Compressed Air Pipe Pressure

Overview

Engineering reference data for Compressed Air Pipe Pressure in gases and compressed air.

Key Formulas

Ideal Gas Law

$PV = nRT$

Pressure × Volume = moles × gas constant × temperature.

Boyle's Law

$P_1 V_1 = P_2 V_2$

At constant temperature.

Charles's Law

$\frac{V_1}{T_1} = \frac{V_2}{T_2}$

At constant pressure.

Variables

Symbol	Description	Unit
$P$	Pressure	Pa
$V$	Volume	m³
$T$	Temperature	K
$R$	Gas constant	8.314 J/(mol·K)

Non-Standard Pipe Calculation

Pressure drop for pipes with dimensions other than Schedule 40 can be calculated using the following relationship:

$$dp = dp_{40} \left( \frac{d_{40}}{d} \right)^5$$

Where:

• $dp$ = actual pressure drop (psi per 100 ft pipe)
• $dp_{40}$ = pressure drop from the Schedule 40 diagram (psi per 100 ft)
• $d_{40}$ = inside diameter of Schedule 40 pipe (inches)
• $d$ = actual inside diameter of the pipe (inches)

Standard Conditions and Units

SCFM Definition (U.S.)

Standard Cubic Feet per Minute (SCFM) is defined at:

• Pressure: 14.696 psia
• Temperature: 60 °F
• Humidity: 0% RH

Unit Conversions

Quantity	Imperial	Metric
Length	1 ft	0.3048 m
Airflow	1 cfm	1.7 m³/h
Airflow	1 cfm	0.028 m³/min
Pressure	1 psi	0.069 bar
Pressure	1 psi	0.070 kg/cm²

References

• Original Source