Life Extension of a High Pressure Steam Turbine Rotor Control Wheel by Means of Weld Repair and Assessment of its Remaining Useful Life
(Room G104, Auditorium Centre, First Floor)
10 Jun 15
9:00 AM
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10:30 AM
Tracks:
Theme: Operational Excellence & Flexibility
Steam turbine generator components are nowadays often exposed to service lives that exceed their intended design hours and cycles. As units cycle on a more frequent basis, fatigue damage accumulates at a much faster rate. Rated conditions may also be exceeded for certain periods of time and, hence, increased steam temperatures can lead to creep damage accumulation. Thus steam turbine rotors can develop cracks in areas of stress and strain concentrations such as rotor bores and disc transition radii.
A life extension of cracked rotor discs by means of weld repair is presented on the example of a cracked impulse stage wheel. In this particular case, cracks penetrated approximately half of the rotor’s radius (e.g., half the wall thickness). The cracks have been excavated and the control wheel has been restored using submerged arc weld.
Experience shows that weld repairs of this nature can extend the remaining useful life of a rotor and bridge the time for a new rotor to be supplied or until the next planned inspection interval. Depending upon the weld repair, the component, and the operation regime, the remaining useful life may vary anywhere from a few months to a few years.
Utility companies can either plan for a replacement component or additional monitoring of the repaired component. Detailed lifetime assessments, coupled with modern repair techniques provide insight on the remaining useful life of repaired components.