Manufacturing & Coating Processes
The plant manufactures Submerged Arc Welded Helical seam steel pipes with diameters ranging from 8 inches to 120 inches, wall thickness ranging from 4 millimetres to 25.4 millimetres and material grades up to API 5l X-100. It has the capability to manufacture pipes up to 120 inches in diameter for water transmission as per AWWA. The company has been gradually enhancing and upgrading its pipe production capacity to the present notional capacity of 200,000 tonnes.
Spiral Pipe Mill
- Hot Rolled Coil is loaded on the de-coiler of the Spiral Pipe machine.
- The strip is straightened and edges are milled to desired joint geometry.
- The strip is then guided into the Forming Station where it is helically formed into a cylindrical shape.
- Once internal and external welding has been completed the weld seam, HAZ and the pipe body is examined by the Automatic Ultrasonic Unit for possible defects.
- The pipes are cut to a predetermined length by an Automatic Plasma Arc cutting device.
Pipe Finishing Line
- Flux and slag left inside the pipes after welding are cleaned.
- Pipes are visually inspected for any possible imperfections.
- During Fluoroscopic inspection the entire spiral seam of the pipe is analysed for the defects identified by the ultrasonic testing machine.
- Both ends of the pipes are bevelled to suit site butt welding.
- Individual pipes are hydrostatically tested as per client specifications.
- At the final stage the X-Ray station radiographs the weld seam on each end of the line pipe.
External Shot Blasting Line
- The bare pipes are received at the incoming racks and are then pre-heated and shot- blasted to specific surface profiles.
- As each pipe is shot blasted, the blasted profile and depth of anchor pattern is tested to ensure quality.
- Pipes which are rejected after shot blasting are re worked and shot blasted again before transferred to coating line.
External Coating Line
- The shot blasted pipes are acid washed and chromate treated before entering the induction heater/Gas Furnace where thePipe is heated to a temperature recommended by the epoxy manufactures.
- Epoxy powder is sprayed onto the pipes in the Epoxy Booth.
- If three layer coating is required co extruded layers of Co Polymer Adhesive and Polyethylene/Polypropylene are wrapped on the pipe surface.
- The pipes are subsequently cooled at the Quench station and 100% inspected for holiday. Before final inspection coating is removed from the pipe ends according to specifications.
- Final Inspection and marking of coated pipes are carried out as required.
Internal Shot Blasting Line
- At the internal shot blasting station bare pipes are shot blasted to achieve desired surface profile.
- Grits/shots in the pipes are then cleaned through tilting or by blowing air through the pipe.
Internal Coating Line
- Internally shot blasted Pipes are transferred to the Coating line.
- Epoxy Paint is pre heated to the temperature recommended by epoxy suppliers.
- The coating is applied through an automatic airless spray machine to attain the uniform coating thickness.
- Once coating is completed the pipe is left for curing and is later 100% inspected for holiday.
- Final inspection of internally coated pipe is carried out.