Patent ID: 6853945

Claim:
A method of monitoring radial clearances in a steam turbine during operation of the turbine, the turbine comprising an outer shell and a rotor, the rotor comprising a rotor shaft and a plurality of rotor blades attached to the rotor shaft, said method comprising: measuring a temperature of the rotor shaft at a time 1 and at a time 2 ; measuring a temperature of at least one of the plurality of rotor blades at time 1 and at time 2 ; measuring a temperature of the shell at time 1 and at time 2 ; calculating a shaft radial growth between time 1 and time 2 ; calculating a blade growth between time 1 and time 2 ; calculating a shell radial growth between time 1 and time 2 ; and determining a change in a radial gap between the shell and a distal end of the rotor blade from time 1 to time 2 using the following equation: change in radial gap=shell radial growth−shaft radial growth−blade growth, where the growth calculations are performed by using a finite difference method to obtain the instantaneous volume averaged temperatures of the rotor and the shell, and wherein at least one of the surrounding gas temperature and the measured blade temperatures is used to approximate the instantaneous averaged temperature of the plurality of rotor blades.