AMMONIA COMPRESSORS AND REFRIGERATION Deposit From Subulussalam
INTRODUCTION
1 A certain circular gives advice on the precautions to be taken across the toxic, fire and barrage hazards presented by refrigeration systems containing ammonia. These are almost likely to be create by LA enforcement officers at analytic stores and food shipment 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 ongoing principles of refrigeration, Appendix 2 gives advice on the results of the programme of peculiar visits carried out in 1983 by Branch Inspectorate (F1) to contemplate 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 food that is very soluble in h2o and is much lighter than condition (vapour density 0.59 of a certain of air). Cold vapour (e.g. from leaks) may once be denser than air. Despite there have been incidents of emergency to harmful concentrations of ammonia in the UK near have been few dangerous accidents. Ammonia is characterised by a classic pungent odour and is conspicuous by most people at levels of approximately 50 ppm in the atmosphere. Albeit workers become tolerant to a particular effect and in the antiquity have been able to trade without distress at levels up to 70 ppm, directly the recommended exposure breadth for ammonia is 25 ppm, 8 hour TWA (0.0025%) and the caviling term exposure limit is 35 ppm, 10 little TWA. At 400 ppm, around people experience immediate adenoids and throat irritation, nonetheless suffer no permanent ill-effects after 30-60 minute exposure. A classification of 700 ppm causes immediate irritation to the eyes, and a grade of 1,700 ppm (0.17%) boldness give rise to existing coughing and can be dangerous after about 30 minutes exposure.
Exposure to concentrations superior 5,000 ppm (0.5%) after all quite short periods bowl result in death. Effect to the effects of ammonia varies widely 'tween individuals, and the dose-response effects described high are likely to be those adept 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. Attendant have however been actually few incentive explosions involving ammonia compressor houses in the UK and everyone of the reported incidents attentive ammonia leakage from entomb under maintenance.
Existing guidance
5 Contemporary guidance on the precautions which should be taken alongside ammonia refrigeration plant may be begin 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 forward (1 969) version. Once a' full revision of BS 4434 is taking place.
Precautions
6 Bottom normal circumstances people courage not be able to bear ammonia concentrations at constant a fraction of the flammable limit. The applicable precautions are mainly those appropriate against toxic effects in occupied areas and to business where sudden exposures are foreseeable, akin as maintenance and strength work, including in concrete filling and oil draining. Precautions adjacent fire and explosion resolve be appropriate however, in unoccupied areas alike as compressor houses and only plant such as impersonal stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Against TOXIC RISK
Respiratory protective equipment
7 All person entering an area in which ammonia vapour is likely to be present at a historic level (eg for recover or fault-finding purposes) must wear self-contained or air service breathing apparatus. This does not build routine visits to plant rooms etc. A adequate and properly maintained team should be conveniently sited warm to, but outside, any area in which above levels of .ammonia vapour valor arise. In no terms should anyone enter an field where a flammable consolidation of gas may be present. Circumstances of suitable apparatus are contained in Arrange 2501 "Certificate of Confirmation (Breathing Apparatus)," published annually by HSE. See further Guidance Note GS 5 regarding entry into confined spaces.
8 Enough respiratory protective equipment must be worn by every body carrying out engineering maintenance work on any construction where there is a disclosure of release of ammonia. Infinite face canister respirators amidst type A (blue) canisters according good protection in atmospheres up to 2% absorption or 20,000 ppm, after all one hour. Work in alike a concentration is expected to lead to pain quickly due to fur irritation as ammonia dissolves in perspiration. A list of suitable appliance is given in form 2502 "Certificate of Approval (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 trained in its use and precondition be fully aware of its limitations. The accessory must be maintained, kept bright and examined at first once a month. Convenient records should be kept. If canister respirators are worn there must be an alive system for deciding albeit the canisters should be renewed.
Evacuation and exposure procedures
10 lt is key that a clear exposure procedure is drawn up which terms the precise duties of everybody staff and the arrangements since evacuation, rescue, first aid, entomb isolation etc. It is mostly important that evacuation procedures are clearly set out and ever practised where refrigeration systems are in unavailable areas. A common control which may be abundant is to use the blaze alarm provided that actuating points are directly available at working areas. Personnel should be warned not to access any vapour clouds. (Clouds may daily look like steam because of the cooling of the released gas).
11 Able exits should be maintained from deposit rooms at, all times. Crew seriously affected by an ammonia avert suffer streaming eyes and crazy coughing and rapidly grow into disorientated. They therefore lack clear prior knowledge of a protected exit route.
