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§ 85.82 Sampling and analytical system (fuel evaporative emissions).
(a) Schematic drawing. (1) The following figures (Figures 2, 3, and 4) are flow diagrams of typical evaporative loss collection applications.
L LOSS MEASURELIENT TRAP
Figure 3. Typical fuel tank evaporative loss collection arrangement (schematic).
-PURGE LINE AIR CLEANERVENT TUBING DA
CONTROL UNIT EQUALIZATION)
FUEL TANK LOSS
AIR CLEANER LOSS COLLECTION LINE
-LOSS MEASURE:SENT TRAP
Figure 4. Typical fuel evaporative loss collection arrangement for vehicle equipped with, evaporative
emission control system (schematic).
(2) Figure 2 represents an arrangement for collecting losses which emanate from the carburetor. Figure 3 depicts the means for separately collecting the vapors which emanate from the fuel tank vent line and filler cap. Figure 4 shows an arrangement for collecting the losses from a closed fuel system, vented to the atmosphere solely through the air cleaner, as might be the case with certain fuel evaporative emission control devices.
(3) Schematic drawings of arrangements to be employed shall be submitted in accordance with $ 85.51(b) (3).
(b) Collection equipment. The following equipment shall be used for this collection of fuel evaporative emissions. (Item quantities are determined by individual test needs.)
(1) Activated carbon trap. See Figure 5 for specifications of one design; other configurations may be used: Provided, That they give demonstrably equivalent results.
(i) Canister-300+25 ml., cylindrical container having a length to diameter
ratio of 1.4+0.1. An inlet tube, it inch ID and 1 inch long is sealed into the top of the canister, at its geometric center. A similar outlet tube is sealed into the wall 14 inch from the bottom of the canister. The canister is designed to withstand an air pressure of 2 p.s.i., when sealed, without evidence of leaking when immersed in water for 30 seconds.
(ii) Activated carbon-meeting the following specifications: Surface area, min. (N, 1,000 square meters BET method).
per gram. Adsorption capacity, 60 percent, by min. (carbon tetra- weight.
chloride). Volatile material in- None.
water vapor. Screen analysis size:
Percent Less than 1.4 mm----1.7-2.4 mm--
90-100 More than 3.0 mm--
1 Brunauer, Emmett & Teller; Journal of the American Chemical Society, Vol. 60, p. 309, 1938.
The activated carbon trap is prepared for the test by attaching clamped sections of vinyl tubing to the inlet and outlet tubes of the canister. The canister is then filled with 150+10 gm. hot activated carbon which had previously been ovendried for 3 hours at 300° F. Loss of carbon through the inlet and outlet tubes is prevented through the use of wire screens of 0.7 mm. mesh or wads of loosely packed glass wool. The canister is closed immediately after filling and the carbon is allowed to cool while the trap is vented through a drying tube via the ur.clamped outlet arm.
(iii) The trap is sealed and weighed after cooling and the weight, to the nearest 0.1 gram, is inscribed on the canister body. Within 12 hours of the scheduled test, the weight of the trap is checked and if it has changed by more than 0.5 gm., it is redried to constant weight. This redrying operation is performed by passing dry nitrogen, heated to 275° F., through the trap, via the inlet tube, at a rate of 1 liter per minute until checks made at 30-minute intervals do not vary by more than 0.1 percent of the gross weight. The trap and its contents are allowed to cool to room temperature, while vented through a drying tube via the outlet arm, before use
(2) Auxilliary collection equipment. (i) Drying tube-transparent, tubular body 34 inch ID, 6 inches long, with serrated tips and removable caps.
(ii) Desiccant-indicating variety, 8 mesh. The drying tube is attached to the outlet tube of the collection traps to prevent ambient moisture from entering the trap. It is prepared by filling the empty drying tube with fresh desiccant using loose wad of glass wool to hold the desiccant in place. The desiccant is renewed when three-quarters spent, as indicated by color change.
(iii) Collection tubing-stainless steel or aluminum, 5/16 inch ID, for connecting the collection traps to the fuel system vents.
(iv) Polyvinyl chloride (vinyl) tubing—flexible tubing, 5,6 inch ID, for sealing butt-to-butt joints.
(v) Laboratory tubing-air tight flexible tubing 546 inch ID, attached to the outlet end of the drying tubes to equalize collection system pressure.
(vi) Clamps-hosecock, open side, for pinching off flexible tubing.
(c) Weighing equipment. The balance and weights used shall be capable of de
termining the net weight of the activated carbon trap within an accuracy of +75 mg.
(d) Temperature measuring equipment. (1) Temperature recorder-multichannel, variable speed, potentiometric, or substantially equivalent, recorder with a temperature range of 50° F. to 100° F. and capable of either simultaneous or sequential recording of the ambient air and fuel temperatures within an accuracy of £1° F.
(2) Fuel tank thermocouples-ironconstantan (type J) construction.
(3) Other types of thermocouples and recording equipment may be used provided they record the information specified in subparagraph (1) of this paragraph with the required accuracy and are self-contained. Type J thermocouples are required to be compatible with recording instruments used in Federal certification facilities.
