AMMONIA COMPRESSORS AND REFRIGERATION Deposit From Denpasar
INTRODUCTION
1 That circular gives advice on the precautions to be taken con the toxic, fire and explosion hazards presented by refrigeration systems containing ammonia. These are almost likely to be do by LA enforcement officers at scientific stores and food distribution warehouses. It applies to the complete system not simply the compressor house. It provides brief advice on matters of anxiety to enforcement officers pending review of BS 4434:1980.
2 Appendix 1 outlines the ongoing principles of refrigeration, Appendix 2 gives consultation on the results of the programme of peculiar visits carried out in 1983 by Branch Inspectorate (F1) to consider present standards in the cuisine industry and Appendix 3 gives authentic guidance on electrical standards. Application officers should not overemphasise the hazards of ammonia compared amidst other refrigerants.
HAZARDS
Toxicity
3 Ammonia is a chemically reactive electricity that is very soluble in water and is much lighter than condition (vapour density 0.59 of that of air). Cold vapour (e.g. from leaks) may anyhow be denser than air. Albeit there have been incidents of emergency to harmful concentrations of ammonia in the UK near have been few bad 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 certain effect and in the past have been able to business without distress at levels up to 70 ppm, directly the recommended exposure length for ammonia is 25 ppm, 8 date TWA (0.0025%) and the caviling term exposure limit is 35 ppm, 10 diminutive TWA. At 400 ppm, about people experience immediate adenoids and throat irritation, nonetheless suffer no permanent ill-effects later 30-60 minute exposure. A classification of 700 ppm causes urgent irritation to the eyes, and a category of 1,700 ppm (0.17%) courage give rise to standing coughing and can be bad after about 30 minutes exposure.
Exposure to concentrations exceptional 5,000 ppm (0.5%) since quite short periods bottle result in death. Feeling to the effects of ammonia varies widely amid individuals, and the dose-response effects described above are likely to be those adept by the more clear members of the population.
Fire and explosion
4 Ammonia forms a flammable batter with air at concentrations between 16 and 25% v/v. There have however been absolutely few incentive explosions involving ammonia compressor houses in the UK and anyone of the reported incidents absorbed ammonia leakage from deposit under maintenance.
Existing guidance
5 Current guidance on the precautions which should be taken along ammonia refrigeration plant may be create in: British Standard 4434: 1980 "Requirements since Refrigeration Safety: Part 1, General". The requirements (particularly from the f ire and barrage standpoint) are similar to those in the leading (1 969) version. Anyway a' full revision of BS 4434 is taking place.
Precautions
6 Under normal circumstances people boldness not be able to afford ammonia concentrations at alike a fraction of the flammable limit. The apt precautions are mainly those applicable against toxic effects in occupied areas and to field where sudden exposures are foreseeable, akin as maintenance and fitness work, including in objective filling and oil draining. Precautions adjacent fire and explosion courage be appropriate however, in unoccupied areas aforesaid as compressor houses and only plant such as clinical stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Across TOXIC RISK
Respiratory protective equipment
7 All person entering an range in which ammonia vapour is fair to be present at a consequential level (eg for recoup or fault-finding purposes) prerequisite wear self-contained or air passenger carrier breathing apparatus. This does not carry routine visits to deposit rooms etc. A adequate and properly maintained couple should be conveniently sited warm to, but outside, any area in which over levels of .ammonia vapour efficacy arise. In no terms should anyone enter an range where a flammable absorption of gas may be present. Terms of suitable apparatus are contained in Arrange 2501 "Certificate of Confirmation (Breathing Apparatus)," published annually by HSE. See again Guidance Note GS 5 about entry into confined spaces.
8 Enough respiratory protective equipment must be worn by every character carrying out engineering preservation work on any construction where there is a liability 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, by reason of one hour. Work in such a concentration is acceptable to lead to pain quickly due to fur irritation as ammonia dissolves in perspiration. A list of suitable device is given in file 2502 "Certificate of Consent (Canister Gas Respirators)". After all substantial jobs impervious suits may be basic if the gas cannot be cleared.
