Patent ID: 7432505
Filing Date: 2008-10-07
Classification: F01D,F02C,F05D,G01N

Abstract:
1. A method for inspecting a rotationally operating steam turbine blade, with the blade potentially undergoing degradation in a relatively low-temperature, and saturated steam environment found in the last blade rows of a low pressure stage steam turbine, the method comprising: remotely monitoring radiant energy from respective first and second areas of the gas turbine blade while the blade is rotating, the monitoring of said first area being performed with a first focal plane array imaging sensor coupled to an optical system disposed along an axis generally parallel to an axis of rotation of the blade to concurrently acquire a plurality of thermal imaging points spatially registered over said first area of the blade, wherein said first area of the blade is part of a suction side of the blade, the monitoring of said second area being performed with a second focal plane array imaging sensor coupled to an optical system disposed at an angle relative to an axis along a radial direction to provide a view substantially along said radial direction, configuring said optical system to provide a sufficient depth of field along the view substantially along said radial direction to concurrently and within-focus acquire a plurality of thermal imaging points spatially registered over said second area of the blade, wherein said second area of the blade is part of a pressure side of the blade, wherein said first and second imaging sensors are each respectively configured to sense an infrared bandwidth selected to avoid an absorption band of water vapor and being further selected to capture a sufficient amount of radiant energy in said steam turbine environment so that said plurality of thermal imaging points have sufficient resolution to identify a crack at any of said first and second areas of the blade prior to said crack growing to a critical length; processing said plurality of thermal imaging points to generate respective images of said first and second areas of the turbine blade to indicate the crack at any of said first and second areas of the turbine blade; and evaluating the crack indicated in any of the respective images, wherein said monitoring, processing and evaluating are effected within a sufficiently short period of time to avert growth of said crack to the critical length.