Welding techniques for pipes

Pipeline transport as rail, road, maritime, civil aviation and five long-distance pipeline transport industry, one of the national economy plays an important role. Its transmission medium to common petroleum, natural gas, in addition to industrial gases such as oxygen, CO2, ethylene, ammonia, pulp, coal slurry and other media. Currently pipeline network must be set up by welding, in order to ensure the quality of welding pipe joints, only local conditions to select the appropriate welding process and appropriate equipment to meet project quality requirements, and also to improve engineering efficiency. As oil and gas fields geographical location, the environment is more harsh, so bring a lot of difficulties for welding construction. Spot welding, using up clamp for pipe butt. To improve efficiency, the interface on the previous one while the welding start the next docking preparations. This will have a greater additional stress. Spot welding position for the tube fixed horizontally or inclined fixed docking, including welding, vertical welding, overhead welding, horizontal welding and other welding position. Therefore, the technical requirements for the operation of the welder is also very high. Pipeline industry today requires a higher supply pressure pipe and a larger pipe diameter and to ensure its safe operation. In order to meet pipeline of highly fortified, high toughening, diameter and wall thick-walled large-scale emergence of a variety of welding methods, welding materials, welding technology and welding equipment.

Pipe welding materials used in the construction of cellulose type electrode, low hydrogen type electrode, self-shielded flux-cored wire and CO2 gas shielded solid wire. Cellulosic next to the electrode coating containing 30% to 50 % of the organic matter, with a strong gas-making functions in the protection of the arc and the weld pool while increasing the Arc force, suitable for all-position side welding shape. Under the low hydrogen type electrode coating containing iron, can increase deposition efficiency, improve the mechanical properties of welded joints, suitable for mountainous terrain or water networks, etc. welding automation degree less demanding situations. Self- shielded flux cored pyrolysis by the release of large amounts of gas to protect the arc and the weld pool, through the weld pool and slag solidified weld metal to be protected is an important pipeline construction welding material. CO2 gas shielded solid wire is mainly used for STT semiautomatic welding and all-position welding. Strong internal welding functions, in addition to a welding function, but also has a counterpart function; equipment hydraulic, pneumatic, protective gas, electricity, control systems, due to space limitations, equipment, compact design complexity. On-site application process mechanical failure rate is higher, be equipped with a considerable amount of spare parts and a high level of maintenance workers to ensure the normal operation. Drivers rely on internal welding torch shielding gas, the design due consideration. Drive with protective gas welding torch, one waste shielding gas, the second is to protect the gas gas complex, easily interfere with welding gas protection. Since the flux-cored welding wire of the high cost of the resulting increase in the cost of its application. External quality assurance welder, the main problem is the wind. There are anti- wind, anti- high-temperature processing issues and conflicts between the two. These are mainly the requirements of the device itself, as long as conditions allow equipment, field operations and quality issues can be controlled.

For large diameter thick wall pipe, in area where human condition than ideal circumstances, self-protection should vigorously promote the use of semi-automatic welding. Double pipe welding technology in the conditions permitting should promote the application; ordinary flash welding pipes can be introduced, but according to the toughness of the weld pipeline design requirements, a pilot study; Double GMAW can improve work efficiency should intensify research and to promote the application; forming side welding process test equipment should be combined to accelerate the development pace. Gas protection force forming process research and development carried out in a foreign country, with an estimated difficult to achieve all-position welding. OUTLOOK China pipeline construction prospects, along with the West-East Gas Pipeline project is about to start, domestic welding equipment, welding materials market is bound to increase competition. On the other hand, toward the high-strength steel pipeline development, the need to have more new welding technology support to improve market competitiveness.