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An oxidation catalyst was installed on an industrial LPG-powered forklift truck. For high conversion efficiency in an oxidation system on a rich burning engine a secondary air supply to the catalyst is necessary. Two simple and cost-effective ways of secondary air supply were tested: an air valve and a venturi type injector. The amount of secondary air supplied by both devices was measured under a variety of conditions - different engine speed, load and exhaust system pressure. Carbon monoxide emissions and the catalyst performance were measured and evaluated in terms of the secondary air flow. Advantages and drawbacks of the air valve and venturi injector systems are discussed and compared.

A diesel emissions control system built and tested on an industrial forklift truck is described. The system utilizes a pleated media type diesel soot filter. The temperature limit of the filter material is well below the temperature of the exhaust gas. Therefore, cooling of the exhaust gas is necessary. A finned-tube heat exchanger is included in the system to cool the exhaust gas to the required level. The performance of the heat exchanger was investigated. The focus was on the fouling of heat transfer surface by soot and the corresponding decrease of the heat transfer rate. The fouling factor was found. Also, a design practice for finned-tube heat exchangers is presented and its applicability to small size mobile equipment is discussed.