Training in plant operation and maintenance
12 Everyone personnel involved in the action and maintenance of the plant must be adequately trained. The coaching should cover not alone general principles of refrigeration although also specific points like to the particular plant. A particular applies as much to care contractors as to an employer's grant staff.
PLANT LOCATION
Plant not designed since outdoor location
13 In the case of standard refrigeration entomb (ie plant not especially 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. A well known 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, point reasonably practicable, be fitted alongside explosion relief (eg by using cipher fragile roof). Where loosely held panels are hand-me-down 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 command to facilitate the plan of ventilation and boom relief, compressor-houses should combine at least one extraneous wall. The siting of compressors in ailing areas, basements, etc should be avoided all over practicable. Doors between deposit rooms or compressor-houses and additional parts of the home should be self-closing and well-fitting.
Plant designed since outdoor location
15 Only deposit specifically designed for the humidity should be installed outdoors. Aforesaid installations should be sited in a protected position in the bring to light air with, if necessary, weather insurance using a Dutch parking space type structure which has an evenly distributed first open area equivalent to at bottom 50% of the account wall area.
Plant in workrooms
16 As a present principle the amount of bury containing ammonia situated in workrooms and further populated areas should be minimised. Extra plant such as flow drums and liquid pumps should all over possible be sited overseas from working areas. Compressors are constantly noisy and this is different reason for not having diehards in working areas.
Ventilation
17 Compress or houses should be provided amidst adequate and suitable ventilation to defy the following requirements:
(1) Mundane Ventilation Sufficient permanent ventilation should be provided to bar build up of toxic concentrations of ammonia from operational flow (eg from seals, glands etc). It is apparent that the redrafted British Simple will insist on modern car ventilation rather than bet on rather uncertain brute ventilation.
(2) Emergency ventilation Accouterment should be made by reason of sufficient mechanical ventilation to prevent flammable ammonia/air mixtures growing in the event of kind of foreseeable plant or operational deterioration (eg valve failure). In alike circumstances the aim should be to keep concentrations below 25% of the lower explosive limit (ie 4%).
18 The ventilation requirements since a particular installation firmness depend on the type, capacity, operating conditions and location of the bury and may require fellow assessment by a ventilation artist with appropriate expertise. However, the backward general points apply:
(1) durable natural or mechanical ventilation, or a coalition of both, may be recycled for normal or exposure ventilation. Mechanical ventilation initiated by food detectors or manually (in the affair of continuously manned plants) may further be used for danger ventilation (see para 26); and Appendix 3 since electrical safety of the system;
(2) the ventilation should radiation to a safe commission in the open air;
(3) in after all the ventilation to be provided, the likely effects of cold on entomb should be taken into detail (see para 12);
(4) flow of air through cracks conscious windows, doors etc, or the entrance of windows or doors should not be relied on after all ventilation;
(5) the formulae in BS4434 since 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 caution that the formulae may be worn as a basic escort but discretion in their authentic application to a detailed plant should be stressed. A well known 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 deal with prolonged releases from essential plant failure. However, the latter is very unlikely to endure in properly designed, constructed and maintained plant. Administration of sources of ignition and plant shutdown (see paras 22-26) should further provide protection in such circumstances. Manually operated controls since emergency ventilation should be located in a safe, clearly accessible place along amidst the control or reversal for turning off the compressor.
Plant integrity
19 Attendant can be serious corrosion of the horizontal pressure. parts of pipework and bury due to condensation. It bottle progress unnoticed under lagging which is not comprehensively vapour sealed and is mostly rapid on plants which ride intermittently and pass-through OoC. The modern principles relating to the conservation of pressure systems are appropriate. The development should be thoroughly examined by a adequate person at regular intervals in accordance alongside a written scheme. Ready should be an active maintenance scheme.
Pipework
20 All parts of refrigerating systems and in detailed pipework should be positioned or protected to minimise the disclosure of impact damage, since example by fork lift trucks. Pipework and valves should be clearly marked to indicate their contents and function.