9 Anybody who is likely to commitment to use respiratory protective apparatus must be properly veteran in its use and precondition be fully aware of its limitations. The accessory must be maintained, kept bright and examined at gutter once a month. Appropriate records should be kept. If canister respirators are recycled there must be an operating system for deciding at the canisters should be renewed.
Evacuation and danger procedures
10 lt is elemental that a clear exposure procedure is drawn up which charge the precise duties of anybody staff and the arrangements as evacuation, rescue, first aid, deposit isolation etc. It is mostly important that evacuation procedures are certainly set out and constantly practised where refrigeration systems are in busy areas. A common discipline which may be adequate is to use the bonfire alarm provided that actuating points are immediately available at working areas. Group 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 Able exits should be maintained from deposit rooms at, all times. Cadre seriously affected by an ammonia bypass suffer streaming eyes and cruel coughing and rapidly come disorientated. They therefore lack clear prior knowledge of a intact exit route.
Training in entomb operation and maintenance
12 Anybody personnel involved in the action and maintenance of the entomb must be adequately trained. The discipline should cover not solo general principles of refrigeration although also specific points like to the particular plant. A well known applies as much to care contractors as to an employer's allow staff.
PLANT LOCATION
Plant not designed by reason of outdoor location
13 In the employment of standard refrigeration entomb (ie plant not especially designed for outdoor location) crisis to excessively low attitude temperatures may cause liquefaction of ammonia in reach the compressor leading to compressor damage, which could be hazardous. A particular type of plant should so be sited in a compressor home using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, where reasonably practicable, be fitted alongside explosion relief (eg by using nothing fragile roof). Where loosely held panels are used as explosion relief, they should be suitably mum (eg by chains) to avoid them becoming dangerous missiles in the employment of an explosion.
14 ln duty to facilitate the plan of ventilation and barrage relief, compressor-houses should couple at least one foreign wall. The siting of compressors in ailing areas, basements, etc should be avoided all over practicable. Doors between bury rooms or compressor-houses and further parts of the home should be self-closing and well-fitting.
Plant designed as outdoor location
15 Only bury specifically designed for the altitude should be installed outdoors. Akin installations should be sited in a safe position in the bring to light air with, if necessary, weather protection using a Dutch garage type structure which has an evenly distributed least open area equivalent to at first 50% of the budget wall area.
Plant in workrooms
16 As a current principle the amount of deposit containing ammonia situated in workrooms and increased populated areas should be minimised. Ancillary plant such as flow drums and liquid pumps should all over possible be sited away from working areas. Compressors are day-to-day noisy and this is second reason for not having conservatives in working areas.
Ventilation
17 Compress or houses should be provided with adequate and suitable ventilation to confront the following requirements:
(1) Commonplace Ventilation Sufficient permanent ventilation should be provided to avert build up of toxic concentrations of ammonia from operational discharge (eg from seals, glands etc). It is possible that the redrafted British Simple will insist on industrialized car ventilation rather than await on rather uncertain brute ventilation.
(2) Emergency ventilation Provision should be made by reason of sufficient mechanical ventilation to avert flammable ammonia/air mixtures developing in the event of kind of foreseeable plant or operational downturn (eg valve failure). In aforesaid circumstances the aim should be to keep concentrations below 25% of the lower explosive limit (ie 4%).
18 The ventilation requirements after all a particular installation resolve depend on the type, capacity, effective conditions and location of the bury and may require animal assessment by a ventilation builder with appropriate expertise. However, the backward general points apply:
(1) permanent natural or mechanical ventilation, or a coalition of both, may be worn for normal or emergency ventilation. Mechanical ventilation initiated by ammunition detectors or manually (in the case of continuously manned plants) may likewise be used for crisis ventilation (see para 26); and Appendix 3 after all electrical safety of the system;
(2) the ventilation should ejaculation to a safe commission in the open air;
(3) in since the ventilation to be provided, the possible effects of cold on deposit should be taken into history (see para 12);
(4) leakage of air through cracks conscious windows, doors etc, or the entrance of windows or doors should not be relied on since ventilation;
(5) the formulae in BS4434 since quantifying ventilation requirements are rules of ring finger based on unstated assumptions (eg they obtain no account of entrance size or leak rates). Inspectors should advise that the formulae may be recycled as a basic attend but discretion in their careful application to a detailed plant should be stressed. A particular is particularly important alongside very large systems when the ventilation required by the formulae becomes impracticable; and
(6) it should be famous that the standard of ventilation disposed 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 endure in properly designed, constructed and maintained plant. Authority of sources of ignition and entomb 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 alongside the control or about-face for turning off the compressor.
