Automotive
Three types of valve failure have been observed:
-valve recession;
-guttering;
-torching.
Valve recession, the most common form of wear in diesel engine inlet valves, is caused by loss of material from the seat insert and/or the valve. Guttering is a hightemperature, corrosive process usually caused by deposit flaking. Torching or melting of a valve is triggered by a rapid rise in the temperature of the valve head, which may be caused by preignition or abnormal combustion.
Inlet valve wear is a particular problem in diesel engines because the fuel is introduced directly into the cylinder. The inlet valve, therefore, receives no liquid on its seating face and seats under rather dry conditions.
Exhaust valve wear is less prominent than inlet valve wear as combustion products deposited on the seating faces provide lubrication. Exhaust valves are more likely to fail due to guttering or torching. Such failures are rarely seen in inlet valves.
E N G I N E E R I N G R E S E A R C H S E R I E S
Automotive Engine Valve Recession
R Lewis and R S Dwyer-Joyce
Series Editor
Duncan Dowson
Professional Engineering Publishing Limited,
London and Bury St Edmunds, UK
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