Gas flow meter calculation formulas
Here you can find calculation formulas for gas flow conversions. Use the conversion formula shown below. Here’s also few examples to help you!
Gas flow conversion formula
Actual flow rate
Q0 = Actual flow rate
ρ0 = Specific gravity of measured gas (Air = 1)
p0 = Actual ABSOLUTE pressure in metering tube
T0 = Actual ABSOLUTE temperature
(Kelvin) in metering tube
(0°C = 273,15°K)
(20° C = 293,15°K)
Flowmeter design (calibration) conditions
Q1 = Flow meter reading
ρ1 = Specific gravity of design gas (Air = 1)
p1 = ABSOLUTE design pressure
(calibration pressure)
T1 = ABSOLUTE design temperature
(Calibration temperature)
Example 1
What is the maximum flow if flow meter EK-3NR is used for carbon dioxide at 3 bar(g) / 25°C.
Ex-3NR scale is
- 1 – 12 NL/min air at 0 bar(g)/20°C
Q1 = 12 NL/min
ρ1 = 1
p1 = (0+1,013) bar = 1,013 bar
T1 = 293,15°K
Q0 = ?
ρ0 = 1,529
p0 = (3+1,013) bar = 4,013 bar
T0 = 298,15°K
Actual flow at 12 NL/min reading
Q0 = 19,15 NL/min CO2 at 3 bar(g)/ 25°C
Example 2
Flow meter LH-JJ32 is calibrated for 30 NL/min nitrogen at 3 bar(g)/ 20°C
What is the actual flow if flow meter LH-JJ32 is used for helium at 5 bar(g) / 10°C.
Q1 = 30 NL/min
ρ1 = 0,9672
p1 = (3+1,013) bar = 4,013 bar
T1 = 293,15°K
Q0 = ?
ρ0 = 0,1380
p0 = (5+1,013) bar = 6,013 bar
T0= 283,15°K
Actual flow at 30 NL/min reading
Q0 = 98,9 NL/min He at 5 bar(g)/ 10°C
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