(e) Assembly and use of the activated carbon vapor collection system. (1) The prepared activated carbon trap, dried to constant weight, cooled to the ambient temperature and sealed with clamped sections of vinyl tubing is carefully weighed to the nearest 20 milligrams and the weight recorded as the “tare weight.”
(2) A drying tube is attached to the outlet tube and the clamp released, but not removed. A length of flexible tubing, for pressure equalization, is connected to the other end of the drying tube.
(3) The inlet tube of the adsorption trap and external vent(s) of the fuel system will be connected by minimal lengths of stainless steel or aluminum tubing and short sections of vinyl tubing. Buttto-butt joints shall be made wherever possible and precautions taken against sharp bends in the connection lines, including any manifold systems employed to connect multiple vents to a single trap.
(4) The clamp on the inlet tube of the trap shall be released but not removed. Care shall be exercised to prevent heating the vapor collection trap by radiant or conductive heat from the engine.
(5) Upon completion of the collection sequence, the vinyl tubing sections on each arm of the collection trap shall be clamped tight and the collection system dismantled.
(6) The sealed vapor collection trap shall be weighed carefully to the nearest 20 milligrams. This constitutes the "gross weight,” which is appropriately recorded. The difference between the “gross
weight” and “tare weight” represents the (2) Zero the hydrocarbon analyzer "net weight" for purposes of calculating with zero grade air and the carbon monthe fuel vapor losses.
oxide, carbon dioxide, and oxides of $ 85.83 Information to be recorded.
nitrogen analyzers with zero grade nitro
gen. The allowable zero gas impurity The following information shall be re concentrations should not exceed 1 p.p.m. corded with respect to each test:
equivalent carbon response, 1 p.p.m. car(a) Test number.
bon monoxide, 300 p.p.m. (0.03 mole per(b) System or device tested (brief de cent) carbon dioxide, and 0.1 p.p.m. scription).
nitric oxide. (c) Date and time of day for each part
(3) Set the CO and CO2 analyzer gains of the test schedule.
to give the desired ranges. Select the de(d) Instrument operator.
sired attenuation scale of the HC ana(e) Driver or operator.
lyzer and set the sample capillary flow (f) Vehicle: Make-Vehicle identifica rate, by adjusting the back pressure regtion number—Model year-Transmission ulator, to give the desired range. Select type-Odometer reading—Engine dis the desired scale of the NOx analyzer and placement-Engine family-Idle r.p.m. adjust the phototube high voltage supply Nominal fuel tank capacity and location to give the desired range. on vehicle—Number of carburetors (4) Calibrate the HC analyzer with Number of carburetor barrels—Inertia propane (air diluent) gases having nomloading—Actual road load HP. at 50 inal concentrations equal to 50 and 100 m.p.h, and drive wheel tire pressure. percent of full scale. Calibrate the CO
(g) Dynamometer serial number and analyzer with carbon monoxide (nitroindicated road load power absorption at gen diluent) gases and the CO, analyzer 50 m.p.h.
with carbon dioxide (nitrogen diluent) (h) All pertinent instrument informa gases having nominal concentrations tion such as tuning-gain-serial num equal to 10, 25, 40, 50, 60, 70, 85, and 100 bers—detector numbers-range.
percent of full scale. Calibrate the NO, (i) Recorder charts: Identify zero, analyzer with nitric oxide (nitrogen span, exhaust gas, and dilution air sample diluent) gases having nominal concentraces.
trations equal to 50 and 100 percent of (j) Barometric pressure, ambient tem full scale. The actual concentrations perature and humidity and the tempera- should be known to within +2 percent ture of the air in front (from 6 to 12 of the true values. inches from the grill) of the radiator (5) Compare values obtained on the during the test.
CO and CO, analyzers with previous cali(k) Fuel temperatures, as prescribed. bration curves. Any significant change
(1) The temperature and pressure of reflects some problem in the system. the mixture of exhaust and dilution air Locate and correct problem, and recalientering the positive displacement pump brate. Use best judgment in selecting and the pressure increases across the curves for data reduction. pump. The temperature of the mixture (6) Check the NO, to NO converter shall be recorded continuously or digi- efficiency by the following procedure: tally at a rate often enough to determine (i) Fill a new (not previously used to temperature variations, or it may be con- collect exhaust gas samples) sample bag trolled to +5° F. of the set point of the with air (or oxygen) and NO span gas temperature control system. In the last in proportions which result in a mix in case only the set point need be recorded. the operating range of the analyzer. Pro
(m) The number of revolutions of the vide enough oxygen for substantial conpositive displacement pump accumulated version of NO to NO2. while the test is in progress and exhaust (ii) Knead bag and immediately conflow samples are being collected.
nect the bag to the sample inlet and (n) The humidity of the dilution air. alternately measure the NO and NO, $ 85.84 Analytical system calibration
concentration at 1-minute intervals by
alternately passing the sample through and sample handling.
the converter and the bypass (close (a) Calibrate the analytical assembly valves N6 and N10 to minimize pump at least once every 30 days. Use the same down rate of bag). After several minutes flow rate as when analyzing samples. of operation, the recording of NO and
(1) Adjust analyzers to optimize per NO, will resemble Figure lc if the conformance.
verter is efficient. Even though the