Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

ASME 31.3 Piping Materials - Allowable Pressure Calculator

Sponsored Links

The ASME code B31.3 recommends allowable tensile stress levels in pipe materials.

  • maximum stress to be applied on a structural material

The equations used in B31.3 are

t = P D / (2 (S E + P Y)                    (1)


t = thickness of pipe (in)

P = internal pressure in pipe (psi)

D = outside diameter of pipe (in)

S = allowable tensile stress (psi)

E = quality factor for the piping according ASME 31.3

Y = wall thickness coefficient according ASME 31.3 (y = 0.5 for thin pipes and y < 0.5 for thick pipes)


t = P (d + 2 c) / (2 (S E - P (1 - Y))                    (2)


d = inside diameter of pipe (in)

c = sum of the mechanical allowances (thread or groove depth) plus corrosion and erosion allowances (in) - typical 0.02 in where tolerances are not specified

Eq. (1) can be rearranged to express allowable internal piping pressure as

p = 2 t S E / (D - 2 t Y)                      (1b)

Eq. (1b) can be modified to compensate for thinner pipes due to the thickness tolerances used by the industry.

p = 2 t (1 - α / 100) S E / (D - 2 t Y)                      (1c)


α = thickness tolerance (%)

For ASTM A53, A106 and other codes the accepted thickness tolerances are 12.5%. 

Example - Allowable Pressure in a Steel Pipe

The allowable pressure in a 4 inch schedule 40 carbon steel pipe with outside diameter 4.5 in, wall thickness 0.237 in, thickness tolerance 12.5% and allowable stress 16000 psi - can with quality factor E for steel 0.8 and wall thickness coefficient 0.4 be calculated as

p = 2 (0.237 in) (1 - 12.5 / 100) (16000 psi) (0.8) / ((4.5 in) - 2 (0.237) 0.4)

   = 1232 psi      

ASME 31.3 Allowable Pressure Calculator (from eq. 1b)


Quality Factors E

Some quality factors according ASME 31.3:

  • furnace butt weld joint, continuous weld joint, straight seam: 0.6
  • electrical resistance weld joint, straight or spiral seam: 0.85  
  • double butt weld joint, straight or spiral seam, 100% radiographed: 1.0

Thickness Coefficients Y

The values of coefficient Y depends on type of material, temperature and thickness limits.

Thickness coefficients when t > D / 6:

Y = (d + 2 c) / (D + d + 2 c)                  (3)

Thickness coefficients when t < D / 6:

ASME 31.3 - Wall Thickness Coefficients Y
MaterialTemperature (oF)
< 900950100010501100> 1150
Ferritic steels 0.4 0.5 0.7 0.7 0.7 0.7
Autenitic steel 0.4 0.4 0.4 0.4 0.5 0.7
Other ductile materials 0.4 0.4 0.4 0.4 0.4
Cast iron 0.0
Sponsored Links

Related Topics

Pressure Ratings of Pipes and Fittings

Pressure ratings of pipes and tubes and their fittings - carbon steel , stainless steel, plastic, copper and more.

Related Documents

Aluminum Tubing - Allowable Pressures

Allowable pressure for aluminum tubes.

ASTM A312 Stainless Steel Pipes - Bursting and Collapsing Pressures

Theoretic bursting and collapsing pressures for stainless steel pipes ASTM A312.

ASTM A53 B Carbon Steel Pipes - Allowable Pressure vs. Schedule and Size

Maximum working pressure of carbon steel pipe at temperature 400oF.

Barlow's Formula - Calculate Internal, Allowable and Bursting Pressure

Calculate pipes internal, allowable and bursting pressure.

Capacitors - Parallel and Serial Circuits

Parallel and serial connected capacitor circuits.

Carbon Steel Pipes - Pressure and Temperature Ratings, Imperial Units

Pressure (psig) and temperature (deg F) ratings for A-53 B and A-106 B, A333, A334 and API 5L carbon steel pipes - temperatures ranging 100 degF - 700 degF.

Carbon Steel Pipes - Pressure and Temperature Ratings, Metric Units

Pressure (kPa)> and temperature (degC) ratings of ASTM A-106, API 5L and ASTM A-53 Seamless Carbon Steel Pipes - temperatures ranging -29 degC - 450 degC.

Copper Tubes Type K, L and M - Working Pressures vs. Size

ASTM B88 seamless copper water tubes - working pressures.

Metals Strength vs. Temperature

The influence of temperature on the strength of metals.

Stainless Steel Pipes - Allowable Pressure vs. Schedule and Size

Allowable pressure for standard seamless A312-TP316/316L stainless steel pipes - temperatures 100oF to 750oF.

Steel Tubes - Working Pressures vs. Size

Normal maximum working pressures for steel tubes - in psi and kPa.

Sponsored Links

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.