1A Study of R134a Leaks inHeavy Duty VehiclesCARB Contract No. 06-342Andrew BurnetteinfoWedgeRick BakerEastern Research Group2Acknowledgements•Dr. Tao Huai, Dr. Tao Zhan, Dr. Alberto Ayala,Dorothy Shimer (CARB)•Dr. Denis Clodic (Center for Energy Studies,Ecole des Mines de Paris)•Dr. Winfried Schwarz (Öko-Recherche GmbH)•Jim Baker (Delphi Corp)•Gary Hansen (Red Dot Corp)•Dr. Stephen Andersen (US EPA)•Multiple Sacramento area fleets (most ofwhom requested to stay anonymous)Outline•Introduction•Methods–Gravimetric–Maintenance (mass-balance)•Results–Gravimetric–Maintenance (mass-balance)•Analysis/Discussion–Gravimetric–Maintenance (mass-balance)•Summary/Recommendation34Background•Refrigerants used in mobile airconditioning (MAC) systems can enterthe atmosphere through a number ofmechanisms–low-level, long-term leaks–rapid leaks caused by discrete incidents(e.g., system failure)–regular system servicing–end-of-life losses51,1,1,2-tetrafluoroethane(HFC-134a)•R134a is one of the most commonrefrigerants used in MAC systems today•It has a global warming potential (GWP) of1,300(1,2)•ARB estimated that total R134a emissionsfrom all MAC systems in California (includinglight-duty vehicle systems) approximately 4-million metric tons of CO2-equivalent (CO2E)in 2004(3)(1)Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4), 2007(2)Updated GWP from AR4 is 1430, but legacy value of 1300 is used here for comparison toprevious inventories(3)California Air Resources Board, Initial Statement of Reasons for Proposed Regulation forSmall Containers of Automotive Refrigerant, December 5, 2008, p. 4.Generic MAC System(vapor compression cycle)6Source: Yingzhong Yu, “GenericApproach of Refrigerant HFC134a Emission Modes FromMobile Air Conditioning (MAC)Systems.” PhD Thesis, Ecole desMines, Paris, France, October23, 2008MACs In Vehicles7Project Objectives•Characterize in-use R134a emissionsfrom heavy-duty onroad and offroadvehicles in California–Estimate low-level, long-term leakagefrom MAC systems that use R134a–Combine with equipment populationestimates into an annual emissioninventory for the state for those types ofleaks8Target Sample for the Study•Heavy-duty, onroad and offroad•Variety of MAC configurations–Joint seal type–Amount of permeable materials–Compressor type•Budget for about 70 vehicles9MAC Configuration Considerations•Used SAE J2727 and industry expertsto determine MAC parametersimportant to leak rates•Limited sample size and probablevariability of field measurementsdictated 1 or 2 MAC parameters to beinvestigated for impacts on estimatedemissions10Sample Selection•Vehicles in professional use•Protected, on-site garage spacewith power required•Turn-key sample process takeshours to complete11Target Number of Samples12Bin IDVehicle Type # Units1 Full Sized Transit Bus 112 Shuttle Bus 53 MD Utility Truck/Van 184 HD Truck Tractor 185Other HD Trucks (dump, waste, etc)96 Construction Equipment 57 Agricultural Equipment 4Total70Gravimetric MeasurementMethod•Several alternatives investigated•Selected method blased upon onedeveloped by Dr. Denis Clodic, Ecole desMines, Paris, France–Originally for light-duty cars in a climatecontrolled area–Modified for application to heavy-dutyequipment in the field–Similar to SAE J2762 (which is also basedupon Clodic’s method)13Gravimetric Method Overview•Recover, evacuate and recharge MAC withknown amount of R134a–Recover from MAC to 20 kPawith compressor–Distill R134a from oil and weigh–Evacuate recovery equipment to 20 Pawithvacuum pump•Release to normal operations for severalmonths at least•Recover the R134a to determine leakage, ifany, using same steps as above14Schematic of GravimetricMethod15RecoverRechargeHeatHeatHeatTempTempTempPressRecovery Equipment List16Item NotesVacuum pump, highvacuum gauge, hoseHigh capacity, 2-stage vacuum pump: Mastercool model90067 with212 LPM (7.5 CFM) capacity and 0.37 kW (0.5 HP) motor. Highvacuum gauge: For reading vacuum at 20 Pa-absolute.Resolution of0.1 Pa.Recovery compressorand hoseCompressor (Bacharach model Stinger 2000) and dedicated hose usedto recover R134a from the MAC into the Recovery tank.Electronic scale Electronic balance: Citizen model SSH 93 with capacity of 30 kg (66lb) and resolution of 0.1 g (0.0035 oz).Recovery tank Cylinder used only to recover R134a fromthe MAC. After recoveryR134a is transferred from this tank to the Recycling tank.Manifold and 3 hoses Service manifold with dedicated hoses and gauges for the low-pressureand high-pressure sides of the MAC and with a hose totransfer R134afrom and to the MAC.Charging tank andhoseCylinder of new or