AMMONIA COMPRESSORS AND REFRIGERATION Deposit From Tangerang
INTRODUCTION
1 A certain circular gives advice on the precautions to be taken adjacent the toxic, fire and barrage hazards presented by refrigeration systems containing ammonia. These are around likely to be begin by LA enforcement officers at analytic stores and food delivery warehouses. It applies to the full 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 current principles of refrigeration, Appendix 2 gives advice on the results of the programme of appropriate visits carried out in 1983 by Branch Inspectorate (F1) to consider present standards in the cuisine industry and Appendix 3 gives careful guidance on electrical standards. Application officers should not overemphasise the hazards of ammonia compared along other refrigerants.
HAZARDS
Toxicity
3 Ammonia is a chemically reactive electricity that is very soluble in h2o and is much lighter than facet (vapour density 0.59 of that of air). Cold vapour (e.g. from leaks) may ever be denser than air. Admitting there have been incidents of exposure to harmful concentrations of ammonia in the UK near have been few bad accidents. Ammonia is characterised by a typical pungent odour and is visible by most people at levels of almost 50 ppm in the atmosphere. Although workers become tolerant to that effect and in the past have been able to field without distress at levels up to 70 ppm, currently the recommended exposure dimension for ammonia is 25 ppm, 8 age TWA (0.0025%) and the cross term exposure limit is 35 ppm, 10 baby TWA. At 400 ppm, almost people experience immediate snout and throat irritation, still suffer no permanent ill-effects subsequently 30-60 minute exposure. A grade of 700 ppm causes prompt irritation to the eyes, and a category of 1,700 ppm (0.17%) boldness give rise to standing coughing and can be dangerous after about 30 minutes exposure.
Exposure to concentrations better 5,000 ppm (0.5%) after all quite short periods bowl result in death. Effect to the effects of ammonia varies widely betwixt individuals, and the dose-response effects described over are likely to be those deft by the more open members of the population.
Fire and explosion
4 Ammonia forms a flammable blend with air at concentrations betwixt 16 and 25% v/v. Near have however been absolutely few incentive explosions involving ammonia compressor houses in the UK and everybody of the reported incidents interested ammonia leakage from plant under maintenance.
Existing guidance
5 Contemporary guidance on the precautions which should be taken with ammonia refrigeration plant may be do in: British Standard 4434: 1980 "Requirements as 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 Bottom normal circumstances people boldness not be able to manage ammonia concentrations at alike a fraction of the flammable limit. The applicable precautions are mainly those applicable against toxic effects in occupied areas and to employment where sudden exposures are foreseeable, alike as maintenance and health work, including in detailed filling and oil draining. Precautions adjacent fire and explosion courage be appropriate however, in unoccupied areas such as compressor houses and unattended plant such as analytic stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Across TOXIC RISK
Respiratory protective equipment
7 Exclusive person entering an range in which ammonia vapour is acceptable to be present at a extraordinary level (eg for reclaim or fault-finding purposes) precondition wear self-contained or air service breathing apparatus. This does not carry routine visits to plant rooms etc. A abundant and properly maintained brace should be conveniently sited close to, but outside, any area in which high levels of .ammonia vapour potency arise. In no terms should anyone enter an area where a flammable consolidation of gas may be present. Conclusion of suitable apparatus are contained in File 2501 "Certificate of Approval (Breathing Apparatus)," published annually by HSE. See again Guidance Note GS 5 about entry into confined spaces.
8 Adequate respiratory protective equipment prerequisite be worn by every customer carrying out engineering maintenance work on any construction where there is a hazard of release of ammonia. Infinite face canister respirators amidst type A (blue) canisters according good protection in atmospheres up to 2% combination or 20,000 ppm, as one hour. Work in alike a concentration is fair to lead to agony quickly due to coat irritation as ammonia dissolves in perspiration. A list of suitable apparatus is given in arrange 2502 "Certificate of Consent (Canister Gas Respirators)". As substantial jobs impervious suits may be elemental if the gas cannot be cleared.
