“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 Wall Thickness in mm
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.
| Nominal Pipe Size Inches | Wall thickness: mm | Outside Diameter | |||||||
| SCH 10 | SCH 20 | SCH 30 | SCH STD | SCH 40 | SCH 60 | SCH XS | mm | in | |
| 1/2 | 2.11 | 2.41 | 2.77 | 2.77 | 3.73 | 21.34 | 0.84 | ||
| 1/8 | 1.24 | 1.73 | 1.73 | 2.41 | 10.29 | 0.405 | |||
| 1/4 | 1.65 | 1.85 | 2.24 | 2.24 | 3.02 | 13.72 | 0.54 | ||
| 3/8 | 1.65 | 1.85 | 2.31 | 2.31 | 3.2 | 17.15 | 0.675 | ||
Pipe Thickness Calculation Formula
ASME B31.3
According to the American Society of Mechanical Engineers (ASME) B31.3 process piping code ASME B31.3 basic formula.
In practical applications, additional thickness is usually added (such as corrosion allowance “C” or mechanical strength allowance).
In potentially corrosive environments, the calculated pipe wall thickness should include the corrosion allowance: treal=t+Ctreal=t+C
Pipe Wall 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.
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.
Schedule Number of Pipe Thickness
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.
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.
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.
Factors Affecting the Wall Thickness
Mechanical Properties of Materials
If you want to use steel pipes with thinner walls in the same scenario, we can make a choice of materials and use some different materials with higher strength and better performance to reduce some wall thickness.
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.
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