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Pipe manufacturing methods

There are 2 main Pipe Manufacturing Processes involving Welded and Seamless pipes. Each of these processes employ different techniques to produce the pipes depending on the ultimate usage for which the pipe is being designed for as indicated in the diagram below.

Each of the techniques used produce pipes with varying degree of diameters, thickness, tolerance and mechanical properties to suit the demands of the customer. The chart below indicates the limitations for each of the above processes:

Electric resistance welded pipe (ERW)

Gulf International Pipe Industry LLC uses the High frequency electric resistance welding process to manufacture pipes ranging in nominal diameter from 168.3 mm (6 inch) to 610 mm (24 inch), and in wall thickness from 4,0mm (0,118 inch) to 25.4 mm (1,00 inch).

Side trimming and Edge milled steel strip is mechanically formed into pipe. There are two break down rolls to make a round shape and feed the strip into cage forming stand. After passing three fin pass stand, a high-frequency electrical current is applied to fuse pipe skelp to form a weld. Unlike the arc-welding process no filler material is added. The weld becomes a homogeneous part of the completed pipe. The welding facilities are equipped with diagnostic system to control and show the all information of operating such as cooling water circulation, input & output voltage, power consumption, and all the weld parameters.

In order to ensure completely smooth pipes, welds are trimmed both internally and externally. Immediate confirmation of welds is assured as pipes pass through a multi-probe ultrasonic inspection system located after the welding and trimming stations.

Following ultrasonic assessment, weld joints are induction heated to normalize the metallic structure of the weld. Seam Normalising calls “N” process also improves toughness of the steel in the region and significantly decreases the weld line corrosion effect.

After air cooling, the pipe goes to water cooling stand to reduce the temperature of weld seam. Prior to hydrostatic testing, pipes are sized to required tolerances before being cut to length and the ends beveled. Weld seams are again ultrasonically tested for not only weld seam but also full body lamination upon client requirements.

Pipes are inspected, weighed and can be varnished and marked prior to final inspection and dispatch, or transferred to the coating plant to continue FBE and 3 Layer PE/PP coating for corrosion protection treatment.

When required, pipe is threaded and coupled at the mill. Couplings are automatically made-up to position with position/torque capability. After coupling make-up, the pipe is transferred to an automatic drift station.

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