What is the Difference Between Seamless and ERW Steel Pipes?

Seamless Steel Pipe is made from a solid round steel ‘billet’ which is heated and pushed or pulled over a form until the steel is shaped into a hollow tube.

Electric Resistance Welding (ERW) pipe is manufactured by rolling metal and then welding it longitudinally across its length. Seamless pipe is manufactured by extruding the metal to the desired length; therefore ERW pipe have a welded joint in its cross-section, while seamless pipe does not have any joint in its cross-section through-out its length.

In Seamless pipe, there are no welding or joints and is manufactured from solid round billets. The seamless pipe is finished to dimensional and wall thickness specifications in sizes from 1/8 inch to 26 inch OD. Applicable in for High-pressure applications such as Hydrocarbon Industries & Refineries, Oil & Gas Exploration & Drilling, Oil & Gas Transportation and Air and Hydraulic cylinders, Bearings, Boilers, Automobiles etc.

ERW (Electric Resistance Welded) pipes are welded longitudinally, manufactured from Strip / Coil and can be manufactured upto 24” OD. ERW pipe cold formed from a ribbon of steel pulled through a series of rollers and formed into a tube which is fused through a electric charge. It is mainly used for low/ medium pressure applications such as transportation of water / oil.

Common sizes for ERW Steel Pipe range from 3/8 inch OD to 24 inch OD in a variety of lengths to over 100 feet. Surface finishes are available in bare and coated formats and processing can be handled on site to customer specifications.

How to Identify Seamless or ERW Stainless Steel pipes?
To identify that a pipe supplied is seamless or ERW, Simply read the stencil on the side of the pipe
If it is ASTM A53, Type S means seamless.
Type F is furnace but welded,
Type E is Electrical resist welded.
Thats how. It is the easiest way to identify wether pipe is seamless or ERW.

In short, Seamless is marketed on an outdated myth that it does not have flaws but that welded has an inherent flaw throughout the length of each tube, as stated above. Intuitively this concept is easily accepted by purchasers and designers with limited experience with the various products. Each product form and manufacturing method has its own inherent problems and potential defects.

Consumers must become familiar with what those problems and defects are, and how they might affect particular applications. Then they can make an informed decision based on facts, rather than myth.