Steel Pipes: Choosing Between Seamless and Welded

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.

Electric Resistance Welded (ERW), Spiral Submerged Arc-Welding Pipe (SSAW), and Longitudinal Submerged Arc-Welding Pipe (LSAW) represent distinct forms of welded steel pipes. Each of these types undergoes manufacturing processes that differ significantly from one another.

The majority of the world's steel production is utilized in constructing buildings, bridges, and various infrastructure elements, taking the form of beams, pipes, and foundation pilings. Steel's strength enables the construction of tall structures, capable of withstanding the pressures exerted by their own weight.

In addition to the quality of the steel itself, architects and contractors must carefully consider the type of steel pipes best suited for their projects. For instance, bridge foundations must withstand diverse environmental challenges such as earthquakes, ship collisions, and strong currents.

In such scenarios, does the choice between seamless or welded pipes matter? Let's delve into the differences to find out.

About Seamless Steel Pipes

Seamless pipes are crafted through either cold rolling or hot rolling methods, which result in the hardening of carbon or alloy steel during production, producing a durable and lightweight product. However, their manufacturing process is more time-consuming, and achieving precise dimensions can be challenging.

Seamless steel pipes offer several advantages, primarily their ability to withstand higher pressure, making them well-suited for applications in the oil and gas industry. Additionally, since there are no seams, they are not susceptible to corrosion and maintain a more aesthetically pleasing appearance, especially in visible areas. However, their production process imposes limitations, making them less suitable for applications requiring very large pipes.

About Welded Steel Pipes

Welded pipes begin as flat metal plates or strips, which are then shaped and the edges welded together. This process allows for the creation of finished products with high precision in terms of diameter and wall thickness.

Welded steel pipes are commonly employed in construction projects where precise dimensions are crucial, offering a cost-effective solution for general applications. Due to their ability to have multiple seams, welded pipes can be manufactured in various shapes and sizes, including very large ones for construction purposes.

The drawbacks include the thinner walls of these pipes, which, combined with the presence of seams, render them more susceptible to pressure. Additionally, slight impurities around the seams expose them to potential corrosion.

Seamless Steel Pipe Vs Welded Steel Pipe

Pipes are essential components within systems tasked with transporting various substances across refineries or industrial facilities. The effectiveness of these pipes and the substances they convey rely heavily on the materials they're composed of. Manufacturers commonly utilize materials such as PVC, stainless steel, alloy steel, carbon steel, nickel alloys, titanium alloys, copper nickel, monel, Inconel, Hastelloy, among others. The selection of these materials is strategic, considering factors like cost during production.

Essentially, there are two primary methods of pipe construction. The first is seamless, characterized by a lack of seams along the circumference, resulting in a smoother and more uniform surface. Conversely, the second method involves welded construction. Unlike the seamless kind, the welded type will have a seam that joins the pipe, which results in the formation of a seamline on its surface.

In short, the main difference between the construction of these two pipes is the inclusion of a seamline in a welded construction.

However, there are other factors that differentiate between these two constructions, including pressure capacity and pricing. Seamless pipes exhibit higher pressure-bearing capabilities compared to welded pipes. On average, the pressure tolerance of seamless pipes is nearly 20% higher than that of conventionally welded ones. This property makes seamless pipes particularly suitable for high-pressure applications.

While welded pipes are also suitable for high-stress environments, their weld seam renders them vulnerable to failure, especially if the heat-affected weld zone is prone to intergranular corrosion. If the pipe is corroded along the sensitized grain boundary, the likelihood of bursting at the seamline increases significantly. This is a critical concern, particularly in industries involved in transporting toxic materials, bio-hazardous substances, or flammable compounds. In such scenarios, vendors often opt for seamless pipes as they are not predisposed to intergranular corrosion, thus drastically reducing the risk of pipe bursts.

Price Difference Between Seamless and Welded Pipes

Another distinguishing factor between these pipe constructions is their price difference, which stems from their respective manufacturing processes. Welded pipes, utilizing metal plates, are relatively economical to produce. Additionally, their production rate is faster, contributing to their lower price point. Conversely, seamless pipes are drawn from billets, requiring a laborious and time-consuming manufacturing process. These factors drive up the cost of seamless pipes. Furthermore, seamless pipes boast higher pressure capacity and smoother surfaces, reducing the likelihood of corrosion. The combination of these factors renders seamless pipes an effective but costlier option compared to welded pipes.

Applications of Seamless and Welded Pipes

The primary purpose of pipes is to transport materials, and their application or end-use depends on various factors such as cost, strength, type of media being transported, alloy resistance to corrosion, as well as temperature and pressure requirements. Industries including pharmaceuticals, building & construction, food processing, beverage production, nuclear & power generation, among others, utilize pipes for material transportation. However, the sector that extensively utilizes these components is the petrochemical and natural gas industry.

Do You Have a Project Requiring Steel Pipes?

Whether you're erecting a towering skyscraper or spanning a wide bridge, steel pipe piles provide the robust and expansive foundation necessary to support heavy loads. While seamless variants excel in handling greater pressure, they come with a higher cost and reduced flexibility. Welded pipes, on the other hand, are typically more suitable for large-scale construction projects, offering precise dimensions at a lower cost.