Pipe Tools & Calculators
Kelly ResourcesBarlows Formula
Barlow’s Formula is used to determine:
- Internal Pressure at Minimum Yield
- Ultimate Bursting Pressure
- Maximum Allowable Operating Pressure
- Mill Hydrostatic Test Pressure
The formula is expressed as P=2St/D, where:
P = pressure, psig
t = nominal wall thickness, in inches(i.e. .375)
D = outside Diameter in inches
S = allowable stress in psi, which depends on the pressure being determined utilizing Yield or Tensile depending on what is trying to be determined
For example:
Internal Pressure at Minimum Yield:
S = SMYS – minimum yield for grade of pipe
Ultimate Bursting Pressure:
S = SMTS – minimum tensile strength for grade of pipe
Maximum Allowable Operating Pressure:
S = SMYS – reduced by a design factor
Mill Hydrostatic Test Pressure:
S = SMYS – reduced by a design factor depending on OD and grade
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