Do you know the method of eddy current non-destructive testing for spiral-welded pipe welds

Pipeline transportation, as a highly efficient and specialized means of transportation, has played an increasingly important role in fields such as oil and gas transportation. Currently, large-diameter transportation pipelines in China are 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 manufacturers. Compared with foreign countries, my country's testing equipment is relatively backward. The inspection of steel pipe welds is basically carried out manually or semi-automatically. Due to extremely low inspection efficiency, sampling methods are usually used, which cannot completely detect any defects that may exist in every steel pipe. In international bidding activities, participating steel pipe manufacturers are usually required to have relatively complete testing measures. Although some companies have spent huge sums of money to import some automatic testing equipment from abroad, due to the limitations of domestic production and testing support conditions, the effect of their use is often not ideal, resulting in much imported equipment being idle and a significant waste of funds. The current situation greatly restricts the international competitiveness of domestic steel pipe manufacturers.

Spiral welded steel pipes are a primary type of steel pipe used for fluid transportation pipelines due to their mature manufacturing process and low cost. Currently, continuous forming and submerged arc welding are commonly used to manufacture spiral welded steel pipes. There are two forming methods: internal bearing and external bearing. Since these two methods generally involve insufficient forming, the steel pipes have significant residual stress after manufacturing, reducing their pressure-bearing capacity. Based on theoretical analysis, a formula for calculating the residual stress of steel pipes under insufficient forming is given, and the residual stress of internally formed spiral welded steel pipes is measured through actual measurements.

Non-destructive testing of steel pipe welds has always been a difficult but urgent problem for enterprises, necessitating the development of automated weld inspection equipment suitable for my country's production conditions. Different ultrasonic methods used for steel pipe flaw detection have significantly different accuracy rates. Due to differences in weld geometry and the uncertainties caused by various complex defects, automated ultrasonic flaw detection of steel pipes is challenging, and human factors also have a significant impact. Improving the effectiveness and reliability of flaw detection results has become the focus of automated ultrasonic flaw detection for steel pipes. Based on investigation, research, and years of experience in steel pipe flaw detection, a fully digital ultrasonic flaw detection system has been developed. This system integrates a precise probe tracking system, single-chip microcomputer technology, and computer signal processing capabilities, operating within the spiral movement of the steel pipe.

Compared to traditional flaw detectors, the spiral steel pipe digital online ultrasonic automatic flaw detection system offers the following advantages:

(1) High detection speed: It can automatically detect, calculate, and record data, and also automatically perform depth compensation and sensitivity setting.

(2) High detection accuracy: The system performs high-speed data acquisition, quantization, calculation, and discrimination of analog signals, achieving higher detection accuracy than traditional instruments.

(3) Recording and archiving: The digital ultrasonic flaw detector can provide detection records, up to defect images.

(4) High reliability and stability: It can comprehensively and objectively acquire and store data, and perform real-time or post-processing on the acquired data. It can perform time-domain, frequency-domain, or image analysis on signals and classify workpiece quality through pattern recognition, reducing the influence of human factors and improving the reliability and stability of the retrieval.

(5) A CCD camera tracking sensor is selected for weld seam tracking. It has advantages such as high detection sensitivity, resistance to water and gas, and simplicity and reliability.

Spiral welded steel pipes are widely used in petrochemical, heating network, and urban water supply and drainage engineering, especially in long-distance oil and natural gas pipelines. Oilfield and gas field pipelines almost entirely use spiral welded steel pipes due to their high safety, durability, and economic rationality. Since the diameter of spiral welded steel pipes is generally not limited by the width of the plate material, it can be made from various specifications of plate material.