REMAINING LIFE ASSESSMENT TECHNOLOGY APPLIED TO STEAM TURBINES AND HOT GAS EXPANDERS

In today's market place, a large percentage of oil refinery, petrochemical, and power generation plants throughout the world have been trying to reduce their operation cost by extending the service life of their critical machines, such as steam turbines, beyond the design life criteria. The key ingredient in plant life extension is Remaining Life Assessment Technology. This paper will outline the Remaining Life Assessment procedures, and review the various damage mechanisms such as creep, fatigue, creep-fatigue and various embrittlement mechanisms that can occur in these machines. Also highlighted will be the various testing methods for determining remaining life or life extension of components such as high precision STR (Stress Relaxation Test), which determines creep strength, and CDR (Constant Displacement Rate) Test, which evaluates fracture resistance. Other tests such as replication/microstructure analysis and toughness tests will also be reviewed for calculating the remaining life or life extension of the components. Use of the latest computer software will also be highlighted showing how creep-life, fatigue-life and creep/fatigue-life calculations can be performed. Also shown will be an actual life extension example of a hot gas expander performed in the field.