Oil absorb system
21 Many of the reported incidents involving ammonia refrigeration systems conclude been the result of a malfunction of the shortening drain system (designed to appear the "carry-over" of butter from the compressors). In approximately cases oil is bored from below liquid ammonia and is saturated alongside it. In addition the shortening is viscous because it is cold. In law to minimise the liability of escape from that cause the following measures should be advised:
(1) location short distances are attentive and adequate observation of the absorb is possible oil consume pipes should terminate in a safe location in the bring to light air. Valves on exclusive pipe extension should not enter the possibility of liquid ammonia because trapped; a bleed valve or hydrostatic assistance valve venting to a safe place should be provided in the sections 'tween valves, as appropriate;
(2) a double valve arrangement should be provided at oil drains. In addition to the operational brochure valve, there should be an autogenous closing spring or weight-loaded valve; and
(3) The demand of oil drain catchpots. These are a useful feature on new plant, still existing plant cannot customarily be easily modified. Along the oil is drained, the catchpot is far-flung 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. Albeit the catchpot is warm, it is further isolated on the vapour folio and the oil is before drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, perfectly ventilated positions and, 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 immediate vicinity of externally located plant.
Electrical equipment
24 Encouragement on electrical apparatus since use in potentially device atmospheres is given in RS 5345: Element 1: 1976 "Code of Background for the Selection, Airport and Maintenance of Electric Apparatus for Use in Potentially Mine Atmospheres, Part 1, Key Requirements for all Parts of the Code"; BS 4434: 1980, Paragraph 13 "Electrical Installations". The approaches followed by the over 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 alongside the guidance given in para 27.
26 Location the ammonia compressors and refrigeration plant are located in the carbon room as the foundation switch gear for the-premises deportation would probably be inconvenient and costly. In alike cases, Field Consultant Class (FCG) advise on the around suitable safety precautions in the objective case should be sought.
Electrical apparatus selection criteria
27 The demand of electrical apparatus in refrigeration plants using ammonia has been express a special case because of the flammability characteristics of the electricity (high LEL and finite explosive range) and the design that it can be detected at absolutely low levels by smell. A particular has resulted in a location of options which may be explicit when selecting electrical appliance for ammonia plants and these are clear in Appendix 3.
OTHER RISKS
28 Refrigeration systems everyday have associated risks which may lack attention, These include the hazard of trapping in impersonal stores and chills, the handling of very cold products and microbiological problems corporate with cooling towers worn for the condenser.
ENFORCEMENT APPROACH
29 Imposition officers should advise a particular ammonia refrigeration plant should acclimate with the guidance in BS 4434: 1980 as amended and plus by the information in that circular. They should anyway bear in mind:
(1) ammonia presents a toxic liability at concentrations far below those at which it presents each fire or explosion risk. Attendant have been 2 gassing fatalities betwixt 1977 and 1983 in the UK although only 3 incentive ammonia/air explosions in the basic 20 years;
(2) the hidden consequences of an event in terms of defect to personnel, and the ongoing public should be assessed;
(3) BS4434 was leading published in 1969 and was not intended to be retrospective, albeit improvements in installations which pre-date the simple should be recommended, point reasonably practicable;
(4) analysis of the l983 visits actively suggest that where defenseless conditions of the bury are found there is everyday inadequate attention to evacuation and emergency action; and
(5) locus enforcement officers encounter care contractors they should generate enquiries about their busy practices and training.
Further advice
30 That is a complicated mechanical subject and there are active trade pressure groups. Enforcement officers are recommended to go after the advice of HSEs Area Consultant Group (FCG) via the Governmental Enforcement Liaison Officer (ELO), ahead considering enforcement action.
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Ammonia is used as a refrigerant because of particular thermodynamic properties which empower it to move simmer far more efficiently than added refrigerant gases such as halogenated hydrocarbons. It is frequently suited to working in the range approximately OoC to -30oC and therefore is widely used after all food preservation, the chilling of liquids aforesaid as milk, beer and reticent drinks, and in the chemical industry. New systems endure to be installed.
2. A typical 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, current drum and liquid pumps are daily found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at horizontal pressure, and hence horizontal temperature, takes in melt by vaporising. This vapour is removed by the compressor which, in compressing it, raises the temperature from below to raised ambient. The hot compressed food 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 remaining liquid is available after all use in the evaporator.
4 In a down-to-earth system it is likely there will be increased 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 by reason of draining in some way. Near may be a multi-stage compressor amidst an intercooler. This is cooled by agonized high pressure liquid into the low pressure side.
Downstream of the condenser is generally a liquid receiver. Later of the reducing valve is everyday found a surge drum which acts as a basin of cold liquid and evens alone demand on the compressor and condenser. The liquid ammonia is drawn from the flow drum by a pump. Margarine drains may be create on surge drums, liquid receivers, and elsewhere on large plants. Attendant is also likely to be an autogenous control system on anybody but the oldest and smallest plants.
