For ordering steel pipes, the necessary pipe dimensions is diameter, wall thickness and length. There are various methods to describe the diameter and wall thickness, here I will introduce you some commonly used type.

Steel Pipe Diameters

For the pipe diameter, there are mainly three ways to describe it.

NPS. NPS means Nominal Pipe Size, a North American standard set of pipe sizes for high or low pressure and temperatures application. The diameter is specified with inches such as NPS 8 pipe means the diameter of pipe is 8 inches. It is used more than the actual size of the pipe as a way to distinguish pipes from each other and name them. NPS is often incorrectly called national pipe size, due to confusion with national pipe thread NPT.

DN: DN is METRIC equivalent to NPS, it is popular in European and international. Its designations conform to International Standard Organization (ISO) usage. DN and NPS can be converted to each other. For example, DN40 = NPS 1 1/2, DN 100 = NPS 4.

OD: That means Outside Diameter of the pipe and is fixed for a given size. Pipes in OD is often described in mm, such as OD108mm. The NPS is very loosely related to the OD in inches, only for NPS 1/8 to NPS 12. For NPS 14 and larger, it is equal to OD in inches.

Steel pipe diameter

Wall Thickness of Pipes

For the wall thickness, schedule and mm （millimeter） are very popular unit.

Pipe schedule is the term used to describe the thickness of a pipe. The outside diameter of a pipe is the same for all schedules in a particular nominal pipe diameter. There are 14 schedule numbers commonly used: Sch5, Sch10, Sch20, Sch30, Sch STD, Sch40, Sch60, Sch XS, Sch80, Sch100, Sch120, Sch140, Sch160 and Sch XXS. The most popular schedule is Sch40.

The schedule number is defined as the approximate value of the expression:

Schedule Number= 1000 P/S

• P = the internal working pressure, psig
• S = the allowable stress (psi) for the material of construction at the conditions of use.

Millimeter is intuitively reflect the thickness of pipe wall. It Can be used with NPS, DN or OD.

Wall thickness range for steel pipe is Sch 5 to Sch XXS.

Steel pipe drawing

Pipe Length

The pipe length is usually expressed in inches, meter or millimeter. Such as L=6m. Pipe length is available in Single Random, Double Random or Cut Length.

Therefore, the description of pipe dimensions can be DN40 Sch 40 x 6m Pipe.

Steel Pipe Manufacturer

What’s more, materials are also important for ordering pipes. The common grades for stainless steel pipes are SS 304, SS316, for carbon steel pipes are API 5LB, A106, A105, A234 WPB.

Hebei Haihao Group is China leading manufacturer for steel pipes, we supply stainless steel pipe, carbon steel pipe, duplex steel pipe, alloy steel pipe in customized dimensions.Email:sales@haihaogroup.com