Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:23:p12
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 23 (pt 12/15)
Character Range: 1929857–1932807

±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 ageing in paragraph 3.6. of this appendix.

              3.6. Setup. 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.

               The air injection system is set to provide the necessary air flow to produce 3.0 per cent 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 3.4. of this appendix) is lambda 1.16 (which is approximately 3 per cent oxygen).

               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 per cent CO).

              3.7. Ageing cycle. The standard bench ageing procedures use the SBC. The SBC is repeated until the amount of ageing calculated from the BAT equation is achieved.

              3.8. Quality assurance. The temperatures and A/F ratio in paragraphs 3.3. and 3.4. of this appendix shall be reviewed periodically (at least every 50 hours) during ageing. Necessary adjustments shall be made to assure that the SBC is being appropriately followed throughout the ageing process.

               After the ageing has been completed, the catalyst time-at-temperature collected during the ageing process shall be tabulated into a histogram with temperature groups of no larger than 10 °C. The BAT equation and the calculated effective reference temperature for the ageing cycle according to paragraph 2.3.1.4. of this annex shall be used to determine if the appropriate amount of thermal ageing of the catalyst has in fact occurred. Bench ageing will be extended if the thermal effect of the calculated ageing time is not at least 95 per cent of the target thermal ageing.

              3.9. Start up and Shutdown. Care should be taken to assure that the maximum catalyst temperature for rapid deterioration (e.g. 1,050 °C) does not occur during start up or shut down. Special low temperature start up and shutdown procedures may be used to alleviate this concern.

              4. Experimentally determining the R-factor for bench ageing durability procedures

              4.1. The R-Factor is the catalyst thermal reactivity coefficient used in the BAT equation. Manufacturers may determine the value of R experimentally using the following procedures.

              4.1.1. Using the applicable bench cycle and ageing bench hardware, age several catalysts (minimum of 3 of the same catalyst design) at different control temperatures between the normal operating