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Seamless Pipes Vs. Welded Pipes


Industries are evolving every day. The piping industry is also changing rapidly to keep up with the pace. From manufacturing methods to finished products – everything has gone through changes. The advancements in the industry ensure that the systems are working correctly. As a result, many seamless pipe manufacturers have evolved with the growing need for reliable piping solutions.
However, one discussion keeps stirring from time to time. And that is the different uses of electric resistance welded pipes, ERW pipes, seamless pipes, or SMLS pipes.


ERW pipes have been in the market for so long that most people feel comfortable using them. Even though welded pipes have certain drawbacks, many people do not want to invest in other pipes as they need to learn more about them.

So, here is a comparative discussion on the differences between Seamless Pipes Vs. Welded Pipes.

Which type of pipe is better and why?

Manufacturing process Seamless Pipes Vs. Welded Pipes manufacturers follow:

Based on the manufacturing process, welded pipes are different from seamless pipes. Both welded and seamless pipe fabricators follow specific techniques to produce these pipes. They not only use dedicated machines but also continuously improve their products.
Here is a short discussion on the manufacturing process of both types of pipes. Even though these pipes transfer fluids, there is a huge difference between them. Let us check it out.

Welded pipes:

The base product of welded pipes is a steel-coiled ribbon. Pipe fabricators call the steel ribbon skelp. Before fabricating welded pipes, they cut these ribbons into rectangular pieces. The manufacturers choose the length of the sheet depending on how long they want the pipes to be.

The outer diameter of the pipe determines the length of the shorter end of the sheet. Therefore, based on the outer diameter, the manufacturers can decide on the pipe’s inner diameter.

Now, unlike the line pipe suppliers, welded pipe fabricators use a curling machine that helps roll the flat sheets into cylindrical shapes. Once the curling machine brings the two open mouths together, welded pipe producers use another device that produces high-frequency electrical currents. The electrical currents melt the two edges and agglutinate them together.

The pipes have a prominent welding mark if the manufacturers produce double sub-merged arc welding (DSAW). However, ERW pipes do not have visible welding marks.

Most manufacturers have updated their manufacturing techniques over the years. For example, many have installed high-frequency electric currents to ensure they get improved welded pipes. As a result, ERW pipes have become improved. Nowadays, welded pipes crack less often than before.

Seamless pipes:

Unlike welded pipes, pipe suppliers do not produce seamless or SMLS pipes from sheet metal. Instead, steel pipe manufacturers use solid steel billets to produce seamless pipes and tubes. They heat the steel billets to the extent that they can use a mandrel to create a hollow inside the billets.

Then they stretch and pull the billets in a controlled environment to give them the desired length. During this process, pipe providers determine the thickness of the walls of seamless pipes. Also, they pass the billets through a straightener while these are hot to make sure that the inner and outer walls are adequately straight.

Depending on the client’s requirements, pipe fabricators can either continue heating the billets while treating them or stop heating them and let them harden themselves.

Pipe manufacturers recommend clients discuss the specifications of the projects in which they intend to use the SMLS pipes. Based on their requirements, the line pipe suppliers can suggest which method to use for the best results.

Also Read: Seamless pipe production Practices

Historical Perspectives of Seamless Pipes Vs. Welded Pipes:

Even though seamless pipe fabricators are relatively new in the market, they have been producing seamless pipes and tubes for many years as well. Hence, there is a historical significance in using seamless pipes or welded pipes.

Throughout centuries of usage, users have noticed that welded pipes are weaker than seamless pipes. Even though welded pipes have been in use in many industries, they cannot withstand as much pressure as seamless pipes. The reason behind the pipes being weak is that these have welded edges. No matter whether the edges are visible (for DSAW pipes) or invisible (for ERW pipes), there is a merging point that makes the pipes weak.

On the contrary, seamless steel pipe manufacturers produce these pipes from solid steel. There are no seams or welded parts that can make the pipes weak. Hence, the seamless pipes can endure more pressure.

Welded pipes work fine if the pressure tolerance of the pipes is nominal. However, it can withstand extreme pressures without being damaged or causing any harm.

One of the most common problems that seamless pipe users have complained about in the past is that these pipes have inconsistent wall thickness. The same problem is visible in welded pipes as well.

However, pipe producers now use advanced technology and upgraded machinery to ensure that the wall thickness is the same throughout the length of the pipes.

In some industries, it is mandatory to use seamless pipes that A-grade manufacturers produce. These industries do not prefer welded pipes because the pipes do not work under high-stress conditions. Some of these industries are oil & gas, petrochemical, pharmaceutical, power plants, automotive industries, etc.

Users can use the two pipes interchangeably. However, pipe producers do not recommend replacing seamless pipes with welded ones. Instead, users can use seamless pipes to replace the welded ones. Users can use welded pipes if they do not expose the pipes to extreme conditions. Welded pipes are also helpful in many industries that do not pressurize the pipes.

Purchasing practices:

Before purchasing welded or seamless pipes from steel pipes manufacturers, they suggest users check the grades that the engineers specify. It will allow them to understand the types of pipes they require for a specific need. The grades may include ASME, API, ASTM, and ANSI. Pipe suppliers cannot produce these grades using one method.

However, when it comes to seamless pipes, they can use two different methods to produce these pipes. These two methods are hot rolling and cold rolling. While manufacturers cannot obtain some grades from hot-rolling, they achieve these grades by cold-rolling.
Most established seamless pipes and tube manufacturers will discuss the requirements based on the specifications. Thus, they ensure that everything is correct in positioning the pipes.



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