Research On Testing By Quantitative Ultrasonic Waves Of Service Line Welding Defects

General length of the long-distance gas pipeline is longer, pipeline design pressure, coupled with difficult terrain along the route, construction-land, so large amount of pipe welding, and80%across the board to rely on combination of welding (SMAW and semi-automatic welding) construction. In the welding process can produce lack of fusion, incomplete penetration, cracks and other defects, but these defects can reduce the strength of weldment structure, the most important reason is the structure of these defects reduce the effective cross-sectional area of load, while the surrounding defects produced a stress concentration region, resulting in the use of welded pieces of performance and life have a negative impact, in-service pipeline in order to ensure safe and reliable operation, should carry out regular checks, to be able to detect problems and take appropriate measures to reduce unnecessary losses. Ultrasonic inspection technique because of its convenient operation, testing speed, reliable data and the advantages of lower cost in-service pipeline defects become a major means of detection. Existing pipelines serving most of the internal defects using ultrasound and testing, and for defects in or near the surface can be magnetic and penetration testing.Based on pipe butt welding process can produce cracks, holes and other defects, analyze the causes of these defects and echo characteristics, using self-made imitation of natural defects, the use of6dB and endpoint detection method of ultrasonic reflection method, select the appropriate probe, K value, frequency of ultrasonic testing parameters, such qualitative and quantitative detection of defects, defect size obtained after the comparison of its actual size, which can draw the applicability of two methods, was found by the detection pipe wall thickness of about8mm, for cracks and incomplete fusion flaw6dB recommended method, when put under the tip of lack of penetration and slag can be preferred endpoint reflection, of course, the other two methods have some shortcomings detection capabilities, but in actual testing can be6dB preferred method, then the quantitative analysis of the factors that affect the defect in the experiment for comparison, and testing standards and compared with the corresponding obtained testing the pipe wall thickness should be used with different extent probe, frequency, test parameters such as die size is appropriate, and finally through the imitation of natural defect detection, found that these defects have some characteristics of the echo, this study summarized the characteristics of these defects out estimates for future testing in practice sub-types of defects provide a scientific basis.