Pipe Thickness Calculator As Per ASME B31.3


Dear friends, I have created this pipe thickness calculator to calculate required pipe thickness for a process pipe based on ASME B31.3 Code. I have provided detail information about behind the back calculations at the end of this calculator.

Pipe Material of Construction
Design Pressure
Design Temperature
Nominal Pipe Diameter
Corrosion Allowance
Depth of Threading, Grooving or Machining
Mill Tolerence Percentage
Pipe Construction Type

Explanation of the Pipe Thickness Calculator

As we know, ASME B31.3 Provides formula and guidelines for calculation of pipe under pressure. Though the formula is quite simple, finding correct values of individual factors can be tricky sometimes. This process pipe thickness calculator uses following formula for calculation of wall thickness.

304.1.2 (a) equation 3a :

  1. Seamless Pipes : Design Thickness t = (PD)/2(SE+PY)
  2. Welded Pipes : Design Thickness t = (PD)/2(SEW+PY)

Where :

P : Internal Design Guage Pressure

D : Outside diameter of pipe

In this calculator, outside diameter is taken from American Pipe Standards for the selected nominal pipe diameter :

  1. ASME B36.10 : Welded and Seamless Wrought Steel Pipe.
  2. ASME B36.19 : Stainless Steel Pipes.

S : Allowable Stress value for material from Table A-1

These are allowable stress values for different materials at different temperatures. Provided in Table A-1 of ASME B31.3. I have included commonly used pipe materials in this calculator. If you want more ASTM materials to be included, please mention in comments section below.


E : Longitudinal Weld Joint Quality factor

  1. Applicable as per ASME B31.3  Table A-1A or A-1B .
  2. 1 For Seamless Pipes.
  3. 0.60 for Furnace Butt Welded Pipes.
  4. 0.85 for Electric Resistance Welded Pipes.

W : Weld Joint Strength Reduction Factor

  1. Applicable as per Para 302.3.5(e) of ASME B31.3
  2. It is applicable only for Welded pipes.
  3. W is Take as 1 for Seamless Pipes.
  4. Value of W is taken as 1.0 at temperatures of 510°C (950°F) and below, and 0.5 at 815°C (1500°F) for all  materials.
  5. Value is linearly interpolated for intermediate temperatures.

Y : Coefficient from Table 304.1.1,

Valid for t < D/6 and for materials shown. The value of Y may be interpolated for intermediate temperatures.

Addition of Allowances

Calculated Design Wall Thickness should be added with Corrosion Allowance, Mechanical Allowance for Grooving, Threading etc and Manufacturing Tolerance to arrive at final value. Next higher standard thickness value from Pipe Standards such as ASME B36.10 and ASME B36.19  is used.

Required Thickness = Design Thickness + Allowances.


Wall Thickness Selection

Designer should select a thickness from schedules of nominal thickness contained in Table 1 specified in ASME B36.10 and B36.19, to suit the value computed to fulfill the conditions for which the pipe is desired.

Please provide your comments / suggestions in comments box below.

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