Welded Vs. Seamless Steel Pipe: Which One to Choose?

As industrial applications evolve and become more complex, the pipeline products and systems that serve them must keep pace. Although many pipe fabrication methods exist, the most prominent discussion in the industry is the comparison of resistance welded (ERW) and seamless (SMLS) pipes.

Both ERW and seamless steel pipes have been made using methods for decades; Over time, the methods used to produce each method have improved. So which is better?

Manufacturing welded pipe

The welded pipe begins with a long, coiled band of steel called skelp. The skeleton is cut to the desired length to form a flat rectangular plate. The width of the shorter end of the piece will become the outer circumference of the pipe and this value can be used to calculate its final outer diameter.

Rectangular sheets are fed through a crimp machine that curls the long sides into each other to form a cylinder. In the ERW process, high-frequency electric currents are passed between the edges, causing them to melt and fuse together.

ERW Pipes

One advantage of ERW pipes is that molten metal is not used and welds cannot be seen or felt. This differs from double submerged arc welding (DSAW), which leaves visible welds that must then be eliminated depending on the application.

Over the years, welded pipe manufacturing technology has improved. Perhaps the most important advance is the switch to high-frequency current for welding. Before the 1970s, low-frequency currents were used. Welds produced by low frequency ERW are more prone to corrosion and weld failure.

Most welded pipe types require heat treatment after manufacture.

Manufacture seamless pipe

Seamless pipes begin with solid cylindrical blocks of steel called billets. It's still hot, but the mandrel drives the billet through the center. The next step is to roll and stretch the hollow stock. The billet is precisely rolled and stretched until it reaches the length, diameter and wall thickness specified in the customer's order.

Some seamless pipe types harden during manufacture and therefore do not require heat treatment after manufacture. Others require heat treatment. Please check the specifications for the type of seamless pipe you are considering to see if it needs heat treatment.

Seamless Pipes

Good purchasing habits for welded and seamless steel pipes

An important point to note when specifying piping products for a project is that the specification books (such as those provided by ASTM, ASME, ANSI and API, etc.) that engineers use to guide them as they write specifications only list piping classes and have no reference whether they are manufactured by ERW or seamless pipe manufacturing. Not all grades can be produced either way.

For example, confusion may occur if an engineer specifies a welded pipe with a large od and wall thickness, unaware that it cannot be manufactured. This error may not be noticed until the purchase order is placed, at which point the plumbing supplier notifies the customer that the order cannot be fulfilled as written.

In addition, a good grasp of industry standards can save costs. The A106 and A53 carbon steel tube standards are a good example. In this article, we discuss that pipes conforming to the former must be seamless, while pipes conforming to the latter can be seamless or welded. For example, if an engineer must follow the A53 standard on a given project, he or she may still have the flexibility to choose the type to specify depending on the application.

Show us your specifications, ask for a quote and get your pipeline quickly

The United States is well stocked with pipeline products and has the best inventory of welded and seamless pipe products in the industry. We source inventory from factories around the world to ensure that buyers can obtain the required pipes more quickly, without any applicable legal restrictions.

In our steel pipe purchasing guide, we will help you navigate through the pipe purchasing process from start to finish to ensure you get what you need as soon as possible when you buy. If you purchase pipes in the near future, please request a quote. We will provide a product that can accurately and quickly provide the products you need.

Getting the right pipes starts here.