Difference and Usage of ERW, LSAW and SSAW Steel Pipe

ERW is high-frequency resistance welding - LSAW; LSAW is submerged arc welding - LSAW; both belong to LSAW, but the welding process and use of the two are different, so they can't represent LSAW alone.SSAW - Spiral Welding - Spiral Welded Pipe is more common.

LSAW high-frequency (ERW steel pipe) is divided into induction welding and contact welding according to different welding methods. It is made of hot rolled wide coils, pre-bent, continuously molded, welded, heat-treated, sized, straightened, and cut with spiral compared to the advantages of short weld seam, high dimensional accuracy, uniform wall thickness, good surface quality and high pressure. However, the disadvantage is that only small and medium diameter thin-walled pipe production. Fusion, corrosion defects similar to grooves. The current widely used areas are urban natural gas and crude oil product transportation.

LSAW (LSAW steel pipe) is produced by using a single medium-thick plate as the raw material, pressing (rolling) the plate in a die or forming machine, double-sided submerged arc welding and expanding the diameter. The finished product has a wide range of specifications, good weld toughness, plasticity, uniformity and denseness, large pipe diameter, thick wall, high pressure, high temperature and corrosion resistance. In the construction of high-strength, high-toughness, high-quality long-distance oil and gas pipelines, most of the steel pipe required for the large-diameter thick-walled straight seam submerged arc. According to API standards, in large oil and gas pipelines, when passing through Class 1 and Class 2 areas (such as high mountainous areas, seabed and densely populated urban areas), straight buried arc is the only type of pipe specified. Depending on the molding method, they can be classified as: U0E / JCOE / HME.

Spiral Submerged Arc Welding (SSAW Pipe) involves rolling the pipe with its forward direction at an angle to the centerline of the formed pipe (adjustable) and welding it as it is formed, with the weld seam forming a helix. Advantages are that the same specification can produce a variety of diameter specifications of the pipe, raw materials to adapt to a larger range, the weld can be avoided to avoid the main stress, and the stress is better. The disadvantage is the poor geometry. The length of the weld is longer than the length of the straight seam. Easy to crack, porosity, slag and welding deviation. For welding defects, the welding stress is in the state of tensile stress.

The general design specification for long-distance oil and gas pipelines stipulates that spiral submerged arc can only be used in class 3 and class 4 areas. After improving the process, the raw material was replaced with steel plates to separate the forming and welding. After pre-welding and accuracy, the welding diameter will be enlarged after cold welding. The quality of the weld is close to that of a UOE pipe. The United States, Japan and Germany have generally rejected the use of SSAW and believe that it should not be used on main lines, while Canada and Italy use it partially, and Russia uses it in small quantities under very strict additional conditions. For historical reasons, most Chinese mainlines still use SSAW.

1. Welded pipe refers to ordinary "submerged arc welded steel pipe", which is denoted by "SC" in electrical engineering.

2. Line pipe (i.e., electrical conduit) is relatively thin. With " T " said, can only be used as threading pipe.