Manufacturing processes of Steel Pipes

Updated July 2026

Pipe manufacturing refers to how the individual pieces of pipe are made in a pipe mill; it does not refer to how the pieces are connected in the field to form a continuous pipeline. Each piece of pipe produced by a pipe mill is called a joint or a length (regardless of its measured length).

In some cases, pipe is shipped to the pipeline construction site as "double joints", where two pieces of pipe are pre-welded together to save time. Most of the pipe used for oil and gas pipelines is seamless or longitudinally welded, although spirally welded pipe is common for larger diameters.

Steel pipes are usually divided into four groups..

Seamless (SMLS)
Electric Resistance Welded (ERW)
Longitudinal Submerged Arc Welded (LSAW)
Spiral Submerged Arc Welded (SSAW)

SMLS

Seamless Pipes seamless pipes are the standard for critical applications. As the name implies, these pipes have no weld seams anywhere along the pipe body.

How it’s made: the process begins with a solid, round steel billet. This billet is heated to extremely high temperatures (over 1200 °C) until it glows orange. It is then pushed or pulled over a mandrel to create a hollow shell. Because it is extruded from a solid piece of steel, the grain structure is uniform throughout.

pplications: high-pressure fluids, hydraulic systems, high-pressure steam lines, and critical oil and gas transmission pipelines, as well as toxic or hazardous substances where a leak in a weld could have catastrophic consequences.

Limitations: it is the most expensive production method due to its energy consumption and complexity, and is limited to approximately 24 inches (600 mm).
Standard seamless rolling mills rarely produce pipes larger than 24 inches, and if a design is specified as “32 inch seamless,” it likely requires a costly production process that utilizes thermal expansion and falls outside the usual standard.

ERW

Electric Resistance Welding is a cost-effective and reliable process and is the most widely used type of steel pipe in construction and infrastructure worldwide.

How it’s made: it starts with a flat steel sheet (coil) that is uncoiled and cold-formed into a cylinder. A high-frequency electric current is passed through the edges, heating them to their melting point. They are pressed together to form a joint without the use of filler metal.
The HFI upgrade: Old-style ERW (from before the 1980s) had a poor reputation due to welding defects. Today, HFI (High-Frequency Induction) welding is widely used. This produces a weld seam that is often stronger than the base metal itself.

Applications: Construction: Scaffolding, fencing, and structural columns. Low/medium pressure: Water pipes, sprinkler systems, and standard HVAC piping.

Additional value: for non-critical applications, seamless pipes can be replaced with ERW, resulting in a 25–30% savings on material costs without compromising performance.

LSAW

Longitudinal Submerged Arc Welding is used for large-diameter high pressure pipes (mostly over 40 inches).

How it’s made: this process uses the JCOE method. A solid, single steel plate is first pressed into a “J” shape, then into a “C” shape, and finally into an “O” shape. The plate is then welded using a double-sided submerged arc welding process (one weld seam on the inside, one on the outside).

Applications: oil and gas pipelines: for transporting large quantities of fuel over long distances, both on land and at sea. It is also used to support skyscrapers, bridges, and other steel structures.

Advantage: LSAW offers the highest reliability among welded pipes. It combines the pressure resistance of seamless pipes with the dimensions of spiral-welded pipes.

SSAW

Spiral Submerged Arc Welding

How it’s made: a continuous strip of steel is unrolled from a coil and bent at an angle, creating a spiral (helical) weld seam along the entire length of the pipe.

Applications: transporting drinking water or wastewater over long distances, and for dredging and pile driving in port construction and foundation work.

Note: SSAW is the most cost-effective option for large diameters (up to 120 inches). However, because the weld seam is much longer than that of a straight pipe, the risk of defects is higher. It is generally not recommended for high-pressure pipelines carrying toxic gases.

Length of steel pipes

Piping lengths from the factory not exactly cut to length but are normally delivered as..

Single random length has a length of around 4.8-7 meter
Double random length has a length of around 11-13 meter

Shorter and longer lengths are available, but for a calculation, it is wise, to use this standard lengths; other sizes are probably more expensive.

Ends of steel pipes

For the ends of pipes are 3 standard versions available.

Plain Ends (PE)
Threaded Ends (TE)
Beveled Ends (BE)

The PE pipes will generally be used for the smaller diameters pipe systems and in combination with Slip On flanges and Socket Weld fittings and flanges.

The TE implementation speaks for itself, this performance will generally used for small diameters pipe systems, and the connections will be made with threaded flanges and threaded fittings.

The BE implementation is applied to all diameters of buttweld flanges or buttweld fittings, and will be directly welded (with a small gap 3-4 mm) to each other or to the pipe. Ends are mostly be beveled to angle 30° (+ 5° / -0°) with a root face of 1.6 mm (± 0.8 mm).