Stainless steel is one of the most versatile and sanitary metal alloys available on the market, so it’s no wonder that stainless steel tubing is always in high demand. That being said, there are technically two kinds of tubing—welded and seamless tubing. Most people are less familiar with seamless tubing, so let’s explore how seamless stainless-steel tubing is made, its benefits, and its applications.

Structural Steel Pipe

Tubing vs. Piping

The terms ‘tubing’ and ‘piping’ are often used interchangeably when talking about sanitary pipe fittings and valves, but there is a distinction. Tubes are measured by the outside diameter and wall thickness because they’re primarily used for aesthetic and structural purposes. Pipes, on the other hand, are measured by their inside diameter because pipes are used specifically for transporting liquids and gases.

Manufacturing Process

As suggested by the name, seamless tubing does not have a visible welding seam; it is perfectly smooth and rounded. Instead, seamless stainless steel tubing is made through an extrusion process where the tube is drawn from a solid stainless steel billet and extruded into a hollow form. The billets are heated and then formed into oblong circular molds that are hollowed in a piercing mill. While they’re still hot, the molds are drawn through a mandrel rod and elongated. This increases the length of the mold by twenty times to form the seamless tube shape. The tubing is then further shaped through a process called pilgering, which is a cold rolling process, or cold drawing.

Because the process of creating seamless tubes is so much more involved, they can be a bit more expensive and harder to provide in bulk than welded tubing.

Benefits and Applications

So why choose seamless tubing at all? Well, by its very nature, seamless tubing is homogenous and, as a result, is stronger and possesses superior corrosion resistance than welded tubing. Seamless tubing can also withstand higher pressures, which is crucial to consider for harsh environments.

Some examples of seamless tubing applications include:

• Oil and gas control lines
• Fluid and gas transfer
• Below sea safety valves
• Chemical injection lines