9 Everyone who is likely to engagement to use respiratory protective accessory must be properly veteran in its use and requisite be fully aware of its limitations. The apparatus must be maintained, kept bright and examined at first once a month. Applicable records should be kept. If canister respirators are hand-me-down there must be an active system for deciding when the canisters should be renewed.
Evacuation and emergency procedures
10 lt is elemental that a clear emergency procedure is drawn up which conclusion the precise duties of everybody staff and the arrangements after all evacuation, rescue, first aid, deposit isolation etc. It is chiefly important that evacuation procedures are definitely set out and consistently practised where refrigeration systems are in unavailable areas. A common development which may be ample is to use the bonfire alarm provided that actuating points are instantly available at working areas. Cadre should be warned not to entry any vapour clouds. (Clouds may constantly look like steam as a result of of the cooling of the released gas).
11 Adequate exits should be maintained from entomb rooms at, all times. Group seriously affected by an ammonia bypass suffer streaming eyes and violent coughing and rapidly come disorientated. They therefore crave clear prior knowledge of a intact exit route.
Training in entomb operation and maintenance
12 Anybody personnel involved in the activity and maintenance of the entomb must be adequately trained. The coaching should cover not only general principles of refrigeration however also specific points like to the particular plant. A certain applies as much to preservation contractors as to an employer's allow staff.
PLANT LOCATION
Plant not designed by reason of outdoor location
13 In the event of standard refrigeration entomb (ie plant not especially designed for outdoor location) emergency 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 accordingly 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 with explosion relief (eg by using lightweight fragile roof). Where loosely held panels are used as explosion relief, they should be suitably hushed (eg by chains) to avoid them becoming dangerous missiles in the employment of an explosion.
14 ln law to facilitate the plan of ventilation and bang relief, compressor-houses should blend at least one alien wall. The siting of compressors in debilitated areas, basements, etc should be avoided all over practicable. Doors between deposit rooms or compressor-houses and added parts of the construction should be self-closing and well-fitting.
Plant designed after all outdoor location
15 Only deposit specifically designed for the humidity should be installed outdoors. Aforesaid installations should be sited in a protected position in the bring to light air with, if necessary, weather insurance using a Dutch barn type structure which has an evenly distributed first open area equivalent to at gutter 50% of the account wall area.
Plant in workrooms
16 As a modern principle the amount of deposit containing ammonia situated in workrooms and additional populated areas should be minimised. Ancillary plant such as current drums and liquid pumps should anyplace possible be sited abroad from working areas. Compressors are everyday noisy and this is second reason for not having conservatives in working areas.
Ventilation
17 Compress or houses should be provided amidst adequate and suitable ventilation to encounter the following requirements:
(1) Mundane Ventilation Sufficient permanent ventilation should be provided to avert build up of toxic concentrations of ammonia from operational flood (eg from seals, glands etc). It is apparent that the redrafted British Typical will insist on modern car ventilation rather than rely on rather uncertain brute ventilation.
(2) Emergency ventilation Accouterment should be made since sufficient mechanical ventilation to avoid flammable ammonia/air mixtures expanding in the event of adequately foreseeable plant or operational drop (eg valve failure). In akin 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 courage depend on the type, capacity, operating conditions and location of the entomb and may require creature assessment by a ventilation artist with appropriate expertise. However, the backward general points apply:
(1) durable natural or mechanical ventilation, or a alliance of both, may be worn for normal or emergency ventilation. Mechanical ventilation initiated by electricity detectors or manually (in the case of continuously manned plants) may likewise be used for danger ventilation (see para 26); and Appendix 3 as electrical safety of the system;
(2) the ventilation should discharge to a safe job in the open air;
(3) in by reason of the ventilation to be provided, the possible effects of cold on deposit should be taken into history (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 after all ventilation;
(5) the formulae in BS4434 after all quantifying ventilation requirements are rules of hook based on unstated assumptions (eg they obtain no account of foyer size or leak rates). Inspectors should admonish that the formulae may be worn as a basic accompany but discretion in their authentic application to a detailed plant should be stressed. That is particularly important amidst very large systems when 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 action with prolonged releases from fundamental plant failure. However, the latter is very unlikely to continue in properly designed, constructed and maintained plant. Authority of sources of ignition and deposit shutdown (see paras 22-26) should further provide protection in such circumstances. Manually operated controls as emergency ventilation should be located in a safe, definitely accessible place along amidst the control or about-face for turning off the compressor.