recycled and purified (of air and water) R134a witha dedicated hose.Recycling tank Cylinder used only to receive R134a distilled from the recovery tank.Thermocouples anddisplaysK-type thermocouples and readouts to monitor various temperatures.Gravimetric MethodConsiderations•Maintain MAC system temperature•Control recovery rate to recoveronly vapor (i.e., vaporize all liquidrefrigerant before recovery)•Minimize recovery hardware,procedural leak sources andfugitive losses17Maintain MAC Temperature•Warm up engine compartment•Heat key components duringrecovery to counteract phasechange cooling•Monitor temperatures duringrecovery (keep above 20°C)18Control Recovery Rate•Recover only vapor (minimize liquidentrainment)–Lubricating oil is dissolved in liquid R134a–Oil is difficult to distill from recoveredR134a and a source of error that can(mostly) be avoided–Watch recovery sight glass for liquid andrecovery port temperature for rapid drop(due to liquid)19Evacuation of Recovery Unitand Hose before Test20Manifold & ThermocouplesDuring Recovery21Weighing Recovery Systemafter Recovery22Recharging MAC after R134awas Removed23Anti-tamper Measures Duringa Test24Types of Participant Fleets•Voluntary participation•Government and private fleets inthe Sacramento area•Electric utilities, waste collection,heavy construction, universities,municipalities, and public andprivate transport25Maintenance Data vs. DirectLeak Rate Measurement•Some fleets could only participate bysupplying maintenance data•Some of these data could be used toestimate total refrigerantconsumption using a “mass balance”approach•This approach was expanded topublic transport fleets statewide26Issues with Mass BalanceApproach•Refrigerant consumption not typically trackedfor each vehicle•Useful mainly for homogenous fleets (e.g.,large buses all using the same refrigerant)•Estimates overall consumption of refrigerant(accounts for all leak sources, includingtechnician practices, faulty serviceequipment, theft, etc.) instead of just longerterm, slow leaks from the MAC27Mass Balance Data Requirements•Quantities and types of buses•Age range of the buses•Type of refrigerant used in eachtype of bus•Consumption rate of R134a for thefleet28Data Analysis•Estimation of leak measurementaccuracy and precision•Quality Assurance•Maintenance Data29Determining Accuracy of LeakRate Measurement•Evacuate and recharge a newvehicle•Recover R134a to determine massbalance closure–Ideally recover 100% of recharge•Perform on multiple vehicles•Estimate accuracy and precision30Data Quality Assurance•Written, step-by-step instructions and datasheets•NIST traceable weights to check the scale atseveral points during the test•“Sanity” checks of temperature and pressurereadings compared to empirical observations•Data post-processing included comparison toprevious same/similar vehicles of capacities,transcription error checking, etc.•Archival of raw data sheets31Results of MeasurementAccuracy Tests•Performed accuracy/precision test on 4 newvehicles–First one used a draft procedure•3 MACs tested with final procedure had massclosure of 99% or greater (“losses” ranging from3.7 g to 14.6 g)•Compare to results from a controlled, lab-likesetting which achieved closure of 1 g forpassenger car MACs(1)(1) D. Clodic, “Research Study on the Definition ofthe Implementation of aMethod of Measurement of Annual Leak Flow Rates (LFRs) of MACSystems”, ACEM/Armines Contract, January 2006.32Mass Based Leak SampleOverview•Leak measurements occurredfrom Jan 2009 to Apr 2010•Total of 65 samples, 3 invalid dueto servicing or failure duringintervening period•3 converted from R12 to R134a•1 (heavy construction) hadelectric compressors33Sample Counts by Sample Binand Model Year34Sample Bin1234567Model Year19891199011991111993119951119961199711998111199913111200021222001220021111200321120041221120052112006132007621200811Sample Bin Key1 – Full-Sized Transit Buses2 – Shuttle Buses3 – Medium-duty Trucks4 – Heavy-duty Tractor Trucks5 – Other Heavy-duty Trucks (e.g., waste haulers)6 – Construction Equipment7 – Agricultural EquipmentSample Counts by Sample Binand MAC Capacity35Sample Bin1234567Capacities (g)65019071110804211341121119013211247112801131055222136011221140011474261700119502124953Sample Bin Key1 – Full-Sized Transit Buses2 – Shuttle Buses3 – Medium-duty Trucks4 – Heavy-duty Tractor Trucks5 – Other Heavy-duty Trucks (e.g., waste haulers)6 – Construction Equipment7 – Agricultural Equipment“As Received” Charge VersusExperimental Charge36-1.0-0.8-0.6-0.4-0.20.00.20.42 2 2 2 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 6 6 6 7