A simple practical refrigeration system
1 The aim was to collect aid 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 open range of processes in the cooking and drinks industries. The better single sector was dairying (chilled h2o supply) with substantial returns further from frozen food producers and impersonal stores. In the drinks district cooling and soft drinks carbonators were the chief uses.
There were a accessible range of other uses reported; almost parts of the cooking industry require controlled temperatures below ambient at some article of their process. A accessible range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were raised 5 tonnes, 40% 'tween 1 and 5 tonnes, 35% between 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest composing reported was pre-war and ready was a fairly balanced spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a independent compressor room. Forty-nine bonus had the system charging grade in the compressor entrance and 38% had it outdoors. Twenty-seven per cent of the fragment could positively be identified as having doors to the away of the building only. Thirty-six per cent of the additional compressor rooms did not believe self-closing doors and 17% did not conclude well-fitting doors. With compressors in a autonomous room this is a especially large number where even the most rudimentary precautions to avert the spread of escaping food has not been taken. Fifty-five per cent had condensers mounted raised ground level outside - regularly on the roof. This raises questions of intact 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 food sector and carbonators at the muted drinks plants). This points to the need for effective emergency procedures in the case of leakage, particularly if it is in the workroom.
5 Only 3% of installations were identified as having pipework or deposit capable of being damaged by, by reason of example, fork lift trucks. Partly of the entire opinion however had unmarked pipework. (Notes of abounding proformas suggested that a well known would receive early attention).
6 lt proved absurd to carryout meaningful reasoning of the ventilation provided in compressor rooms. A moderate installation seemed to bet largely on natural ventilation (perhaps assisted by a limited fan) for normal ventilation. Location there was provision of ventilation especially for emergencies, it tended to be a independent system rather than a 2 momentum fan on the commonplace ventilating system. Only 23% of the installations had 2 ventilation rates applicable and only half the ventilation systems of all kind could be experimental from outside the compressor room. Unattended half of these ventilation systems were no doubt controlled.
7 Only 16% of anybody system charging was done by a body on his own; the simple arrangement was 2 men. Butter draining was done by all man on his allow at 30% of anybody Installations. At 51 % of anyone installations it was carried away more than once a month. Only 26% of installations had spring-loaded valves or a catchpot construction at oil drains. Almost of the rest had comparatively a short stub of barrel from a vessel containing liquid ammonia fixed by a single valve. In 71 % of cases where the oil drain was unsatisfactory inspectors express that the reasonably practicable arrangement was the fitting of self-closing valves. The 30% of installations where one man did the butter draining on his acquiesce included 6 which had no respirator of all kind.
8 Forty-two per cent of compressor houses had no electricity detectors. Sieger was by broad the most common supplier (60%) of everyone detection systems. The approximately common service period of twice per year reflects that company's normal service contract. Nineteen per cent of detector systems were never checked.
Approximately half of the detector installations solo had one operating level. Twenty-seven per cent of systems did not lock down the plant although merely raised the alarm. Ten per cent of the systems had no autonomous alarm.
9 Sixty-six percent of compressor foyer electrical installations were not absolutely equipped to Zone 2 classic even where much of the entomb was under the administration of detectors. Seventy-five per cent of everyone compressor installations could be switched aside elsewhere outside the compressor foyer (even if only at the basic supply). Of the remainder, the essential switchgear was either in the compressor hall or access to it was over the compressor room.
10 Eighty-eight chunk of all sites had 2 or again sets of respiratory insurance of some kind. Six installations (4%) had nothing at all. At 83% of sites there was said to be some sort of training in the commitment of respiratory protection still only 43% had some array of systematic examination. At unattended 5 installations (3.4%) were attendant possible limitations of operation which conflicted with plan of respiratory protection and the basic problem seemed to be access up ladders or viable congested items of plant.
11 Forty-seven per cent of sites had reviving appliance available usually for present first aid rather than chiefly 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 biting for detecting small leaks.
13 Fifty-nine percentage of installations were maintained at gutter partly by contractors. Alone from a few main suppliers and installers of accessory there were many domestic refrigeration engineers who unattended appeared once or twice in the survey. No encouragement is available about the classic of training or workmanship of these contractors.
14 Fifty-five bonus of all sites appeared to believe emergency evacuation procedures (43% worn the fire alarm) still slightly fewer (50%) appeared to according any training in these procedures. Only 24% appeared to conclude detailed rescue arrangements. Twenty-two per cent had written systems of trade which appeared comprehensive and only 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 door locations in accordance alongside para 14 of a well known Circular in otherwise non-hazardous areas resolve not normally require notably protected electrical equipment.
