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Gas Correction Factors for Variable Area Flow Meters

To determine corrected flowrate: find the gas for which the meter is calibrated in the left column, move to the right to the gas that is being used. Multiply the flowrate indicated on the meter by the correction factor. This will equal an approximation of the flowrate of the gas being used.

Please note: this correction factor is only accurate within ±10%. This is also inaccurate for extremely low flow, or elevated pressure; consult factory for your specific condition.

Gas being used / S.G.


Gas for which meter is calibrated


H2


Cracked
Ammonia


Methane


Ammonia


Gas


Neon


Acetylene


N2 or O2


Air


Ethane


O2


Argon


CO2 or N2O


Propane


Butane



0.070

0.294

0.554

0.588

0.620

0.700

0.899

0.967

1.000

1.038

1.105

1.520

1.523

1.523

2.007



Air

3.78

1.84

1.34

1.30

1.27

1.20

1.05

1.02

1

0.98

0.95

0.85

0.81

0.81

0.71



Oxygen

3.97

1.94

1.41

1.37

1.34

1.26

1.11

1.07

1.05

1.03

1

0.90

0.85

0.85

0.74


 


Calculating Conversion Factors

Based on Specific Gravity

Conversion Factor Calculations


Pressure & Temperature Corrections

Pressure Effects

• Elevated pressures (above atmosphere)
allow for greater capacity for a given flowmeter

• To determine the actual flowrate (at the elevated
pressure), the following formula is used:

Pressure Effects Correction Calculation 

• All pressures are in absolute, not gauge

Temperature Effects

• Elevated temperatures (above standard
atmospheric temperature) decrease maximum
flowrate for a given flow body

• To determine the actual flowrate,
the following formula is used:

Temperature Effects Correction Calculation

• All temperatures are in absolute

Pressure Correction Example

• Our flowmeters are calibrated at a standard
pressure of 14.696 PSIA (which is equivalent
to 0 PSIG)

• If a customer is operating the meter at 20 PSIG,
what will the effect be on the flow reading?

– The actual flowrate will be higher than
that indicated by the flowmeter
– How much higher will it be?

Pressure Correction Calculation

Pressure Correction Example 

Pressure Correction Actual Flow Rate

Temperature Correction Example

• Our flowmeters are calibrated at a standard
temperature of 20 °C or 68 °F

• If a customer is using the meter at 30 °C, what
will the effect be on the flow reading?

– The actual flowrate will be lower than
that indicated by the flowmeter
– How much lower will it be?

 

 Temperature Correction Calculation

Temperature Correction Example

Temperature Correction Actual Flow Rate