AUTOMATIC CALIBRATION IN ULTRASONIC FLAW DETECTION APPARATUS OF PIPE TO BE INSPECTED

摘要

PURPOSE:To continuously perform calibration, by automating gate setting by correcting the theoretical formula of a beam distance so as to coincide said formula with an actual pipe in order to take out a max. flaw signal through ultrasonic flaw detection by performing gate setting under an optimum condition corresponding to the shape of the actual pipe to register the same in an operator. CONSTITUTION:When the ultrasonic flaw detection of a pipe to be inspected is performed, a gate is preset. At first, a beam distance Wth based on a theoretical value from the inner or outer surface of the pipe to be inspected to a point, where a max. flaw echo is obtained, is calculated from a theoretical formula I [wherein, D is an outer diameter, t is a wall thickness, theta is the angle of refraction of an ultrasonic wave and n is the number of skips (the number of probes)]. Next, a correction item Y (the shift amount of the beam distance) is calculated so as to be coincided with an actual pipe by the flaw detection of said pipe and obtained as quadratic equation of function X(D/t) as represented by formula II (wherein, a, b and c are each a real number). Next, the correction formula III of a beam distance Wact fitted to the actual pipe is obtained and the gate setting of a flaw signal is performed by using this beam distance Wact. Therefore, by registering the formula III in an operator, gate setting is automated and a calibration time can be shortened.