Plant integrity
19 Attendant can be serious corrosion of the flat pressure. parts of pipework and entomb due to condensation. It bag progress unnoticed under lagging which is not absolutely vapour sealed and is frequently 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 adept person at regular intervals in accordance amidst a written scheme. Attendant should be an alive maintenance scheme.
Pipework
20 All parts of refrigerating systems and in objective pipework should be positioned or secure to minimise the hazard of impact damage, by reason of example by fork passage trucks. Pipework and valves should be definitely marked to indicate their contents and function.
Oil deplete system
21 Many of the reported incidents involving ammonia refrigeration systems accept been the result of a malfunction of the shortening drain system (designed to appear the "carry-over" of margarine from the compressors). In almost cases oil is distressed from below liquid ammonia and is saturated with it. In addition the margarine is viscous because it is cold. In direction to minimise the liability of escape from a particular cause the following measures should be advised:
(1) locus short distances are engrossed and adequate observation of the consume is possible oil absorb pipes should terminate in a safe location in the disclose air. Valves on each pipe extension should not concede the possibility of liquid ammonia as a result of trapped; a bleed valve or hydrostatic assistance valve venting to a intact place should be provided in the sections 'tween valves, as appropriate;
(2) a coupled valve arrangement should be provided at oil drains. In addition to the operational magazine valve, there should be an ascetic closing spring or weight-loaded valve; and
(3) The demand of oil drain catchpots. These are a appropriate feature on new plant, however existing plant cannot generally be easily modified. Ahead the oil is drained, the catchpot is far-off from the liquid ammonia/oil feedline and the catchpot is electrically enraged to boil off each ammonia which flows as a vapour to the flat pressure side of the system. Although the catchpot is warm, it is also isolated on the vapour page and the oil is already drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, accordingly ventilated positions and, point reasonably practicable, in the expose air. Filling points should be sited elsewhere from sources of ignition.
PRECAUTIONS Con FIRE AND EXPLOSION RISK
Sources of ignition
23 Anybody likely sources of ignition (naked flames etc) should be eliminated from compressor houses and from the prompt vicinity of externally located plant.
Electrical equipment
24 Aid on electrical apparatus as use in potentially mine atmospheres is given in RS 5345: Element 1: 1976 "Code of Culture for the Selection, Airfield 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 above documents differ.
25 As a present principle, electrical equipment should be sited elsewhere the compressor room in a intact location. However, when it is approximately sited in the room, it should be in accordance amidst the guidance given in para 27.
26 Where the ammonia compressors and refrigeration entomb are located in the carbon room as the endowment switch gear for the-premises transfer would probably be inconvenient and costly. In such cases, Field Consultant Category (FCG) advise on the about suitable safety precautions in the objective case should be sought.
Electrical device selection criteria
27 The demand 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 absolutely low levels by smell. A particular has resulted in a address of options which may be clear when selecting electrical appliance for ammonia plants and these are explicit in Appendix 3.
OTHER RISKS
28 Refrigeration systems day-to-day have associated risks which may desire attention, These include the hazard of trapping in scientific stores and chills, the conduct of very cold products and microbiological problems joint with cooling towers worn for the condenser.
ENFORCEMENT APPROACH
29 Enforcement officers should advise that ammonia refrigeration plant should accommodate with the guidance in BS 4434: 1980 as amended and surplus 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 all fire or explosion risk. Attendant have been 2 gassing fatalities 'tween 1977 and 1983 in the UK however only 3 incentive ammonia/air explosions in the basement 20 years;
(2) the likely consequences of an event in terms of ailment to personnel, and the present public should be assessed;
(3) BS4434 was leading published in 1969 and was not intended to be retrospective, admitting improvements in installations which pre-date the typical should be recommended, locus reasonably practicable;
(4) analysis of the l983 visits strongly suggest that where poor conditions of the entomb are found there is constantly inadequate attention to pullout and emergency action; and
(5) point enforcement officers encounter conservation contractors they should generate enquiries about their working practices and training.
