Page images
[blocks in formation]

Figure 3. Typical fuel tank evaporative loss collection arrangement (schematic).

[merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

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 arrange

ments to be employed shall be submitted in accordance with $ 1201.51(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.

[merged small][merged small][ocr errors][merged small][merged small]


Figure 5. Typical activated carbon trap (schematic). (i) Canister-300+25 ml., cylindrical Screen analysis size:


Less than 1.4 mm.--------------container having a length to diameter

1.7-2.4 m m .--

90–100 ratio of 1.4+0.1. An inlet tube, te inch

More than 3.0 mm.--ID and 1 inch long is sealed into the top

1 Brunauer, Emmett & Teller; Journal of of the canister, at its geometric center. the American Chemical Society, Vol. 60, p. A similar outlet tube is sealed into the 309, 1938. wall 1/4 inch from the bottom of the

The activated carbon trap is prepared for canister. The canister is designed to

the test by attaching clamped sections withstand an air pressure of 2 p.s.i., when of vinyl tubing to the inlet and outlet sealed, without evidence of leaking when tubes of the canister. The canister is immersed in water for 30 seconds.

then filled with 150+10 gm. hot activated (ii) Activated carbon-meeting the

carbon which had previously been oven

dried for 3 hours at 300° F. Loss of carfollowing specifications:

bon through the inlet and outlet tubes Surface area, min. (N, 1,000 square meters is prevented through the use of wire BET method). per gram.

screens of 0.7 mm. mesh or wads of Adsorption capacity, 60 percent, by

loosely packed glass wool. The canister is min. (carbon tetra- weight.

closed immediately after filling and the chloride). Volatile material in- None.

carbon is allowed to cool while the trap cluding adsorbed

is vented through a drying tube via the water vapor.

unclamped outlet arm.

(iii) The trap is sealed and weighed prepared activated carbon trap, dried to after cooling and the weight, to the constant weight, cooled to the ambient nearest 0.1 gram, is inscribed on the temperature and sealed with clamped canister body. Within 12 hours of the sections of vinyl tubing is carefully scheduled test, the weight of the trap is weighed to the nearesı 20 milligrams and checked and if it has changed by more the weight recorded as the “tare weight." than 0.5 gm., it is redried to constant (2) A drying tube is attached to the weight. This redrying operation is per outlet tube and the clamp released, but formed by passing dry nitrogen, heated not removed. A length of flexible tubing, to 275° F., through the trap, via the for pressure equalization, is connected to inlet tube, at a rate of 1 liter per minute the other end of the drying tube. until checks made at 30-minute intervals (3) The inlet tube of the adsorption do not vary by more than 0.1 percent trap and external vent(s) of the fuel sysof the gross weight. The trap and its tem will be connected by minimal lengths contents are allowed to cool to room tem of stainless steel or aluminum tubing perature, while vented through a drying and short sections of vinyl tubing. Butttube via the outlet arm, before use

to-butt joints shall be made wherever (2) Auxilliary collection equipment. possible and precautions taken against (i) Drying tube-transparent, tubular sharp bends in the connection lines, inbody 34 inch ID, 6 inches long, with cluding any manifold systems employed serrated tips and removable caps.

to connect multiple vents to a single trap. (ii) Desiccant-indicating variety, 8 (4) The clamp on the inlet tube of the mesh. The drying tube is attached to the trap shall be released but not removed. outlet tube of the collection traps to Care shall be exercised to prevent heatprevent ambient moisture from entering ing the vapor collection trap by radiant the trap. It is prepared by filling the or conductive heat from the engine. empty drying tube with fresh desiccant (5) Upon completion of the collection using loose wad of glass wool to hold the sequence, the vinyl tubing sections on desiccant in place. The desiccant is re each arm of the collection trap shall be newed when three-quarters spent, as in clamped tight and the collection system dicated by color change.

dismantled. (iii) Collection tubing-stainless steel (6) The sealed vapor collection trap or aluminum, 5516 inch ID, for connecting shall be weighed carefully to the nearest the collection traps to the fuel system 20 milligrams. This constitutes the "gross vents.

weight," which is appropriately recorded. (iv) Polyvinyl chloride (vinyl) tub The difference between the "gross ing—flexible tubing, 76 inch ID, for seal weight" and "tare weight” represents the ing butt-to-butt joints.

