1、CHAPTER 9REFRIGERANT CONTAINMENT, RECOVERY, RECYCLING, AND RECLAMATIONEmissions Types . 9.1Design 9.1Installation . 9.1Servicing and Decommissioning 9.1Training 9.2Leak Detection . 9.2Recovery, Recycling, and Reclamation 9.2CONTAINMENT of refrigerant is an important considerationduring service and m
2、aintenance of refrigeration systems. The poten-tial environmental effect of chlorofluorocarbon (CFC) and hydro-chlorofluorocarbon (HCFC) refrigerants on ozone depletion, and ofthese and hydrofluorocarbon (HFC) refrigerants on global warming,make it imperative that refrigerants are confined to closed
3、 systemsand recovered during service and at the end of life. Containmentmust be considered in all phases of a systems life, including (1) de-sign and construction of leaktight and easily serviced systems,(2) leak detection and repair, (3) recovery during service, and(4) recovery system disposal. Add
4、itional reference can be found inASHRAE Standard 147-2002.EMISSIONS TYPESRefrigerant emissions to the atmosphere are often genericallycalled losses, without distinguishing the causes. However, emissiontypes are very different, and their causes must be identified beforethey can be controlled. Clodic
5、(1997) identified six types:Sources of fugitive emissions cannot be precisely located.Tightness degradation is caused by temperature variations, pres-sure cycling, and vibrations that can lead to unexpected and sig-nificant increases of refrigerant emission rates.Component failures mostly originate
6、from poor construction orfaulty assembly.Losses during refrigerant handling occur mainly when charg-ing the system, and opening the system without previously recov-ering the refrigerant.Accidental losses are unpredictable and are caused by fires, ex-plosions, sabotage, theft, etc.Losses at equipment
7、 disposal are caused by intentionally vent-ing, rather than recovering, refrigerant at the end of system life.DESIGNThe potential for leakage is first affected by system design. Everyattempt must be made to design systems that are leaktight for thelength of their useful service lives, and reliable,
8、to minimize theneed for service. Selection of materials, joining techniques, anddesign for easy installation and service access are critical factors indesigning leaktight systems.For example, leaktight service valves should be installed to allowremoval of replaceable components from the cooling syst
9、em, andlocated for effective liquid refrigerant recovery.Systems should be designed to minimize refrigerant charge to re-duce the amount of released refrigerant in case of catastrophic loss.There are many opportunities for refrigerant charge reduction in ini-tial design. Heat exchangers, piping, and
10、 components should be se-lected to reduce the amount of refrigerant in the system (but not atthe expense of energy efficiency).INSTALLATIONProper installation of air-conditioning and refrigeration systemsis critical to proper operation and containment during the useful lifeof the equipment. Tight jo
11、ints and proper piping materials are re-quired. Later service requirements are minimized by proper clean-ing of joints before brazing, purging the system with an inert gas(e.g., nitrogen) during brazing, and evacuation to remove noncon-densables. Use an inert gas purge to prevent oxides, which can c
12、on-taminate the system. Proper charging and careful systemperformance and leak checks should be performed. At installation,systems should be carefully charged per design specifications toprevent overcharging, which can potentially lead to a serious releaseof excess refrigerant, and make it impossibl
13、e to transfer the entirecharge into the receiver for service. The installer also has the oppor-tunity to find manufacturing defects before the system begins oper-ation.SERVICING AND DECOMMISSIONINGProper service is critical in reducing emissions. Refrigeratingsystems must be monitored to ensure that
14、 they are well sealed,properly charged, and operating properly. The service technicianmust study and maintain service records to determine any history ofleakage or malfunction. The equipment should be checked to detectleaks before significant charge is lost. During system maintenance,refrigerant sho
15、uld not be released; instead, it should be isolated inthe system or recovered by equipment capable of handling the spe-cific refrigerant.An up-to-date maintenance document allows the user to monitoradditions and removals of refrigerant, and whether rechargingoperations are actually associated with r
16、epairs of leaks. In a retrofit,the new refrigerant must be noted in the service record and clearlymarked on equipment. Technicians must follow manufacturersretrofit procedures, because some system components may beincompatible with different refrigerants. Failure to perform properretrofits may resul
17、t in system failure and subsequent loss of refrig-erant.When a system is decommissioned, recover the refrigerant forrecycling, reuse, or disposal. Special care is required to properlyclean or reclaim used refrigerants to industry-recognized standards(see AHRI Standard 700).The preparation of this ch