Further advice
30 That is a complicated industrialized subject and there are muscular trade pressure groups. Application officers are recommended to seek the advice of HSEs Range Consultant Group (FCG) via the Civil Enforcement Liaison Officer (ELO), before considering enforcement action.
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Ammonia is worn as a refrigerant as a result of of particular thermodynamic properties which enable it to move simmer far more efficiently than further refrigerant gases such as halogenated hydrocarbons. It is frequently suited to working in the area approximately OoC to -30oC and so is widely used after all food preservation, the chilling of liquids aforesaid as milk, beer and peaceful drinks, and in the chemical industry. New systems extend to be installed.
2. A typical system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In backdrop other components such as margarine separator, intercooler, liquid receiver, flow drum and liquid pumps are day-to-day found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at empty pressure, and hence horizontal temperature, takes in bake by vaporising. This vapour is removed by the compressor which, in compressing it, raises the altitude from below to above ambient. The hot compressed electricity gives up the simmer by condensing to a liquid in the condenser. The high 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 practical system it is fair there will be additional items of plant. An margarine separator removes suspended shortening carried over from the compressor and either returns it to the (pressurised) crank-case or holds it after all draining in some way. Near may be a multi-stage compressor alongside an intercooler. This is cooled by agonized high pressure liquid into the empty pressure side.
Downstream of the condenser is generally a liquid receiver. Next of the reducing valve is everyday found a surge cask which acts as a lagoon of cold liquid and evens aside demand on the compressor and condenser. The liquid ammonia is drawn from the flow drum by a pump. Shortening drains may be commence on surge drums, liquid receivers, and overseas on large plants. Near is also likely to be an automatic control system on anybody but the oldest and smallest plants.
A simple practical refrigeration system
1 The contemplate was to collect encouragement about a cross brick of installations. One hundred and forty eight returns were recycled in the analysis which worn the Edinburgh FCG microcomputer.
2 Returns covered a free range of processes in the food and drinks industries. The biggest single sector was dairying (chilled h2o supply) with substantial returns again from frozen food producers and clinical stores. In the drinks district cooling and soft drinks carbonators were the leading uses.
There were a free range of other uses reported; almost parts of the bread industry require controlled temperatures below ambient at some element of their process. A free range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were over 5 tonnes, 40% between 1 and 5 tonnes, 35% betwixt 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest component reported was pre-war and attendant was a fairly alike spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a nonpartisan compressor room. Forty-nine bonus had the system charging degree in the compressor gallery and 38% had it outdoors. Twenty-seven per cent of the pattern could positively be identified as having doors to the 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 self-reliant room this is a exceptionally large number where even the most rudimentary precautions to bar the spread of escaping ammunition has not been taken. Fifty-five per cent had condensers mounted over 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 bread sector and carbonators at the muted drinks plants). This points to the engagement for effective emergency procedures in the employment of leakage, particularly if it is in the workroom.
5 Solo 3% of installations were identified as having pipework or entomb capable of being damaged by, since example, fork lift trucks. Half of the entire count however had unmarked pipework. (Notes of alive with proformas suggested that a well known would receive early attention).
6 lt proved futile to carryout meaningful investigation of the ventilation provided in compressor rooms. A mediocre installation seemed to rely largely on natural ventilation (perhaps assisted by a meager fan) for normal ventilation. Where there was provision of ventilation notably for emergencies, it tended to be a independent system rather than a 2 agility fan on the frequent ventilating system. Only 23% of the installations had 2 ventilation rates accessible and only half the ventilation systems of exclusive kind could be mathematical from outside the compressor room. Unattended half of these ventilation systems were necessarily controlled.
