When shopping for used steel pipe or steel pipe piles, you are likely going to have to choose from two options: seamless steel pipe, or welded? Both are made from the same base materials, but produced in different ways. The names are indicative of the manufacturing process and end-result, but they don’t tell the whole story.

There is a wider variety of sizes for welded steel pipe because it is easier to produce, even though the manufacturing process involves more steps.

We have previously discussed uses and applications for steel pipe. In this post, we’ll discuss the differences between seamless and welded steel pipes, plus their advantages and the strengths of each over the other.

SEAMLESS

Seamless steel pipes are pipes without welds or joints. It is manufactured using a single piece of steel. A machine pushes the center of the rod out of the billet, creating a hollow tube. The pipe is then rolled and stretched to the desired length, diameter, and wall thickness. This type of steel pipe can be formed into hot-rolled or cold-rolled pipe, cold-drawn or extruded tubes. It is more expensive than welded pipe, but offers greater strength.

Seamless steel pipe’s ASME-rated working pressure is typically 20% higher than that of welded steel pipe piles. It also offers higher resistance to corrosion or damage because of lower risk of impurities along seams.

Carbon Steel Pipes

Seamless pipe is often used in pile driving applications as structural support for heavy civil and marine construction, including docks and bridges. Seamless steel pipe can also be used to transport flammable and some solid materials, which makes it a good choice for oil and natural gas exploration and transportation.

WELDED

The two most common methods for steel pipe welding are straight seam or spiral seam welding. Welded steel pipes are typically used to transport fluid (water or oil) and natural gas. It is typically less expensive than seamless steel pipe. Both types of welding are applied after the pipe has been rolled, which involves shaping a sheet of steel into the end shape.

• Straight Seam: Straight seam welded steel pipes are manufactured by adding a welding parallel to the pipe seam. The process is fairly straightforward: Straight seam pipes are formed when a sheet of steel is bent and formed into a pipe shape, then welded longitudinally. Straight seam pipes can be submerged arc welded (SAW) or double-submerged arc welded (DSAW).
• Spiral Seam: Spiral seam welded pipes are manufactured when hot-rolled strip steel is formed into a pipe through spiral bending and welded along the then spiraled seam of the pipe. This results in the weld length being 30-100% longer than that of a straight seam welded pipe. This method is more commonly used on large diameter pipe. (Note: this method of welding may also be referred to as helical submerged arc welded, or HSAW. Spiral seam pipes are also available as DSAW.)

Welded steel pipe can also be electric resistance welded (ERW), which is cold-formed rather than hot-rolled. Rather than using heat or a flame to weld the seams, an electric current is used to heat the edges. The seam on ERW pipe cannot be seen by the naked eye or felt by hand.

Depending upon the size of pipe needed, you may be able to use either straight or spiral welded steel pipe piles for your project. However, spiral welded pipes typically have a greater strength than straight seam pipe. Always refer to the ATSM and ASME standards for specific guidelines for your project.

Welded steel pipe is used for pile driving, marine construction, water and oil and gas transportation, and by utility companies.