# UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY

2565 PLYMOUTH ROAD

ANN ARBOR, MICHIGAN 48105

- 2498



# MEMORANDUM

SUBJECT: Presentation on Evaporative Emission System Leaks for a Fuel Tank Under

Pressure

FROM: Glenn W. Passavant

, S e nior Mechanical Engineer

Assessment and Standards Division

TO: Docket Number EPA

- HQ

- OAR

- 2011

- 0135

DATE: February 27, 2013

Background

As part of it Tier 3 NPRM, EPA is proposing to add a more stringent evaporative emission

standard for hot soak plus diurnal emissions, a leak emission standard

, and a more stringen t

leak monit oring and detection orifice diameter for Onboard Diagnostic (OBD) systems. These

tools are all designed to help assure z e ro fuel evaporative emissions ( “ zero evap ” ) over the

vehicle useful life.

Presentation

In developing these requirements we were provided information which compared fuel tank leak

emission rates for a system under pressure such as o ccur s in some designs today and has the

potential f or increased application i n the future with more typi cal designs which vent to the

canister

. The attached informations shows that when leaks of various orifice diameter are

implanted in a fuel /evaporative system

, the leak rate to the atmosphere is significantly greater

from a pressurized system than for one which is vented to the canister

. For example, compare

the emission rate information on slides 46 and 52.

Discussion

EPA is providing this information for p ublic consideration and review

. Th e information in the

attached charts seems to indicate that if OBD monitoring on a pressurized system indicated a

detectable fuel/ evaporative system leak

, the hot soak plus diurnal emissions to atmosphere

would be greatly re d uced if the tank valve was programmed to vent to the caniste r

. OFFICE OF

AIR AND RADIATION1Leak Impact onSealed Fuel Tanks2PurposeTo determine the relationship between leak size and emissions insealed systems and compare that with an open system having a0.02”leak.Conclusion:•Very small leaks (as small as 0.005”) in sealed systems can result intotally uncontrolled diurnal emissions.•Leaks as small as 0.002”on a sealedsystem release as much as 14times the allowable Tier II limit per day3Overview1.Baseline Testing2.Installed Leak Orifice Testing3.Open System with Leak Orifice Testing4.Next Steps5.Theoretical Emission Calculations4Baseline TestingPURPOSE: Establish emissions forcompletely sealed system, no leaksTest Procedure:♦Precondition Volt canister with 3-6 ORVR cycles♦Use of a trap canister for fueltank fill and initial temperaturestabilization (prior to mini-shed test)♦Fill Volt tank with 3.7 gallons (40% fill) of 9 RVP (62 kPa) E-10 fuel♦Condition Volt tank in chamber at 72°F♦After fuel in Volt tank is 72°F, place Volt system in Mini-Shed♦Run EPA profile of 72-96°F♦Monitor emissions, tank pressure, chamber temperatureTests 9166, 9170, 9210, and9214 run with modified tankTests 9202 and 9206 run onnon-modified Volt tank5Setup #1: Sealed Tank Baseline6657075808590951009/4/201216:199/4/201218:439/4/201221:079/4/201223:319/5/2012 1:55 9/5/2012 4:19 9/5/2012 6:43 9/5/2012 9:07 9/5/201211:319/5/201213:55

Temperature (F)-0.500.511.522.533.5 Pressure (psi)Chamber TemperatureTank Pressure DataBaseline #1 (Test 9166)Tank Pressure and Chamber Temperature3.3 psi pressure build atpeak temperature70100020003000400050009/4/12 4:19PM9/4/12 6:43PM9/4/12 9:07PM9/4/12 11:31PM9/5/12 1:55AM9/5/12 4:19AM9/5/12 6:43AM9/5/12 9:07AM9/5/12 11:31AM9/5/12 1:55PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber TemperatureBaseline #1 (Test 9166)Emissions and Chamber Temperature705 mg total emissionsgenerated for sealedsystem—later found leakat temperature weld port8657075808590951009/7/12 12:14PM9/7/12 3:07PM9/7/12 6:00PM9/7/12 8:52PM9/7/12 11:45PM9/8/12 2:38AM9/8/12 5:31AM9/8/12 8:24AM9/8/12 11:16AM

