SEAMLESS PIPE Vs Welded Steel Pipe

January 12, 2021

SEAMLESS PIPE And Its Advantages Over The Welded Pipe

Welded and Seamless  pipes find extensive use in industrial applications. Its vast applications include boiler, thermal heating systems, and gas and liquid transportation from one point to another. The manufacturing of seamless and welded pipes employ unique technologies to fabricate durable and flexible pipes.

The manufacturing of seamless pipe employs billets to manufacture hollow spherical pipes while welding techniques fabricate welded pipes. The seamless pipes don't require post-testing methods to prove their strength. However, welded pipes employ ultrasonic and radiological methods to inspect the power of the pipes and joints.

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There are several pipes employed in industries like Furnace Weld or the Continuous Weld, Electric Resistance Weld (ERW), Submerged Arc Weld (SAW), also DSAW, and Seamless (SMLS) method. This article discusses the difference between the two most common types, i.e. Seamless and the welded pipes.


Seamless Pipe

The seamless pipes as the name indicates is the pipe without seams that mean they have no welded joints have a smooth hollow cylindrical structure. The pipe has a unique manufacturing process. First, the process warms and heats a round steel rod or a 'billet'.

This hot billet then moves to another zone where it passes over a strong rod and hence acquires a shape of a tube and forms a hollow pipe. Then, several processes shape the pipe's output diameter, and thus the manufacturer achieves the desired smooth pipe.

Seamless pipe finds great application in industries. It has a better weight limit, or we can say pressure capacity. It means it can withstand the flow of pressurized flows. Seamless pipe mostly finds its use in petroleum drilling, petrochemical industries, and boiler applications.

Welded Pipe

The manufacturing process of welded pipes is simple. It is highly efficient, has various specifications, and requires less equipment. However, the general strength is lower than the seamless pipe. The steel first acquires the required curves and thickness, and then the process well the steel joints together. The industries can easily manufacture a large number of various sized welded pipes without any restriction.

Welded pipes find extensive use in the transportation of water, gases, and oil in large quantities. It has lesser strength than a seamless pipe as it has welded joints. Thus it is hard for welded pipes to bear a flow of high-pressure fluids, and it is susceptible to corrosion and erosion. The welded joints might leak in the long run, and therefore, they are less trustworthy than the seamless pipe.

Difference Between Seamless And The Welded Pipe

The seamless pipe and welded pipes differ in their manufacturing processes, but they also have different characteristics, strength, and applications.


The appearance of both the pipes is almost similar as both the pipes have hollow cylindrical shapes. But seamless pipes have no seams while welded joints, fabricated using joints, have seams on their surface.

In seamless pipe manufacturing, the hot molten steel rod passes over the billet and attains its shape. Once it acquires the billet's shape and forms a hollow cylinder, some rollers finish its outer surface. So the manufacturer has no direct control over the surface quality of the seamless pipe.

On the other hand, welded pipes first form into bends of desired thickness and then into the desired outer surface. So appearance-wise manufacturer has reasonable control over the welded pipe and hence welded pipes take the lead.

Moulding And Manufacturing Difference

The seamless pipe is easy to manufacture as there are few steps to fabricate a finished right strength pipe. On the other hand, welded pipe manufacturing requires several steps; steel strips, the pipe's thickness, and the welding strips. So the fabrication process of the seamless pipe is convenient and easy.

Performance Quality

Although welded pipes have a robust appearance, quality surpasses the appearance when it comes to use in industrial applications. The manufacturer fabricates the seamless pipe on the go. Hence the whole pipe has the same tensile strength and pressure capacity.

When transferring fluid from one point to another, high pressurized pumps impart high energy to the fluid to pass through the underground piping systems. One cannot afford to bear any loss in the gas flow or the liquid from the pipes; hence, seamless pipes are preferable.

The welded joints have lesser tensile strength, although it has a robust appearance. The joints might leak out if the temperature or the pressure of the flowing fluid rises. Therefore welded pipes find more extensive use in aerospace, electronics, and automobile industries. However, the manufacture molds the characteristics according to the application, yet seamless pipes strength is more incredible.


Before discussing the size difference, let's look at the standard size terminologies. The outer diameter is the distance from the center of the hollow pipe to the outer surface.

In contrast, the inside diameter is the distance from the center to the inside surface. The thickness is the distance from the inside to the outside diameter. Welded pipes offer a great range of sizes as the final fabrication requires welding of the joints. While to achieve customized od in seamless pipes, the manufacturer employs a hot expanding machine.

Corrosion And Erosion Resistance

Corrosion is a chemical attack that degrades the pipe material over time, and erosion removes the material from the surface. The degree to which the pipe is susceptible to corrosion depends on the employment of alloys.

However welded surfaces are more prone to chemical attack. Seamless pipes are smooth and hence have no seams and equal grain size throughout the pipe's length. Welded joints are therefore more susceptible to corrosive attacks and consequently degrade over a long period.


The manufacturing costs of both the seamless and welded pipes are the same. However, seamless pipes don't require any testing before installation. On the other hand, it is essential to perform testing of the welded joints, as there might be any leakage or irregular surface. Seamless pipes have no seams or joints; therefore, they are always ready to use.

Inter Surface Check

The pipe might look finished apparently, but it may have an irregular inside surface. In welded pipes, the first step is to manufacture the bends and then comes joining.

So the manufacturer can have an in-depth analysis of the inside surfaces before joining the pipe strips. However, it is not possible to check the inside surface of the seamless pipe.


The welded pipe provides a wide variety of length specifications while seamless pipe requires special billets to achieve longer length. The seamless pipe's shape is more round and oval than the welded pipes as the joints might make surfaces uneven.

Seamless pipes are suitable for high pressure and corrosion susceptible environments, while welded joints are suitable for the domains that are less corrosion resistant.  The seamless is not readily available as their manufacturing process is unique while the welded pipe is readily available as the manufacturing process is conventional.

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Regarding the differences mentioned earlier, we can conclude that the seamless pipes are more reliable and durable than the welded pipes. Seamless pipes are more flexible and are ideal for high-pressure applications and environments that are prone to corrosion.

On the other hand, welded joints are more readily available and are more economical than seamless pipes, but they are easily prone to corrosive actions. Also, welded pipes cannot bear high-pressure flows.

The differences mentioned above also concludes that the welded pipes provide various size ranges and lengths. But as far as durability and flexibility are concerned, seamless pipes take the lead as they can bear the harsh environment and high pressures.

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