18、apter is assigned to TC 3.8, Refrigerant Contain-ment.9.2 2010 ASHRAE HandbookRefrigerationTRAININGTechnician training is essential for proper handling and contain-ment of refrigerants. Training must provide a basic understanding ofthe environmental effects of refrigerants; recovery, recycling, andr
19、eclamation of refrigerants; leak checks and repairs; and introduc-tion to new refrigerants. The service operator requires continuoustraining to understand new designs, new refrigerants and their com-patibility with lubricants, new low-emission purge units, retrofittingrequirements, and service pract
20、ices.LEAK DETECTIONLeak detection is a basic element for manufacturing, installing,and servicing systems, because it makes it possible to measure andimprove containment of refrigerant. Leak detection must be per-formed as the final step after the system is completed in the factoryor in the field. It
21、 is good practice to regularly leak test the equip-ment.There are three general types of leak detection: global, local, andautomated performance monitoring.Global DetectionThese methods indicate whether a leak exists, but do not identifyits location. They are useful at the end of construction, and w
22、hen thesystem is opened for repair or retrofit.System Checking. These approaches are applicable to a systemthat has been emptied of its charge.Pressurize the system with a tracer gas and isolate it. A pressuredrop within a specified time indicates leakage.Evacuate the system and measure the vacuum l
23、evel over a speci-fied time. A pressure rise indicates leakage.Place the system in a chamber and charge with a tracer gas. Thenevacuate the chamber and monitor it for leaks with a mass spec-trometer or residual gas analyzer.Evacuate the system and place it in an atmosphere with a tracergas. Monitor
24、for leaks with a mass spectrometer or residual gasanalyzer.Many of these tests use a tracer gas, often nitrogen or helium. Itis not good practice to use a refrigerant as the tracer gas.Continuous Monitoring During Operation. Electronic leakdetectors in machinery rooms may be effective if (1) they ar
25、e sensi-tive enough to refrigerant dilution in the air, and (2) air is circulatedproperly in the room. Note, however, that these detectors only mon-itor equipment in the room.Receiver Monitoring. On large systems that have a receiver andreceiver-level monitoring device, the following procedure can m
26、on-itor refrigerant levels over time:1. Set evaporator pressure regulator and solenoid valves fully open.2. Close heat reclaim valve (if equipped).3. Open split condenser valve (if equipped).4. Ensure that no system or circuit is in defrost.5. Pump refrigerant into receiver and condenser until press
27、urereaches 5 psi minimum.6. Allow system to equalize and pump down again to 5 psi mini-mum.7. Check and record receiver level.This level should remain fairly constant if all of the system set-tings are consistent. From this record, large leaks over time can bedetected.Local DetectionThese methods pi
28、npoint locations of leaks, and are usually usedduring servicing. Sensitivity varies widely; it is usually stated asppm/volume but, for clarity, mass flow rates (oz/year) are oftenused. Table 1 compares sensitivities of various testing methods.Visual checks locate large leaks (3 oz/year) by seeking t
29、elltaletraces of oil at joints.Soapy water detection (bubble testing) is simple and inexpen-sive; a trained operator can pinpoint leaks of 2 oz/year maximum.Tracer color added to the oil/refrigerant mixture shows the leakslocation. The tracer must be compatible with the various materialsused in the
30、refrigeration circuit.Electronic detectors of different types can detect leaks as low as0.1 to 2 oz/year, according to their sensitivity. They must be usedwith proper care and training.Ultrasonic detectors register noise generated by the flow of gasexiting through the leak, and are less sensitive th
31、an electronic de-tectors; they are easily disturbed by air circulation.Helium and HFC mass spectrometers with probes or hoods candetect leaks at very low levels (less than 0.05 oz/year).Automated Performance Monitoring SystemsMonitoring parameters such as temperatures and pressures helpsidentify any
32、 change in the equipment. It also provides data useful forperforming diagnostics on the condition of heat exchanger surfaces,proper refrigerant pumping, and shortage of refrigerant charge.Automated diagnostic programs are now being developed to pro-duce pre-alarm messages as soon as a drift in refri
33、gerant charge isobserved. These developments are in their early stages, but theirgeneral adoption would give better control over discovering refrig-erant leaks. Equipment room monitors are currently used. On low-pressure systems, it is also possible to monitor equipment tightnessby monitoring purge