**(mass found - mass recommended) mass recommended** **Sample Bin Number "As Received" Charge Fraction** -1.0-0.8-0.6-0.4-0.20.00.20.42 2 2 2 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 6 6 6 7

**(mass charged - mass recommended) mass recommended** **Sample Bin Number Experimental Charge Fraction** Length of Sample Time,Grouped by Sample Bin370.00.20.40.60.81.01.2

**Sample Duration (yr) Time Allowed for Leakage From MAC** 

shuttle md truck hd hwy tractor other hd truck construction agricultureAnnualized Leak Rate: EachData Point, by Sample Bin38-500050010001500200025003000

**Leaked Amount (g/yr) Annualized Leak Rate** **in Each Sample Bin**

shuttle md truck hd hwy tractor other hd truck construction agriculture-0.500.511.522.5

**Annual Leak / MAC Capacity (g/g) Annualized Leak per MAC Capacity** 

shuttle md truck hd hwy tractor other hd truck construction agricultureLeak Rate Projection Analysis•Linear interpolation used to extrapolatefrom actual sample period to 12 months•Linear assumption probably results inover-estimate of leak rate because ratewould taper off as system workingpressure decreases–Note that several high leak rate systems areprojected to empty in less than 1-year39Measured Leak Rate Modeling•The measured (annualized) leak rate data wereplotted by various parameters to find obviousmodeling variables (e.g., model year, MACcapacity, etc.)•Given the variability of the data and the smallsample size, statistical rigor was not possible•A model year split at 2006 was selected because ofthe voluntary IMAC leak standards the onroadmanufacturers agreed to follow (1)–This is not applicable to offroad equipment, whichare assumed to have the pre-2006 leak rate(1) Personal communication with Gary Hansen, Red Dot Corporation, April 2008.40Annualized Leak Rate, byModel Year41-5000500100015002000250030001985 1990 1995 2000 2005 2010

**Leaked Amount (g/yr) Model Year** **Annualized Leak Rate vs Model Year**Average Results by AgeGroup, and for All Vehicles4230610325725664792566-30-7-30-50005001000150020002500300005- 06+ All

