Pipe wall thickness calculator

When is this calculator suitable?

The calculator is intended for calculating the thickness of the pipe wall based on the known value of the internal pressure and the permitted specified minimum yield stress in the pipe.

The calculator is applicable for carbon steel, stainless steel, copper and PVC pipes.

The pipe wall thickness calculation is based on the ASME B31.8 standard. The calculator allows three types of calculations:

• Calculation of the minimum pipe wall thickness
• Calculation of actual stress in the pipe
• Checking the thickness of the pipe wall for the known value of the permissible stress

In each of these three calculation cases, it is necessary to enter the gauge pressure of the fluid in the pipe, as well as the outer or inner diameter of the pipe

What are the calculator restrictions?

The calculator requires knowledge of the internal pressure of the fluid in the pipe, the material the pipe is made of, and the outside or inside diameter of the pipe.

How is the calculation executed?

The calculator displays the calculated value of the pipe wall thickness, which is calculated solely based on the entered or selected values of pressure, permissible stress, factors affecting the calculation and permissible allowances. In this regard, if any of the entered or selected data is not correct, the calculated value will not be correct either. Therefore, before using the calculator, the user should familiarize himself with the ASME B 31.8 standard, which defines in detail all the requirements for the correct calculation of pipe wall thickness.

Pipe pressure

The calculator for calculating the pipe wall thickness requires the input of the actual gauge pressure in the pipe in the field provided for it.

Pipe diameter

The calculator allows selection of the pipe diameter entered, so it is possible to choose whether to enter the outside or inside diameter of the pipe. In the section for input selection, it is necessary to choose the diameter of the pipe that needs to be entered from the offered outer or inner diameter. The calculator also allows the selection of a standard pipe size through the Pipe Size tab, where it is possible to choose one of the offered pipe dimensions for the selected Schedule from the list of standards. The selected pipe from the list is simultaneously entered in the fields for entering the pipe diameter in the calculator.

Also, the calculator calculates the mean air velocity at the beginning and end of the pipeline.

The calculation involves calculating the Reynolds number (Re).

Calculator presents values of Reynolds number and flow regime - laminar or turbulent, as well as calculated velocities on the pipe start and the pipe end.

Pipe wall thickness

Calculation of pipe wall thickness is carried out in accordance with the ASME B 31.8 standard. Calculating the thickness of the pipe wall requires entering three factors for the calculation, namely:

Longitudinal efficiency factor

This factor depends on the way the pipe is manufactured, and its value is 1 in the case of seamless pipes, and it has a value less than 1 in the case of other applied technologies. Its value is automatically entered when selecting the pipe manufacturing type in the Pipe Material tab.

Design and location factor

The location factor includes the reduction of the permitted voltage depending on the location of the pipeline in relation to other objects at the installation site. This factor is a maximum of 1, i.e. it is always less than 1 depending on the location class. Its value can be selected in the tab Pipe Material - Location Class.

Temperature influence factor

The temperature influence factor implies a reduction of the allowable stress in the pipe in case the pipe is exposed to elevated temperatures. The value of this factor is up to 1 when the pipe temperature does not exceed 250 F, and for higher temperature values it is less than 1. The value of this factor is available through the Pipe Material - Temperature tab.

Calculation of the minimum pipe wall thickness

For the calculation, it is necessary to enter the size of the permitted stress in the pipe in the SMYS field. If the material from which the pipe is made is known, and if the standard pipe material is known, the calculator enables the selection of SMYS based on the pipe material standard, type of pipe manufacturing technology and material class, using the Pipe Material tab. The calculator will enter the calculated pipe wall thickness in the t field.

Calculation of actual stress in the pipe

For the calculation of the actual stresses in the pipe, it is necessary to enter the actual thickness of the pipe wall in the field t. The calculator will calculate the actual stress in pipe wall and present it in the SMYS field.

Checking the thickness of the pipe wall for the known value of the permissible stress

The calculator enables the display of information whether for the entered values of the pipe wall thickness and the known maximum stress in the pipe, the thickness of the pipe wall satisfies. The calculator displays the information whether the pipe wall thickness is satisfactory or not by printing the corresponding statement.

Allowances

Corrosion allowance

The calculator allows input of an assumed CA - corrosion allowance. The value of the corrosion allowance can be entered if you select the check box in the selection section. The entered value of the corrosion allowance is included in the displayed value of the pipe wall thickness t, i.e. the calculated pipe wall thickness based on the internal pressure is increased by the entered value of the corrosion allowance. Therefore, the value of the pipe wall thickness must be greater than the entered value of the corrosion allowance.

Mill tolerance allowance

The mill tolerance allowance for wall thickness assumes that the actual pipe wall thickness may deviate from the nominal by a certain predefined percentage. In the field MT, it is necessary to enter the tolerance in % (eg: 12.5 if the mill tolerance is 12.5%).

By entering this information, the calculated pipe wall thickness due to internal pressure will be increased by the value of this addition and the presented wall thickness value t will also include this value.

Pipe wall thickness calculation formula

$p=\frac{2\cdot S\cdot t}{D}F\cdot E\cdot T$

where is: p - design pressure; S - specified minimum yield strength; t - nominal wall thickness; T - temperature derating factor; F - design factor; E - longitudinal joint factor; D - pipe external diameter.

All needed factor values are available in the calculator.

When is this calculator not relevant?

The calculator is applicable only for flat round pipes, i.e. it is not applicable for pipes with a square or rectangular cross-section. Also, the calculator is not applicable for bent pipes, pipes with openings and reinforcements.

The calculator is not applicable for wall thickness calculations due to external pressure.

What else has to be known to perform the calculation?

To calculate the actual stresses in the pipes, it is necessary to enter the thickness of the pipe wall, the internal pressure, as well as the diameter of the pipe - internal or external.

When selecting a standard pipe dimension from the pipe table, check the standard pipe wall thickness by selecting the third option of the calculation type - pipe wall thickness check for known maximum stress in the pipe.