erw pipe and LSAW pipe are welded pipes, and what is the difference? Today we will explain it in detail.

ERW - Electric Resistance Welded

For pipes or tubes size 4 inch (114.3mm) OD and below, the strip is fed into a set of forming rolls which consist of horizontal and vertical rollers so placed as to gradually from the flat strip into a tube which is then allowed to pass the welding electrodes. The electrodes are copper disks connected to the secondary of a revolving transformer assembly.

The copper disk electrodes make contact on each side of the seam and the temperature is raised to the welding point. The outside flash is removed by a cutting tool as the tube leaves the electrodes, inside flash is removed either by an air hammer or by passing a mandrel through the welded tube after the tube has been cooled.

This is termed an Electric Resistance welded or ERW tube/pipe. If this ERW is being drawn further to get the desired size of tubes or pipes, in the cold condition is called a Cold Drawn welded or CDW.

LSAW - Submerged Arc Welded

This process is used for pipes from 16" to 40" i.e 219mm to 1422mm OD. The flat plate is first pressed into U and later O shape.

The O shape is placed in an automatic welder and backed up on the inside by a water-cooled copper shoe. Two electrodes in close proximity and used. The electrodes are not in actual contact with the pipe. The current passes from one electrode through a granular flux and across the gap in the pipe to the second electrode. The high temperature of the arc heats the edges of the plate, a welding rod placed just over the seam is thereby melted and metal is deposited in the groove.

After the outside weld has been made, the pipe is conveyed to an inside welder where a similar operation is carried on, except that no backup shoe is needed.

Commonly used spot welding, seam welding, and butt three.

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