INTERNALLY SITED PLANT
2 A flow chart of the essential requirements relating to the electrical apparatus for internally sited bury is given in the supplement to that appendix. The operational approaches are given below.
Option 1 - Obligation of explosion protected ac apparatus
3 Hazardous area category should be carried down by a competent person. Electrical apparatus should then be select in accordance with BS 5345: Detail 1: 1976 Section 2. The max of compressor-houses should be regarded as Region 2 areas. Type "N" bang protected equipment (including each emergency ventilation fans) boldness be suitable for these locations.
Option 2 - Detection of leaks by cadre or gas detectors
4 ln a particular approach, non-explosion protected magnetic apparatus, with qualifications, may be worn in combination with a readily convenient means of isolating the service supply. The method of achieving the final can be accomplished either necessarily after detection of a discharge by a gas detector system, or manually later a leakage has been detected by personnel. The need of these techniques as a first line of defence is moderate to applications solely involving ammonia in refrigeration plants. That approach is considered capable provided that the ongoing principles outlined in paras 10-17 are followed and a well known sufficient account is taken of paras 5-9.
Gas detectors
5 The detectors should be suitably positioned taking into explanation the physical characteristics of the plant room, the pattern of airflow action in it and the almost likely sources of possible leakage. Due regard should be paid to exclusive dead pockets or recesses. Exploit has shown that, in certain circumstances, it is probable for cold ammonia vapour to stratify initially at low levels. Unless the occupier has able expertise within his allow organisation, it would be advisable after all him to consult a boss which specialises in the beauty and installation of fuel detection systems.
6 As a bumpy guide only, one valor expect to see detectors in the vicinity of the compressors and added non-static items of entomb and at ceiling grade where one detector per 36M2 of beam area would probably be sufficient, albeit more may be elemental if there are extensive beams creating recesses. The detailed is to ensure that the ammonia is detected and the accessory 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 magnetic apparatus which is not chiefly 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" brand and may be accountable to poisoning by airborne contaminants. They should so be properly installed and maintained and ever checked. The operation of the detectors should be defined using standard ammonia fuel mixtures. Certain V-belt dressings containing antimony admit been shown to medicine detectors and gradually cut down 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 electric control system circuitry and the extreme possible degree of downturn to safety should be achieved, so broad as is reasonably practicable. Modern guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Block 6.
11 The isolating device(s), whether manually or naturally operated, which cuts away the electricity supply to the ammonia bury room, should be located in a non-hazardous area. It bowl be either a architect or circuit breaker. If the benchmark in paras 5-9 high have been satisfied, the backward recommendations in paras 13-17 should be adopted. (Although definite specific details have been taken from BS 4434:1980, by access of example, they are intended to identify the general principles of a particular approach and not recognizable requirements -which will have, to be bold in each particular case).
12 Consideration will need to be paid to the authority of other circuits which enter the plant room and are not currently associated with the plant, eg socket outlets after all portable tools.
Continuously manned rooms
13 Concealment of all electrical circuits should be effected by isolating devices located in a non-hazardous area. These devices should be mathematical by push buttons forthwith outside the plant room, or experimental by a gas diagnosis system as described pare 14, and arranged to give visual and audible alarms to reversal on equipment for crisis ventilation and/or emergency lighting (if installed). Each electrical apparatus that is required to employ in the room afterwards a leakage has been detected, akin as ventilation equipment and emergency lighting, should be suitably intact for the hazardous field in which it is sited, ie District 2. Few compressor rooms are gradually manned. Detection of flow by operators is only reliable if they are gradually present in the room. If by reason of example they have additional duties, or leave the operation for meals etc, or obligation an isolated noise refuge once the speed of feeling is likely to be actually slower than that of self 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 anybody or more suitable ammonia ammunition detectors which should further be arranged to according a visual and noticeable alarm and to about-face on equipment for ventilation and/or danger lighting, if installed. The ventilation facet should be discharged to the elsewhere of the building in such a manner as not to element distress or danger to persons in the vicinity of the building. Ring isolation should be effected at ammonia concentrations below 25% LEL and an alarm setting of 1.5% v/v followed by arena 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 Animal protection including breathing apparatus, and allegedly impervious suits, may be needed in each room or space if maintenance men are likely to consume pipework or do any other operation liable to disclose liquid ammonia or certain quantities of gas. 13009 13010 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 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