Which is better, seamless or welded pipe?

As industrial applications have evolved and grown more complex, the piping products and systems that serve them have had to keep pace.

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While many pipe manufacturing methods exist, the most prominent discussion in the industry compares electric resistance welded (ERW) vs. seamless (SMLS) steel pipe.

Both ERW and seamless steel pipe manufacturing methods have been in use for decades; over time, the methods used to produce each have advanced. So which is better?

Manufacturing welded pipe

Welded pipe starts out as a long, coiled ribbon of steel called a skelp. The skelp is cut to the desired length, resulting in a flat rectangular sheet. The width of that sheet&#;s shorter ends will become the pipe&#;s outside circumference, a value that can be used to calculate its eventual outside diameter.

The rectangular sheets are fed through a rolling machine that curls the longer sides up toward one another, forming a cylinder. In the ERW process, high-frequency electrical current is passed between the edges, causing them to melt and fuse together.

An advantage of ERW pipe is that no fusion metals are used and the weld seam cannot be seen or felt. That&#;s opposed to double submerged arc welding (DSAW), which leaves behind an obvious weld bead that must then be eliminated depending on the application.

Welded pipe manufacturing techniques have improved over the years. Perhaps the most important advancement has been the switch to high-frequency electric currents for welding. Prior to the s, low-frequency current was used. Weld seams produced from low-frequency ERW were more prone to corrosion and seam failure.

Most welded pipe types require heat treatment after manufacture.

Manufacturing seamless pipe

Seamless piping begins as a solid cylindrical hunk of steel called a billet. While still hot, billets are pierced through the center with a mandrel. The next step is rolling and stretching the hollow billet. The billet is precisely rolled and stretched until it meets the length, diameter and wall thickness as specified by the customer order.

Some seamless pipe types harden as they&#;re manufactured, so heat treatment after manufacturing is not required. Others do require heat treatment. Consult the specification of the seamless pipe type you&#;re considering to learn whether it will require heat treatment.

Historical perspectives and use cases for welded vs. seamless steel pipe

ERW and seamless steel piping exist as alternatives today largely due to historical perceptions.

Generally, welded pipe was considered inherently weaker because it included a weld seam. Seamless pipe lacked this perceived structural flaw and was considered safer. While it&#;s true that welded pipe does include a seam that makes it theoretically weaker, manufacturing techniques and quality assurance regimens each have improved to the extent that welded pipe will perform as desired when its tolerances aren&#;t exceeded. While the apparent advantage is clear, a critique of seamless piping is that the rolling and stretching process produces an inconsistent wall thickness compared to the more precise thickness of steel sheets destined for welding.

The industry standards that govern the manufacture and specification of ERW and seamless steel pipe still reflect those perceptions. For example, seamless piping is required for many high-pressure, high-temperature applications in the oil & gas, power generation and pharmaceutical industries. Welded piping (which is generally cheaper to produce and is more widely available) is specified across all industries as long as the temperature, pressure and other service variables do not exceed parameters noted in the applicable standard.

In structural applications, there&#;s no difference in performance between ERW and seamless steel pipe. While the two can be specified interchangeably, it wouldn&#;t make sense to specify for seamless when cheaper welded pipe works equally well.

Good purchasing practice for welded and seamless steel pipe

An important note to make as piping products are specified for a project is that the specification books (such as those provided by ASTM, ASME, ANSI and API, among others) that engineers use to guide the specs they write only list pipe grades without referencing whether they&#;re produced via ERW or seamless pipe manufacturing. Not all grades can be produced by both means.

For example, a potential mix-up can occur if an engineer specifies welded pipe with a large outside diameter and wall thickness without knowing it would be impossible to manufacture it. This error would likely go unnoticed until a purchase order is placed, at which time a pipe supplier would notify the customer that the order couldn&#;t be fulfilled as written.

Also, a good grasp of industry standards could lead to cost savings. The A106 and A53 carbon steel pipe standards are a good example. In this article, we discuss how pipe complying with the former must be seamless while pipe complying with the latter can either 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 which type to specify based on the specifics of the application.

Show us your specs, request a quote and get your pipe fast

American Piping Products stays fully-stocked with the best inventory of welded and seamless steel piping products in the industry. We source our stock from mills around the world, ensuring buyers get the pipe the need faster regardless of any applicable statutory restrictions.

In our steel pipe buyer&#;s guide, we&#;ll help you navigate the piping procurement process from start to finish to ensure you get what you need as quickly as possible when it&#;s time to buy. If a piping purchase is in your near future, request a quote. We&#;ll provide one that gets you exactly the products you need&#;fast.

Getting the right pipe starts here.

Welded and seamless steel pipes are the two most common types of steel pipes on the market.

A seamless steel pipe has no seams, as the name indicates and produced via hot rolling and cold rolling.

A welded pipe, on the other hand, is made by rolling of a steel coil to the required gauge thickness, a manufacturing procedure that leaves a seam on the pipe's body. Cutting the seams to the width that corresponds to the size of the pipe to be constructed is the next phase.

If you want to learn more, please visit our website Longitudinal Welded Pipe.

Electric Resistance Welded (ERW), Spiral Submerged Arc-Welding Pipe (SSAW), and Longitudinal Submerged Arc-Welding Pipe are three different forms of welded steel pipe (LSAW). These three types of welded steel pipe are manufactured in significantly different ways.

Most of the world&#;s steel production finds its way into buildings, bridges, and other infrastructure in the form of beams, pipes, and foundation pilings. It makes it possible to build tall because steel can handle the pressures created by the structure&#;s weight.

In addition to the quality of steel, architects and contractors have to make choices about the kind of steel pipes that serve their project best. For example, bridge foundations have to be able to handle various environmental factors like earthquakes, ship collisions, and strong currents.

In those situations, does it matter if they use seamless or welded pipes? Let&#;s take a look at the differences to see.

About Seamless Steel Pipes

Seamless pipes are engineered through cold rolling or hot rolling extraction. The process hardens the carbon or alloy steel as it is made to create a strong and light product. They take longer to make and are harder to get dimensions just right.

The advantages of seamless steel pipes are they generally can handle more pressure, which makes them ideal for oil and gas industry applications. There&#;s no seam exposed to corrosion nor to look unsightly if the pipe is in a visible area. The limits of the production process make it not a great option when you need really big pipes.

About Welded Steel Pipes

Welded pipes start as flat metal plate or strips. These are bent into shape, and the edges are welded together. This means the finished product can be highly precise in terms of diameter and wall thickness.

These are usually used in construction where accurate dimensions are critical and are good for general use since they are usually a more affordable option. Because they can have multiple seams, welded pipes can be made into lots of different shapes and sizes, including extremely big ones for construction.

The downsides are that these pipes usually have thinner walls, which along with the seams make them more vulnerable to pressure. Slight impurities around the seam also leave them exposed to potential corrosion.

Seamless Steel Pipe Vs Welded Steel Pipe

Each pipe has advantages and disadvantages depending on your ultimate use. While seamless has a higher pressure rating, that might not be the highest priority for your project.

The lower cost and larger potential size of a welded pipe might be more important if you&#;re building a bridge and need a lot of pilings.

Have a Project That Needs Steel Pipes?

Whether you&#;re constructing a tall building or a wide bridge, steel pipe piles make it possible to get the deep and large foundation you need to handle the load. While seamless versions can handle more pressure, there is a higher cost and less flexibility with them. Welded tends to be better for large construction uses as you can get very accurate dimensions for your project while keeping costs down.

If you have more questions about the steel pipes you need for your construction project, contact our team at whichever global office is closest to you.