Manual for Refrigeration Servicing Technicians - UNEP - Division of ...

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6 Safe Refrigerant Handling Safety checks to electrical devices Repair and maintenance to electrical components shall include initial safety checks and component inspection procedures. If a fault exists that could compromise safety, then no electrical supply should be connected to the circuit until it is satisfactorily dealt with. If the fault cannot be corrected immediately but it is necessary to continue operation, an adequate temporary solution shall be used, but this must be reported to the owner of the equipment so all parties are aware. Initial safety checks should be as follows: • Ensure that capacitors are discharged. This should be done in a safe manner to avoid the possibility of sparking. • Do not work on “live” electrical components and wiring whilst charging, recovering or purging the system. • Continuity of earth bonding. During repairs to sealed components, all electrical supplies must be disconnected from the equipment being worked upon prior to any removal of sealed covers, etc. If it is absolutely necessary to have an electrical supply to equipment during servicing, then a permanently operating form of leak detection shall be located at the most critical point to forewarn the individual of a potentially hazardous situation. For repairs to sealed components, particular attention should be paid to the following: • Ensure that by working on electrical components, the casing is not altered in such a way that the level of protection is affected. This should include damage to cables, too many connections, terminals not made to the original specification, damage to seals, incorrect fitting of glands, etc. This includes the secure mounting of the apparatus. • Ensure that seals or sealing materials have not degraded such that it is no longer serving the purpose of preventing the ingress of flammable atmospheres. • Replace only with parts specified by the manufacturer. Other parts may result in the ignition of refrigerant in the atmosphere from a leak. Check that cabling will not be subject to wear corrosion, excessive pressure, sharp edges or any other adverse environmental effects. This should also take into account the effects of ageing or continual vibration from sources such as the compressor or fans. Detection of hydrocarbon refrigerants Under no circumstances should potential sources of ignition be used in the searching or detection of refrigerant leaks. A halide torch (or any other detector using a naked flame) must not be used. The following leak detection methods can be used on systems containing hydrocarbons: • Electronic leak detectors may be used to detect hydrocarbons, but the sensitivity may not be adequate, or may need calibration (detection equipment should be calibrated in a refrigerantfree area). Ensure that the detector is not a potential source of ignition and is suitable for hydrocarbon refrigerants. 134
6 Safe Refrigerant Handling • Leak detection equipment should be set at a percentage of the LFL of the refrigerant and should be calibrated to the refrigerant employed and the appropriate percentage of gas (25% maximum) is confirmed. • Leak detection fluids are suitable for use with hydrocarbon refrigerants but the use of detergents containing chlorine should be avoided as the chlorine may react with the refrigerant and corrode the copper pipework. • Oil additives such as those used in fluorescent leak detection systems will operate with hydrocarbons. • If a leak is suspected from a hydrocarbon refrigerant system all naked flames should be removed or extinguished. If a leakage of refrigerant is found which requires brazing, all of the refrigerant shall be recovered from the system, or isolated (by means of shut off valves) in a part of the system remote from the leak. Oxygen Free Nitrogen (OFN) should then be purged through the system both before and during the brazing process. Breaking into a system and removal of refrigerant When breaking into the refrigerant circuit to make repairs - or for any other purpose – conventional procedures are used. However, it is important that best practice is followed since flammability is now a consideration. The following procedure shall be adhered to: • remove the refrigerant • purge the circuit with inert gas • evacuate • purge again with inert gas • open the circuit by cutting or brazing. The refrigerant charge should be recovered into the correct recovery cylinders. The system is then to be “flushed” with OFN to render the unit safe; this process may need to be repeated several times. Do not use compressed air or oxygen for this task. Flushing is achieved by breaking the vacuum in the system with OFN and continuing to fill until the working pressure is achieved, then venting to the atmosphere, and finally pulling down to a vacuum. This process is repeated until the technician is satisfied that no hydrocarbons are within the system. When the final OFN charge is used, the system can be vented down to atmospheric pressure to enable work to take place. This operation is absolutely vital if brazing operations on the pipe work are to take place. Ensure that the outlet for the vacuum pump is not close to any ignition sources and ventilation is available. 135
