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Welding knowledge of oil and gas pipeline

更新日期:2013-06-03  浏览:1627

With the development of the oil industry, oil and gas pipes get rapid development due to it’s to economic, professional and efficient quality. Long distance, large diameter and high pressure are becoming the development direction of oil and gas pipelines. Steel X56 - X70 - series high strength steel has been widely used for pipeline construction in the pipeline, X80- high strength pipeline is in the development and application stage, such as in 1993 Germany has completed a X80 pipeline with 1200mm diameter and 126km long, in 1994 the Canadian Trial established a 1200mm\33km diameter, X80 pipeline. Due to the rapid development of oil and gas pipelines, pipeline welding process, welding equipment, welding material also have very great progress. Many manufacturers participate in market competition; both domestic and foreign companies have a lot of pipeline construction mature welding equipment and welding materials. The following are the investigation of equipments and material used in pipelines’ welding of famous manufacturers both domestic and foreign.

1 General introduction to the welding process commonly used in oil and gas pipeline both domestic and international

In 1970s and 1980s, the welding of pipeline mainly focused on manual welding of cellulose electrode and semi-automatic CO2 welding. Because these methods are manual operation, so the efficiency is low, and the welding quality is also restrained by artificial skill level. In 1980s, due to the continuous development of power electronic technology and computer technology, control technology of welding equipment entered the era of intelligence, all of which create the conditions for successful implementation of pipe wildings’’ new automation equipments and new process, greatly improving the pipeline welding efficiency and welding quality, such as the Lincoln Company to develop STT (The Surface Tension Transfer) CO2 gas shielded arc welding power supply technology and equipment, with whose soft arc, small splash and excellent backing weld quality, attracted the attention of the world and become the pipeline welding, especially one of the preferred method of backing welding. And as the pipeline MAGNATECH company‘s position automatic welding equipment. With the adaptive control technology, it not only overcomes the restriction of artificial operation level, but also greatly improves the welding efficiency and quality.

By summing up, the construction technologies of pipeline welding mainly are the following several kinds:

1.1 With the cellulose to electrode manual welding, when the pipeline corrosion serious or pipeline operation in a cold environment, using low hydrogen type vertical down welding. Because of the flexibility of manual welding and welding equipment requirements are not high, the outdoor pipeline welding, manual arc welding workload still accounts for 40 - 50%, for example, in recent years the pipeline engineering in our country from Shaanxi to Beijing from Bio-Rad bought various kinds of cellulose electrode 1 more than 1000 tons. It is predicted that the next few years, China's need for oil and gas pipeline will be 3 - 5 tons and there is an increasing trend.

1.2 Set to the cellulose electrode backing welding, CO2 gas shielded welding filler surface.

Because the CO2 welding of high productivity and low cost, this method has been greatly promoted and implicated in recent years. But for oil and gas pipeline welding, welding must be in a small scope in order to achieve the full position. So it should be completed with short circuit transition form, while the short circuit transition for backing welds prone to have incomplete welding defects. So you should use cellulose electrode backing to realize one-side welding, forming the back, then fill the surface with the high efficiency of CO2 gas shielded welding. This method is widely used.

1.3 Self-shielded flux-cored wire semi-automatic welding

Self-shielded flux-cored wire semi-automatic welding is especially suitable for the occasions in the outdoor air. It is protected by the gas generated drug core instead of CO2. It is have good wind resistance and can be used for pipeline high deposition rate for all position welding. Lincoln Company’s self-shielded flux-cored wire is generally identified in many countries, the brand are NR-207, NR-204-H, NR-208-H etc, all which can be applied to X70, X80 pipeline vertical down welding. But this method is prone to have defects of incomplete fusion when backing welding weld root.

1.4 CO2 gas with high performance in welding protects semi-automatic or fully automatic welding.

Due to the results of in-depth study for CO2 gas shielded arc welding short circuit transition process, at present foreign production have the timely control and high performance power control on the output characteristics of the welding current and voltage waveforms, the United States Lincoln Company STT surface tension of the transition welding technology belongs to the category of waveform control. Based on the improvement of welding equipment performance, it is easy to realize semi-automatic and fully automatic CO2 gas shielded welding, which greatly improves the efficiency and quality of welding. In addition, automatic TIG welding is used in the factory for pipeline welding, which is of good quality, but low efficiency.

2 Welding materials for welding pipe

2.1 Cellulose vertical down welding rod

(1) Bole company in Austria is world-renowned manufacturers for the production of pipe welding, which has committed to the development and improvement of specially used pipeline welding electrode many years. Its products are of all varieties and good quality and it has large market in Europe, Australia, the Middle East and China. There are FOXCEL85 for welding cellulose electrode X60-X70 and FOXCELMOFOXBVD100 for welding X80 tubes.

(2) As one of the famous manufacturers for the production of cellulose electrode, Lincoln Company, located in the United States, produced the equivalent of AWSE6010, E7010G, E8010G electrode pipeline, all of which also accounted for a considerable proportion of domestic market.

In addition, pipeline down electrode PIPEMASTER series produced by Bio-Rad Company and E6010, E7010G electrode produced by Rui Tienysa Company in recent years have participated in the competition in the domestic market.

2.2 Solid wire and flux cored wire

There are many foreign suppliers of solid wire and flux cored, such as Suffolk in France, Kobelco in Japan, Suffolk Kobelco in the United States of America and Lincoln and other large companies, all of which produce various solid wire and flux cored wire for pipelines. In Chinese market, Lincoln Company accounts for the largest proportion referring to flux-cored wire welding of pipeline. Solid wire, such as LN50, LN56, LN70, flux-cored wire, such as OUTERSHIELD71H/81B2H and self-protective welding wire, such as NR207, NR232 can be used for different grades of steel strength. The application of self-protective welding wire FABSHIELD811K6S produced by Bio-Rad Company is very mature.

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