Brief Description and Comparisons of LSAW, SSAW, and ERW Pipes
High quality steel pipes are produced from three (3) manufacturing processes: Seamless, LSAW (longitudinal-seam submerged arc welding), and ERW (electric resistance welding). LSAW and ERW pipes are highly regarded for their numerous fields of application. They are tremendously used in foundation solutions and systems, marine construction, structural construction, and diverse applications in water projects, petrochemical, chemical, and power industry, agricultural irrigation, urban construction, and more.
LSAW Pipes has two types: Longitudinal (Single or Double Straight-seam Weld, DSAW) and Spiral (also called SSAW, HSAW, or SAWL). What makes DSAW pipes differ from other LSAW pipes is that DSAW have a seam weld in the inside and outside of the pipe, while the latter have a single seam weld on the outer surface, longitudinal or cross sectional.
SSAW and LSAW pipes employ a common manufacturing procedure called “JCOE and UOE forming process”. The difference is SSAW pipes are welded in the helix or spiral position while LSAW pipes are welded in the longitudinal direction.
SSAW pipe takes form by rolling and welding a steel strip in a way that the pivotal direction is oblique to the axis or pipe center, making the weld seam in a spiral line. LSAW pipes are produced by molding steel sheets to a cylinder and joining the ends together by welding in a straight line.
The LSAW pipe diameter range is normally from 16 inch to 60 inch (406mm to 1500mm). They have good performances on high pressure resistance, and low-temperature corrosion resistance.
ESC Steel however can supply pipes between 1 inch to 167 inch (21mm up to 4267mm) in diameter and thicknesses between 3/32 inch to 4 inch (2.1mm up to 100mm). Largest diameters and thickness of ESC Steel Pipes are manufactured using LSAW which are highly recommended for load bearing piles, combination wall piles and other applications. In the oil and gas industry, large-diameter API 5L LSAW pipes are use d to transport hydrocarbons over long distances efficiently.
HSAW (helical submerged arc welding) or SSAW pipe diameter range is generally 20 inch to 100 inch (406mm to 2540mm). One advantage of SSAW is the possibility to obtain different diameter
of SSAW pipes from a standard size of steel strip without cutting. On the other hand, spiral welding seam length is quite longer than the pipe length, making it more costly and prone to cracks, air holes, cinder inclusion, partial welding, and more.
HSAW or spiral weld pipes are used for non-critical applications such as water distribution and not for oil & gas. ESC recommends SSAW pipes as King Piles for our Combination Walls and also as Dredging Pipe.
Overall, it appears that LSAW Pipes has slight edge over SSAW Pipes. Below points explains it why.
SSAW Pipes has greater residual stress than LSAW pipes. LSAW pipes passes through uniform expansion process.
SSAW pipes weld stress concentration phenomenon is considered serious by category. The heat affected zone of SSAW pipes is larger than LSAW pipes. Heat affected zones are considered weak points where failure might start.
Geometry accuracy of LSAW pipes is better than SSAW pipes, a key in the ease of installation.
The welding line of LSAW pipe is around 60% lesser than of SSAW pipes.
Using steel plates, quality of LSAW pipe can be tested by non-destructive procedures. While SSAW pipes using hot-rolled coils should be tested with destructive methods such as x-ray.
LSAW pipes adopt welding after molding process where various checks can take place. SSAW pipes employ molding and welding at the same time, pre-checks are not being carried out.
ESC Steel LLC’s wide range of steel pipes also includes ERW pipes. ERW pipes are manufactured using steel coils: the coil is first uncoiled, smoothed, cut, and finally formed into a pipe shape by joining its two extremities by high-frequency electrical welding (HFI & HFW). ERW pipes are available in sizes between ½ inch and 20 inches (12mm to 508mm) and rapidly becoming a popular alternative to seamless pipes, both in terms of price and performance.