# Barlow's Formula

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Barlow's formula, abbreviated as Ba, relates to burst pressure, the point just before or at when a pipe or tubing fails under pressure.

## Barlow's formulas

$$\large{ p = \frac{2 \; S \; t}{D} }$$

$$\large{ p = \frac{4 \; S \; t}{ D \;+\; 2 \; t } }$$

$$\large{ p = \frac{2 \; S \; t}{ \left(D \;-\; 2 \; t \right) \; SF } }$$

$$\large{ p = \frac{2 \; S \; t}{D \; SF} }$$

Symbol English Metric
$$\large{ p }$$ = pressure $$\large{\frac{lbf}{in^2}}$$  $$\large{Pa}$$
$$\large{ S }$$ = allowable stress $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ D }$$ = outside diameter of pipe $$\large{in}$$ $$\large{mm}$$
$$\large{ t }$$ = pipe thickness $$\large{in}$$ $$\large{mm}$$
$$\large{ SF }$$ = safety factor (generally 1.5 - 10, 1 for bursting pressure) $$\large{ dimensionless }$$