Eddy Current Non-destructive Testing Method for Welds of Spiral Welded Pipes

As an efficient means of special transportation, pipeline transportation has played an increasingly important role in oil and gas transportation and other fields. Domestic large-diameter transportation pipelines are currently mainly constructed using spiral welded steel pipes. To ensure the reliable operation of transportation pipelines, the quality of the spiral steel pipes used must be strictly guaranteed. Therefore, researching and adopting an effective online ultrasonic automated flaw detection system has become an inevitable choice for steel pipe production enterprises. Compared with foreign countries, the level of testing equipment in my country is relatively backward. The detection of steel pipe welds is basically carried out with manual or semi-automatic equipment. Because the detection efficiency is extremely low, spot inspections are usually only used, and it is impossible to fully detect the defects in each steel pipe. possible defects. In international bidding activities, steel pipe manufacturers participating in the bidding are usually required to have relatively complete testing measures. Although some companies have spent huge sums of money to introduce some automatic testing equipment from abroad, due to the limitations of domestic production and testing supporting conditions, their results are often unsatisfactory, resulting in many imported equipment being idle and a large amount of money wasted. The current situation has greatly restricted the international competitiveness of domestic steel pipe manufacturers.

Spiral steel pipe is the main steel pipe used in fluid transportation pipelines because of its mature manufacturing process and low cost. At present, continuous forming and submerged arc welding methods are commonly used to manufacture spiral steel pipes. There are two molding methods: internal support type and external hug type. Since these two forming methods are generally insufficient forming, the steel pipe has a large residual stress after manufacturing, which reduces the pressure-bearing capacity of the steel pipe. After theoretical analysis, the residual stress calculation formula of steel pipes when insufficient forming is given. By actually measuring the residual stress of internally formed spiral steel pipes, the correctness of the residual stress calculation formula given in this article is verified. For spiral steel pipes The manufacturing and application of

The non-destructive testing of steel pipe welds has always been an important problem that is difficult to solve but urgently needs to be solved by various enterprises. There is an urgent need to develop automated weld testing equipment suitable for my country's production conditions. Different ultrasonic methods are used for flaw detection of steel pipes, and their flaw detection accuracy varies greatly. Due to the differences in weld bead geometry and the uncertainty caused by various composite defects, automated ultrasonic flaw detection of steel pipes is difficult, and human factors also have a great impact. How to improve the validity and reliability of flaw detection results has become the focus of automated ultrasonic flaw detection of steel pipes. After investigation and research and many years of experience in steel pipe flaw detection, a fully digital ultrasonic flaw detection system was developed that integrates an accurate probe tracking system with single-chip microcomputer technology and computer signal processing functions when the steel pipe is spirally traveling. Compared with traditional flaw detectors, the spiral steel pipe digital online ultrasonic automatic flaw detection system has the following advantages: (1) The detection speed is fast, it can automatically detect, calculate, and record, and it can also automatically perform depth compensation and automatically set the sensitivity. (2) The detection accuracy is high. The system performs high-speed data collection, quantification, calculation, and discrimination of analog signals, and its detection accuracy can be higher than the detection results of traditional instruments. (3) Record and file inspection. Digital ultrasonic flaw detectors can provide inspection records and defect images. (4) High reliability and good stability, it can collect and store data comprehensively and objectively, perform real-time processing or post-processing on the collected data, conduct time domain, frequency domain, or image analysis on the signal, and also use modes Identification classifies the quality of workpieces, reducing the impact of human factors and improving the reliability and stability of retrieval. (5) Use a CCD camera tracking sensor for weld seam tracking, which has the advantages of high detection sensitivity, not being afraid of water, not afraid of gas, simple and reliable, etc.

Spiral welded steel pipes are widely used in the fields of petrochemical industry, thermal pipe networks, and urban water supply and drainage projects, especially in long-distance transportation of oil and natural gas pipelines. Almost all oil and gas field pipeline networks use spiral welded steel pipes, which have high safety, durability, and economic rationality. Since the diameter of spiral welded steel pipes is generally not limited by the width of the plate, it can be made of plates of many different specifications.