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ASME B31.3 Sample Wall Thickness Calculations

ASME B31.3 is a set of design and construction standards for process piping systems used in the chemical, petrochemical, and natural gas industries. One of the requirements of ASME B31.3 is that the wall thickness of piping must be sufficient to withstand the expected loads and stresses that the piping will be subjected to during operation. There are several methods that can be used to calculate the required wall thickness of a piping system as per ASME B31.3. One common method is the Barlow's formula, which is used to calculate the minimum required wall thickness for a pipe based on its internal pressure, diameter, and material properties. The formula is as follows: t = PD / (2SE + PY) where: t = required wall thickness (in inches)

P = internal pressure (in psig)

D = pipe diameter (in inches)

S = material stress value (in psig)

E = quality factor (a value determined based on the type of piping and the conditions it will be subjected to)

Y = a factor that accounts for the strength of the material at elevated temperatures (for materials that will be subjected to high temperatures)

There are also other methods that can be used to calculate wall thickness, such as the maximum allowable stress method and the minimum required thickness method. It is important to use the appropriate method and to consider all relevant factors when calculating the wall thickness of a piping system to ensure that it is safe and reliable.

What is the required thickness of NPS 2 threaded A53 Grade B seamless pipe for the following conditions?:

  • Design pressure = 150 psi

  • Design temperature = 500°F

  • Corrosion allowance (CA) = 1/16 in.

  • SE = 18,900 psi

  • W = 1.0

  • D = 2.375 in.

  • f = 150(2.375)/[2( 18,900 + 0.4 x 150)) = 0.0094 in.

  • c = CA + thread depth = 0.0625 + 0.07 in.

  • tm = 0.0094 + 0.0625 + 0.07 = 0.14 in.

The minimum nominal pipe thickness, considering mill tolerance, is

minimum nominal pipe thickness

Schedule 80, XS pipe, with a nominal wall thickness of 0.218 in. is acceptable. #Little_PEng


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