I. Project Overview The second line of the West-East Gas Pipeline Project has a total length of about 5,000km, a design pressure of 12MPa and a diameter of 1219mm. The material is X80 steel, and the annual designed gas transmission capacity is 30 billion m3/year. The 2B section of the Second West Pipeline Project (West Section) of the West-East Gas Pipeline undertaken by our company has a line length of approximately 131.91km. This standard section mainly has three pipe wall thicknesses of 18.4 mm (type 1 area), 22 mm (type 2 area), 26.4 mm (three types of areas and special points). The area where the line passes is located in the hinterland of the Eurasian continent in the mid-latitude, with the characteristics of large daily temperature changes, dry and less rain, and more wind and strong. The average annual temperature is 7.6 °C, the average annual precipitation is 163.2 m, and the maximum maximum frozen soil depth is 1.5 m. Second, the key welding technology 1. CRC P600 pipe automatic welding The second-line pipeline project of the West-East Gas Pipeline has large diameter, high strength, tight time and heavy tasks. In order to be completed on time under the premise of ensuring welding quality, our unit has introduced the CRC P600 pipeline automatic welding technology produced by American CRC Company. (1) Welding method CRC internal welding machine gas protection solid wire underneath root welding + CRC P260 welder gas protection solid wire underneath heat welding + CRC P600 welder gas protection solid wire underneath filling and cap welding. (2) Equipment introduction The CRC P600 pipeline automatic welding equipment introduced by our company is mainly composed of CRC groove processing machine (see Figure 1), CRC internal welding machine (see Figure 2), P260 hot welding machine (see Figure 3) and P600. It consists of an outer welder (see Figure 4) for filling and covering. The inner welding machine header group is welded integrally with the root, and the root welding is performed from the inside of the tube by using eight welding guns, which largely overcomes the adverse effect of the wrong amount of the nozzle on the quality of the root welding. Figure 1 Groove processing machine Figure 2 Internal welder root welding Figure 3 P260 outer welder heat welding Figure 4 P600 external welder filling, cover welding The P260 and P600 welding systems have an automatic tracking function, and process monitoring can be realized through the display panel (human-machine interface) during the welding process. The P260 heat welding system consists of a welding trolley and a power supply junction box. Except for the arc voltage, all important parameters are completed by the control box. The P600 welding system adopts double torch and pulse control for filling and cap welding. The double welding torch is used for surface welding during cover welding and adopts narrow gap groove to form beautiful appearance. (3) Welding material welding wire is BOEHLER SG3-P solid wire and BOEHLER SG8-P solid wire produced by Austria Bole Company. The shielding gas is 75% Ar + 25% CO2, 100% CO2 and 85% Ar + 15% respectively. CO2. 2. STT semi-automatic welding (1) Welding method STT gas protection solid wire semi-automatic down-root welding + self-protecting flux cored wire semi-automatic down-welding, fill welding, cover welding. (2) The root welding of welding equipment is selected from the STT-II welding power source with surface tension transition characteristics produced by Lincoln Company of the United States and the corresponding wire feeder; the filling and cover welding are selected from DC-400 welding power supply produced by Lincoln Company of the United States. Wire machine, as shown in Figure 5. Figure 5 semi-automatic welding (3) Welding material The root welding wire is JM-58 solid wire produced by Jinzhou Jintai Co., Ltd., the shielding gas is 100% CO2; the filling and surface welding wire is selected from JC30/φ2.0mm self-protecting drug core produced by Tianjin Jinqiao Company. Welding wire and E81T8-Ni2/φ2.0mm self-shielded flux cored wire produced by Haobot Company of the United States. Third, technological innovation After the introduction of CRC P600 automatic welding technology, we have improved and improved the process from the following aspects for the actual situation in China: (1) Improvement of weld appearance CRC P600 welding technology is a relatively mature welding process in foreign countries. It is formulated for foreign welding standards. After we introduce from abroad, some indicators cannot fully meet domestic related standards. The requirements of welding quality standard, such as the weld height, the foreign requirements for the weld height are relatively loose, but in order to avoid the generation of air bubbles in the anti-corrosion process, to ensure the quality of anti-corrosion construction, the weld height requirements are stricter . Therefore, in the process of intensive training, we fill the hand and cover welding from the last pass, adjust the control parameters, and repeatedly test to ensure that the weld height is in line with the relevant national standards. (2) Matching with domestic welding power source In order to save investment, when the CRC P600 automatic welding equipment was introduced, the welding power supply matched with the inner welding machine and the P260 outer welding machine was not introduced. Through the partial modification of a certain type of generator used by the company, the protection circuit board and other components have been improved to make the CRC P600 automatic welding equipment and domestic power supply can be well matched. (3) Innovation of construction process The foreign CRC P600 welding process adopts the welding method of the heel, that is, after the root welding and the heat welding are completed by the flow operation, each group of welders in the back completes all the processes from filling to the cover. However, due to the limitation of the width of the working belt, each equipment can only walk in the order of front and rear. Therefore, we have improved the construction process. Each group of welders only performs special filling or cap welding, avoiding the turning over. When the time is over the work belt. However, in order to avoid other conditions affecting production, when we were training, every welder required the mastery of the technology of each layer of welding. (4) Important breakthroughs In foreign countries, CRC P600 welding technology is already a very mature construction process, and its welding qualification rate is generally 90%~92%. After the introduction of technology, our company through continuous research, testing, summarization, continuous continuous improvement, and finally achieved the qualification rate of this standard segment welding at 98% or more, than the foreign welding qualification rate has been greatly improved. Fourth, the conclusion The pipeline project of this tender section started on April 12, 2008 (ignition and welding), and the production conditions were met on December 31, 2009. All the 14 sub-projects included in the project were all qualified, and the pass rate was 100%. The pass rate of pipe welding is 99.42%, which achieves the predetermined engineering excellence goal, and lays a good foundation for the subsequent welding of CRC P600 automatic welding technology to other pipeline projects.
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