



First Forming Section
The first forming section, composed of breakdown stands, begins the process of forming the strip from flat steel to a round pipe section. The roll transition section then receives the strip and continues the rounding-up process.








![]()

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.

Straightening
Any bow in the pipe is removed by running through a series of horizontal deflection rolls.

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

Flying Cut-Off
While the continuous length moves down the mill, the flying cut-off sections the pipe to designated lengths without interrupting the continuous product flow of the mill.

Sizing Mill
Here, the pipe passes through the sizing mill with idler side-closing rolls between stands. This process sizes the pipe to proper outside, while straightening the pipe at the same time.

Air/Water Cooling
The weld is cooled by air to a predetermined temperature, then further cooled by water before being sized.

High Frequency Welder
The edges of the strip are heated to approximately 2600°F at the fusion point. Pressure rolls then squeeze the heated edges together to for a fusion weld.

Seam Normalizer
Here, the weld area is subjected to a post-weld treatment as metallurgically required to remove welding stresses and produce a uniform, normalized grain structure.

In-Process Inspection of Weld
After welding, the seam is inspected by independent, non-destructive inspection units.

Fin Pass Section
This section of the forming rolls completes the rounding process and contours the edges of the strip for welding.

Coil Feed Ramp
Here, each coil is positioned on the centerline of the mill and fed into the uncoiling unit. The leading edge feeds into the pinch rolls preceding the flattener. An electrically operated shear cuts off each end so that coils can be welded together.
The following diagrams and much of the process descriptions are from the Grinnell Supply Sales Company's P-90 catalog from 3/1990.
How Pipe Is Made
Electric Resistance Weld (ERW)