Barlow's Formula Calculator
This calculates how much pressure any given tube can handle.
Three of the fields must be filled and one must be left blank!
(It does not matter which field is left blank)
The field that is left blank will be filled with the number derived from the formula calculation of the other three fields.
What fields are what:
- Pressure this is the pressure in pounds per square inch inside the tubing.
- Wall Thickness this is the thickness in inches of the tubing wall.
- Outside Diameter This is the tubing's outside diameter in inches.
- Allowable Tensile Stress This is the ultimate tensile strength (or yield strength) in pounds per square inch of the metal that the tube is made out of.
Tensile stress is what a rope undergoes when it is stretched.
Steel with a tensile strength of 10,000psi, means a 1 inch square steel bar would break when you pulled 10,001 pounds worth on the ends in opposite directions.
Most metals have a yield strength far below their tensile strength. (ie, they start to stretch before they break)
You do not want the tensile stress created by your working pressure to be equal to either the tensile or yield strengths of your tubing!
Otherwise, you might get an unexpected Boom!
The four Barlow formulas are as follows:
Pressure = ( 2 × Allowable Tensile Stress × Wall Thickness ) ÷ Outside Diameter
Wall Thickness = ( ( Pressure × Outside Diameter ) ÷ Allowable Tensile Stress ) ÷ 2
Outside Diameter = ( 2 × Allowable Tensile Stress × Wall Thickness ) ÷ Pressure
Allowable Tensile Stress = ( ( Pressure × Outside Diameter ) ÷ Wall Thickness ) ÷ 2
You can click clear next to each field to clear it.
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