Plant integrity
19 Near can be serious corrosion of the flat pressure. parts of pipework and deposit due to condensation. It bag progress unnoticed under lagging which is not completely vapour sealed and is essentially rapid on plants which run intermittently and pass-through OoC. The present principles relating to the protection of pressure systems are appropriate. The plan should be thoroughly examined by a adequate person at regular intervals in accordance amidst a written scheme. There should be an operating maintenance scheme.
Pipework
20 All parts of refrigerating systems and in detailed pipework should be positioned or secure to minimise the disclosure of impact damage, by reason of example by fork journey trucks. Pipework and valves should be clearly marked to indicate their contents and function.
Oil devour system
21 Many of the reported incidents involving ammonia refrigeration systems conclude been the result of a malfunction of the shortening drain system (designed to show up the "carry-over" of oil from the compressors). In about cases oil is distressed from below liquid ammonia and is saturated alongside it. In addition the shortening is viscous because it is cold. In command to minimise the exposure of escape from a particular cause the following measures should be advised:
(1) point short distances are interested and adequate observation of the devour is possible oil consume pipes should terminate in a safe location in the expose air. Valves on each pipe extension should not accept the possibility of liquid ammonia as a result of trapped; a bleed valve or hydrostatic comfort 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 butter drains. In addition to the operational magazine valve, there should be an automatic closing spring or weight-loaded valve; and
(3) The need of oil drain catchpots. These are a convenient feature on new plant, although existing plant cannot commonly be easily modified. Advanced the oil is drained, the catchpot is far-flung from the liquid ammonia/oil feedline and the catchpot is electrically bitter to boil off exclusive ammonia which flows as a vapour to the flat pressure side of the system. At the catchpot is warm, it is further isolated on the vapour leaf and the oil is earlier drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, properly ventilated positions and, point reasonably practicable, in the disclose air. Filling points should be sited overseas from sources of ignition.
PRECAUTIONS Against 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 immediate vicinity of externally located plant.
Electrical equipment
24 Advice on electrical apparatus after all use in potentially mine atmospheres is given in RS 5345: Article 1: 1976 "Code of Education for the Selection, Airfield and Maintenance of Magnetic Apparatus for Use in Potentially Mine Atmospheres, Part 1, Key Requirements for all Parts of the Code"; BS 4434: 1980, Clause 13 "Electrical Installations". The approaches followed by the raised documents differ.
25 As a ongoing 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 with the guidance given in para 27.
26 Location the ammonia compressors and refrigeration deposit are located in the same room as the fund switch gear for the-premises deportation 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 accessory selection criteria
27 The demand of electrical apparatus in refrigeration plants using ammonia has been expressed a special case as long as of the flammability characteristics of the fuel (high LEL and finite explosive range) and the detail that it can be detected at actually low levels by smell. That has resulted in a zip code 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 everyday have associated risks which may require attention, These include the exposure of trapping in impersonal stores and chills, the management of very cold products and microbiological problems amalgamated with cooling towers recycled for the condenser.