Temperature (F)-0.500.511.522.533.54 Pressure (psi)Chamber TemperatureTank Pressure DataBaseline #2 (Test 9170)Tank Pressure and Chamber Temperature3.5 psi pressurebuild at peaktemperature(similar toBaseline #1 Test)90100020003000400050009/7/12 12:14PM9/7/12 3:07PM9/7/12 6:00PM9/7/12 8:52PM9/7/12 11:45PM9/8/12 2:38AM9/8/12 5:31AM9/8/12 8:24AM9/8/12 11:16AM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber TemperatureBaseline #2 (Test 9170)Emissions and Chamber TemperatureBaseline Emissions = 710 mgTried to seal leak attemperature weld portbut did not hold10025507510012515017520010/2/12 3:07 PM 10/2/12 6:00 PM 10/2/12 8:52 PM 10/2/12 11:45PM10/3/12 2:38 AM 10/3/12 5:31 AM 10/3/12 8:24 AM 10/3/12 11:16AM10/3/12 2:09 PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber TemperatureBaseline #3 (Test 9202)Emissions and Chamber TemperatureBaseline Emissions = 24 mgNon-modified Volttank used so no tankpressure data11025507510012515017520010/5/12 4:33 PM 10/5/12 7:26 PM 10/5/12 10:19PM10/6/12 1:12 AM 10/6/12 4:04 AM 10/6/12 6:57 AM 10/6/12 9:50 AM 10/6/12 12:43PM10/6/12 3:36 PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber TemperatureBaseline #4 (Test 9206)Emissions and Chamber TemperatureBaseline Emissions = 30 mg(similar to Baseline #3 results)Non-modified Volttank used so no tankpressure data16Summary: Baseline Testing EmissionsBaseline Emissions0100200300400500600700800916691709202920692109214Tests

Emissions (mg)Tests performed with non-modified Volt tank•Observed 179 to 710 mg total emissions from modified Volt tank•Observed 24 to 30 mg total emissions from unmodified Volt tank◦Unmodified Volt tank was brand new and only “baked” for one day.Emissions could be from adhesives on the tank.17Summary: Baseline Testing Tank Pressure•Theoretical Pressure Build for completely sealed system (at 96 F) ~ 4 psi•Observed 3.3 to 3.9 psi build with modified tank (with known small leak attemperature transmitter weld port)•Unable to record pressure with non-modified tank (tests 9202&9206)Baseline Tank Pressures00.511.522.533.544.59166 9170 9202 9206 9210 9214Tests

Pressure (psi)Tests performed with non-modified Volt tank so NOPRESSURE DATA18Installed Leak Orifice TestingPURPOSE: Determine impact of varying leak sizes on sealed systemTest Procedure:♦Precondition Volt canister with 3-6 ORVR cycles♦Use of a trap canister for fuel tank fill and initial temperature stabilization (priorto mini-shed test)♦Fill Volt tank with 3.7 gallons (40%fill) of 9 RVP (62 kPa) E-10 fuel♦Condition Volt tank in chamber at 72°F♦After fuel in Volt tank is 72°F, attach preconditioned Volt canister and ensuresystem set up in #2 configuration♦Place Volt system in Mini-Shed♦Monitor tank pressure and chamber temperature♦Run 1 day diurnal with EPA profile of 72-96°F♦Monitor emissionsAll leak tests run on modified Volt tank (see set-up #2)Leak orifice sizes range from 0.002”to 0.02”(max OBD II allowed leak size)19Setup #2: Sealed Tank with Leak Orifice20Setup #2: Sealed Tank with Leak OrificeFTIVTemperatureTransmitterLeakOrificePressureIndicatorCanister21657075808590951009/10/12 2:24 PM 9/10/12 5:16 PM 9/10/12 8:09 PM 9/10/12 11:02PM9/11/12 1:55 AM 9/11/12 4:48 AM 9/11/12 7:40 AM 9/11/12 10:33AM9/11/12 1:26 PM

