Steam Turbine Driver Blade Erosion

Following a lengthy period of service, the LP stages of a nuclear plant boiler feed pump turbine were found to have suffered erosion damage. A mechanical redesign of those stages was undertaken by MSI engineers. Analytical modal analysis found the first several natural frequencies for each stator blade. A possible vibration problem in one redesigned turbine blade was discovered, and was avoided by shortening the blade chord. The casing stresses were also investigated, and the alteration in stress field was determined due to modification of the inner casing. Both the casing and stator blade stress analyses were performed for worst case pressure and transient thermal loading. The stator blade vibration and stress analyses and casing stress analysis predicted that all aspects of the redesigned LP turbine components should perform satisfactorily in terms of structural and reliability characteristics.