# Pressure Loss

Written by Matt Milbury on . Posted in Pump

Pressure loss, abbreviated as $$\Delta P$$, also called pressure drop, is the difference in pressure between two points, usually caused by friction resistance in the pipe, but moisture can also affect it.

## Pressure Loss formulas

 $$\large{ \Delta P = \frac{f \; l \;v^2}{2 \; g \; d} }$$ $$\large{ \Delta P = 2 \; f_f \left( \frac{ l }{ d } \right) \left( \rho \; \bar {v}^2 \right) }$$

### Where:

 Units English SI $$\large{ \Delta P }$$ = pressure loss $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$ $$\large{ \bar {v} }$$ = average velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$ $$\large{ \rho }$$   (Greek symbol rho) = density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$\large{ f_f }$$ = Fanning friction factor $$\large{ dimensionless }$$ $$\large{ f }$$ = friction factor $$\large{ dimensionless }$$ $$\large{ g }$$ = gravirational acceleration $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$ $$\large{ d }$$ = inside diameter of pipe $$\large{ in }$$ $$\large{ mm }$$ $$\large{ l }$$ = lenght of pipe $$\large{ ft }$$ $$\large{ m }$$ $$\large{ v }$$ = velocity of fluid $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$