Takemi Yamada

Development of High Durability Exhaust Valves for Marine Diesel Engines

The exhaust valve damage simulator and the testing method have been developed to evaluate the durability at a laboratory scale in a shorter duration and at a lower cost than that by actual ship. It has been verified that the volume loss of tested valve measured by simulation test correlates the shortest life of actual valve and is taken to be the index of the durability.Applied the simulation test to the development of exhaust valves, new metal deposited exhaust valves of PC engine have been commercialized, which have durability about four times as long as the conventional one. Development of ceramic exhaust valve is also carried out in order to meet the lower grade heavy fuel oil and higher thermal efficiency of the future diesel engine. The ceramic coated valves with durability about three times as long as the conventional one, have been already developed and the study on their improvement is now under way.