The two most popular varieties of steel pipes on the market are welded and seamless steel pipes. As the name implies, a seamless steel pipe has no seams and is made via hot rolling and cold rolling. In contrast, a welded pipe is created by rolling a steel coil to the necessary gauge thickness; this manufacturing process results in a seam on the pipe’s body. The next step is to cut the seams to the width that matches the size of the pipe that will be built. Welded steel pipe (LSAW) comes in three main varieties: longitudinal submerged arc welding (LSAW), spiral submerged arc welding (SSAW), and electric resistance welding (ERW). These three different types of welded steel pipe are made in quite different ways. In the form of beams, pipes, and foundation pilings, the majority of the world’s steel production is used in the construction of buildings, bridges, and other infrastructure. Steel can withstand the pressures caused by the weight of the structure, making it possible to construct tall buildings.
Architects and builders must decide which kind of steel pipes will best serve their project in addition to the steel’s quality. For instance, the foundations of bridges need to be resilient enough to withstand environmental hazards like earthquakes, shipwrecks, and strong currents.
Does it matter if they utilize welded or seamless pipes in certain circumstances? Let’s examine the differences to find out.
What is Seamless Steel Pipes?
The engineering of seamless pipes involves either cold rolling or hot rolling extraction. In order to produce a robust and lightweight product, the procedure hardens the carbon or alloy steel as it is manufactured. They are more difficult to create and require longer to get the appropriate dimensions.
Seamless steel pipes have the advantage of often being able to withstand more pressure, which makes them perfect for applications in the oil and gas industry. No seam is exposed to corrosion, and if the pipe is in a visible position, there is no seam that might be ugly. When you require particularly large pipes, it is not a fantastic alternative due to the limitations of the production process.
What is Welded Steel Pipes?
Flat metal plate or strips are the precursor to welded pipes. These are welded together at their edges after being bent into shape. This implies that the completed product’s diameter and wall thickness can be very precisely controlled.
They are ideal for general use because they are frequently a more economical option and are frequently utilized in construction when precise dimensions are crucial. Welded pipes can be created in a wide variety of forms and sizes, including very large ones for use in construction, because they can have several seams.
These pipes often have thinner walls, which along with their seams make them more pressure-sensitive. Additionally, they are susceptible to possible corrosion because of minor contaminants along the seam.
Seamless Pipe vs Welded pipe
The titles make it clear that the fundamental production process is different. While welded tube is created from a strip that is roll shaped into a tube and then welded, seamless tube is extruded and drawn from a billet. Welded tube is readily available in lengthy continuous lengths and is significantly less expensive than seamless tube.
Even if a welded tube’s working pressure is 20% lower than that of a comparable seamless tube, working pressure is not the deciding criterion when choosing between welded and seamless tubes for analyzer sample lines. The specification of seamless tube is due to the variation in possible contaminants, which lower the completed tube’s corrosion resistance.
Because of the weld area’s perceived inhomogeneity, it exhibits different malleability, weaker corrosion resistance, and more dimensional variation. These abnormalities are lessened when welding tube. The majority of tubing, both welded and seamless, is drawn to create final dimensional tolerances. Drawing is a process that “pulls” a tube through a die. Although there are several ways to draw a tube, the two most common ones are sunk drawing and plug drawing. The ID surface roughness demonstrates the difference. Without internal support, a sinking drawn tube is constructed. The diameter of a sink drawn tube is reduced without affecting the wall thickness. There is some “crunching” of the ID, and the tube takes on a “sun burst” cross section as well as wrinkles all the way around the inside surface.
On welded tube, this may be especially obvious around the weld. A significantly smoother inner surface is produced when a plug or rod drawn tube is dragged through a die with internal support. The weld bead on welded tubing is broken apart, and any dimensional markings are removed, by rod or plug drawing. A homogenous tube is further promoted by final annealing. The phrase “full finished” describes welded tubes that have undergone sufficient rod or plug drawing and annealing to break up the dendritic structure of the weld bead and speed up homogeneity, as well as to remove any dimensional evidence of the weld area. Often, it is exceedingly challenging to tell welded tube apart from seamless tubing.
It is clear from the aforementioned paragraphs that the production processes for seamless and welded pipes are different. The following are the other differences:
Strength
Seamless pipes can sustain more pressure and load since there are no weak seams. Welded pipes are thought to bear 20% less pressure and load than seamless pipes due to welding.
Length
Due to production difficulties, seamless pipes are significantly shorter in length. Welded pipes are available in long continuous lengths.
Size
Seamless pipes are often made in nominal sizes of 24 inches or less.Welded pipe manufacture has no such size restrictions.
Corrosion Protection
Sealless pipes are less prone to corrosion, implying that they are more corrosion-resistant. Welded pipe weld regions are more prone to corrosion assaults, resulting in lower corrosion resistance.
Surface Excellence
Because of the extrusion process, the surface quality of seamless pipes is rough. When compared to seamless pipes, welded pipes have a smooth, high-quality surface.
Cost
Seamless pipe is more expensive than welded pipe.
Production Methodology
The seamless pipe manufacturing process is highly complex, with a lengthy procurement lead time. Welded pipe production is a relatively straightforward operation with a short procurement lead time.
Tests
Seamless pipes do not require weld integrity testing. Before using welded pipes, they must be tested.
Application
Seamless pipes are commonly used in high-pressure, high-temperature, and corrosive environments. Welded pipes are typically utilized in non-corrosive, low-pressure situations.
Availability
Seamless pipes have a lower availability, fewer material options, and a longer delivery time. Welded pipes are easily available in a variety of materials and have a quicker delivery time.
Thickness of the Wall
Seamless pipes have varying wall thicknesses over their length, with thicker walls being heavier.Welded pipes have more constant wall thickness than seamless pipes, and they are thinner.
Ovality
Seamless pipes have greater ovality and roundness. Welded pipes have low ovality and roundness as compared to seamless pipes.
How to choose Steel Pipes?
Despite many advantages of welded tubes, seamless tubes are still preferred over welded tubes, particularly in harsh environments, due to stronger strength, higher pressure, and better corrosion resistance.Determine which type is the best to utilize based on the individual application and cost considerations.Depending on the application, tubes and pipes can be made in both seamless and welded forms.
Reference:
