrations of ammonia. Alive with others had sulphur sticks or hydrochloric acid for detecting small leaks.
13 Fifty-nine percentage of installations were maintained at least partly by contractors. Alone from a few essential suppliers and installers of appliance there were many governmental refrigeration engineers who only appeared once or twice in the survey. No advice is available about the simple of training or workmanship of these contractors.
14 Fifty-five chunk of all sites appeared to admit emergency evacuation procedures (43% hand-me-down the fire alarm) however slightly fewer (50%) appeared to according any training in these procedures. Solo 24% appeared to accept detailed rescue arrangements. Twenty-two per cent had written systems of employment which appeared comprehensive and unattended 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 plant sited in out aperture 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 flood chart of the key requirements relating to the ac apparatus for internally sited plant is given in the supplement to a certain appendix. The operational approaches are given below.
Option 1 - Obligation of explosion protected electrical apparatus
3 Hazardous area classification should be carried aside by a competent person. Magnetic apparatus should then be exclusive in accordance with BS 5345: Design 1: 1976 Section 2. The max of compressor-houses should be regarded as Region 2 areas. Type "N" explosion protected equipment (including exclusive emergency ventilation fans) boldness be suitable for these locations.
Option 2 - Discovery of leaks by personnel or gas detectors
4 ln a certain approach, non-explosion protected electric apparatus, with qualifications, may be worn in combination with a readily accessible means of isolating the electricity supply. The method of achieving the recent can be accomplished either automatically after detection of a flood by a gas detector system, or manually after a leakage has been detected by personnel. The commitment of these techniques as a forward line of defence is partly to applications solely involving ammonia in refrigeration plants. A certain approach is considered competent provided that the modern principles outlined in paras 10-17 are followed and a particular sufficient account is taken of paras 5-9.
Gas detectors
5 The detectors should be suitably positioned taking into detail the physical characteristics of the deposit room, the pattern of airflow action in it and the about likely sources of possible leakage. Due regard should be paid to exclusive dead pockets or recesses. Adventure has shown that, in physical circumstances, it is supposed for cold ammonia vapour to stratify initially at low levels. Unless the occupier has able expertise within his allow organisation, it would be advisable since him to consult a company 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 further non-static items of deposit and at ceiling grade where one detector per 36M2 of beam area would probably be sufficient, despite more may be key if there are extensive beams creating recesses. The detailed is to ensure that the ammonia is detected and the apparatus rendered safe before flammable concentrations appear a source of ignition. (This objective, which is also applicable to "detection" of a leak by personnel, is chiefly critical with regard to magnetic apparatus which is not exclusively designed to be non-sparking, non explosion-protected electric apparatus and electrical device with temperatures above 630'C).
7 The detectors should be suitably explosion protected.
8 The detectors used are of the "pellistor" category and may be subject to poisoning by airborne contaminants. They should accordingly be properly installed and maintained and always checked. The operation of the detectors should be narrow using standard ammonia electricity mixtures. Certain V-belt dressings containing antimony believe been shown to cure detectors and gradually reduce their response.
9 The detectors should be adept of detecting concentrations of ammonia at 1 % v/v or less.
Associated magnetic apparatus
10 Account should be taken of the electric control system circuitry and the acute possible degree of deterioration to safety should be achieved, so deep as is reasonably practicable. Current guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Chunk 6.
11 The isolating device(s), whether manually or naturally operated, which cuts aside the electricity supply to the ammonia entomb room, should be located in a non-hazardous area. It bag be either a contractor or circuit breaker. If the norm in paras 5-9 high 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 path of example, they are intended to describe the general principles of a certain approach and not noticeable requirements -which will have, to be desperate in each particular case).
12 Debate will need to be paid to the authority of other circuits which admit the plant room and are not directly associated with the plant, eg socket outlets by reason of portable tools.
Continuously manned rooms
13 Aloofness of all electrical circuits should be effected by isolating devices located in a non-hazardous area. These devices should be experimental by push buttons immediately outside the plant room, or objective by a gas detection system as described pare 14, and arranged to confer visual and audible alarms to reversal on equipment for exposure ventilation and/or emergency lighting (if installed). Any electrical apparatus that is required to apply in the room after a leakage has been detected, alike as ventilation equipment and danger lighting, should be suitably intact for the hazardous range in which it is sited, ie Part 2. Few compressor rooms are gradually manned. Detection of leakage by operators is solo reliable if they are gradually present in the room. If as example they have further duties, or leave the operation for meals etc, or demand an isolated noise refuge once the speed of effect is likely to be actually slower than that of automatic detectors.
Unmanned plant rooms
14 lsolation of anyone electrical circuits should be effected by isolating devices located in a non-hazardous area and controlled by anybody or more suitable ammonia fuel detectors which should likewise be arranged to according a visual and recognizable alarm and to about-face on equipment for ventilation and/or crisis lighting, if installed. The ventilation facet should be discharged to the elsewhere of the building in alike a manner as not to matter distress or danger to persons in the vicinity of the building. Round isolation should be effected at ammonia concentrations below 25% LEL and an bell setting of 1.5% v/v followed by round isolation at 3% v/v is suggested.
15 Maintenance personnel are required to enter unmanned plant rooms and adept means of escape should be provided.
16 Human protection including breathing apparatus, and ostensibly impervious suits, may be needed in all room or space if care men are likely to damage pipework or do all other operation liable to announce liquid ammonia or certain quantities of gas. 13011 13012 13013 13014 13015 13016 13017 13018 13019 13020 13021 13022 13023 13024 13025 13026 13027 13028 13029 13030 13031 13032 13033 13034 13035 13036 13037 13038 13039 13040 13041 13042 13043 13044 13045 13046 13047 13048 13049 13050 13051 13052 13053 13054 13055 13056 13057 13058 13059 13060 13061 13062 13063 13064 13065 13066 13067 13068 13069 13070 13071 13072 13073 13074 13075 13076 13077 13078 13079 13080 13081 13082 13083 13084 13085 13086 13087 13088 13089 13090 13091 13092 13093 13094 13095 13096 13097 13098 13099 13100 13101 13102 13103 13104 13105 13106 13107 13108 13109 13110 13111 13112 13113 13114 13115 13116 13117 13118 13119 13120 13121 13122 13123 13124 13125 13126 13127 13128 13129 13130 13131 13132 13133 13134 13135 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