Temperature (F)-0.500.511.522.533.5 Pressure (psi)Chamber TemperatureTank Pressure Data0.020” Leak (Test 9172)Chamber Temperature and Tank PressureNo pressurebuild up insystem with leak22020004000600080001000012000140001600018000200009/10/12 2:24PM9/10/12 5:16PM9/10/12 8:09PM9/10/1211:02 PM9/11/12 1:55AM9/11/12 4:48AM9/11/12 7:40AM9/11/1210:33 AM9/11/12 1:26PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber Temperature0.020” Leak (Test 9172)Emissions and Chamber TemperatureEmissions increase with leak to 19grams vs. baseline at 0.024 grams23-55152535455565759/10/12 2:24PM9/10/12 5:16PM9/10/12 8:09PM9/10/12 11:02PM9/11/12 1:55AM9/11/12 4:48AM9/11/12 7:40AM9/11/12 10:33AM9/11/12 1:26PM

Emission Rate (mg/min )65707580859095100 Temperature (F)Emissions SlopeChamber Temperature0.020” Leak (Test 9172)Emissions Rate and Chamber TemperatureEmissions RateInitially Elevated286570758085909510010/22/128:52 PM10/22/1211:45 PM10/23/122:38 AM10/23/125:31 AM10/23/128:24 AM10/23/1211:16 AM10/23/122:09 PM10/23/125:02 PM10/23/127:55 PM

Temperature (F)-0.500.511.522.533.5 Pressure (psi)Chamber TemperatureTank Pressure Data0.005” Leak (Test 9217)Chamber Temperature and Tank PressureSlight initial buildof pressure, butreduced to zero290200040006000800010000120001400016000180002000010/22/128:52 PM10/22/1211:45 PM10/23/122:38 AM10/23/125:31 AM10/23/128:24 AM10/23/1211:16 AM10/23/122:09 PM10/23/125:02 PM10/23/127:55 PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber Temperature0.005” Leak (Test 9217)Emissions and Chamber TemperatureTotal emissions of 18.6grams similar to other0.005” and 0.02” tests306570758085909510011/7/12 4:04PM11/7/12 6:57PM11/7/12 9:50PM11/8/12 12:43AM11/8/12 3:36AM11/8/12 6:28AM11/8/12 9:21AM11/8/12 12:14PM11/8/12 3:07PM

Temperature (F)-1-0.500.511.522.533.5 Pressure (psi)Chamber TemperatureTank Pressure Data0.003” Leak (Test 9233)Chamber Temperature and Tank PressureMax Pressure:2.19 psi310200040006000800010000120001400016000180002000011/7/12 4:04 PM 11/7/12 6:57 PM 11/7/12 9:50 PM 11/8/12 12:43AM11/8/12 3:36 AM 11/8/12 6:28 AM 11/8/12 9:21 AM 11/8/12 12:14PM11/8/12 3:07 PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber Temperature0.003” Leak (Test 9233)Emissions and Chamber TemperatureTotal emissions of 13.4grams + 1.5 gramscanister weight gain366570758085909510012/4/12 1:55PM12/4/12 4:48PM12/4/12 7:40PM12/4/1210:33 PM12/5/12 1:26AM12/5/12 4:19AM12/5/12 7:12AM12/5/1210:04 AM12/5/1212:57 PM