"net weight" for purposes of calculating (v) Laboratory tubing-air tight flex the fuel vapor losses, ible tubing 516 inch ID, attached to the

$ 1201.83 Information to be recorded. outlet end of the drying tubes to equalize collection system pressure.

The following information shall be re(vi) Clamps-hosecock, open side, for corded with respect to each test: pinching off flexible tubing.

(a) Test number. (c) Weighing equipment. The balance (b) System or device tested (brief deand weights used shall be capable of de scription). termining the net weight of the activated (c) Date and time of day for each part carbon trap within an accuracy of of the test schedule. +75 mg.

(d) Instrument operator. (d) Temperature measuring equip (e) Driver or operator. ment. (1) Temperature recorder-multi

(f) Vehicle: Make-Vehicle identificachannel, variable speed, potentiometric, tion number—Model year–Transmission or substantially equivalent, recorder with type-Odometer reading-Engine disa temperature range of 50° F. to 100° F. placement-Engine family-Idle r.p.m.and capable of either simultaneous or Nominal fuel tank capacity and location sequential recording of the ambient air

on vehicle-Number of carburetorsand fuel temperatures within an accu Number of carburetor barrels—Inertia racy of +1° F.

loading—Actual road load HP. at 50 (2) Fuel tank thermocouples-iron- m.p.h. and drive wheel tire pressure. constantan (type J) construction.

(g) Dynamometer serial number and (e) Assembly and use of the activated indicated road load power absorption at carbon vapor collection system. (1) The 50 m.p.h.


(h) All pertinent instrument informa- judgment in selecting curve for data tion such as tuning-gain-serial num- reduction. bers—detector numbers-range.

(b) HC and Co measurements: Allow (i) Recorder charts: Identify zero, a minimum of 20 minutes warmup for span, exhaust gas, and dilution air sample the HC analyzer and 2 hours for the CO traces.

analyzer. (Power is normally left on in(j) Barometric pressure, ambient tem frared analyzers continuously; but when perature and humidity and the tempera not in use, the chopper motor is turned ture of the air in front of the radiator, if off.) The following sequence of operaany, during the test.

tions should be performed in conjunction (k) Fuel temperatures, as prescribed. with each series of measurements:

(1) The temperature and pressure of (1) Zero on prepurified air. Obtain a the mixture of exhaust and dilution air stable zero on the amplifier meter and entering the positive displacement pump recorder. Recheck after test. and the pressure increase across the (2) Introduce span gas and set the pump. The temperature of the mixture CO analyzer gain ana HC analyzer samshall be recorded continuously during ple flow rate to match calibration curves. the test.

In order to avoid correction for sample(m) The number of revolutions of the cell pressure, span and calibrate at the positive displacement pump accumulated same ficw rates used to analyze the test while the test is in progress and exhaust samples. Span gases should have conflow samples are being collected.

centrations equivalent to approximately

80 percent of full scale. If gain has shifted $ 1201.84 Analytical system calibration

significantly on the CO analyzer, check and sample handling.

tuning. If necessary, check calibration, (a) Calibrate HC and CO instrument Recheck after test. Show actual concenassembly at least once every 30 days. trations on chart. Use the same flow rate as when analyzing (3) Check zero, using prepurified air; samples.

repeat the procedure in subparagraphs (1) Adjust analyzers to optimize per- (1) and (2) of this paragraph if required. formance.

(4) Check flow rates and pressures. (2) Zero on prepurified air, i.e., less (5) Measure HC and CO concentrathan 6 p.p.m. carbon equivalent of hydro- tion of samples. Care should be exercised carbon and 10 p.p.m. of carbon monoxide. to prevent moisture from condensing in Check each cylinder of prepurified air the sample collection bag. for contamination with hydrocarbons (6) Check zero and span points. and carbon monoxide.