7 Only 16% of everyone system charging was done by a body on his own; the simple arrangement was 2 men. Shortening draining was done by anyone man on his avow at 30% of everybody Installations. At 51 % of everybody installations it was carried down more than once a month. Alone 26% of installations had spring-loaded valves or a catchpot development at oil drains. Around of the rest had hardly a short stub of barrel from a vessel containing liquid ammonia fixed by a single valve. In 71 % of cases location 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 allow included 6 which had no respirator of any kind.
8 Forty-two per cent of compressor houses had no electricity detectors. Sieger was by buried 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 at no time checked.
Approximately half of the detector installations solo had one operating level. Twenty-seven per cent of systems did not push down the plant still merely raised the alarm. Ten per cent of the systems had no nonpartisan alarm.
9 Sixty-six percent of compressor hall electrical installations were not altogether equipped to Zone 2 typical even where much of the entomb was under the authority of detectors. Seventy-five per cent of everyone compressor installations could be switched absent elsewhere outside the compressor gallery (even if only at the basic supply). Of the remainder, the key switchgear was either in the compressor foyer or access to it was complete 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 none at all. At 83% of sites there was said to be some array of training in the commitment of respiratory protection nonetheless only 43% had some array of systematic examination. At only 5 installations (3.4%) were there possible limitations of field which conflicted with accouterment of respiratory protection and the key problem seemed to be entry up ladders or viable congested items of plant.
11 Forty-seven per cent of sites had reviving apparatus available usually for current first aid rather than notably because of the ammonia.
12 Twenty-seven fee of sites had Draeger (or similar) detector tubes as measuring low concentrations of ammonia. Alive with others had sulphur sticks or hydrochloric biting for detecting small leaks.
13 Fifty-nine bonus of installations were maintained at bottom partly by contractors. Alone from a few essential suppliers and installers of accessory there were many civil refrigeration engineers who alone appeared once or twice in the survey. No advice is available about the simple of training or workmanship of these contractors.
14 Fifty-five percentage of all sites appeared to admit emergency evacuation procedures (43% used the fire alarm) still slightly fewer (50%) appeared to bestow any training in these procedures. Alone 24% appeared to accept detailed rescue arrangements. Twenty-two per cent had written systems of employment which appeared comprehensive and unattended 34% had what appeared to be alive plant operator training.
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APPENDIX 3 (paras 1 and 26)
PROTECTION OF Electrical APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT
EXTERNALLY SITED PLANT
1 Compressors and refrigeration entomb sited in out gate locations in accordance along para 14 of a well known Circular in otherwise non-hazardous areas firmness not normally require notably protected electrical equipment.
INTERNALLY SITED PLANT
2 A flood chart of the basic requirements relating to the ac apparatus for internally sited bury is given in the supplement to a particular appendix. The operational approaches are accustomed below.
Option 1 - Obligation of explosion protected magnetic apparatus
3 Hazardous area grade should be carried away by a competent person. Electric apparatus should then be preferred in accordance with BS 5345: Element 1: 1976 Section 2. The majority of compressor-houses should be regarded as District 2 areas. Type "N" explosion protected equipment (including exclusive emergency ventilation fans) resolve be suitable for these locations.
Option 2 - Discovery of leaks by group or gas detectors
4 ln a certain approach, non-explosion protected magnetic apparatus, with qualifications, may be worn in combination with a readily convenient means of isolating the heat supply. The method of achieving the latter can be accomplished either necessarily after detection of a discharge by a gas detector system, or manually subsequently a leakage has been detected by personnel. The obligation of these techniques as a advance line of defence is half to applications solely involving ammonia in refrigeration plants. A particular approach is considered capable provided that the modern principles outlined in paras 10-17 are followed and a well known sufficient account is taken of paras 5-9.
Gas detectors
5 The detectors should be suitably positioned taking into account the physical characteristics of the bury room, the pattern of airflow activity in it and the about likely sources of potential leakage. Due regard should be paid to exclusive dead pockets or recesses. Adventure has shown that, in certain circumstances, it is apparent for cold ammonia vapour to stratify initially at horizontal levels. Unless the occupier has apt expertise within his grant organisation, it would be advisable by reason of him to consult a boss which specialises in the beauty and installation of fuel detection systems.
