Evaporative Emissions Testing

Sealed Housing for Evaporative Determination (SHED)

A SHED (Sealed Housing for Evaporative Determination) is a drive-in test chamber built for the specific purpose of testing the fuel emissions of a vehicle that are not related to exhaust. It is a completely sealed chamber designed to create the conditions specified by the EPA and CARB for evaporative emissions testing. Software and analytical equipment are used to determine the level of volatile organic compounds coming from the vehicle. SHED’s can include; variable temperature, variable volume, onboard refueling and vapor recovery.

Evaporative emissions, including those resulting from leaks of liquid fuel, can be classified into five categories: diurnal, hot soak, running loss, resting loss, and refueling loss.

• Hot-soak emissions occur after vehicle operation has been terminated.
• Running-loss emissions occur as the tank is heated during vehicular operation.
• Resting-loss emissions include escape of fuel vapor by means of permeation of nonmetallic components of the fuel system while the vehicle is inoperative.
• Refueling emissions consist of the fuel vapor displaced from the tank headspace by the new liquid fuel being pumped into the tank.

Variable Temperature SHED (VT SHED)

Four VT SHED test fixtures are available, meeting the evaporative emissions testing requirements outlined in CFR Title 40 Part 86. The specifications of the VT SHED fixtures are:

• Manufactured by California Analytical
• Analytical console equipped with 2 FID analyzers
• Computer controlled and operated on LAN
• UPS - Battery backup on analytical console
• Attached to a central span gas distribution system
• Pneumatic door seal
• Fully insulated to approximately R-20
• VT SHED 1 Interior dimensions: 22’L X 10’W X 8’ H / 6.7L X 3W X 2.4H
• VT SHED 3 Interior dimensions: 18’L X 10’W X 8’ H / 5.4L X 3W X 2.4H
• VT SHED 4 Interior dimensions: 22’L X 10’W X 8’ H / 6.7L X 3W X 2.4H

Onboard Refueling Vapor Recovery Determination (ORVR)

An ORVR Test is run to simulate the refueling activity done in the real world. It measures any loss of gasoline vapors that might escape the vehicle’s onboard refueling vapor recovery systems (ORVR ) during the refueling activity.

• Hydrocarbon emissions emitted by a vehicle during refueling contribute significantly to a vehicle's overall evaporative emissions.
• To control the refueling emissions, vehicles will be equipped with onboard refueling vapor recovery systems (ORVR).
• A typical system consists of canisters that will trap and store the refueling vapors until they are burned under normal vehicle operating conditions. The refueling emissions, like
• diurnal and hot soak emissions, are measured using the enclosure (SHED) technique.
• The test vehicle is placed in a sealed, temperature controlled evaporative emissions enclosure during refueling.
• The fueling nozzle penetrates the SHED wall using a sealed "boot", and the vehicle is fueled according to a standard protocol.
• Samples of the enclosure's atmosphere are taken at the beginning and end of the refueling sequence and are analyzed for hydrocarbon emission using a flame ionization detector (FID).

ETC has one ORVR test fixture meeting the existing evaporative emissions testing requirements outlined in CFR Title 40 Part 86. The specifications of the ORVR fixture are:

• Large volume design with large door openings for trucks
• Manufactured by California Analytical
• Analytical console equipped with 2 FID analyzers
• Computer controlled and operated on LAN
• UPS - Battery backup on analytical console
• Attached to a central span gas distribution system
• Four (4) independent fuel fill points
• Located in an explosion proof rated area
• 300-gallon (1135 L) “day tank” with high capacity pump
• Pneumatic door seal
• Capable of VTSHED operation
• SHED 5 interior dimensions: 28’L X 10.5’W X 9.5’H / 8.5L X 3.2W X 2.8H
• Fully insulated to approximately R-20
• Specialized cart system for use with novelty fuels

Running Loss Test

The Running Loss Test is part of the Enhanced 3 Day Evap Process and is performed to measure any evaporative emissions (hydrocarbon fuel vapors) given off by a vehicle during vehicle operation. ETC uses the Point Source sampling method to conduct the Running Loss Test. Site 4 is equipped with multiple louvers in the floor to provide underbody heating and an auxiliary CVS for Point Source Running Loss Determination. The CVS sampler is of the critical flow venturi (CFV) type and has a single flow rate. All sample lines, filters and pumps are heated.

• The Running Loss Test is a 3-phase bag test that includes an ambient and sample bag for each phase. Proportional samples of diluted hydrocarbon vapors and ambient air are continuously collected during each phase for subsequent hydrocarbon analysis.
• Site 4 is configured to collect samples from up to 3 sources of evaporative emissions during the running loss drive cycle.
• Sample probes are typically placed at the vehicle’s fuel cap, the canister vent, and at the engines air intake. (Actual locations may vary based on vehicle configuration)

The lab is equipped with a California Analytical FID hydrocarbon analyzer. Site 4 also has built in capability to use a California Analytical INNOVA 3433 for speciation of bag samples.

To simulate actual vehicle operating conditions, hydrocarbon emissions are measured during high-ambient temperature drive cycles performed on a chassis dynamometer.

• EPA = 95° ± 5° F
• EPA = 95° ± 5° F
• Regulations also require that the sample pump and the sample lines from the collector to the sample pump be heated to between 175° F and 200° F to prevent condensation.

During the running loss drive cycle, in-use conditions are simulated by controlling the fuel tank's liquid and vapor temperature to a specified on-road profile. The on-road temperature profile is measured while driving the running loss cycle, typically at a desert proving ground, with high ambient and road surface temperatures. During the test, the fuel tank liquid and vapor temperatures are controlled to match the road profile using a fuel tank temperature management system (FTTMS) to blow heated air at the fuel tank and a road speed modulated (RSM) fan to simulate the on-road wind speeds. The RSM fan speed matches the dynamometer speed during the running loss test.

Evaporative Canister Loading Station

Evaporative canister preconditioning is handled by automated loading stations placed throughout each soak area. Automated canister loaders are capable of loading standard 2-day and 3-day loadings, as well as customer specified loading rates and durations.

Each soak area is humidity and temperature controlled to facilitate canister loading. Temperature and humidity excursions are recorded directly on the canister loading report.