GAS ENGINE DURABILITY IMPROVEMENT. FINAL REPORT, OCTOBER 1985-SEPTEMBER 1989. VOLUME 1

A need to improve the durability of natural gas-fueled engines by eliminating or reducing exhaust valve and valve seat recession is addressed. A literature search was conducted and discussions were held with natural gas-fueled engine users, maintenance shops, engine manufacturers, valve and valve seat insert manufacturers to review historical treeatment of valve wear. Engines, equipped with various types of valve seat inserts, were used as test beds to obtain data relevant to the understanding of the mechanisms in exhaust valve recession, comparing the recession characteristics of various insert materials, and determining the influence of engine operating conditions on recession. Instrumentation was selected to monitor realtime valve recession, valve insert temperatures, and cylindrical pressure. Each set of valves, inserts, valve guides, and springs were dimensionally recorded before and after testing. Each exhaust valve and insert was visually inspected after the test and selected components were examined using metallurgical techniques. The influence of valve and cylinder head design, operating conditions, and material characteristics are discussed.