The following diagrams and much of the process descriptions are from the Grinnell Supply Sales Company's P-90 catalog from 3/1990.

Roller Leveler

The coil end is fed into the roller leveler which flattens the skelp for further processing.

Sizing Mill

The pipe proceeds to the sizing mill for final OD sizing.

Hydrostatic Tester

Every  length of pipe undergoes a hydrostatic test as a strength and leak check.

Final Inspection

A final visual inspection is preformed on the pipe prior to shipment as an additional quality control measure.

Facing and End Finish

Following galvanizing, if ordered, the pipe is faced, beveled or threaded and coupled.

Rotary Straightener

The pipe is cut to finished length, straightened and visually inspected.

Cut-Off Saw

The flying cut-off saw cuts the pipe into double lengths.

Stretch Reducing

The pipe passes directly from the welding rolls to a stretch reduction mill, where the OD is reduced and the desired wall thickness is obtained.

High Frequency Welder

The high frequency welder heats the edge of the strip to approximately 2600°F at the fusion point. Pressure rolls then squeeze the heated edges together to form a fusion weld.

Forming Rolls

The skelp proceeds through forming rolls that bend it into an oval with the opening facing downward and is then passed on to the welding stand.

Flash Welding

Next, the leading coil end is fed into the flash welder where it is welded on to the trailing end of the preceding skelp coil. This process delivers a continuous strip of skelp to the mill.

Skelp Loop

End welding completed, the skelp to the floor on edge on edge and formed into a large loop.

Shear Trimming

 Before welding, an up-cut shear trims the ends of the skelp square.

Coiled Skelp

The process begins with coiled skelp being loaded on to the uncoiler feed table. It is then advanced by the coil pusher to the uncoiler box.

How Pipe Is Made

Electric Resistance Weld (ERW) - Stretch Reduced Process