Session: 08-10. Gas Turbine Outage Optimization

Paper Number: 125009

125009 - Risk Assessment and Probabilistic Projection of IN706 Gas
Turbine Rotor 

As the limits of starts or hour are approached, a gas turbine owner is presented with several options: replace with a new rotor, swap for a rebuilt rotor, or ship to a shop for disassembly and full inspection.  This paper outlines a general two-step procedure which has been used to assess the potential risks of extending the OEM's proscribed interval limits.  The approach starts with a form of failure mode and effects analysis (FMEA).  It focuses on and ranks the most relevant durability issues, based on the rotor's design features, operating history and maintenance-inspection records.  For certain F-class rotors, particular attention is focused on the high nickel IN706 turbine discs and spacers, which have been susceptible to both creep and stress-accelerated grain boundary oxidation (SAGBO) degredation.  The importance of this issue has prompted an extensive test program of IN706 specimens in order to better document and define the material properties, which in turn are used to characterize its resistance to SAGBO and creep.  These properties come into play one the durability issues have been ranked and a probabilisitc assessment is performed.  The assessment focuses on one or more of the most predominant issues which pose the highest risk of failure. The probability or chances to achieve a projected interval of hours or starts is calculated, based on an annual record of actual GT operating data.

Presenting Author: Robert Dewey Turbine Technology International Incorporated

Presenting Author Biography: Robert Dewey has over thirty years experience as an independent consultant to the power generation industry. A former officer in the United States Marine Corps, he is currently a senior consultant with Turbine Technology International, Inc.

Authors:

John Scheibel Electric Power Research Institute
Huawei Shi Turbine Technology International, Incorporated
Robert Dewey Turbine Technology International Incorporated