At the pipe mill the strip is uncoiled, levelled and crop-sheared. It is then trimmed on both sides simultaneously to correct width and immediately fed into the forming and welding line. During the process, the strip is closely checked for surface defects.
A series of cold forming rolls changes the strip progressively into tubular form with abutting edges on the top. The longitudinal edges are joined by high frequency electric resistance welding. The weld is then heat treated electrically. Special devices remove inside and outside flash from the weld to give uniform wall thickness of the pipe. The welded part is then heat-treated by post annealing to ensure adequate ductility at the weld and adjacent zone. The pipes is passed through a series of cold sizing rolls to progressively reduce the diameter to accurate size. This operation also increases strength and improves surface condition. The pipe is then cut to specified length by a flying cut-off machine. After the straightening operation, end of the pipes are cropped, then squared or beveled depending on end finish requirements.?? The pipe is then hydrostatically tested to specified pressure. Also test specimen are taken during the process to check chemical and mechanical properties. Each length of pipe is inspected by the ultrasonic method on the weld and checked as to diameter, wall thickness, surfaces, end finish, camber and concentricity. The length and weight of pipe is measured and recorded and protective coating is applied on the outside surface.
Specifications: API 5L & 5LX, ASTM A53, A135, ASTM A252, A333
Sizes: Up to 80??? O.D.