Ultrasonic time-of-flight diffraction (TOFD) detection method for weld seam

Abstract

The invention relates to an ultrasonic time-of-flight diffraction (TOFD) detection method for a weld seam. The ultrasonic TOFD detection method comprises the following steps of: respectively taking two probes with different refraction angles as a transmitting probe and a receiving probe; arranging the transmitting probe and the receiving probe at the same side of the weld seam; connecting the transmitting probe and the receiving probe with a TOFD instrument; scanning the weld seam; carrying out interpretation on scanned images; finishing the scanning if no defected signal images are discovered; if defected signal images are discovered, changing probe clearance space (PCS), keeping the other settings and parameters unchanged, and carrying out scanning once again; calculating according to two-time scanned results; and achieving the positioned and quantitative detection of the defects of the weld seam. According to the ultrasonic TOFD detection method, a single-face one-sided scanning manner is adopted, the original advantages of TOFD detection are kept, meanwhile, the TOFD detection for the butt-jointed weld seams between a tube body of a pressure vessel and an end enclosure as well as between a pressure conduit and irregular members, such as an elbow, a pipe reducer or a tee joint and the like, is achieved, and thus, the ultrasonic TOFD detection method is wide in scope of application.

Description

technical field [0001] The invention relates to an ultrasonic time-of-flight diffraction detection method for weld seams. technical background [0002] In the early 1970s, Dr. Smith Kline invented the ultrasonic time-of-flight diffraction detection (TOFD) technology. TOFD technology is a crack size detection technology, which consists of two probes, one for transmitting and the other for receiving. The principle is to calculate the position of the crack by re-emitting energy after ultrasonic diffraction. Compared with conventional pulse echo technology, TOFD technology has two biggest advantages: 1. It has high quantitative accuracy, and the absolute error is plus or minus one millimeter; 2. It is not sensitive to the angle of defects during the detection process , quantification is based on the time of the diffracted signal rather than the amplitude of the signal. At present, for the conventional TOFD detection of welds, the TOFD probes need to be placed on both sides of ...

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Problems solved by technology

[0003] However, for the butt welds between pressure pipes and special-shaped components such as elbows, elbows or tees, due to the structure of the base metal on both sides of the weld is not the same height or the elbow side is inclined, etc. Often the TOFD probe cannot be placed on the tee side, so TOFD inspection of such welds cannot be realized

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