Two Siemens Westinghouse SW501F D2 industrial gas turbines were successfully upgraded during a Modified HGP service interval. This paper details the technical aspects of this upgrade and validation of critical turbine blade flutter related parameters during commissioning. Significant performance improvement was achieved by implementation of aerodynamic redesigns of certain compressor and turbine components. An upgraded combustion system and newly installed continuous tuning and health monitoring systems provided operational flexibility and reduction in emissions. Due to historical issues with the 4th stage blade flutter, significant analytical efforts were invested in the structural redesign of the 4th stage blade to predict and avoid flutter and resonance regions. Latest methods of aerodynamic work calculations were employed during design to ensure flutter free operation of this component. Validation steps were implemented using blade tip timing technology to determine synchronous and non-synchronous vibration characteristics of the 4th stage blades during commissioning.
Performance tests per ASME PTC-22 were conducted immediately before and after the outage to provide an accurate measurement of engine performance. Analysis of the performance data after installation and commissioning of the upgrade package confirmed the performance improvement objectives on power output and heat rate were achieved on these two units. Live monitoring and analysis of blade instrumentation data during commissioning and further analysis afterward confirmed flutter free operation of the 4th stage turbine blade.