Detection method for weld joint defect of thick-wall small-diameter tube

Abstract

The invention discloses a detection method for a weld joint defect of a thick-wall small-diameter tube. The method comprises the steps of selecting a probe; processing a wedge with radian fit with the small-diameter tube according to the detected outer diameter of the small-diameter tube; coating coupling agent between the wedge and the probe, and then tightly connecting the wedge with the probe via a fixing screw; installing the probe on a scanner which completes verification, coating the coupling agent on the surface of the small-diameter tube, then fixing the scanners on one side of the weld joint of the small-diameter tube and symmetrical positions on the other side of the weld joint of the small-diameter tube, thus ensuring that a distance between the front edge of the probe and the central line of the weld joint is invariable, and manually scanning around the weld joint for scanning; analyzing a collected phased array image to determine the defect condition in the small-diameter weld joint, and if no, ending the detection; otherwise, determining the position of the defect in the small-diameter tube according to the collected phased array image, and performing CR detection by selecting a transillumination angle, thus acquiring a CR image; and comparing the CR image with the collected phased array image to finally determine the property of the defect in the weld joint of the small-diameter tube.

Description

technical field [0001] The invention belongs to the field of defect detection of small-diameter pipes, in particular to a method for detecting weld seam defects of thick-walled small-diameter pipes. Background technique [0002] Small-diameter tubes generally refer to tubes with an outer diameter less than or equal to 100mm. The water-cooled wall tubes, superheater tubes, and reheater tubes of thermal power plants are all small-diameter tubes, which are subjected to high temperature and pressure. The welding quality is directly related to the safe operation of the boiler. Once the welding quality is unqualified and the pipe bursts, the unit will not stop, which will cause major economic losses. Therefore, it is particularly important to detect the welding quality of small-diameter pipes. [0003] The most commonly used methods are radiographic and ultrasonic testing. With the development of supercritical and ultra-supercritical units, the thickness of many superheater tub...

AI Technical Summary

Problems solved by technology

Aiming at the problem of difficult radiographic inspection of thick-walled small-diameter tubes, the present invention adopts a detection method combining phased array and CR (Computed Radiography) technology to solve the difficulty of low defect detection rate caused by too large transillumination thickness ratio during radiographic inspection. And the shortcomings that cannot be recorded by conventional ultrasonic testing can realize reliable detection of weld seams of thick-walled small-diameter pipes in power plants and ensure the safe operation of units

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