Appendix VIII to Part 86 - Aging Bench Equipment and Procedures
40:21.0.1.1.5.21.1.12.66 : Appendix VIII
Appendix VIII to Part 86 - Aging Bench Equipment and Procedures
This appendix provides specifications for standard aging bench
equipment and aging procedures which may be used to conduct bench
aging durability under the provisions of § 86.1823-08.
1. Aging Bench Configuration
The aging bench must provide the appropriate exhaust flow rate,
temperature, air-fuel ratio, exhaust constituents and secondary air
injection at the inlet face of the catalyst.
a. The EPA standard aging bench consists of an engine, engine
controller, and engine dynamometer. Other configurations may be
acceptable (e.g. whole vehicle on a dynamometer, or a burner that
provides the correct exhaust conditions), as long as the catalyst
inlet conditions and control features specified in this appendix
are met.
b. A single aging bench may have the exhaust flow split into
several streams providing that each exhaust stream meets the
requirements of this appendix. If the bench has more than one
exhaust stream, multiple catalyst systems may be aged
simultaneously.
2. Fuel and Oil
The fuel used by the engine shall comply with the mileage
accumulation fuel provisions of § 86.113 for the applicable fuel
type (e.g., gasoline or diesel fuel). The oil used in the engine
shall be representative of commercial oils and selected using good
engineering judgement.
3. Exhaust System Installation
a. The entire catalyst(s)-plus-oxygen-sensor(s) system, together
with all exhaust piping which connects these components, [the
“catalyst system”] will be installed on the bench. For engines with
multiple exhaust streams (such as some V6 and V8 engines), each
bank of the exhaust system will be installed separately on the
bench.
b. For exhaust systems that contain multiple in-line catalysts,
the entire catalyst system including all catalysts, all oxygen
sensors and the associated exhaust piping will be installed as a
unit for aging. Alternatively, each individual catalyst may be
separately aged for the appropriate period of time.
4. Temperature Measurement
Catalyst temperature shall be measured using a thermocouple
placed in the catalyst bed at the location where the highest
temperature occurs in the hottest catalyst (typically this occurs
approximately one-inch behind the front face of the first catalyst
at its longitudinal axis). Alternatively, the feed gas temperature
just before the catalyst inlet face may be measured and converted
to catalyst bed temperature using a linear transform calculated
from correlation data collected on the catalyst design and aging
bench to be used in the aging process. The catalyst temperature
must be stored digitally at the speed of 1 hertz (one measurement
per second).
5. Air/Fuel Measurement
Provisions must be made for the measurement of the air/fuel
(A/F) ratio (such as a wide-range oxygen sensor) as close as
possible to the catalyst inlet and outlet flanges. The information
from these sensors must be stored digitally at the speed of 1 hertz
(one measurement per second).
6. Exhaust Flow Balance
Provisions must be made to assure that the proper amount of
exhaust (measured in grams/second at stoichiometry, with a
tolerance of ±5 grams/second) flows through each catalyst system
that is being aged on the bench. The proper flow rate is determined
based upon the exhaust flow that would occur in the original
vehicle's engine at the steady state engine speed and load selected
for the bench aging in paragraph (7).
7. Setup
a. The engine speed, load, and spark timing are selected to
achieve a catalyst bed temperature of 800 °C (±10 °C) at
steady-state stoichiometric operation.
b. The air injection system is set to provide the necessary air
flow to produce 3.0% oxygen (±0.1%) in the steady-state
stoichiometric exhaust stream just in front of the first catalyst.
A typical reading at the upstream A/F measurement point (required
in paragraph 5) is lambda 1.16 (which is approximately 3%
oxygen).
c. With the air injection on, set the “Rich” A/F ratio to
produce a catalyst bed temperature of 890 °C (±10 °C). A typical
A/F value for this step is lambda 0.94 (approximately 2% CO).
8. Aging Cycle
The standard bench aging procedures use the standard bench cycle
(SBC) which is described in appendix VII to part 86. The SBC is
repeated until the amount of aging calculated from the bench aging
time (BAT) equation [ref. § 86.1823-08 (d)(3)] is achieved.
9. Quality Assurance
a. The temperatures and A/F ratio information that is required
to be measured in paragraphs (4) and (5) shall be reviewed
periodically (at least every 50 hours) during aging. Necessary
adjustments shall be made to assure that the SBC is being
appropriately followed throughout the aging process.
b. After the aging has been completed, the catalyst
time-at-temperature collected during the aging process shall be
tabulated into a histogram with temperature bins of no larger than
10 °C. The BAT equation and the calculated effective reference
temperature for the aging cycle [ref. § 86.1823-08(d)] will be used
to determine if the appropriate amount of thermal aging of the
catalyst has in fact occurred. Bench aging will be extended if the
thermal effect of the calculated aging time is not at least 95% of
the target thermal aging.
10. Startup and Shutdown
Care should be taken to assure that the maximum catalyst
temperature for rapid deterioration (e.g., 1050 °C) does not occur
during startup or shutdown. Special low temperature startup and
shutdown procedures may be used to alleviate this concern.
[71 FR 2837, Jan. 17, 2006]