Appendix G: Flow of Water/Air through Schedule 40 Pipe

Table G.1
Flow of Water through Schedule 40 Steel Pipe

Note:  For pipe lengths other than 100 ft, the pressure drop is proportional to the length. Thus, for 50 ft of the pipe, the pressure drop is approximately one-half the value given in the table; for 300 ft, three times the given value, etc.

Table G.2
Flow of Air through Schedule 40 Steel Pipe

For pipe lengths other than 100 ft, the pressure drop is proportional to the length. Thus, for 50 ft of the pipe, the pressure drop is approximately one-half the value given in the table; for 300 ft, three times the given value, etc.

The pressure drop is also inversely proportional to the absolute pressure and directly proportional to the absolute temperature.

Therefore, to determine the pressure drop for inlet or average pressures other than 100 psi and at temperatures other than 60°F, multiply the values given in the table by the following ratio:

$\left(\frac{100+147}{P+14.7}\right)\left(\frac{460+T}{520}\right)$

where

P is the inlet or average gauge pressure in psi

T is the temperature in °F under consideration

The cubic feet per minute of compressed air at any pressure is inversely proportional to the absolute pressure and directly proportional to the absolute temperature.

To determine the cubic feet per minute of compressed air at any temperature and pressure other than standard conditions, multiply the value of cubic feet per minute of free air by the following ratio:

$\left(\frac{14.7}{14.7+P}\right)\left(\frac{460+T}{520}\right)$

G.1 CALCULATIONS FOR PIPE OTHER THAN SCHEDULE 40

To determine the velocity of water, or the pressure drop of water or air, through a pipe other than Schedule 40, use the following formulas:

$\begin{array}{l}{V}_a=V_{40}{\left(\frac{d_{40}}{d_a}\right)}^2\\ \text{Δ}{P}_a=\text{Δ}{P}_{40}{\left(\frac{d_{40}}{d_a}\right)}^5\end{array}$

Subscript “a” refers to the schedule of pipe through which velocity or pressure drop is desired.

Subscript “40” refers to the velocity or pressure drop through a Schedule 40 pipe, as given in Table G.1.