Method for inspecting bolt heater hole

A method for inspecting a bolt heater hole comprising:

• carrying out cleaning processing in which a cleaning processing jig in which a waste cloth is attached to a tip of a cleaning stick, is inserted into a bolt heater hole provided in a turbine casing fixing bolt, and pollution such as extraneous matter on an inner surface of the bolt heater hole is removed by the waste cloth while moving the cleaning stick straight;
• after the cleaning processing, carrying out penetration processing in which a penetration processing jig in which a sponge is attached to a tip of a penetration stick, is inserted into the bolt heater hole after a penetrant is applied onto the sponge, and the penetrant is made to uniformly penetrate into the inner surface of the bolt heater hole by the sponge while moving the penetration stick straight;
• carrying out the cleaning processing when a predetermined time elapses after the penetrant has been uniformly applied to the inner surface of the bolt heater hole, and carrying out developing processing in which a developing processing jig, in which a head having an injection tip which injects a developer is fixed to a guide attached to a tip of a pipe, is inserted into the bolt heater hole, and the inner surface of the bolt heater hole is developed by injecting the developer guided into the guide through the pipe toward the inner surface of the bolt heater hole from the injection tip provided on the head while moving the pipe backward from a deeper portion;
• and
• when a predetermined time elapses after the developing processing, carrying out inspection processing in which a visual inspection tool in which a visible head is attached to a tip of a pipe is inserted into the bolt heater hole, and the inner surface of the bolt heater hole is visually inspected through a light pipe connected to the visible head while moving the pipe straight,
• wherein at least three center supporting pins which are extensible radially are provided at even intervals in a circumferential direction at an peripheral surface of the guide of the developing processing jig, and the developing processing jig is supported by the supporting pins so as to bring a central axis line of the visible head on a central line of the bolt heater hole.