Understanding Pipe wall thickness charts and formula for calculating pipe thickness
The determination of a pipe’s wall thickness is of fundamental importance in pipe engineering especially in the area of piping systems that are to be exposed to certain internal pressures and external loads. This guide details the methods of thickness calculation of pipes with an emphasis on the principles outlined in the ASME B31.3 code.
How to calculate thickness of pipe | How to calculate pipe wall thickness ?
The wall thickness of a pipe is of utmost importance in maintaining the stability and safety of piping systems. Since pipes carry fluids, they have internal pressure and when the wall thickness is not enough, failures such as leaks and burst may occur. The most common equation applied for determining the minimum allowable thickness is based on Barlow’s formula, which is,
Pipe thickness formula | Formula for calculating pipe thickness
t = PD / 2(S+PY)
Where:
- t = required wall thickness
- P = internal pressure (psi)
- D = outside diameter of the pipe (inches)
- S = allowable stress value for the material (psi)
- E = longitudinal weld joint quality factor
- Y = coefficient based on temperature and material properties
Key Parameters Affecting Pipe Thickness
Several factors influence the required thickness of a pipe:
- Design Pressure: Higher internal pressures necessitate thicker walls to withstand the stress.
- Design Temperature: Increased temperatures can reduce material strength, requiring greater thickness.
- Pipe Material: Different materials have varying stress values; for example, carbon steel and stainless steel will have different thickness requirements under the same conditions.
- Corrosion Allowance: Additional thickness may be required to account for potential corrosion over time.
- Manufacturing Tolerance: A percentage of tolerance is added to ensure that the final product meets safety standards.
Pipe thickness calculation | Pipe wall thickness calculation
Steps for calculating pipe thickness | Step-by-Step Calculation
To illustrate the calculation process, consider a seamless carbon steel pipe with specific parameters:
- Material: ASTM A106 Gr. B
- Nominal Pipe Size (NPS): 4 inches
- Design Pressure: 1200 psig
- Design Temperature: 500°F
- Corrosion Allowance: 3 mm
- Mill Tolerance: 12.5%
1. Calculate Pipe Thickness using Barlow’s formula:
- Convert units if necessary (1 inch = 25.4 mm).
- Substitute values into the formula. For example:
t = (1200×114.3) / 2(19000+1200×0.4) = 3.52 mm
2. Add Corrosion Allowance:
- Total thickness after adding corrosion:
tc = t+c = 3.52+3 = 6.52 mm
3. Add Manufacturing Tolerance:
- Calculate required thickness considering manufacturing tolerance:
tm = tc / 0.875 = 6.52 / 0.875 = 7.45 mm
4. Select Standard Pipe Thickness:
- From ASME B36.10M, choose the next available standard thickness that meets or exceeds this calculated value, which would be approximately 8.56 mm or Schedule 80.
Pipe thickness chart | Pipe schedule and thickness chart | Pipe wall thickness chart
Here is a comprehensive pipe thickness chart based on the ASME B36.10M and B36.19 standards, which detail the dimensions, wall thicknesses, and weights of various pipe sizes. This chart includes common schedules and their corresponding specifications.
Pipe Thickness and Schedule Chart
| NPS (inches) | Outside Diameter (OD) (inches) | Wall Thickness (inches) | Schedule 5 | Schedule 10 | Schedule 20 | Schedule 30 | Schedule 40 | Schedule 80 |
|---|---|---|---|---|---|---|---|---|
| 1/8 | 0.405 | 0.049 | 0.065 | 0.109 | 0.147 | 0.188 | 0.237 | 0.337 |
| 1/4 | 0.540 | 0.065 | 0.088 | 0.119 | 0.154 | 0.203 | 0.254 | 0.370 |
| 1/2 | 0.840 | 0.109 | 0.120 | 0.147 | 0.203 | 0.254 | 0.300 | 0.430 |
| 3/4 | 1.050 | 0.113 | 0.120 | 0.154 | 0.218 | 0.276 | 0.300 | 0.480 |
| 1 | 1.315 | 0.133 | 0.140 | 0.179 | 0.237 | 0.300 | 0.364 | 0.506 |
| 1-1/4 | 1.660 | 0.140 | – | – | – | – | – | – |
| 1-1/2 | 1.900 | 0.145 | – | – | – | – | – | – |
| 2 | 2.375 | 0.154 | – | – | – | – | – | – |
| 2-1/2 | 2.875 | 0.203 | – | – | – | – | – | |
| 3 | 3.500 | 0.216 | – | |||||
| 3-1/2 | ||||||||
| 4 |
Additional Information
- With each increasing schedule number, the wall thickness tends to increase; thus, decreasing the internal diameter due to the thicker walls.
- Wall thickness values are essential in exercises related to rating the pressure and strength of pipes in different utilizations.
- This chart is mainly concerned with the standard specifications for pipes made of carbon steel regardless of other materials having other specifications.
Reference Standards
The data provided in this chart is based on the following standards:
- ASME B36.10M: Welded and Seamless Wrought Steel Pipe
- ASME B36.19: Stainless Steel Pipe
For detailed specifications and additional sizes, it is best that official documents or engineering libraries be consulted as they provide extensive tables for the many dimensions and weights of pipes.
This chart is a simple tool for designers, constructors and maintenance engineers that assists in the piping systems layouts, installation and assuring
Pipe Thickness Chart PDF Download
(Credit: Octal Steel)
Conclusion
One of the main goals in engineering practice is determining the pipe wall thickness, which guarantees safety and reliability of the piping systems. By employing appropriate formulas, which take into account various parameters, it is possible to calculate suitable wall thicknesses for fulfilling the service requirements of the piping, and comply with the likes of ASME B31.3.
This not only alleviates and mitigates the risk of failures but also improves materials usage, thereby enhancing the economical design solutions in the diverse industrial applications.
