The steel plate is examined on an on-line ultrasonic testing machine for lamination and to detect any other rolling and metal based defects before being passed through an Edge Planer where it achieves the required width and also the requisite bevel angles suitable for subsequent automatic submerged arc welding.
The edge-planed plate is fed through the crimping press, where the edges of the plate are crimped to a profile suitable to the diameter of the pipe. The crimped plate then passes through either a 'U' & 'O' press at Kosi Kalan facility or through a 'J, C & O' press at Port Mundra facilities; in sequence to form a circular shape.
Continuous Tack Welding
After having achieved the rounded form, the next sequential process is Continuous Tack Welding; in this process, the gap between the two edges is welded continuously along the full length of pipe from outside. Unlike other commonly used tack-welding operations, in Continuous Tack Welding process, the seam of the pipe is completely welded thereby eliminating causes of weld defects, including burn-through and weld cracks in subsequent submerged arc welding.
Inside and Outside Welding
Continuous Tack Welding is followed by Inner Longitudinal Seams welding and Outer Longitudinal Seam Welding under Submerged Arc to avoid any atmospheric contamination. The welding beads are controlled by guide rolls along the length of the seam and on-line monitor scanning to avoid any possible defect due to off-track