40 Protection of Environment 20 2007-07-01 2007-07-01 false Catalyst thermal stress test. 91.329 Section 91.329 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM MARINE SPARK-IGNITION ENGINES Emission Test Equipment Provisions
§ 91.329 Catalyst thermal stress test.

(a) Oven characteristics. The oven used for termally 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:

Constituent Volume
  • percent
    •  Parts per million     Carbon Monoxide 1 1 Oxygen 1.3 Carbon Dioxide 9 Water Vapor 10 Sulfur Dioxide 20 Oxides of Nitrogen 280 Hydrogen 3500 Hydrocarbon 1,2 4000 Nitrogen=Balance 1 Alternatively, the carbon monoxide and hydrocarbon proportions of the mixture may be changed to 1.2% and 4650 ppm, respectively (using on of these alternative concentrations requires that the other be used simultaneously). 2 Propylene/propane ratio=2/1.     [61 FR 52102, Oct. 4, 1996; 62 FR 20066, Apr. 24, 1997]