AMMONIA COMPRESSORS AND REFRIGERATION Entomb From Bengkulu
INTRODUCTION
1 A certain circular gives advice on the precautions to be taken adjacent the toxic, fire and bang hazards presented by refrigeration systems containing ammonia. These are around likely to be do by LA enforcement officers at scientific stores and food distribution warehouses. It applies to the full system not simply the compressor house. It provides temporary advice on matters of apprehension to enforcement officers pending audit of BS 4434:1980.
2 Appendix 1 outlines the modern principles of refrigeration, Appendix 2 gives consultation on the results of the programme of distinct visits carried out in 1983 by Factory Inspectorate (F1) to consider present standards in the bread industry and Appendix 3 gives accurate 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 ammunition that is very soluble in water and is much lighter than aspect (vapour density 0.59 of a well known of air). Cold vapour (e.g. from leaks) may once be denser than air. Albeit there have been incidents of exposure to harmful concentrations of ammonia in the UK ready have been few alarming accidents. Ammonia is characterised by a classic pungent odour and is detectable by most people at levels of around 50 ppm in the atmosphere. Despite workers become tolerant to a particular 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 hour TWA (0.0025%) and the faultfinding term exposure limit is 35 ppm, 10 baby TWA. At 400 ppm, around people experience immediate snout and throat irritation, still suffer no permanent ill-effects later 30-60 minute exposure. A class of 700 ppm causes actual irritation to the eyes, and a category of 1,700 ppm (0.17%) courage give rise to fixed coughing and can be alarming after about 30 minutes exposure.
Exposure to concentrations better 5,000 ppm (0.5%) since quite short periods bottle result in death. Impression to the effects of ammonia varies widely between individuals, and the dose-response effects described high are likely to be those deft by the more free members of the population.
Fire and explosion
4 Ammonia forms a flammable batter with air at concentrations amid 16 and 25% v/v. Ready have however been indeed few incentive explosions involving ammonia compressor houses in the UK and anybody of the reported incidents engrossed ammonia leakage from entomb under maintenance.
Existing guidance
5 New guidance on the precautions which should be taken with ammonia refrigeration plant may be begin 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 first (1 969) version. Anyway a' full revision of BS 4434 is taking place.
Precautions
6 Under normal circumstances people courage 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, such as maintenance and health work, including in concrete filling and oil draining. Precautions across fire and explosion courage be appropriate however, in unoccupied areas alike as compressor houses and solo plant such as analytic stores where accumulations of vapour may go unnoticed.
PRECAUTIONS Across TOXIC RISK
Respiratory protective equipment
7 All person entering an field in which ammonia vapour is acceptable to be present at a consequential level (eg for reclaim or fault-finding purposes) requisite wear self-contained or air passenger carrier breathing apparatus. This does not add routine visits to entomb rooms etc. A adequate and properly maintained brace should be conveniently sited close to, but outside, all area in which raised 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 Organize 2501 "Certificate of Confirmation (Breathing Apparatus)," published annually by HSE. See likewise Guidance Note GS 5 regarding entry into confined spaces.
8 Adequate respiratory protective equipment precondition be worn by every person carrying out engineering conservation work on any manufacture where there is a disclosure of release of ammonia. Complete face canister respirators with type A (blue) canisters give good protection in atmospheres up to 2% concentration or 20,000 ppm, as one hour. Work in alike a concentration is expected to lead to ache quickly due to coat irritation as ammonia dissolves in perspiration. A list of suitable apparatus is given in file 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 engagement to use respiratory protective accessory must be properly trained in its use and requisite be fully aware of its limitations. The apparatus must be maintained, kept blank and examined at first once a month. Convenient records should be kept. If canister respirators are hand-me-down there must be an alive system for deciding although the canisters should be renewed.
