Patent ID: 7922825

Claim:
A method of removing extraneous matter from the blades of a steam turbine having a casing defining a duct, and turbine blades housed in the duct, the turbine blades including a moving blade which rotates together with a rotor and a stator blade which is located on the upstream side of the moving blade and is held on the casing side, wherein the stator blade comprises opposing surfaces, the duct is operatively positioned to introduce a fluid to the turbine blades, and the moving blade is rotated by said fluid introduced into the duct, comprising: disposing a first water injection nozzle at a position upstream of the stator blade and connected to a water supply source via a first valve, the first water injection nozzle operatively positioned to inject water onto the stator blade; disposing a plurality of water injection nozzles in the stator blade and connected to a water supply source via a second valve, wherein the plurality of water injection nozzles comprises a first plurality of nozzles operatively positioned to cause water to flow onto both opposing surfaces of the stator blade and a second plurality of nozzles operatively positioned to inject water directly onto a back surface of the moving blade located downstream; detecting the pressure between the stator blade and the moving blade while steam flows through the duct and past the turbine blades; and regulating the opening of said first and second valves according to the pressure detected between the stator blade and the moving blade so that, when the detected pressure has a value exceeding a predetermined minimum pressure, one or both of the valves are opened while steam flows through the duct in order to remove extraneous matter adhering to the surface of the turbine blades; wherein the angle of the second plurality of water injection nozzles is set such that a difference in phase between the steam flow toward the moving blade and the water injected from the second plurality of water injection nozzles is eliminated.