Pipe Thickness- Expression Of Wall Thickness/ Size Chart

“Pipe thickness” usually refers to the thickness of the pipe wall, referred to as W.T. The wall thickness of steel pipes is extremely important in the design, construction, safety and maintenance of pipelines. The wall thickness used in different usage scenarios is also different. The factors affecting the wall thickness include the type of material transported (gas, liquid gasoline or water, etc.), variables during operation (temperature during operation and external pressure on the pipeline, etc.), the impact of the external environment on the steel pipe (such as corrosive external environment) and the expected service life of the steel pipe. Under the influence of these various factors (including but not limited to the above factors), the required wall thickness is also different.

Pipe Thickness in mm Size Chart

Wall thickness is one of the three elements of steel pipes

The three elements of steel pipes include the following aspects

Outer diameter (OD), wall thickness (WT), and pipe length.

Expression of pipe thickness

In the use of steel pipes, different wall thicknesses should be used in different scenarios. Using the correct wall thickness is very critical. If the incorrect wall thickness is used, it will directly affect the applicability and performance of the pipeline. The following four points are several common wall thickness expressions, as well as the scenarios used for each expression and their respective advantages.

Pipe Thickness Nominal Wall Thickness

Refers to the wall thickness formulated according to international or regional standards (ASTM, ISO, etc.). This method ensures global consistency and interchangeability. It may not be the actual thickness of the steel pipe, but it provides a reference range for industrial standards.

Pipe Thickness-Schedule Number

In some specific countries (such as the United States and other countries), they use the schedule number to indicate the thickness of the steel pipe. Different schedule numbers indicate the wall thickness of pipes with different pressure levels. The schedule number is formulated by the American Standards Association, for example, SCH 40, SCH 80, etc. The thickness of the steel pipe is positively correlated with the schedule number. The thicker it is, the stronger the pressure it can withstand, and the larger the schedule number.

Pipe Thickness-Direct Designation (Wall Thickness, WT)

Direct designation is to directly specify the thickness. Compared with other methods, it will be easier to communicate and understand, and it will be more accurate. It is often used in some situations with high safety factors, extreme temperatures and high pressures, and some special material properties.

Pipe Thickness-Millimeter (mm) or Inch (in)

This simple and clear method is very intuitive and clear. Even people who don’t understand the wall thickness can know the thickness simply and clearly at the first time, so some misunderstandings are reduced. This method is the most common in international engineering implementation.

External corrosion and erosion

Internal corrosion and erosion: During transportation, some corrosive gases or liquids will be transported in the steel pipe, which will damage the wall of our steel pipe. In order to extend the service life of the steel pipe, when transporting these corrosive gases or liquids, thicker steel pipes should be used
External corrosion: In other usage scenarios such as buried or underwater, it is also necessary to consider other external corrosion of steel pipes such as soil or water.

Temperature effect

The mechanical properties of the material will be affected by temperature, so the wall thickness of the steel pipe must be required to cope with these effects. So as not to affect the service life or performance of the steel pipe.

According to the American Society of Mechanical Engineers (ASME) B31.3 process piping code ASME B31.3 basic formula.