Failure analysis of high temperature studs

Studs in the interceptor valve of a 110 MW unit failed after a service life of 148,700 It. The studs were operated under a steam pressure of 35 kg/cm( 2) and a temperature of 535 degreesC. The studs were fractured at one end o f the threaded end. Various techniques were employed to analyse the failure of the studs. It has been concluded that the failure of the studs was due to reverse temper embrittlement. The failure was delayed due to the presenc e of Mo and V. To reduce the tendency to this kind of failure, the followin g steps were recommended: (a) reduce the phosphorus content in the steel to a low level or (b) reduce the grain size to about 10 mum. (C) 2001 Elsevie r Science Ltd. All rights reserved.