SAW STEEL PIPE (SUBMERGED ARC WELDING)
The two main types of SAW pipes are the longitudinal (with a single or double straight seam weld, DSAW) and the spiral type (called, HSAW or SSAW pipe). The difference between DSAW vs. LSAW is that DSAW pipes have a seam weld in the inside and outside of the pipe, whereas LSAW pipes have a single seam weld on the outer surface.
An SAW pipe (“submerged arc welding”) is manufactured by cutting, bending and welding steel plates.
SAW pipes compete with seamless and ERW pipes in the size range between 12 and 72 inches (SSAW can do even larger diameters), but are “must-go” option for pipelines above 24 inches (as 24 inches is the maximum size for commercial seamless & ERW pipes).
COMPARISION OF LSAW WITH SSAW
Spiral submerged arc welded steel pipe(SSAW) is its forward direction and forming tube centerline hose reel molding angle (adjustable), side molding edge welding and weld them into a spiral, the advantage is that same width of steel plate is able to produce a variety of diameter sizes steel pipes, raw materials to adapt to a wider range, the weld can avoid the main stress force better. The disadvantage is the poor geometry of the weld length compared to the long straight seam pipe, prone to cracking, porosity, slag, welding partial welding defects such as welding stress was tensile stress state. For General Oil and Gas Pipeline design specification, SSAW can only be used for Class 3, Class 4 regional. United States, Japan and Germany, the overall negative SSAW, think the mainline unfit for SSAW; It is used for a part of Canada and Italy projects, Russian is using small amount of SSAW, and have developed a very strict supplementary conditions.
Generally, in the oil and gas industry, large diameter API 5L LSAW pipes are used to transport hydrocarbons over long distances efficiently. HSAW/SSAW pipes are used for non-critical applications, as water transmission and distribution (not for oil & gas).