Patent ID: 8113055

Claim:
A method for evaluating a fastening state of a threaded joint of pipes or tubes including a pin having an external thread part, a metal seal part, and a shoulder part on an outer peripheral surface, and a box having an internal thread part, a metal seal part, and a shoulder part corresponding to each part of the pin on an inner peripheral surface and being fastened with the pin, the method comprising the steps of: transmitting and receiving ultrasonic waves to and from a plurality of locations along a longitudinal axial direction of the threaded joint in at least one of the internal thread part, the metal seal part, and the shoulder part of the box; detecting echo intensities for the plurality of locations along the longitudinal axial direction of the threaded joint; and comparing the echo intensities detected for the plurality of locations along the longitudinal axial direction of the thread joint with each other to determine whether the fastening state of the threaded joint is good or bad.