§ 1201.85 Dynamometer test runs. (3) Set the CO analyzer gain to give the desired range. Select the desired at

(a) The vehicle shall be allowed to tenuation scale of the HC analyzer and

stand with engine turned off for a period set the sample flop rate to give the de

of not less than 12 hours before the sired range. The operating range of the

exhaust emission test, at an ambient analyzers shall be such that the analyzer

temperature as specified in $ $ 1201.73 and deflection which indicates an emission

1201.74. The vehicle shall be stored prior level equivalent to the respective stand

to the emission tests in such a manner ards is in the upper two-thirds of the

that precipitation (e.g., rain or dew) does scale.

not occur on the vehicle. During the run (4) Calibrate the HC analyzer with

the ambient temperature shall be bepropane (prepurified air diluent) gases

tween 68° F. and 86°F. For exhaust having nomina: concentrations equiva

emission testing which is unrelated to lent to 50 and 100 percent of scale. Cali

fuel evaporative emission control, the brate the CO analyzer with carbon

ambient temperature requirement during monoxide (nitrogen diluent) gases which

storage shall be between 60° F. and 86° F. are equivalent to 10, 25, 40, 50, 60, 70, 85,

(b) The following steps shall be taken and 100 percent of scale. The actual con

- for each test: centrations should be known to within

(1) Place drive wheels of vehicle on +2 percent of the true values.

dynamometer without starting engine. (5) Compare values obtained on the

(2) Start the cooling fan with the CO analyzer with previous calibration

vehicle engine compartment cover open. curves. Any significant change reflects

(3) With the sample solenoid valves some problem in the system. Locate and in the "dump" position, connect eracucorrect problem, and recalibrate. Use best ated sample collection bags to the dilute

exhaust sample and the dilution air sample line connectors.

(4) Start the positive displacement pump, the sample pumps and the temperature recorder. (The heat exchanger of the constant volume sampler should be preheated to its operating temperature before the test begins.)

(5) Adjust the sample flow rates to the desired flow rate (minimum of 5

[ocr errors]

(6) Attach the flexible exhaust tube to the vehicle tailpipe(s).

(7) Simultaneously start the revolution counter for the positive displacement pump, position the sample solenoid valves to direct the sample flows into the bags, and start cranking the engine.

(8) Fifteen seconds after the engine starts, place the transmission in gear.

(9) Twenty seconds after the engine starts, begin the initial vehicle acceleration of the driving schedule.

(10) Operate the vehicle according to the dynamometer driving schecule. (8 1201.75.)

(11) Five seconds after the last deceleration, simultaneously turn off the

revolution counter and position the sample solenoid valve to the "dump" position.

(12) Immediately disconnect sample bags, transfer to analytical system and process samples according to $ 1201.84 as soon as practicable, and in no case longer than 10 minutes after the dynamometer run.

(13) Disconnect the exhaust tube from the vehicle tailpipe(s) and remove vehicle from dynamometer.

(14) Turn off the positive displacement pump. $ 1201.86 Chart reading.

(a) Determine the HC and CO concentrations of the dilution air and dilute exhaust sample bags from the instrument deflections or recordings making use of appropriate calibration charts.

(b) Determine the average dilute exhaust mixture temperature from the temperature recorder trace. $ 1201.87 Calculations (exhaust emis.

sions). The final reported test results shall be computed by use of the following formulae:


(a) For light duty vehicles, excluding off-road utility vehicles:
(1) Hydrocarbon Mass:
HCmass=VmixX Densityhc X-

1,000,000 (2) Carbon Monoxide Mass:

COmass=Vm11 X Densityco x

100 (b) For off-road utility vehicles:

HCcone X 0.85 (1) HCmı..=Vmix X Densityucx


COcone X 0.85 (2) COmass=Vmio X Densityco x– (c) Meaning of symbols: Vmix=Total dilute exhaust volume in cubic feet per mile, corrected to standard conditions

(528° Rand 760 mm. Hg). V 1x2KxVqXNX


[ocr errors]
[ocr errors]


528° R

-=0.09263 31-760 mm. Hg x 7.5 milesV. Vo=Volume of gas pumped by the positive displacement exhaust dilution

pump, in cubic feet per revolution. This volume is dependent on the

pressure differential across the positive displacement pump. N=Number of revolutions of the positive displacement pump during the test

while samples are being collected. Pp=Absolute pressure of the dilute exhaust entering the positive displacement

pump, i.e., barometric pressure minus the pressure depression below

atmospheric of the mixture entering the positive displacement pump. Tp=Average temperature of dilute exhaust entering positive displacement

pump during test while samples are being collected, in degrees Rankine. (c) Meaning of symbols-Continued next page

« PreviousContinue »