PREDICTION OF RESIDUAL LIFE OF INSERVICE 0LDER STEM TURBINES-BHEL'S APPROACH

Thermal power plants have traditionally been built with an envisaged design life of 20-25 years .It has been established that for most of- the plants the available life is much more than that originally envisaged some 20 years ago. The cost of setting up new power plants has gone up extremely high, hence there is general interest worldwide to extend the life of older sets. However ,to assure continued safe, reliable and economic operation of these old sets it is necessary to accurately evaluate the residual life of the critical components steam turbines, which are subjected to high temperatures and thermal transients. The most critical components of steam turbines are HP rotor, IP rotor, LP rotor ,HP casing IP casing, Emergency Stop Valve and Control Valve Casings and inlet pipes. Most of these components are subjected to elevated pressures and temperatures and thermal transients. This paper provides an insight to BHEL’s approach to residual life evaluation and life extension of older inservice steam turbines .In this paper basic concepts of life evaluation procedure have been discussed. The paper presents the various criteria used and methods adopted. It also demonstrates the effectiveness of FEM (Finite Element Method) and CAD(Computer Aided Design) while evaluating life.