Thick walled components such as high pressure (HP) steam turbine casings
operating under high parameter conditions are subjected to a complex stress
state. As a result of that stress state, some parts of HP turbine casing
undergo to the creep fatigue caused by the combination of thermal fatigue
resulted from repeated start/stop operation and the creep which occurs during
long-term operation at high temperature and high-pressure. It is well known
that domestic thermal power plants have been in use over 100000 h which means
that significant cost is required not only for maintenance, but often for
renewal of equipment. Based on comprehensive investigation, the results of
residual life assessment of one high pressure steam turbine casing, which
belongs to the older turbine generation, taking into account simultaneous
action of thermal fatigue and creep, are presented in this paper. Also, the
critical flaw crack size of HP turbine casing is determined because this
parameter has a strong influence on casing integrity and residual life. The
results of residual life assessment provide not only a basis for further
maintenance, but also estimated time for reparation or renewal.
Damodar Valley Corporation, Chandrapura Unit 2 Thermal Power Station Residual Life Assessment Summary report