Natural Gas Pipe Calculator

Overview

Engineering reference data for Natural Gas Pipe Calculator 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)

Practical Notes

Application Range

• Spitzglass formula applies to low pressure natural gas systems: less than 1 psi (6.9 kPa)
• Valid for systems with small pressure losses

Typical Values

Specific Gravity of Natural Gas

• Range: *0.55 to 1.0
• Typical: *0.60 to 0.70
• Use 0.60 as a default when specific data is unavailable

Downstream Pressure (after meter/regulator)

• Household systems: 7 to 11 inches Water Column (approximately 1/4 psi)

BTU Content

Conversion	Value
Natural gas BTU content	900 – 1100 BTU per CF
1 Cubic Foot (CF)	≈ 1000 BTU
1 CFH	= 1 MBH

Example Calculation

Calculate the capacity of a 100 ft natural gas pipe with nominal diameter 0.5 inches (actual ID = 0.622 in) and 0.5 inches WC pressure drop. Assume SG = 0.60.

Step 1: Calculate the pipe constant k

$k = \sqrt{\frac{d^5}{1 + \frac{3.6}{d} + 0.03d}} = \sqrt{\frac{(0.622)^5}{1 + \frac{3.6}{0.622} + 0.03(0.622)}} = 0.117$

Step 2: Calculate the flow rate q

$q = 3550 \times k \times \sqrt{\frac{h}{l \times SG}} = 3550 \times 0.117 \times \sqrt{\frac{0.5}{100 \times 0.60}} = 37.9 \text{ cfh}$

The pipe delivers approximately 37.9 cfh (cubic feet per hour) under these conditions.

References

• Original Source