**Leak Rate (g/yr) Model Year Bin** **Average Annualized Leak Rate by Model Year Bin and Overall** AverageMaxMinMY-BinCountAverageMaxMinStdDev05- 47 306 2566 -30 55806+15103479-7125All622572566-30496Analysis of Maintenance Data•Assumptions–Accurate tracking of R134apurchases and recycling–Accurate records of whichvehicles use R134a–Average annual R134a purchasesequal average annual R134aleaks (mass balance)43Maintenance Record LeakRate Sample•Five transit bus fleets participated•Operated all across California–Los Angeles air basin–Northwest coastal–Northern in-land–Sacramento region–San Joaquin Valley44Maintenance Record LeakRate Analysis•329 buses in these fleets were 29- to45-foot long coaches–181 used R134a–The rest used R22 or R407c or none•Fleet-average leak rate (all buses usingR134a) was 1,340 grams per year–All types of “leaks” from maintenanceequipment, maintenance practices,recycling, slow leaks from MAC, MACsystem failure, etc.45R134a Emission Inventoryfrom Heavy-Duty Fleet•Use to get an initialestimate of thecontribution from MD and HD vehicleswhile acknowledging the uncertainties ofthe method•Estimate number of medium-duty andheavy-duty vehicles with air-conditionedcabs•Multiply the estimated annual leak rateper vehicle by the number of vehicles46Onroad Heavy-Duty Fleet for2010•EMFAC default fleet–About 55% of urban and “other”buses use R134a (per fleet managerestimates)–About 100% of the rest of the MD &HD fleet use R134a•Total estimated fleet = 3,857,000(2,684,000 model year 2005-,1,173,000 model year 2006+)47Offroad Heavy-Duty Fleet for2010•OFFROAD default fleet–Equipment types with enclosedcab options (per ERG knowledge)–Assume only equipment withengines 50 HP or larger wouldhave MAC•Total estimated fleet = 316,60048Estimate: 2010 Leaks ofR134a directly from HD MACs49EMFAC Vehicle CategoryPre-2006 Mg/yr(short ton/yr)2006+ Mg/yr(short ton/yr)All Model YearsMg/yr(short tons/yr)On-Road Equipment[Pre-2006: 2,684,000*306=821 Mg][2006+: 1,173,000*103=121 Mg][All: 3,857,000 * 257=991 Mg]821(905)121(133)991(1,089)Off-Road Equipment[Age Basis1: 316,600*306=97 Mg][All: 316,000*257=81 Mg]97(107)81(89)Grand Total1,039(1,145)1,072(1,178)Note:These estimates account only for in-use leaks directly from the MAC.Leaks from other sources, such as maintenance procedures, are not included andare probably significant for certain vehicle types.1Assumes offroad MAC systems emit at the same rateas pre-2006 on-road systems.CO2-Equivalent Emissions 2010•Assume R134a greenhouse warmingpotential of 1,300 (IPCC guidelines)•1,039 Mg/yr * 1,300 CO2E =1,350,000 CO2E Mg/yrfrom HDequipment•Compare to CARB estimate of4,000,000 CO2E Mg/yr from allsources50Sources of Uncertainty in thisEstimate•Undocumented measurement error (e.g., impact of “difficult” MAC layoutsnot assessed in QA)–A few systems difficult to evacuate without entraining liquids•Linear projection for annualized leak rate (assumesno tapering of leak rate)–Regional ambient differences may play a role here since cooler areas tend to usemore for defogging windows, less for summer cooling, which may impact drivertolerance of low refrigerant levels•Only attempts to account for in-use leakage from MAC–Maintenance/service leaks for public transport might be significant due tocomplexity and “preventative” nature (e.g., quarterly) of service•The impact of the measurement method has not been empirically assessed–Clodic has not seen adverse impacts on systems tested by Ecol des Mines–Some evidence from this study indicate that impactsare possible•Some systems may be “pushed” to leak more due to higher than normal vacuum conditionsduring testing – especially older systems•One system could not be tested due to in-leakage ofair at high vacuum (higher thanservice vacuum levels)51Summary & Main Conclusions•MACs in heavy-duty equipment appear to be significantin the R134a leak inventory•This leak estimate does not account for leaks due tomaintenance, equipment failure, etc•Linear projection of leak rate to annual rate is probablyan over-estimate•Gravimetric