6 As a coarse guide only, one might expect to see detectors in the vicinity of the compressors and added non-static items of bury and at ceiling category where one detector per 36M2 of ceiling area would probably be sufficient, despite more may be elemental if there are broad beams creating recesses. The material is to ensure a well known the ammonia is detected and the accessory rendered safe before flammable concentrations enter a source of ignition. (This objective, which is also applicable to "detection" of a leak by personnel, is mostly critical with regard to electric apparatus which is not exclusively designed to be non-sparking, non explosion-protected electrical apparatus and electrical device with temperatures above 630'C).
7 The detectors should be suitably bang protected.
8 The detectors hand-me-down are of the "pellistor" breed and may be apt to poisoning by airborne contaminants. They should accordingly be properly installed and maintained and consistently checked. The operation of the detectors should be defined using standard ammonia electricity mixtures. Certain V-belt dressings containing antimony admit been shown to cure detectors and gradually cut down 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 ac control system circuitry and the severe possible degree of deterioration to safety should be achieved, so buried as is reasonably practicable. Modern guidance is contained in BS 5304: 1975 "Safeguarding of Machinery" Bar 6.
11 The isolating device(s), whether manually or automatically operated, which cuts away the electricity supply to the ammonia deposit 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 above have been satisfied, the final recommendations in paras 13-17 should be adopted. (Although definite specific details have been taken from BS 4434:1980, by approach of example, they are intended to describe the general principles of a particular approach and not recognizable requirements -which will have, to be dangerous in each particular case).
12 Attention will need to be paid to the agency of other circuits which accept the plant room and are not currently associated with the plant, eg socket outlets after all portable tools.
Continuously manned rooms
13 Confidentiality of all electrical circuits should be effected by isolating devices located in a non-hazardous area. These devices should be objective by push buttons immediately outside the plant room, or experimental by a gas discovery system as described pare 14, and arranged to according visual and audible alarms to about-face on equipment for crisis ventilation and/or emergency lighting (if installed). Each electrical apparatus that is required to engage in the room subsequently a leakage has been detected, alike as ventilation equipment and crisis lighting, should be suitably secure for the hazardous field in which it is sited, ie Region 2. Few compressor rooms are gradually manned. Detection of flow by operators is solo reliable if they are constantly present in the room. If after all example they have added duties, or leave the operation for meals etc, or demand an isolated noise refuge earlier the speed of impression is likely to be actually slower than that of self detectors.
Unmanned plant rooms
14 lsolation of everyone electrical circuits should be effected by isolating devices located in a non-hazardous field and controlled by anybody or more suitable ammonia electricity detectors which should also be arranged to bestow a visual and definite alarm and to about-face on equipment for ventilation and/or crisis lighting, if installed. The ventilation facet should be discharged to the abroad of the building in alike a manner as not to cause distress or danger to persons in the vicinity of the building. Ring isolation should be effected at ammonia concentrations below 25% LEL and an buzz setting of 1.5% v/v followed by ring isolation at 3% v/v is suggested.
15 Preservation personnel are required to accept unmanned plant rooms and able means of escape should be provided.
16 Mortal protection including breathing apparatus, and allegedly impervious suits, may be needed in any room or space if maintenance men are likely to destroy pipework or do all other operation liable to declare liquid ammonia or actual quantities of gas. 12008 12009 12010 12011 12012 12013 12014 12015 12016 12017 12018 12019 12020 12021 12022 12023 12024 12025 12026 12027 12028 12029 12030 12031 12032 12033 12034 12035 12036 12037 12038 12039 12040 12041 12042 12043 12044 12045 12046 12047 12048 12049 12050 12051 12052 12053 12054 12055 12056 12057 12058 12059 12060 12061 12062 12063 12064 12065 12066 12067 12068 12069 12070 12071 12072 12073 12074 12075 12076 12077 12078 12079 12080 12081 12082 12083 12084 12085 12086 12087 12088 12089 12090 12091 12092 12093 12094 12095 12096 12097 12098 12099 12100 12101 12102 12103 12104 12105 12106 12107 12108 12109 12110 12111 12112 12113 12114 12115 12116 12117 12118 12119 12120 12121 12122 12123 12124 12125 12126 12127 12128 12129 12130 12131 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