The welded pipe begins with a long coiled steel strip called skelp. The turf is cut to the desired length to obtain a flat rectangular sheet. The width of the shorter end of the sheet will be the outer circumference of the pipe and this value can be used to calculate its final outer diameter.welded pipe manufacturers
The rectangular sheets are fed by a rolling machine that curls the long sides toward each other to form a cylinder. In the ERW process, high frequency currents pass between the edges, causing them to melt and fuse together.
One advantage of an ERW tube is that no molten metal is used and the weld is not visible or felt. This is in contrast to double submerged arc welding (DSAW), which leaves a significant weld and must be eliminated depending on the application.
Welded pipe manufacturing technology has improved over the years. Perhaps the most important advancement is switching to high frequency currents for soldering. Before the 1970s, low frequency currents were used. Welds produced by low frequency ERW are more susceptible to corrosion and seam failure.
Historical views and use cases of welding and seamless steel tubes
ERW and seamless steel tubes now exist as substitutes, mainly due to historical cognition.
Generally, a welded pipe is considered to be inherently weak because it includes a weld. Seamless pipes lack this perceived structural flaw and are considered safer. Although the welded pipe does include seams that are theoretically weaker, the manufacturing techniques and quality assurance schemes have each been improved to the extent that the welded pipe will perform as desired without exceeding its tolerances. While the obvious advantages are obvious, the criticism of seamless piping is that the rolling and drawing processes produce inconsistent wall thicknesses compared to the more precise steel sheet thickness used for welding.Galvanized Steel Tube
The industry standards for the development and specification of ERW and seamless steel tubes still reflect these views. For example, many high pressure, high temperature applications in the oil and gas, power generation and pharmaceutical industries require seamless piping. As long as the temperature, pressure and other service variables do not exceed the parameters specified in the applicable standard, welded pipes can be specified in all industries (usually at a lower production cost and widely available).
In structural applications, there is no difference in performance between ERW and seamless steel tubes. Although the two can be specified interchangeably, it is meaningless to specify seamless when a cheaper welded pipe works equally well.