Temperature (F)-1-0.500.511.522.533.5 Pressure (psi)Chamber TemperatureTank Pressure Data0.002” Leak (Test 9253)Chamber Temperature and Tank PressureMax Pressure =2.9 psi370200040006000800010000120001400016000180002000012/4/12 1:55 PM 12/4/12 4:48 PM 12/4/12 7:40 PM 12/4/12 10:33PM12/5/12 1:26 AM 12/5/12 4:19 AM 12/5/12 7:12 AM 12/5/12 10:04AM12/5/12 12:57PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber Temperature0.002” Leak (Test 9253)Emissions and Chamber TemperatureTotal emissions =7.5 grams38Summary: Leak Orifice Testing Emissions•Emissions observed for 0.005”& 0.02”orifices in range of 18.5 to 23 grams,similar to tank open to atmosphere, with no environmental control•Per Wade Reddy equation, range of theoretical emissions for TF-1 fuel used(RVP range of 9 –10.5) is 16.7 to 28.4 grams•Observed reduction in emissions as leak orifice size decreased to 0.002”, butstill significantNOTE: Weight gain by canister NOT included in these valuesLeak Orifice Test Emissions05000100001500020000250000.02"91720.02"91760.005"91790.005"92170.003"92330.003"92380.002"92490.002"9253

Emissions (mg)39Summary: Leak Orifice Testing EmissionsLeak Orifice Impact on Emissions05000100001500020000250000 10 20 30 40Data Points

Normalized Total Emissions (mg)0.02" Test 91720.02" Test 91760.005" Test 91790.005" Test 92170.003" Test 92330.003" Test 92380.002" Test 92490.002" Test 925340Summary: Leak Orifice Testing Pressure•Negligible pressure build with≥0.005”orifice, behaves like opensystem•Pressure build 2 -2.2 psi for 0.003”orifice tests and 2.9 psi for 0.002”Leak Orifice Test Tank Pressure00.511.522.533.50.02"91720.02"91760.005"91790.005"92170.003"92330.003"92380.002"9253

Pressure (psi)41Open System Testing with Leak OrificePURPOSE: Determine total emissions released with conventional system(ambient pressure) and leak orifice; Compare results to sealed systemTest Procedure:♦Precondition Volt canister with 3-6 ORVR cycles♦Use of a trap canister for fuel tank fill and initial temperature stabilization (priorto mini-shed test)♦Fill Volt tank with 3.7 gallons (40%fill) of 9 RVP (62 kPa) E-10 fuel♦Condition Volt tank in chamber at 72°F♦After fuel in Volt tank is 72°F, attach preconditioned Volt canister and ensuresystem set up in #3 configuration(NOTE: FTIV removed)♦Place Volt system in Mini-Shed♦Monitor tank pressure and chamber temperature♦Run 1 day diurnal with EPA profile of 72-96°F♦Monitor emissionsAll open system tests run on modified Volt tank (see set-up #3A and 3B)42Setup #3A: Open Tank with Leak OrificeFTIVRemoved456570758085909510010/26/121:12 PM10/26/124:04 PM10/26/126:57 PM10/26/129:50 PM10/27/1212:43 AM10/27/123:36 AM10/27/126:28 AM10/27/129:21 AM10/27/1212:14 PM

Temperature (F)-0.500.511.522.533.5 Pressure (psi)Chamber TemperatureTank Pressure Data0.020” Leak w/o FTIV (Test 9218)Chamber Temperature and Tank PressureAs expected, nopressure build up460500100015002000250030003500400010/26/121:12 PM10/26/124:04 PM10/26/126:57 PM10/26/129:50 PM10/27/1212:43 AM10/27/123:36 AM10/27/126:28 AM10/27/129:21 AM10/27/1212:14 PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber Temperature0.020” Leak w/o FTIV (Test 9218)Emissions and Chamber Temperature3.1 g emitted to Chamber17.9 g to Canister.01 g to Kynar Bag =21.0 g Total48Setup Adjustment from 3A to 3B•Removed Kynar Bag attachment and opened canister atmosphereport to inside of Mini-SHED•Noticed significant change in system behavior♦Majority of emissions flow through the canister vs. leak orifice•Exact cause for different results is unknown49Setup #3B: Open Pressure Tank withLeak OrificeFTIVRemoved,no KynarBag50Setup #3B: Vented Pressure Tank with Leak OrificeCanister Vent Open toMini-SHEDTemperatureTransmitterLeakOrificePressureIndicatorCanister51657075808590951001/4/13 4:19PM1/4/13 7:12PM1/4/13 10:04PM1/5/13 12:57AM1/5/13 3:50AM1/5/13 6:43AM1/5/13 9:36AM1/5/13 12:28PM1/5/13 3:21PM

