Our manufacturing process generally involves the following stages in a step by step procedure.
HR Coils are slitted to pre-determined widths for each and every size of pipes
Uncoiling, End Shearing And Welding
The slitted coil is uncoiled at the entry of ERW mill and the ends are sheared and welded one after another. This results in a single endless strip.
The slitted coils are initially formed into U shape and after that into a cylindrical shape with open edges utilizing a series of forming rolls.
In this stage, the open edges are heated to the forging temperature through high-frequency, low-voltage, high current and press welded by forge rolls making perfect and strong but weld without filler materials.
In this stage, the weld flash on top and inside (if required) is trimmed out using the carbide tools.
If required, the welding portion and heat affected zone is put to normalizing and then are cooled down in a air cooling bed.
After water quenching, slight reduction is applied to pipes with sizing rolls. This results in producing desired accurate outside diameter.
In cutting stage, the pipes are cut to required lengths by flying cut off disc/saw cutter.
End Facing And Bevelling
This is usually stage, where the pipes ends are faced and bevelled by the end facer. All these processes are continuous with automatic arrangements. These plain ended tubes further go for processing as per the customer requirements such as galvanizing, threading, black varnishing and more.
Continuous Hot-Dip galvanizing mill roll out galvanized coils of International quality. These lines are supported with on line tension leveling, trimming lines and skin pass mills, to take care of special requirements of customers in terms of coating mass, width, thickness etc..
Corrugation machine (Sheet-to-Sheet type) capable of profiling Galvanized sheets upto 3 meters length with maximum dimensional accuracy.
All these facilities are also supported by a service center, which tailor makes the coils to customer- requirements by slitting & cutting and by delivering sheets/ coils to customer specifications.
Electric Resistance Welded (ERW)
->Solid phase butt weld, was produced using resistance heating & high pressure to make the longitudinal weld (ERW),
->Nowadays Most pipe mills now use high frequency induction heating (HFI) for better control and consistency. However, the product is still often referred to as ERW pipe, even though the weld may have been produced by the HFI process.
->The defects that can occur in ERW/HFI pipe are those associated with strip production, such as laminations and defects at the narrow weld line.
->Lack of fusion due to insufficient heat and pressure is the principal defect, although hook cracks can also form due to realignment of non metallic inclusions at the weld interface. Because the weld line is not visible after trimming, and the nature of the solid phase welding process, considerable lengths of weld with poor fusion can be produced if the welding parameters fall outside the set limits.
->In addition, early ERW pipe was subject to pressure reversals, a problem that results in failure in service at a lower stress than that seen in the pre-service pressure test. This problem is caused by crack growth during the pressure test hold period, which in the case of early ERW pipe was due to a combination of low weld line toughness and lack of fusion defects.