leak measurement method accurate toabout 20 g or 2% of original MAC charge•A possibly significant source (not accounted for with thismethod) is the frequent, preventative maintenance onlarge MACs in public transport vehicles•Regional usage differences may impact leak rates (MACfor defrost-only is effective at lower charges thanMACfor comfort)52Primary Recommendation•Survey large fleet operators and certifiedtechnicians to find obvious sources of leaks otherthan during typical MAC system operation–Estimate leak rate ranges from sources other than thein-use MAC (e.g., maintenance) using a mass-balanceapproach (net R134a purchased = total leaked)–Compare to leak rates measured in this study and useto update the inventory–Use results to prioritize future studies aimed atimproving the inventory53End of PresentationQ&A54Supplementary Slides•The following slides have somedetails behind the summaries inthe main presentation...55Supplementary Slide –Equipment Customization•Permanent joints whereverpossible•Custom hose with heavy-dutycompression fittings•Ball valves at hose ends•Frequent replacement of gasketsand vacuum oil56Supplementary Slide –Evacuate-Recharge Schedule57Supplementary Slide –Data from Accuracy Tests58VehicleIDModelYearSystemCapacity(g)Charge(g)Recovered(g)Difference(g)%DifferenceNoteUtil2-012007907907.6871.735.94.0DraftProcedureGarb2-02 2006 1,190 1,217.9 1,214.2 3.7 0.3 Final procedurePriv4-120021,0801,104.71,094.110.61.0Final procedurePriv5-1 2003 1,758 1,784.4 1,769.8 14.6 0.8 Final procedureSupplementary Slide–Bus Fleet and R134aMaintenance Data Summary59Fleet Location PeakMonthAvg.DailyHighAvg.AnnualR134aPurchaseR134a Fleet EstimatedR134aLeakRate (pervehicle)NotesFleet 1LA Basin 32°C(90°F)27 kg(60 lb)40-ft coaches:170 total; 51use R134a,119 use R407c540 g/yr(1.2 lb/yr)Approx. 180 lb of R134aused in 3 years for 51 buses.150 lb purchased, 30 lbalready in stock.Fleet 2NW CA 18°C(64°F)2.0 kg(4.3 lb)40-ft coaches:33 total; 5 w/oAC, 28 useR134a68 g/yr(0.15lb/yr)30 lb cylinder of R134apurchased 7/18/2006. About1⁄2 used so far.Fleet 3N CA 37°C(99°F)55 kg(120 lb)Shuttle buses:23 total; alluse R134a2,400 g/yr(5.2 lb/yr)Purchase approx. 120 lbR134a per year for shuttlebusesFleet 4Sacramentoregion34°C(93°F)Notprovided40-ft coaches:22 total; alluse R134a1,100 g/yr(2.4 lb/yr)Maintenance records:average of 103 lb R134a peryear total for 40-ft coachbusesFleet 4Sacramentoregion34°C(93°F)NotprovidedShuttle buses:21 total; alluse R134a2,700 g/yr(5.9 lb/yr)Maintenance records:average of 138 lb R134a peryear total for cutaway busesFleet 5SanJoaquinValley34°C(94°F)180 kg(390 lb)Shuttle buses:32 total; alluse R134a.29 ft to 45 ftcoaches: 104total; 80 usingR134a, 24using R22.1,600 g/yr(3.5 lb/yr)Projected “year to date” useas of Nov 4 (325.7 lb R134a& 147.1 lb R22) to end ofyear.Supplementary Slide –Estimate of 2010 On-roadHDVs with R134a60EMFAC Vehicle Category Pre-2006 Count2006+ Count04 - Medium-Duty Trucks (T3)1,722,000746,00005 - Light HD Trucks (T4)239,000188,00006 - Light HD Trucks (T5) 119,00049,00007-Medium HD Trucks (T6)188,00070,00008 - Heavy HD Trucks (T7) 179,00051,00009 - Other Buses 9,0003,00010-Urban Buses7,0001,00012 - School Buses 23,0004,00013-Motor Homes198,00061,000Total2,684,0001,173,000Supplementary Slide –OFFROAD Equipment WithMAC61•Rollers•Trenchers•Cranes•Rough Terrain Forklifts•Rubber Tire Loaders•Tractors/Loaders/Backhoes•Skid Steer Loaders•Other ConstructionEquipment•Forklifts•Sweepers/Scrubbers•Other General IndustrialEquipment•Other Material HandlingEquipment•Agricultural Tractors•Combines•Balers•Sprayers•Swathers•Other AgriculturalEquipment•Cargo Tractor•A/C Tug, Narrow Body•A/C Tug, Wide Body•Air Conditioner (GSE)•Baggage Tug•Bobtail•Fuel Truck•Lavatory Truck•Maintenance Truck•Passenger Stand•Sweeper•Service Truck•Catering Truck•Hydrant Truck•Scrapers•Excavators•Graders•Off-highway Trucks•Rubber Tire Dozers•Crawler Tractors•Off-Highway Tractors•Skidders•Fellers/Bunchers•Other GSE•Other WorkoverEquipment•Drill Rig•Military Tactical SupportEquipment•Dredger•Other Dredging