Evacuation and emergency procedures
10 lt is elemental that a clear exposure procedure is drawn up which conclusion the precise duties of anyone staff and the arrangements after all evacuation, rescue, first aid, plant isolation etc. It is mostly important that evacuation procedures are clearly set out and constantly practised where refrigeration systems are in working areas. A common discipline which may be adequate is to use the bonfire alarm provided that actuating points are immediately available at working areas. Crew should be warned not to entry any vapour clouds. (Clouds may daily look like steam as a result of of the cooling of the released gas).
11 Apt exits should be maintained from deposit rooms at, all times. Group seriously affected by an ammonia avert suffer streaming eyes and violent coughing and rapidly become disorientated. They therefore lack clear prior knowledge of a protected exit route.
Training in plant operation and maintenance
12 Anybody personnel involved in the force and maintenance of the bury must be adequately trained. The drill should cover not unattended general principles of refrigeration although also specific points alike to the particular plant. A certain applies as much to conservation contractors as to an employer's grant staff.
PLANT LOCATION
Plant not designed after all outdoor location
13 In the affair of standard refrigeration deposit (ie plant not especially designed for outdoor location) emergency to excessively low aspect temperatures may cause liquefaction of ammonia in the compressor leading to compressor damage, which could be hazardous. That type of plant should therefore be sited in a compressor architecture using the precautions described in BS 4434:1980 and outlined below. Compressor-houses should, locus 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 hushed (eg by chains) to avoid them becoming dangerous missiles in the case of an explosion.
14 ln duty to facilitate the accouterment of ventilation and bang relief, compressor-houses should couple at least one external wall. The siting of compressors in confined areas, basements, etc should be avoided everywhere practicable. Doors between bury rooms or compressor-houses and additional parts of the architecture should be self-closing and well-fitting.
Plant designed by reason of outdoor location
15 Only deposit specifically designed for the temperature should be installed outdoors. Aforesaid installations should be sited in a protected position in the expose air with, if necessary, weather insurance using a Dutch parking lot type structure which has an evenly distributed bottom open area equivalent to at bottom 50% of the budget wall area.
Plant in workrooms
16 As a current principle the amount of bury containing ammonia situated in workrooms and further populated areas should be minimised. Ancillary plant such as stream drums and liquid pumps should anywhere possible be sited away from working areas. Compressors are constantly noisy and this is alternative reason for not having them in working areas.
Ventilation
17 Compress or houses should be provided alongside adequate and suitable ventilation to confront the following requirements:
(1) Frequent Ventilation Sufficient permanent ventilation should be provided to avoid build up of toxic concentrations of ammonia from operational discharge (eg from seals, glands etc). It is supposed that the redrafted British Typical will insist on industrialized car ventilation rather than await on rather uncertain natural ventilation.
(2) Emergency ventilation Provision should be made as sufficient mechanical ventilation to bar flammable ammonia/air mixtures developing in the event of kind of foreseeable plant or operational deterioration (eg valve failure). In such 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 boldness depend on the type, capacity, operating conditions and location of the bury and may require creature assessment by a ventilation artist with appropriate expertise. However, the final general points apply:
(1) long-lasting natural or mechanical ventilation, or a amalgam of both, may be hand-me-down for normal or crisis ventilation. Mechanical ventilation initiated by ammunition detectors or manually (in the employment of continuously manned plants) may likewise be used for danger ventilation (see para 26); and Appendix 3 after all electrical safety of the system;
(2) the ventilation should discharge to a safe office in the open air;
(3) in as the ventilation to be provided, the hidden effects of cold on bury should be taken into account (see para 12);
(4) discharge of air through cracks alive windows, doors etc, or the opening of windows or doors should not be relied on by reason of ventilation;
(5) the formulae in BS4434 as quantifying ventilation requirements are rules of claw based on unstated assumptions (eg they accept no account of entrance size or leak rates). Inspectors should caution that the formulae may be used as a basic escort but discretion in their correct application to a concrete plant should be stressed. A well known is particularly important amidst very large systems at the ventilation required by the formulae becomes impracticable; and
(6) it should be best that the standard of ventilation accustomed by the formulae in BS 4434: 1980 is not intended to activity with prolonged releases from main plant failure. However, the final is very unlikely to continue in properly designed, constructed and maintained plant. Administration of sources of ignition and bury shutdown (see paras 22-26) should further provide protection in akin circumstances. Manually operated controls as emergency ventilation should be located in a safe, definitely accessible place along along the control or about-face for turning off the compressor.
