Valve cone burning caused by bad valve cone seal leakage, overheating and burning will ultimately make the valve

Valve cone burning caused by bad valve cone seal leak, will ultimately make the valve overheating and burning. Causes more bad seal seat centerline offset, tilt or seat, the valve is deformed, so that the sealing cone is bad; valve tap coke or slag accumulation  Double ferrule fitting , the sealing cone indentation and gradually expand to form pits; accumulation of  Needle valve  and shedding forming a trench; carbide surfacing impact stress and thermal stress generated by joint action of the valve seat and cracks occur; valve clearance cold too small, so that the valve can not be seated;