Pipeline transportation, as a highly efficient means of special transportation, has played a more and more important role in oil and gas transportation. At present, spiral welded steel pipe is mainly used in large diameter transportation pipeline in China. In order to ensure the reliable operation of transportation pipeline, the quality of spiral steel pipe must be strictly guaranteed. So it is necessary to study and adopt an effective on-line ultrasonic automatic flaw detection system. Compared with foreign countries, the level of detection equipment in our country is relatively backward, and the detection of steel pipe welding seam is basically carried out by manual or semi-automatic equipment. Because the detection efficiency is very low, usually can only use the spot-check method, can not completely detect the possible defects in each steel pipe. In international bidding activities, it is usually required that the steel pipe manufacturer participating in the bidding have relatively perfect testing measures. Although some enterprises spend a huge amount of money to import some automatic testing equipment from abroad, but due to the domestic production and testing conditions, the use of the effect is often not ideal, resulting in many imported equipment in idle state, a lot of money wasted. The current situation greatly limits the international competitiveness of domestic steel pipe production enterprises.
Spiral steel pipe because of its mature manufacturing process, low cost, is the main use of fluid delivery pipe. At present, continuous forming and embedded arc welding are widely used to make spiral steel pipe. Forming method has two kinds of internal and external embrace. Because these two molding methods are generally not enough molding, steel pipe after manufacturing has a large residual stress, reducing the pressure of the steel pipe. Based on theoretical analysis, the calculating formula of residual stress of the steel tube under the condition of insufficient forming is given. By measuring the residual stress of the spiral steel tube, the validity of the formula is verified. It is useful for the manufacture and application of spiral steel tubes.
Nondestructive testing of steel pipe welds has always been an important and difficult problem to be solved in many enterprises. It is urgent to develop a kind of automatic testing equipment suitable for domestic production conditions. Different ultrasonic methods are used in steel pipe flaw detection, and their accuracy is quite different. Because of the difference of weld bead geometry and the uncertainty caused by various complex defects, it is difficult to automatic ultrasonic testing of steel pipes, and the influence of human factors is also great. How to improve the effectiveness and reliability of the inspection results has become the focus of automatic ultrasonic inspection of steel pipe. After investigation and research and many years of experience in steel pipe flaw detection, a fully digital ultrasonic flaw detection system is developed, which integrates precise probe tracking system, single chip microcomputer technology and computer signal processing function under the condition of steel pipe spiral. Compared with traditional flaw detector, the digital on – line ultrasonic flaw detection system for spiral steel pipe should have the following advantages: (1) fast detection speed, automatic detection, calculation, recording, depth compensation and automatic sensitivity setting. (2) high precision, the system carries on the high speed data acquisition, the quantification, the computation and the discrimination to the analog signal, its detection precision may be higher than the traditional instrument detection result. (3) record and file inspection, the digital ultrasonic flaw detector can provide the inspection record up to the defect image. (4) high reliability, good stability, comprehensive and objective collection and storage of data, and the collected data for real time processing or post-processing, The signal is analyzed in time domain, frequency domain or image, and the quality of the workpiece can be graded by pattern recognition, which reduces the influence of human factors and improves the reliability and stability of retrieval. (5) CCD camera tracking sensor is used in seam tracking. It has the advantages of high sensitivity, no fear of water and gas, simple and reliable
Spiral welded steel pipe is widely used in petrochemical industry, heat pipe network and urban water supply and drainage engineering, especially in long-distance transportation of oil and gas pipelines. Oil and gas fields almost all use spiral welded steel pipe network, with high security, durability and economic rationality. Because the diameter of spiral welded steel pipe is generally not limited by the width of the plate, can be made of a variety of different specifications plate.
