Device for Detecting Defect of Turbine Rotor Blade and Method for Detecting Defect of Turbine Rotor Blade

A defect detection device for a turbine rotor blade having a turbine rotor blade implanting portion constructed by fitting a set of rotor grooves formed on a rotor disc portion of a turbine rotor with a set of blade grooves formed on a root portion of the turbine rotor blade, wherein the turbine rotor is rotatably installed inside a turbine casing and around an outer circumference of which turbine rotor, a plurality of turbine rotor blades are annularly arranged,

• and a stationary blade diaphragm where a plurality of stationary blades are annularly arranged adjacent to the turbine rotor blades, is provided with an annular web in an inner circumference side thereof, and an outer circumference side thereof is fixed with the turbine casing, comprising:
• an eddy current probe for detecting a state of the turbine rotor blade implanting portion;
• a groove portion for inserting the eddy current probe, provided on a side surface of the web of the stationary blade diaphragm facing the turbine rotor blade implanting portion, opened toward a radial direction of the stationary blade diaphragm, having a tapered surface on a bottom surface thereof for making the groove shallower toward a rotor shaft, the tapered surface abuts on other tapered surface corresponding to the tapered surface formed on the bottom surface of the groove portion, the other tapered surface formed on a stationary blade diaphragm side of the eddy current probe is to move the eddy current probe toward or away from the turbine rotor blade implanting portion by a sliding action of these tapered surfaces;
• a rod provided with a signal line for transmitting a signal detected by the eddy current probe, connected to the eddy current probe, and set up to be movable through a hole formed in the turbine casing and a space between the stationary blades installed in the stationary blade diaphragm to move the eddy current probe connected to the rod toward or away from the turbine rotor blade implanting portion;
• and
• a data analyzer for determining a condition of the defect occurred in the turbine rotor blade implanting portion based on the detection signal of the turbine rotor blade implanting portion detected by the eddy current probe transmitted through the rod.

A method for detecting a defect of a turbine rotor blade having a turbine rotor blade implanting portion constructed by fitting a set of rotor grooves formed on a rotor disc portion of a turbine rotor with a set of blade grooves formed on each root portion of a plurality of turbine rotor blades annularly arranged around an outer circumference of the turbine rotor rotatably installed in a turbine casing, comprising:

• movably setting up an eddy current probe in a recess formed on a side surface of a web facing the turbine rotor blade implanting portion, the web is among those provided to an inner circumference side of a stationary blade diaphragm where a plurality of stationary blades are annularly arranged;
• operating a rod provided with a signal line for transmitting a signal detected by the eddy current probe, connected to the eddy current probe, from outside of the turbine casing to move through a hole formed in the turbine casing and an air gap formed in the stationary blade of the stationary blade diaphragm when a state of the defect in the turbine rotor blade implanting portion is to be inspected;
• moving the eddy current probe connected to the moving rod toward or away from the turbine rotor blade implanting portion to inspect a state of the turbine rotor blade implanting portion using the eddy current probe;
• and
• determining a condition of the defect occurred in the turbine rotor blade implanting portion based on the detection signal of the state of the turbine rotor blade implanting portion detected by the eddy current probe transmitted through the rod.

A method for detecting a defect of a turbine rotor blade having a turbine rotor blade implanting portion constructed by fitting a set of rotor grooves formed on a rotor disc portion of a turbine rotor with a set of blade grooves formed on each root portion of a plurality of turbine rotor blades annularly arranged around an outer circumference of the turbine rotor rotatably installed in a turbine casing, comprising:

• removably setting up an eddy current probe in a groove portion formed on a side surface of a web, facing the turbine rotor blade implanting portion, opened toward a radial direction of a stationary blade diaphragm, the web is among those provided to an inner circumference side of the stationary blade diaphragm where a plurality of stationary blades are annularly arranged;
• inserting a rod provided with a signal line for transmitting a signal detected by the eddy current probe, connected to the eddy current probe, from outside of the turbine casing to move through a hole formed in the turbine casing and a space between the stationary blades installed in the stationary blade diaphragm when a state of the defect in the turbine rotor blade implanting portion is to be inspected;
• inserting the eddy current probe connected to the moving rod into the groove portion formed on the side surface of the web of the stationary blade diaphragm and positioning the eddy current probe closer to the turbine rotor blade implanting portion to inspect the state of the turbine rotor blade implanting portion using the eddy current probe;
• and
• determining a condition of the defect occurred in the turbine rotor blade implanting portion based on the detection signal of the state of the turbine rotor blade implanting portion detected by the eddy current probe transmitted through the rod.