34、unit run time, which can indicate leaks.RECOVERY, RECYCLING, AND RECLAMATIONThe procedures involved in removing contaminants when recy-cling refrigerants are similar to those discussed in Chapter 7. Ser-vice techniques, proper handling and storage, and possible mixingor cross contamination of refrig
35、erants are of concern. Building own-ers, equipment manufacturers, and contractors are concerned aboutTable 1 Leak Test Sensitivity ComparisonTesting MethodLeakage Rate at 1 atm, oz/yr1,000,000 100,000 10,000 1000 100 10 1 0.1 0.001Bubble testing (air under water) X X XPressure decay X X XVacuum deca
36、y (outside-in) X X X XAcoustical (ultrasonic) X X X XAtmospheric accumulation X X X X XHalogen sniffer (heated diode) X X X X X XHalogen sniffer (infrared) X X X X X X XHydrogen sniffing X X X X X X XHelium sniffing X X X X X X XMass spectrometer (hard vacuum) X X X X X X X X XRefrigerant Containmen
37、t, Recovery, Recycling, and Reclamation 9.3reintroducing refrigerants with unacceptable levels of contaminantsinto refrigeration equipment. Contaminated refrigerant can nega-tively affect system performance, and may lead to equipment failureand release of refrigerant into the atmosphere.Installation
38、 and Service PracticesProper installation and service procedures, including proper evac-uation and leak checking, are essential to minimize major repairs.Service lines should be made of low-permeability hose material andshould include shutoff valves. Larger systems should include isola-tion valves a
39、nd pumpdown receivers. ASHRAE Standard 147describes equipment, installation, and service requirements.Recovering refrigerant to an external storage container and thenreturning the refrigerant for cleanup inside the refrigeration systemis similar to the procedure described in Chapter 7. Some addition
40、alair and moisture contamination may be introduced in the serviceprocedure. In general, because contaminants are distributedthroughout the system, the refrigeration system must be cleanedregardless of whether the refrigerant is isolated in the receiver,recovered into a storage container, recycled, r
41、eclaimed, or replacedwith new refrigerant. The advantage of new, reclaimed, or recycledrefrigerant is that a properly cleaned system is not recontaminatedby impure refrigerant.ContaminantsContaminants found in recovered refrigerants are discussed indetail in Chapter 7. The main contaminants are mois
42、ture, acid,noncondensables, particulates, high-boiling residue (lubricant andsludge), and other condensable gases (Manz 1995).Moisture is normally dissolved in the refrigerant or lubricant,but sometimes free water is present. Moisture is removed by passingthe refrigerant through a filter-drier. Some
43、 moisture is also removedby lubricant separation.Acid consists of organic and inorganic types. Organic acids arenormally contained in the lubricant and are removed in the oil sep-arator and in the filter-drier. Inorganic acids, such as hydrochloricacid, are removed by noncondensable purging, reactio
44、n with metalsurfaces, and the filter-drier.Noncondensable gases consist primarily of air. These gases cancome from refrigeration equipment or can be introduced during ser-vicing. Control consists of minimizing infiltration through properequipment construction and installation (ASHRAE Standard 147).P
45、roper service equipment construction, connection techniques, andmaintenance procedures (e.g., during filter-drier change) also reduceair contamination. Typically, a vapor purge is used to remove air.Particulates can be removed by suction filters, oil separators, oilfilters, and filter-driers.High-bo
46、iling residues consist primarily of refrigerant lubricantand sludge. Because different refrigeration systems use differentlubricants and because it is a collection point for other contami-nants, the lubricant is considered a contaminant. High-boiling resi-dues are removed by separators designed to e
47、xtract lubricant fromvapor-phase refrigerant, or by distillation.Other condensable gases consist mainly of other refrigerants.They can be generated in small quantities by high-temperature oper-ation or during a compressor motor burnout. To maintain purity ofthe used refrigerant supply as well as the
48、 performance and durabilityof the particular system, refrigerants should not be mixed. In gen-eral, separation of other condensable gases, if possible, can only bedone at a fully equipped reclamation center. Mixed refrigerants are a special case of other condensable gasesin that the refrigerant woul
49、d not meet product specifications even ifall moisture, acids, particulates, lubricant, and noncondensableswere removed. Inadvertent mixing may occur because of a failure toDedicate and clearly mark containers for specific refrigerantsClear hoses or recovery equipment before switching to a differentrefrigerantTest suspect refrigerant before consolidating it into large batchesUse proper retrofit proceduresRecoveryTo recover means to remove refrigerant in any condition from asystem and to store it in an external container. Recovery reducesrefrigerant emissions to the atmosphere and is a n
