In the long-distance pipeline construction, pipe-line account for a large proportion, generally 35% to 40% of line pipe accounts for investment projects total investment. How to choose a reasonable price, excellent performance pipe is particularly important to a reasonable choice of pipe to save construction investment, easy construction and safe operation of the pipeline system has a very important influence. Gas Pipelines straight seam steel high-frequency electric resistance welded steel pipe, spiral submerged arc welded pipe, LSAW steel pipe. Limited frequency straight seam electric resistance welded steel pipe diameter range is generally limited to domestic steel Φ406.4 mm or less, the largest in Japan has reached a diameter Φ508mm. For large diameter pipe in the form of a spiral SAW, LSAW two kinds. Spiral welded steel pipe because the pipe forming process and characteristics of many shortcomings, the proportion is gradually declining in the long-distance pipeline. In other countries, especially in many European countries, it has banned the use of spiral submerged arc welded pipe used as the main line pipe. The advantage of its unique LSAW are widely used in long-distance oil and gas pipelines, and its advantages are as follows.
(1) Without unwind process, the base material indentation, scratch less.
(2) The wrong side of the slit, the diameter perimeter of easy control and excellent welding quality.
(3) Elimination of the pipe expansion substantially no residual stress after stress.
(4) Because it is a straight line weld, the weld is short, so a small probability of occurrence of defects.
(5) After expanding, pipe geometry accuracy is improved greatly facilitates the site welding.
(6) A straight line weld, less impact on the quality of anti-corrosion coating material.