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Manual for Refrigeration Servicing
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Introduction When to use the manual
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Introduction The Factors affecting
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Introduction How to assess conditio
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Introduction Characteristics of Sel
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Introduction Another form of refere
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Introduction Choose your chapter Th
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1 Environmental impact of refrigera
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1 Environmental Impact The ozone la
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1 Environmental Impact RADIATION FR
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1 Environmental Impact The ozone la
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1 Environmental Impact Effects of o
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1 Environmental Impact The greenhou
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1 Environmental Impact Timeline act
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1 Environmental Impact Alternative
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1 Environmental Impact The way forw
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2 Refrigerants 2.1. Section objecti
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2 Refrigerants Chemical properties
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2 Refrigerants Safety characteristi
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2 Refrigerants Types of refrigerant
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2 Refrigerants Those with ozone dep
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2 Refrigerants Those with zero ozon
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2 Refrigerants Carbon dioxide (CO2,
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2 Refrigerants Azeotropic Blends An
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2 Refrigerants Using Refrigerant Bl
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2 Refrigerants Lubricants Today, al
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2 Refrigerants Refrigerants and app
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2 Refrigerants Properties of most c
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3 Refrigerants Content Management M
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3 Refrigerant Management The majori
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3 Refrigerant Management Handling o
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3 Refrigerant Management Recovery c
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3 Refrigerant Management Refrigeran
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3 Refrigerant Management Refrigeran
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3 Refrigerant Management Open Refri
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3 Refrigerant Management CHAPITRE 3
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3 Refrigerant Management Recycling
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3 Refrigerant Management equipment
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3 Refrigerant Management PAGE 22 Ex
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Page 83 and 84: 3 Refrigerant Management Further re
Page 85 and 86: Summary This section will provide t
Page 87 and 88: 4 Servicing Practices Moisture Mois
Page 89 and 90: 4 Servicing Practices Non-condensab
Page 91 and 92: 4 Servicing Practices Evacuation A
Page 93 and 94: 4 Servicing Practices 7 - For large
Page 95 and 96: 4 Servicing Practices Pressure unit
Page 97 and 98: CHAPITRE 4 4PAGE 10 LEAK DETECTION
Page 99 and 100: 4 Servicing Practices Detection met
Page 101 and 102: 4 Servicing Practices CHAPITRE 4 PA
Page 103 and 104: 4 Servicing Practices Volumetric ch
Page 105 and 106: 4 Servicing Practices Electronic ch
Page 107 and 108: 4 Servicing Practices Why charge re
Page 109 and 110: 5 Retrofitting Content General retr
Page 111 and 112: 5 Retrofitting • Upon evaluation
Page 113 and 114: 5 Retrofitting General retrofitting
Page 115 and 116: 5 Retrofitting procedures that you
Page 117 and 118: 5 Retrofitting MVAC retrofitting pr
Page 119 and 120: 5 Retrofitting Although, in general
Page 121 and 122: 5 Retrofitting Further reading UNEP
Page 123 and 124: 6 Summary 6.1. Overview of refriger
Page 125 and 126: 6 Safe Refrigerant Handling Oxygen
Page 127 and 128: 6 Safe Refrigerant Handling The com
Page 129 and 130: 6 Safe Refrigerant Handling • Nev
Page 131 and 132: 6 Safe Refrigerant Handling Safe ha
Page 133: 6 Safe Refrigerant Handling leak de
Page 137 and 138: 6 Safe Refrigerant Handling Storage
Page 139 and 140: 6 Safe Refrigerant Handling Recomme
Page 141 and 142: 6 Safe Refrigerant Handling 3 - Sho
Page 143 and 144: Glossary Glossary Absolute pressure
Page 145 and 146: Glossary Fossil fuels Carbon-based
Page 147 and 148: Glossary hole in late 1985, governm
Page 149 and 150: Glossary Sealed system A refrigerat
Page 151 and 152: Acknowledgements Acknowledgements I
Page 153: Copyright Copyright © United Natio
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