Why Is Pipe Wall Thickness So Important?
Pipe Wall Thickness is a very important parameter of the pipeline. When using the pipeline, if the appropriate pipe wall thickness is not selected, it will directly affect the safety, efficiency and cost of the entire system. It is mainly reflected in the following aspects:
- Pressure bearing capacity
The thicker the wall thickness, the more internal and external pressure it can withstand, and the less likely the pipeline will deform, rupture or leak. If a pipeline with insufficient wall thickness is selected during use, stress concentration will occur, increasing the risk of damage. - Corrosion and wear resistance
If corrosive media or granular abrasive media are transported, these media will gradually thin the wall thickness until it breaks. Corrosion allowance is also a key parameter in wall thickness design, which is usually determined based on the corrosion rate of the medium (such as 0.1 mm/year) and the design life (such as 15 years) (corrosion allowance = corrosion rate × design life). - Medium transportation efficiency
If the pipeline wall thickness is too thick, it will cause flow resistance due to excessive friction. Thin wall thickness will reduce friction and energy loss. Therefore, choosing a suitable pipeline requires accurately balancing the most suitable wall thickness based on pressure, flow rate, and corrosion rate. - Economy and adaptability
The thicker the wall thickness, the more corresponding materials will be used, the weight and difficulty of transportation and installation will also increase greatly, and the price will be more expensive. Therefore, it is not the case that the thicker the pipeline, the better. It should be selected based on specific scenarios and budgets.
Calculation Of Pipe Wall Thickness
Calculation of pipe wall thickness
T = (P×D)/(2(SEW + PY)) + C
Note: Please make sure that you include the corrosion allowance in your calculations and verify the values after calculation (e.g. whether the material warranty meets the s value, hydrostatic test pressure = 1.5 times the design pressure, etc.)
-
- t: minimum wall thickness (mm or inches)
- P: design pressure (MPa or psi)
- D: pipe outer diameter (OD, mm or inches)
- S: material allowable stress (MPa or psi), see table below.
- E: weld factor (seamless pipe: E=1.0; welded pipe: E=0.6-0.85)
- W: temperature derating factor (usually W=1.0)
- Y: material factor (steel: Y≈0.4)
- C: corrosion allowance (added according to the nature of the medium, usually 1-3 mm)
Minimum required thickness calculation
The pressure design thickness needs to be added with allowance (mechanical, corrosion, erosion) to obtain the minimum required thickness:
tmin=t+c1+c2+c3
Allowance description:
-
- c1: mechanical allowance (such as thread depth, usually 1.0 mm);
- c2: corrosion allowance (determined according to the corrosiveness of the medium, such as 2.0-3.0 mm for acidic medium);
- c3: erosion allowance (such as 0.5-1.0 mm for medium containing particles).
How To Measure Pipe Wall Thickness
- 1. Traditional measurement
Use calipers and micrometers to measure pipe wall thickness (suitable for thin-walled pipes, such as polyethylene pipes and PVC pipes)
Advantages: simple, no need for operation, low cost
Disadvantages: can only measure the surface, cannot detect internal defects - 2. Ultrasonic non-destructive thickness measurement
The ultrasonic wave is transmitted to penetrate the pipe wall thickness, receive the reflected wave, and calculate the thickness through “wall thickness = sound speed × propagation time/2”.
Advantages: non-destructive, fast, accurate (error within ±0.1 mm)
Application: widely used in corrosion detection of metal pipelines (such as gas pipelines, oil pipelines).