ENFORCEMENT APPROACH
29 Enforcement officers should advise a particular ammonia refrigeration plant should adapt with the guidance in BS 4434: 1980 as amended and surplus by the information in a well known circular. They should ever bear in mind:
(1) ammonia presents a toxic disclosure at concentrations far below those at which it presents exclusive fire or explosion risk. Ready have been 2 gassing fatalities betwixt 1977 and 1983 in the UK although only 3 incentive ammonia/air explosions in the base 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 advance published in 1969 and was not intended to be retrospective, despite improvements in installations which pre-date the usual 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 withdrawal and emergency action; and
(5) where enforcement officers encounter preservation contractors they should bring about 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 accompany the advice of HSEs Field Consultant Group (FCG) via the Domestic Enforcement Liaison Officer (ELO), along considering enforcement action.
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Ammonia is used as a refrigerant as long as of particular thermodynamic properties which empower it to move heat far more efficiently than additional refrigerant gases such as halogenated hydrocarbons. It is chiefly suited to working in the field approximately OoC to -30oC and so is widely used after all food preservation, the chilling of liquids akin as milk, beer and peaceful drinks, and in the synthetic industry. New systems endure to be installed.
2. A usual system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In culture other components such as 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 horizontal pressure, and hence horizontal temperature, takes in heat by vaporising. This vapour is removed by the compressor which, in compressing it, raises the altitude from below to over ambient. The hot compressed food gives up the simmer by condensing to a liquid in the condenser. The over pressure liquid then passes buttoned up the pressure reducing valve to the evaporator. At the valve the liquid is cooled as some vapour flashes off. The resting liquid is available as use in the evaporator.
4 In a businesslike system it is expected there will be further 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 since draining in some way. There may be a multi-stage compressor along an intercooler. This is cooled by aggrieved high pressure liquid into the flat pressure side.
Downstream of the condenser is approximately a liquid receiver. Downstream of the reducing valve is constantly found a surge cask which acts as a basin of cold liquid and evens alone demand on the compressor and condenser. The liquid ammonia is drawn from the current drum by a pump. Margarine drains may be begin on surge drums, liquid receivers, and overseas 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 intend was to collect advice about a cross block of installations. One hundred and forty eight returns were hand-me-down in the analysis which worn the Edinburgh FCG microcomputer.
2 Returns covered a accessible range of processes in the bread and drinks industries. The biggest single sector was dairying (chilled rain supply) with substantial returns likewise from frozen food producers and clinical stores. In the drinks sector cooling and soft drinks carbonators were the chief uses.
There were a accessible range of other uses reported; approximately parts of the cuisine industry require controlled temperatures below ambient at some design of their process. A clear range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were high 5 tonnes, 40% amid 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 there 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 chunk had the system charging amount in the compressor foyer and 38% had it outdoors. Twenty-seven per cent of the case could positively be identified as having doors to the outside of the building only. Thirty-six per cent of the added 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 constant the most rudimentary precautions to bar the spread of escaping fuel has not been taken. Fifty-five per cent had condensers mounted high ground level outside - normally on the roof. This raises questions of secure access and also avert in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were continually 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 affair 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, after all example, fork lift trucks. Partly of the entire count however had unmarked pipework. (Notes of abounding proformas suggested that a well known would receive early attention).
6 lt proved impossible to carryout meaningful reasoning of the ventilation provided in compressor rooms. A average installation seemed to bet largely on natural ventilation (perhaps assisted by a cramped fan) for normal ventilation. Where there was provision of ventilation especially for emergencies, it tended to be a self-reliant system rather than a 2 acceleration fan on the frequent ventilating system. Only 23% of the installations had 2 ventilation rates applicable and only half the ventilation systems of exclusive kind could be experimental from outside the compressor room. Alone half of these ventilation systems were naturally controlled.
7 Only 16% of everyone system charging was done by a person on his own; the typical arrangement was 2 men. Shortening draining was done by anybody man on his allow at 30% of anybody Installations. At 51 % of anybody installations it was carried away more than once a month. Alone 26% of installations had spring-loaded valves or a catchpot construction at oil drains. About of the rest had comparatively a short stub of drum from a vessel containing liquid ammonia still by a single valve. In 71 % of cases locus the oil drain was unsatisfactory inspectors clear that the reasonably practicable improvement was the fitting of self-closing valves. The 30% of installations point one man did the shortening draining on his acquiesce included 6 which had no respirator of any kind.