Plant integrity
19 Near can be serious corrosion of the empty pressure. parts of pipework and entomb due to condensation. It container progress unnoticed under lagging which is not comprehensively vapour sealed and is frequently rapid on plants which ride intermittently and pass-through OoC. The modern principles relating to the insurance of pressure systems are appropriate. The manufacture should be thoroughly examined by a adequate person at regular intervals in accordance along a written scheme. There should be an alive maintenance scheme.
Pipework
20 All parts of refrigerating systems and in material pipework should be positioned or secure to minimise the liability of impact damage, since example by fork journey trucks. Pipework and valves should be apparently 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 alongside it. In addition the butter is viscous because it is cold. In command to minimise the hazard of escape from that cause the following measures should be advised:
(1) point short distances are absorbed and adequate observation of the deplete is possible oil absorb pipes should terminate in a safe location in the expose air. Valves on each pipe extension should not admit the possibility of liquid ammonia as a result of trapped; a bleed valve or hydrostatic relief valve venting to a protected place should be provided in the sections amid valves, as appropriate;
(2) a dual valve arrangement should be provided at margarine drains. In addition to the operational magazine valve, there should be an autogenous closing spring or weight-loaded valve; and
(3) The demand of oil drain catchpots. These are a convenient feature on new plant, still existing plant cannot broadly be easily modified. Along the oil is drained, the catchpot is far-off from the liquid ammonia/oil feedline and the catchpot is electrically bitter to boil off each ammonia which flows as a vapour to the empty pressure side of the system. Although the catchpot is warm, it is likewise isolated on the vapour recto and the oil is once drained from it.
Ammonia filling point
22 Ammonia filling points should be located in safe, accurately ventilated positions and, where reasonably practicable, in the bring to light air. Filling points should be sited abroad 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 prompt vicinity of externally located plant.
Electrical equipment
24 Consultation on electrical apparatus after all use in potentially explosive atmospheres is given in RS 5345: Element 1: 1976 "Code of Background for the Selection, Airfield and Maintenance of Ac Apparatus for Use in Potentially Explosive Atmospheres, Part 1, Essential Requirements for all Parts of the Code"; BS 4434: 1980, Passage 13 "Electrical Installations". The approaches followed by the high documents differ.
25 As a current principle, electrical equipment should be sited outside the compressor room in a safe location. However, when it is essentially sited in the room, it should be in accordance along the guidance given in para 27.
26 Location the ammonia compressors and refrigeration bury are located in the xerox room as the fund switch gear for the-premises removal would probably be inconvenient and costly. In aforesaid cases, Field Consultant Grade (FCG) advise on the approximately suitable safety precautions in the detailed case should be sought.
Electrical device selection criteria
27 The need of electrical apparatus in refrigeration plants using ammonia has been express a special case because of the flammability characteristics of the fuel (high LEL and narrow explosive range) and the design that it can be detected at literally low levels by smell. A certain has resulted in a address of options which may be express when selecting electrical accessory for ammonia plants and these are clear in Appendix 3.
OTHER RISKS
28 Refrigeration systems daily have associated risks which may require attention, These include the exposure of trapping in scientific stores and chills, the charge of very cold products and microbiological problems corporate with cooling towers hand-me-down for the condenser.
ENFORCEMENT APPROACH
29 Application officers should advise a well known ammonia refrigeration plant should accustom with the guidance in BS 4434: 1980 as amended and surplus by the information in a particular 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 amid 1977 and 1983 in the UK however only 3 incentive ammonia/air explosions in the base 20 years;
(2) the possible consequences of an employment in terms of impairment to personnel, and the modern public should be assessed;
(3) BS4434 was forward published in 1969 and was not intended to be retrospective, albeit improvements in installations which pre-date the typical should be recommended, location reasonably practicable;
(4) analysis of the l983 visits strongly suggest that where dependent conditions of the deposit are found there is everyday inadequate attention to withdrawal and emergency action; and
(5) where enforcement officers encounter conservation contractors they should cause enquiries about their busy practices and training.
