Barlow's formula refers to a mathematical relationship that is used to quantify and determine the following parameters as they relate to piping, tubing and hydraulic industrial applications:
- Internal pressure at minimum yield
- Ultimate burst pressure
- Maximum allowable pressure
Once determined, corresponding corrosion preventative measures may be put in place to support the required pressure performance outcomes.
Barlow's formula is generally used to determine the bursting pressure of pipes and tubing. The formula is:
P = 2 s t / [(do – 2 t) SF]
Where:
P = maxium working pressure (psig)
s = material strength (psi)
t = wall thickness (in)
do = outside diameter (in)
SF = safety factor (in general 1.5 to 10)
Barlow's formula is based on ideal conditions at room temperature and is used for rough estimation calculations only. According to the American Society of Mechanical Engineers (ASME) codes, further design and testing criteria must be met to confirm a pipe's or tube's bursting pressure.