Abstract: A method is disclosed for operating a steam turbine using turbine reserve capacity for attaining operation at elevated loads. In a preferred form of the invention, a bypass overload valve is provided in parallel with the steam admission control valves but is connected to discharge steam to a lower pressure stage of the turbine. During operation of the turbine at less than full load, the bypass overload valve is maintained closed and the control valves are positioned to sustain a preselected load. As load on the turbine increases, the control valves are increasingly opened until they have all reached their fully opened position corresponding to a nominal rated capacity of the turbine. Then, at the discretion of operating personnel, the bypass overload valve is fully opened while simultaneously one or more of the control valves is throttled to offset any steam passing through the bypass overload valve in excess of the amount required to sustain the preselected turbine load.

Abstract: A method and apparatus is disclosed for determining whether certain rotor stress values are exceeded during the thermal cycle of a turbomachine. The invention takes into account the rotor material and the behavioral characteristics of the rotor material above and below the Fracture Appearance Transition Temperature (FATT). The acquired data is stored to develop a rotor history useful in determining a rotor condition for maintenance and longevity purposes and further useful in determining the operating pattern of the turbomachine.