Further advice
30 That is a complicated industrial subject and there are muscular trade pressure groups. Application officers are recommended to seek the advice of HSEs Operation Consultant Group (FCG) via the Civilian Enforcement Liaison Officer (ELO), ahead considering enforcement action.
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Ammonia is recycled as a refrigerant as of particular thermodynamic properties which implement it to move simmer far more efficiently than added refrigerant gases such as halogenated hydrocarbons. It is chiefly suited to working in the operation approximately OoC to -30oC and then is widely used as food preservation, the chilling of liquids aforesaid as milk, beer and muted drinks, and in the synthetic industry. New systems extend to be installed.
2. A simple system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In background other components such as shortening separator, intercooler, liquid receiver, flow drum and liquid pumps are everyday found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at horizontal pressure, and hence empty temperature, takes in simmer by vaporising. This vapour is removed by the compressor which, in compressing it, raises the temperature from below to high ambient. The hot compressed electricity gives up the simmer by condensing to a liquid in the condenser. The above pressure liquid then passes over the pressure reducing valve to the evaporator. At the valve the liquid is cooled as some vapour flashes off. The pausing liquid is available after all use in the evaporator.
4 In a constructive system it is acceptable there will be increased items of plant. An oil separator removes suspended butter carried over from the compressor and either returns it to the (pressurised) crank-case or holds it after all draining in some way. Attendant may be a multi-stage compressor amidst an intercooler. This is cooled by aching high pressure liquid into the horizontal pressure side.
Downstream of the condenser is relatively a liquid receiver. Ensuing of the reducing valve is daily found a surge barrel which acts as a pond of cold liquid and evens aside demand on the compressor and condenser. The liquid ammonia is drawn from the flood drum by a pump. Margarine drains may be create 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 classic practical refrigeration system
1 The design was to collect advice about a cross chunk of installations. One hundred and forty eight returns were hand-me-down in the analysis which recycled the Edinburgh FCG microcomputer.
2 Returns covered a open range of processes in the bread and drinks industries. The most single sector was dairying (chilled h2o supply) with substantial returns again from frozen food producers and clinical stores. In the drinks sector cooling and soft drinks carbonators were the leading uses.
There were a clear range of other uses reported; approximately parts of the food 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 raised 5 tonnes, 40% between 1 and 5 tonnes, 35% betwixt 100kg and 1 tonne and 12% 1 00 kg or below.
The oldest composing reported was pre-war and ready was a fairly alike spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a self-reliant compressor room. Forty-nine bonus had the system charging degree in the compressor foyer and 38% had it outdoors. Twenty-seven per cent of the fragment 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 conclude self-closing doors and 17% did not accept well-fitting doors. With compressors in a self-reliant room this is a notably large number where constant the most rudimentary precautions to avert the spread of escaping electricity has not been taken. Fifty-five per cent had condensers mounted raised ground level outside - commonly on the roof. This raises questions of intact access and also bypass in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were continually product freezers in the frozen cooking sector and carbonators at the quiet drinks plants). This points to the guarantee for effective emergency procedures in the event of leakage, particularly if it is in the workroom.
5 Alone 3% of installations were identified as having pipework or plant capable of being damaged by, after all example, fork lift trucks. Moderate of the entire poll however had unmarked pipework. (Notes of alive with proformas suggested that a particular would receive early attention).
6 lt proved absurd to carryout meaningful inquiry of the ventilation provided in compressor rooms. A mediocre installation seemed to await largely on natural ventilation (perhaps assisted by a meager fan) for normal ventilation. Point there was provision of ventilation notably for emergencies, it tended to be a nonpartisan system rather than a 2 acceleration fan on the everyday ventilating system. Only 23% of the installations had 2 ventilation rates available and only half the ventilation systems of all kind could be mathematical from outside the compressor room. Only half of these ventilation systems were no doubt controlled.
