Steel pipes can be classified according to multiple criteria, such as:

  • Manufacturing process: seamless, erw, lsaw, dsaw, hsaw pipes

  • Finishing: cold rolled, hot rolled, cold finished

  • Materials: metal, plastic, cement, glass, fiberglass, etc and material grades (carbon steel, stainless steel, nickel alloy steel pipes)

  • Manufacturing norms





Seamless pipeSeamless pipes are manufactured by drawing a solid billet through a piercing rod that creates the hollow section. These tubulars are considered superior to other types as they do not require welding activities and the final product is obtained from a monolithic block of steel (a steel billet). Seamless pipes from 1/8 to 6 inch. are manufactured with the so called "plug mill process" or the "extrusion process" (used for smaller diameters), whereas the "mandrell mill process" is used for larger diameters. Seamless pipes have an higher price when compared to erw and saw pipes, as the manufacturing process is more complex and requires higher investements (several mills have vertically integrated processes, from raw material to billets and final products). For specific sizes and specifications (diameter / thickness / materials), the number of companies is the world is limited and prices are remarkably higher (these should be accounted for properly when estimating project costs by weight). 




ERW pipeERW pipes (electric resistance welding) are manufactured by welding steel coils longitudinally. The high-frequency induction technology (HFI) is the most widespread process for this type of pipes and tubes: an induction coil is applied on the outer surface of the bar and it generates a current which joins the two sides of the coil together very tightly. They HFI welding technology is superior to the ordinary welding tecniques and is used for critical pipes applications (such as pipelines and chemical processes). ERW tubulars are a good alternative to seamless pipes for specific applications and size ranges.



SAW pipeSubmerged arc welded tubulars are manufactured by bending and welding ordinary steel plates. The SAW type is commonly used for oil and gas transmission lines (the recurring specification for this type of pipes is API 5L in various material grades). These tubulars are generally more expensive than ERW's in the size range from 16 to 24 inches (whereas they are the only choice for sizes above 28 inch., which can't be covered by seamless pipes or other type of pipes). The most common variations of submerged arc welding pipes are: LSAW (longitudinal welding), DSAW (double submerged arc welding, the weld is applied on both the inner and outer surface) and SSAW or HSAW (spiral welded pipe, generally used for water transmission and distribution but not for oil & gas applications).


In terms of construction materials, pipes can be grouped in these main types:

  • Ferrous materials (carbon steel, stainless steel, nickel alloys, galvanized steel pipes)

  • Non Ferrous materials (copper, bronze and aluminium pipes)

  • Ductile iron (potable water and sewerage systems)

  • Ceramic

  • Glass

  • Fiberglass

  • Plastic (PVC pipes are the most common, other typical materials are PE, PP, ABS, etc)

  • Cement


Considering construction norms, pipes can be divided into the following main types:

  • ASME B36.10 (carbon / alloy pipes) and ASME B36.19 (stainless and nickel alloy pipes)

  • API 5L (linepipes for midstream oil & gas)

  • API 5CT (octg tubing / casing pipes for upstream applications)

  • EN / DIN / BS (european pipe standards)

Whereas other pipes classifications exist (example by application: water, plumbing, oil & gas, linepipes, compressed air, octg, process piping, etc or by pipe end: BE, PE, T&C, THD, etc) the one outlined above are considered the most important ones.



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Useful links: ANSI | ASME | ASTM | API | MSS | BS | DIN | ISO