As industrial applications have evolved and grown more complex, the piping products and systems that serve them have had to keep pace.
Although many pipeline manufacturing methods exist, the most prominent discussion in the industry is the comparison of resistance welded (ERW) and seamless (SMLS) steel pipes. So which one is better?
The difference between seamless stainless steel pipe and welded pipe in the most popular terms is the difference without the weld, however, this is essentially the difference in the production process. It is this difference in the production process that gives them both performance and purpose.
Manufacturing Seamless Pipe
Seamless steel pipe is made of single sheet metal, the surface of the steel pipe without the trace of connection, called seamless steel pipe. According to the production method, the hot rolled pipe, cold rolled pipe, cold pull pipe, extrusion pipe and pipe pipe pipe are seamlessly divided.
Seamless piping begins as a solid cylindrical hunk of steel called a billet. While still hot, the billet uses a mandrel pierced through the center. The next step is to roll and stretch the hollow billet. The billets are accurately rolled and stretched until the length, diameter and wall thickness specified in the customer order.
Manufacturing Welded Pipe
The original state of the welded pipe is a long, coiled steel strip. Cut to the desired length and width to form a flat rectangular steel sheet. The width of the sheet will become the outer circumference of the pipe, and this value can be used to calculate its final outer diameter. The rectangular sheet passes through a rolling unit so that the longer sides bend to each other to form a cylinder. During ERW, high-frequency currents are transmitted between the edges, causing them to melt and fuse together.
The General Difference is that：
The welded pipe is considered to be inherently weak because it includes one weld. Seamless tubes lack this apparent structural defect and are therefore considered safer. Although the welded pipe does include a joint, this production method makes the welded pipe's tolerance not exceed the customer's requirements and the thickness is uniform. Although the seamless pipe has obvious advantages, the criticism of the seamless pipe is that the rolling and stretching processes produce an inconsistent thickness.
In the oil, gas, power generation and pharmaceutical industries, many high pressure and high temperature applications require seamless piping. Welding pipes are generally cheaper to produce and widely used as long as temperature, pressure and other service variables do not exceed the parameters specified in the applicable standards.
Similarly, there is no difference in performance between ERW and seamless steel pipes in structural applications. While the two are interchangeable, it makes no sense to specify a seamless pipe when the cheaper welded pipe is equally effective.