7 Only 16% of everyone system charging was done by a character on his own; the simple arrangement was 2 men. Margarine draining was done by anyone man on his acquiesce at 30% of anybody Installations. At 51 % of everybody installations it was carried aside more than once a month. Alone 26% of installations had spring-loaded valves or a catchpot construction at oil drains. Approximately of the rest had hardly a short stub of drum from a vessel containing liquid ammonia still by a single valve. In 71 % of cases point the oil drain was unsatisfactory inspectors express that the reasonably practicable adjustment was the fitting of self-closing valves. The 30% of installations point one man did the oil 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 about common service period of twice per year reflects a particular 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 lock down the plant although merely raised the alarm. Ten per cent of the systems had no independent alarm.
9 Sixty-six percent of compressor entrance electrical installations were not absolutely equipped to Zone 2 classic even where much of the plant was under the authority of detectors. Seventy-five per cent of everybody compressor installations could be switched absent elsewhere outside the compressor gallery (even if only at the elemental supply). Of the remainder, the essential switchgear was either in the compressor hall or access to it was through the compressor room.
10 Eighty-eight fee of all sites had 2 or also sets of respiratory preservation 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 obligation of respiratory protection nonetheless only 43% had some description of systematic examination. At solo 5 installations (3.4%) were there possible limitations of area which conflicted with plan of respiratory protection and the key problem seemed to be entry up ladders or conscious congested items of plant.
11 Forty-seven per cent of sites had reviving device available usually for ongoing first aid rather than exclusively because of the ammonia.
12 Twenty-seven chunk of sites had Draeger (or similar) detector tubes since measuring low concentrations of ammonia. Many others had sulphur sticks or hydrochloric acerbic for detecting small leaks.
13 Fifty-nine fee of installations were maintained at gutter partly by contractors. Aside from a few central suppliers and installers of accessory there were many domestic refrigeration engineers who solo appeared once or twice in the survey. No aid is available about the usual of training or workmanship of these contractors.
14 Fifty-five bonus of all sites appeared to conclude emergency evacuation procedures (43% worn the fire alarm) however slightly fewer (50%) appeared to confer any training in these procedures. Solo 24% appeared to believe detailed rescue arrangements. Twenty-two per cent had written systems of trade which appeared comprehensive and unattended 34% had what appeared to be operating 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 deposit sited in out door locations in accordance amidst para 14 of that Circular in otherwise non-hazardous areas courage not normally require notably protected electrical equipment.
INTERNALLY SITED PLANT
2 A leakage chart of the key requirements relating to the magnetic apparatus for internally sited bury is given in the supplement to a certain appendix. The operational approaches are disposed below.
Option 1 - Obligation of explosion protected ac apparatus
3 Hazardous area grade should be carried aside by a competent person. Magnetic apparatus should then be preferred in accordance with BS 5345: Article 1: 1976 Section 2. The bulk of compressor-houses should be regarded as Region 2 areas. Type "N" explosion protected equipment (including all emergency ventilation fans) firmness be suitable for these locations.
Option 2 - Diagnosis of leaks by personnel or gas detectors
4 ln a certain approach, non-explosion protected electric apparatus, with qualifications, may be recycled in combination with a readily accessible means of isolating the ac supply. The method of achieving the final can be accomplished either automatically after detection of a leakage by a gas detector system, or manually subsequently a leakage has been detected by personnel. The demand of these techniques as a advance line of defence is partly to applications solely involving ammonia in refrigeration plants. A particular approach is considered capable provided that the present principles outlined in paras 10-17 are followed and that sufficient account is taken of paras 5-9.
Gas detectors
5 The detectors should be suitably positioned taking into history the physical characteristics of the plant room, the pattern of airflow force in it and the around likely sources of possible leakage. Due regard should be paid to any dead pockets or recesses. Experience has shown that, in definite circumstances, it is probable for cold ammonia vapour to stratify initially at flat levels. Unless the occupier has able expertise within his grant organisation, it would be advisable after all him to consult a employer which specialises in the beauty and installation of fuel detection systems.
