With the development of the petroleum industry, pipeline transportation of oil and gas has developed rapidly due to its safety, economy, specialization, and efficiency. Long distance, large diameter, and high pressure are becoming the development direction of onshore oil and gas transmission pipelines. Pipeline steel x56 - A X80 pipeline with a diameter of 1200mm and a length of 126km was built in 1994. In 1994, Canada trial-built an X80 pipeline with a length of 1200m\33km. Due to the rapid construction of oil and gas pipelines, pipeline welding processes, joint equipment, and joint materials have also developed greatly. Many manufacturers have participated in market competition, and many mature welding methods for pipeline construction have been developed at home and abroad. Equipment and welding materials. The following is a survey of equipment and materials for pipeline welding produced by famous foreign manufacturers for reference.
Overview of commonly used welding processes for oil and gas pipelines at home and abroad
In the 1970s and 1980s, pipeline welding was mainly based on manual forging with downward cellulose electrodes and semi-automatic C02 welding. Since these methods were manual operations, they were inefficient, and the welding quality was also restricted by the level of manual skills. In the mid-1980s, due to the continuous development of power electronics technology and computer technology, the control technology of welding equipment entered the intelligent era, thus creating conditions for the successful implementation of new pipeline welding automation equipment and new processes, so that the welding efficiency and welding quality of pipelines have improved. Great improvement. For example, the STT (The Surface Tension Transfer) C02 gas-shielded welding power source technology and equipment developed by Lincoln Company has attracted the attention of the world with its soft arc, minimal spatter, and excellent bottom welding quality. It has become one of the preferred methods for pipeline welding, especially bottom welding. Another example is the all-position automatic pipe welding equipment produced by MAGNATECH, which applies adaptive control technology, which not only overcomes the horizontal constraints of manual operation but also greatly improves the welding efficiency and quality. To summarize, the current construction techniques for pipeline welding mainly include the following:
1.1 Use cellulose downward welding rods for manual welding. When there are pipelines with serious hydrogen sulfide corrosion or pipelines running in cold environments, use low hydrogen vertical downward welding rods for welding. Due to the flexibility of manual welding and the low requirements for welding equipment, manual arc welding still accounts for 40-50% of outdoor pipeline welding jobs. For example, in recent years, the pipeline from Shaanxi to Beijing in my country was purchased from Bole Company More than 1,000 tons of various cellulose welding rods have been produced. It is predicted that the annual demand for welding rods for my country's oil and gas pipelines in the next few years will be 3-5,000 tons, and there is an increasing trend.
1.2 Vertical downward cellulose electrode, bottom welding, C02 gas-shielded welding filling surface. Due to the high productivity and low cost of C02 welding, this method has been continuously promoted and applied in recent years. However, for oil and gas pipeline welding, to achieve full-position welding, it must be completed within a smaller current range using the short-circuit transition method. The short-circuit transition method is used Because primer welding is prone to defects such as incomplete penetration, vertical downward cellulose electrodes are used to achieve single-sided welding, the back side is formed, and then the highly efficient C02 gas-shielded welding is used to fill the surface. This process is more commonly used.
1.3 Self-shielded flux-cored wire semi-automatic self-shielded flux-cored wire semi-automatic welding is especially suitable for outdoor windy occasions. It does not use C02 and relies on the gas protection generated by the flux core. It has good wind resistance and can be used for pipes with high deposition rates. For all-position welding, the self-protected flux-cored welding wire produced by Lincoln Company is currently recognized by various countries. Its brands include HR-207, HR-204-H, HR: -208, etc., which can be applied to x70, X80, and other pipelines. The vertical downward welding. However, this method also has the defect that the welding root is prone to not being fused during bottom welding.
1. 4 C02 gas-shielded semi-automatic or fully automatic welding with a high-performance welding machine. As a result of in-depth research on the control technology of the C02 gas-shielded welding short-circuit transition process, high-performance power supplies that can timely control the welding current and voltage waveforms or control the output characteristics of electric energy have been produced abroad. The aforementioned STT surface of Lincoln Company of the United States Tension transfer welding technology belongs to the category of waveform control. Based on the improvement of the performance of welding equipment, semi-automatic and fully automatic C02 gas-shielded welding of pipelines can be realized, which greatly improves the welding efficiency and welding quality. In addition, automatic IG welding is also used for pipe welding in factories. This method has good quality but low production efficiency.