40 CFR § 90.329
Catalyst thermal stress test
June 9, 2020
(a) Oven characteristics. The oven used for thermally stressing the test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10 °C.
(b) Evaluation gas composition.
(1) A synthetic exhaust gas mixture is used for evaluating the effect of thermal stress on catalyst conversion efficiency.
(2) The synthetic exhaust gas mixture must have the following composition:
Open Table
| Constituent | Volume percent | Parts per million |
|---|---|---|
| Carbon Monoxide | 1 | |
| Oxygen | 1.3 | |
| Carbon Dioxide | 3.8 | |
| Water Vapor | 10 | |
| Sulfer dioxide | 20 | |
| Oxides of nitrogen | 280 | |
| Hydrogen | 3500 | |
| Hydrocarbon* | 4000 | |
| Nitrogen = Balance |
*Propylene/propane ratio = 2/1.
(c) Phase 2 engines. The catalyst thermal stress test is not required for engine families certified to the Phase 2 standards.
[60 FR 34598, July 3, 1995, as amended at 64 FR 15243, Mar. 30, 1999]
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