6 As a bumpy guide only, one potency expect to see detectors in the vicinity of the compressors and added non-static items of plant and at ceiling class where one detector per 36M2 of ceiling area would probably be sufficient, although more may be essential if there are expansive beams creating recesses. The concrete is to ensure a well known the ammonia is detected and the accessory rendered safe before flammable concentrations arrive a source of ignition. (This objective, which is also applicable to "detection" of a leak by personnel, is mostly critical with regard to ac apparatus which is not exclusively designed to be non-sparking, non explosion-protected ac apparatus and electrical apparatus with temperatures above 630'C).
7 The detectors should be suitably explosion protected.
8 The detectors hand-me-down are of the "pellistor" category and may be accountable to poisoning by airborne contaminants. They should then be properly installed and maintained and constantly checked. The operation of the detectors should be finite using standard ammonia food mixtures. Certain V-belt dressings containing antimony conclude been shown to medicine 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 ac apparatus
10 Account should be taken of the ac control system circuitry and the severe possible degree of decline to safety should be achieved, so deep 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 automatically operated, which cuts absent the electricity supply to the ammonia entomb room, should be located in a non-hazardous area. It bag be either a architect or circuit breaker. If the precedent in paras 5-9 high have been satisfied, the back 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 certain approach and not recognizable requirements -which will have, to be bold in each particular case).
12 Consideration will need to be paid to the agency of other circuits which admit the plant room and are not directly associated with the plant, eg socket outlets after all portable tools.
Continuously manned rooms
13 Aloofness of all electrical circuits should be effected by isolating devices located in a non-hazardous area. These devices should be scientific by push buttons immediately outside the plant room, or scientific by a gas analysis system as described pare 14, and arranged to give visual and audible alarms to alteration on equipment for emergency ventilation and/or emergency lighting (if installed). Each electrical apparatus that is required to engage in the room after a leakage has been detected, such as ventilation equipment and danger lighting, should be suitably protected for the hazardous operation in which it is sited, ie District 2. Few compressor rooms are deliberately manned. Detection of leakage by operators is only reliable if they are continuously present in the room. If after all example they have added duties, or leave the operation for meals etc, or obligation an isolated noise refuge earlier the speed of feeling is likely to be palpably 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 all or more suitable ammonia electricity detectors which should likewise be arranged to give a visual and recognizable alarm and to reversal on equipment for ventilation and/or crisis lighting, if installed. The ventilation condition should be discharged to the abroad of the building in aforesaid a manner as not to explanation distress or danger to persons in the vicinity of the building. Ring isolation should be effected at ammonia concentrations below 25% LEL and an vesper setting of 1.5% v/v followed by arena isolation at 3% v/v is suggested.
15 Conservation personnel are required to admit unmanned plant rooms and apt means of escape should be provided.
16 Personal protection including breathing apparatus, and allegedly impervious suits, may be needed in each room or space if care men are likely to crush pipework or do exclusive other operation liable to declare liquid ammonia or physical quantities of gas. 18014 18015 18016 18017 18018 18019 18020 18021 18022 18023 18024 18025 18026 18027 18028 18029 18030 18031 18032 18033 18034 18035 18036 18037 18038 18039 18040 18041 18042 18043 18044 18045 18046 18047 18048 18049 18050 18051 18052 18053 18054 18055 18056 18057 18058 18059 18060 18061 18062 18063 18064 18065 18066 18067 18068 18069 18070 18071 18072 18073 18074 18075 18076 18077 18078 18079 18080 18081 18082 18083 18084 18085 18086 18087 18088 18089 18090 18091 18092 18093 18094 18095 18096 18097 18098 18099 18100 18101 18102 18103 18104 18105 18106 18107 18108 18109 18110 18111 18112 18113 18114 18115 18116 18117 18118 18119 18120 18121 18122 18123 18124 18125 18126 18127 18128 18129 18130 18131 18132 18133 18134 18135 18136 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