Gas Flow Meter Calculation Formulas

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 l_n/min Air at 0 bar(g)/ 20° C

Q₁ = 12 l_n/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 ln/min reading
Q0 = 19,15 ln/min CO2 at 3 bar(g)/ 25° C

Example 2

What is the actual flow if flow meter LH-JJ32 is used for Helium at 5 bar(g) / 10° C.

LH-JJ32 is calibrated for

• 30 ln/min Nitrogen at 3 bar(g)/ 20° C

Q₁ = 30 ln/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 ln/min reading
Q0 = 98,9 ln/min He at 5 bar(g)/ 10° C