8 Forty-two per cent of compressor houses had no fuel detectors. Sieger was by buried the most common supplier (60%) of everybody 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 never checked.
Approximately half of the detector installations alone 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 independent alarm.
9 Sixty-six percent of compressor hall electrical installations were not completely equipped to Zone 2 usual even where much of the bury was under the authority of detectors. Seventy-five per cent of everybody compressor installations could be switched aside elsewhere outside the compressor gallery (even if only at the key supply). Of the remainder, the key switchgear was either in the compressor entrance or access to it was buttoned up the compressor room.
10 Eighty-eight bonus of all sites had 2 or likewise sets of respiratory conservation 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 demand of respiratory protection although only 43% had some array of systematic examination. At only 5 installations (3.4%) were ready possible limitations of area which conflicted with provision of respiratory protection and the basic problem seemed to be approach up ladders or conscious congested items of plant.
11 Forty-seven per cent of sites had reviving appliance available usually for present first aid rather than especially because of the ammonia.
12 Twenty-seven fee of sites had Draeger (or similar) detector tubes as measuring low concentrations of ammonia. Many others had sulphur sticks or hydrochloric acerbic for detecting small leaks.
13 Fifty-nine bonus of installations were maintained at least partly by contractors. Alone from a few fundamental suppliers and installers of device there were many governmental refrigeration engineers who alone appeared once or twice in the survey. No encouragement is available about the usual of training or workmanship of these contractors.
14 Fifty-five percentage of all sites appeared to accept emergency evacuation procedures (43% recycled the fire alarm) still slightly fewer (50%) appeared to confer any training in these procedures. Only 24% appeared to conclude detailed rescue arrangements. Twenty-two per cent had written systems of business which appeared comprehensive and alone 34% had what appeared to be effective plant operator training.
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APPENDIX 3 (paras 1 and 26)
PROTECTION OF Ac APPARATUS AT AMMONIA COMPRESSORS AND REFRIGERATION PLANT
EXTERNALLY SITED PLANT
1 Compressors and refrigeration entomb sited in out door locations in accordance alongside para 14 of that Circular in otherwise non-hazardous areas courage not normally require chiefly protected electrical equipment.
INTERNALLY SITED PLANT
2 A discharge chart of the key requirements relating to the electric apparatus for internally sited entomb is given in the supplement to a particular appendix. The operational approaches are disposed below.
Option 1 - Need of explosion protected magnetic apparatus
3 Hazardous area classification should be carried down by a competent person. Electrical apparatus should then be select in accordance with BS 5345: Article 1: 1976 Section 2. The max of compressor-houses should be regarded as Sector 2 areas. Type "N" bang protected equipment (including each emergency ventilation fans) resolve be suitable for these locations.
Option 2 - Detection of leaks by crew or gas detectors
4 ln a particular approach, non-explosion protected ac apparatus, with qualifications, may be worn in combination with a readily convenient means of isolating the ac supply. The method of achieving the closing can be accomplished either no doubt after detection of a flow by a gas detector system, or manually later a leakage has been detected by personnel. The commitment of these techniques as a first line of defence is moderate to applications solely involving ammonia in refrigeration plants. A certain approach is considered competent provided that the ongoing principles outlined in paras 10-17 are followed and a certain sufficient account is taken of paras 5-9.
Gas detectors
5 The detectors should be suitably positioned taking into history the physical characteristics of the bury room, the pattern of airflow deal in it and the about likely sources of potential leakage. Due regard should be paid to each 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 adequate expertise within his acquiesce organisation, it would be advisable as him to consult a employer which specialises in the composition and installation of electricity detection systems.
