Updated: Dec 27, 2020
There are three (3) manufacturing processes high quality steel pipes are being produced: SSAW (Spiral Submerged Arc Welded), LSAW (longitudinal submerged arc welding), and ERW (electric resistance welding).
Let us take further on LSAW and ERW pipes.
The two main types of LSAW pipes are: Longitudinal (single or double straight seam weld, DSAW) and Spiral (SSAW, HSAW, or SAWL pipe). The difference between DSAW and LSAW is that DSAW pipes have a seam weld in the inside and outside of the pipe, while LSAW pipes have a single seam weld on the outer surface, longitudinal or cross sectional.
LSAW and SSAW employ the same manufacturing technology – JCOE process.
The difference is SSAW pipes are welded in the helix or spiral position while LSAW pipes are welded in the longitudinal direction. Manufacturing process of SSAW pipe is 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 16inch to 60inch (406mm to 1500mm). They have good performances on high pressure resistance, and low-temperature corrosion resistance.
ESC 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 used to transport hydrocarbons over long distances efficiently.
The 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. 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 SSAW 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, LSAW Pipes has better performance than 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 serious. 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’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.