Eddy current non-destructive testing method for welding seam of spiral welded pipe
As an efficient and dedicated transportation method, 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 of 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 inspection equipment in my country is relatively backward. The inspection of steel pipe welds is carried out by manual or semi-automatic equipment. Because the inspection efficiency is extremely low, it is usually only possible to use random inspection methods, and it is impossible to fully detect each steel pipe. Possible defects.
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, continuous forming and submerged arc welding are commonly used to manufacture spiral steel pipes. There are two molding methods: inner-bearing and outer-holding. Because these two forming methods are generally insufficient forming, the steel pipe has large residual stress after manufacture, which reduces the pressure-bearing capacity of the steel pipe. After theoretical analysis, the calculation formula for the residual stress of the steel pipe when the insufficient quantity is formed is given, and the residual stress of the spiral steel pipe formed by the inner-bearing type is measured.
After investigation and research and years of experience in steel pipe flaw detection, a fully digital ultrasonic flaw detection system is developed that uses a precise probe tracking system, single-chip technology, and computer signal processing functions under the spiral travel state of the steel pipe. Compared with traditional flaw detectors, the spiral steel pipe digital online ultrasonic automatic flaw detection system has the following advantages:
(1) Fast detection speed, automatic detection, calculation, recording, automatic depth compensation, and automatic sensitivity setting.
(2) The detection accuracy is high. 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, digital ultrasonic flaw detector can provide inspection records up to defect images.
(4) High reliability, good stability, can collect and store data comprehensively and objectively, and perform real-time processing or post-processing on the collected data, and perform time domain, frequency domain or image analysis on the signal, and pass the mode Recognition classifies the quality of workpieces, reduces the influence of human factors, and improves the reliability and stability of retrieval.
(5) CCD camera tracking sensor is used for welding seam tracking. It has the advantages of high detection sensitivity, no fear of water, no fear of gas, simple and reliability.