Eddy's current non-destructive testing method for welding seam of spiral steel pipe

As an efficient special means of transportation, pipeline transportation has played an increasingly important role in the fields of oil and natural gas transportation. At present, domestic large-diameter transportation pipelines are mainly constructed with spiral welded steel pipes. To ensure the reliable operation of the transportation pipeline, the quality of the spiral steel pipe used must be strictly guaranteed. Therefore, researching and adopting an effective online ultrasonic automatic flaw detection system has become an inevitable choice for steel pipe manufacturers. Compared with foreign countries, the level of testing equipment in my country is relatively backward, and the detection of steel pipe welds is carried out by manual or semi-automatic equipment. Because the detection efficiency is extremely low, it is usually only possible to use the method of random inspection, and it is impossible to completely detect each steel pipe. possible defects. In international bidding activities, steel pipe manufacturers that participate 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 The use effect is often unsatisfactory, and as a result, many imported equipment is idle and a lot of money is wasted. The current situation greatly limits the international competitiveness of domestic steel pipe manufacturers.

Spiral steel pipe is a kind of steel pipe mainly used in fluid transportation pipelines because of its mature manufacturing process and low cost. At present, the method of continuous forming and submerged arc welding is generally used to manufacture spiral steel pipes. There are two types of molding methods: inner support type and outer embrace type. Since these two forming methods are generally insufficient, there is large residual stress after the steel pipe is manufactured, which reduces the pressure-bearing capacity of the steel pipe. After theoretical analysis, the calculation formula of the residual stress of the steel pipe during insufficient forming is given, and the correctness of the residual stress calculation formula given in this paper is verified by actually measuring the residual stress of the spiral steel pipe formed by the inner support. The manufacturing and application of the

The non-destructive testing of steel pipe welds has always been an important problem that is difficult and urgent to solve for various enterprises. It is urgent to develop an automatic weld testing equipment suitable for my country's production conditions. Steel pipe flaw detection adopts different ultrasonic methods, and its flaw detection accuracy varies greatly. Due to the difference in the geometry of the weld bead and the uncertainty formed by various composite defects, it is difficult to automate the ultrasonic flaw detection of steel pipes, and the influence of human factors is also great. How to improve the validity and reliability of flaw detection results has become the focus of ultrasonic automatic flaw detection of steel pipes. After investigation and research and many years of experience in steel pipe flaw detection, we have developed a fully digital ultrasonic flaw detection system that integrates a precise probe tracking system, single-chip technology, and computer signal processing functions when the steel pipe is spiraling. Compared with the traditional flaw detector, the digital online ultrasonic automatic flaw detection system for spiral steel pipe 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) High detection accuracy, the system performs high-speed data acquisition, 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, the digital ultrasonic flaw detector can provide inspection records to 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, and perform time domain, frequency domain, or image analysis on the signal, and also through the mode The identification classifies the quality of the workpiece, reduces the influence of human factors, and improves the reliability and stability of retrieval. (5) The CCD camera tracking sensor is used for welding seam tracking, which has the advantages of high detection sensitivity, no fear of water, no gas, simplicity, and reliability.

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