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

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4CHAPITRE 4 PAGE 06 EVACUATION Servicing Practices Procedures to perform evacuation To evacuate and dehydrate a system, before filling with refrigerant, take the following steps: 1 - First, the system should be tightness tested (i.e., “leak tested”). This can be done by pressurising the system with oxygen free, dry nitrogen (OFDN). Shut off the supply of nitrogen and check the pressure over a period of time (a minimum of 15 minutes, but it depends upon the size of the system; a larger system requires more time). Keep checking the pressure gauge to see if the pressure reduces. 2 - If the pressure does fall, it is likely that the system has a leak, so leak searching and repair procedures must be carried out. OPEN OPEN Vacuum pump connexion OPEN Exhaust 3 - When the system is confirmed to be leak-tight, release the OFDN and immediately connect a proper vacuum pump to both suction side and discharge the side of the compressor (see diagrams), and make sure the vacuum gauge is connected. Open all the valves, including solenoid valves, so there is no part of the circuit that is “locked” in. 4 - Switch on the vacuum pump and wait. 5 - When satisfactory vacuum has been reached (below 100 Pa abs.) stop the pump and leave it for an appropriate length of time (around half an hour for a small hermetic system, to several hours for a large site-installed system) to see if the vacuum gauge indicates an increase in internal pressure. If the pressure rises there could be two reasons for it: either there is a leak or moisture still in the system. In this case, the evacuation procedure should continue, but if a constant vacuum pressure is never achieved, then it is likely that a leak is present and the tightness test should be repeated. Vacuum Pump 6 - If the vacuum pressure remains constant over a period of time, the circuit is correctly evacuated; dry and free of leakage. 92
4 Servicing Practices 7 - For large systems where is expected excess of moisture content, apply indirect heat (using a heat lamp or hot air-blower, see the diagram) to the system tubing (applying heat to one side only will cause moisture condensation in the coolest part). REFRIGERANT DRUM VACUUM PUMP Refrigeration system evacuation CENTER GAGE HOSE USED FOR BOTH PUMP AND SUPPLY CYLINDER HEAT MOISTURE ALL SERVICE VALVES ARE MIDSEATED AND LEAKPROOF PROTECTIVE CAPS ARE ON TIGHT MOISTURE HEAT U TUBE MERCURY MANOMETER LIQUID WATER VAPOR MOISTURE HEAT LAMP 93
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Manual for Refrigeration Servicing
Page 3 and 4:
Introduction When to use the manual
Page 5 and 6:
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
Page 41 and 42: 2 Refrigerants Those with ozone dep
Page 43 and 44: 2 Refrigerants Those with zero ozon
Page 45 and 46: 2 Refrigerants Carbon dioxide (CO2,
Page 47 and 48: 2 Refrigerants Azeotropic Blends An
Page 49 and 50: 2 Refrigerants Using Refrigerant Bl
Page 51 and 52: 2 Refrigerants Lubricants Today, al
Page 53 and 54: 2 Refrigerants Refrigerants and app
Page 55 and 56: 2 Refrigerants Properties of most c
Page 57 and 58: 3 Refrigerants Content Management M
Page 59 and 60: 3 Refrigerant Management The majori
Page 61 and 62: 3 Refrigerant Management Handling o
Page 63 and 64: 3 Refrigerant Management Recovery c
Page 65 and 66: 3 Refrigerant Management Refrigeran
Page 67 and 68: 3 Refrigerant Management Refrigeran
Page 69 and 70: 3 Refrigerant Management Open Refri
Page 71 and 72: 3 Refrigerant Management CHAPITRE 3
Page 73 and 74: 3 Refrigerant Management Recycling
Page 75 and 76: 3 Refrigerant Management equipment
Page 79 and 80: 3 Refrigerant Management PAGE 22 Ex
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: 4 Servicing Practices Evacuation A
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 and 134: 6 Safe Refrigerant Handling leak de
Page 135 and 136: 6 Safe Refrigerant Handling • Lea
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
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Glossary Glossary Absolute pressure
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Glossary Fossil fuels Carbon-based
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Glossary hole in late 1985, governm
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Glossary Sealed system A refrigerat
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Acknowledgements Acknowledgements I
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Copyright Copyright © United Natio
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