6 As a bumpy guide only, one valor expect to see detectors in the vicinity of the compressors and further non-static items of entomb and at ceiling category where one detector per 36M2 of ceiling area would probably be sufficient, albeit more may be key if there are extensive beams creating recesses. The objective is to ensure a well known the ammonia is detected and the apparatus rendered safe before flammable concentrations appear a source of ignition. (This objective, which is again applicable to "detection" of a leak by personnel, is essentially critical with regard to electrical apparatus which is not chiefly designed to be non-sparking, non explosion-protected ac apparatus and electrical appliance with temperatures above 630'C).
7 The detectors should be suitably barrage protected.
8 The detectors worn are of the "pellistor" brand and may be apt to poisoning by airborne contaminants. They should so be properly installed and maintained and always checked. The operation of the detectors should be limited using standard ammonia ammunition mixtures. Certain V-belt dressings containing antimony believe been shown to drug detectors and gradually curtail their response.
9 The detectors should be adequate of detecting concentrations of ammonia at 1 % v/v or less.
Associated magnetic apparatus
10 Account should be taken of the electrical control system circuitry and the severe possible degree of deterioration 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 no doubt operated, which cuts absent the electricity supply to the ammonia deposit room, should be located in a non-hazardous area. It bottle be either a architect or circuit breaker. If the criteria in paras 5-9 above have been satisfied, the back recommendations in paras 13-17 should be adopted. (Although physical specific details have been taken from BS 4434:1980, by approach of example, they are intended to characterize the general principles of that approach and not definite requirements -which will have, to be daring in each particular case).
12 Attention will need to be paid to the agency 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 Privacy 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 mathematical by a gas detection system as described pare 14, and arranged to give visual and audible alarms to alteration on equipment for crisis ventilation and/or emergency lighting (if installed). All electrical apparatus that is required to employ in the room later a leakage has been detected, such as ventilation equipment and crisis lighting, should be suitably safe for the hazardous field in which it is sited, ie Region 2. Few compressor rooms are gradually manned. Detection of discharge by operators is solo reliable if they are deliberately present in the room. If after all example they have added duties, or leave the area for meals etc, or commitment an isolated noise refuge already the speed of feeling is likely to be actually slower than that of autogenous 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 anyone or more suitable ammonia food detectors which should again be arranged to give a visual and definite alarm and to alteration on equipment for ventilation and/or exposure lighting, if installed. The ventilation facet should be discharged to the outside of the building in alike a manner as not to explanation distress or danger to persons in the vicinity of the building. Round isolation should be effected at ammonia concentrations below 25% LEL and an buzz setting of 1.5% v/v followed by round isolation at 3% v/v is suggested.
15 Care personnel are required to admit unmanned plant rooms and apt means of escape should be provided.
16 Human protection including breathing apparatus, and apparently impervious suits, may be needed in exclusive room or space if maintenance men are likely to damage pipework or do each other operation liable to call liquid ammonia or actual quantities of gas19014 19015 19016 19017 19018 19019 19020 19021 19022 19023 19024 19025 19026 19027 19028 19029 19030 19031 19032 19033 19034 19035 19036 19037 19038 19039 19040 19041 19042 19043 19044 19045 19046 19047 19048 19049 19050 19051 19052 19053 19054 19055 19056 19057 19058 19059 19060 19061 19062 19063 19064 19065 19066 19067 19068 19069 19070 19071 19072 19073 19074 19075 19076 19077 19078 19079 19080 19081 19082 19083 19084 19085 19086 19087 19088 19089 19090 19091 19092 19093 19094 19095 19096 19097 19098 19099 19100 19101 19102 19103 19104 19105 19106 19107 19108 19109 19110 19111 19112 19113 19114 19115 19116 19117 19118 19119 19120 19121 19122 19123 19124 19125 19126 19127 19128 19129 19130 19131 19132 19133 19134 19135 19136 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