Cylinder head overhaul intervals, in stationary four-cycle gaseous-fueled engines, are often determined by the wear of intake and exhaust valves. To extend valve and seat life, engine manufacturers select premium materials and use different design criteria (compared to diesel or gasoline engines) for the valve-faces, seats, and guides of gas engines. The most demanding design requirements for valves and seats are for lean-burn (air/fuel ratio) and landfill gas high-speed, four-cycle gas engines.
First, this paper defines the three major types of valve wear (recession, guttering, and torching), describes valve wear measuring techniques, and reviews valve recession variables that are not lubricant related (engine design, mechanical assembly and maintenance, operating conditions, and metallurgy).
The second part of this paper includes a study of the effect of lubricants on valve recession wear. Field test results and analysis of valve, seat, and combustion chamber deposits are covered. Based on results from field tests, in several types of gas engines, a new family of gas engine lubricant additive packages has been developed which can extend valve life and reduce the frequency of engine cylinder head overhaul.