Temperature (F)-0.500.511.522.533.5 Pressure (psi)Chamber TemperatureTank Pressure Data0.020” Leak w/o FTIV (Test 9272)Chamber Temperature and Tank PressureAs expected, nopressure buildobserved5205001000150020002500300035001/4/13 4:19PM1/4/13 7:12PM1/4/13 10:04PM1/5/13 12:57AM1/5/13 3:50AM1/5/13 6:43AM1/5/13 9:36AM1/5/13 12:28PM1/5/13 3:21PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber Temperature0.020” Leak w/o FTIV (Test 9272)Emissions and Chamber Temperature0.25 g emitted to Chamber25.5 grams to Canister =25.7 g Total54657075808590951001/9/13 3:07PM1/9/13 6:00PM1/9/13 8:52PM1/9/13 11:45PM1/10/13 2:38AM1/10/13 5:31AM1/10/13 8:24AM1/10/1311:16 AM1/10/13 2:09PM

Temperature (F)-0.500.511.522.533.5 Pressure (psi)Chamber TemperatureTank Pressure Data0.005” Leak w/o FTIV (Test 9274)Chamber Temperature and Tank PressureNo pressurebuild observed,same as 0.02”leak OPEN testresults5505001000150020002500300035001/9/13 3:07PM1/9/13 6:00PM1/9/13 8:52PM1/9/13 11:45PM1/10/13 2:38AM1/10/13 5:31AM1/10/13 8:24AM1/10/1311:16 AM1/10/13 2:09PM

Emissions (mg)65707580859095100 Temperature (F)EmissionsChamber Temperature0.005” Leak w/o FTIV (Test 9274)Emissions and Chamber Temperature0.20 g emitted to Chamber21.1 g to Canister =21.3 g Total57Impact of Leaks on Open vs. SealedSystemAny leak size >0.002" (and likely smaller) in a sealed systemwill generate emissions higher than an open system with0.02" leak orifice, vented through the canister0510152025 

# 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016 0.017 0.018 0.019 0.020Leak Orifice Size (in)

Day 1 Diurnal Emissions (g )Sealed SystemOpen SystemTrendline Sealed SystemTrendline Open SystemChevrolet Volt Fuel Tank9.3 gal capacity; EPA Temp Profile9 RVP E-10 Fuel58Impact of Leaks on Open vs. Sealed System0.05.010.015.020.025.00.020.0050.0030.002

Avg Day 1 Diurnal Emissions (g)Sealed SystemOpen System59Appendix: Orifice Flow CalculationQ = C * A (2 * P /ρ)0.5M = Q *ρQ = Volumetric Flow Rate m3/sC = Orifice CoefficientA = Area of orifice m2P = Pressure Paρ= Density kg/m3M = Mass Flow Rate kg/sAssumptions:1.HC concentrationemitting from tankis the same asinside the tank2.Orifice coefficientis 0.760Appendix: Orifice Flow Calculation0.003” Actual vs. Predicted Emissions0200040006000800010000120001400016000180000 100 200 300 400 500 600 700 800 900Time (min)

Emissions (mgs)0.003in Leak Actual0.003in Predicted61Appendix: Orifice Flow Calculation0.002” Actual vs. Predicted Emissions0200040006000800010000120001400016000180000 100 200 300 400 500 600 700 800 900 1000Time (min)

Emissions (mgs)0.002in Actual0.002in Predicted