Electric Resistance Welded (ERW) Pipes are manufactured from Hot Rolled Coils / Slits. All the incoming coils are verified based on the test certificate received from steel mill for their chemistry and mechanical properties. ERW pipe is cold-formed into a cylindrical shape, not hot-formed. Instead of flame, electric current is used for heating edges of the strip for weld fusion. This welding process does not need any filler metal. Instead, the welding pressure causes some of the metal to be squeezed from the joint, forming a bead of metal on inside and outside of the tube. This bead or welding flash is trimmed or completely removed during the process.
During production, online visual inspection is also carried out for surface defects, diameter accuracy, ovality and weld bead shape. Required sample rings as per specification are cut to carry out mechanical testing of weld and body e.g. flattening test, bend test etc. All pipes are then processed in finishing and testing area for pipe end preparation i.e. Facing/Bevelling followed by hydrostatic pressure testing as per specification.
Individual pipe is then visually inspected for the parameters specified in the specification before offering to the customer’s inspection, if any. Data of all tests is re-verified and submitted to the customers.