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.
Conversion factors should not be used for variable are flow meters with ball floats.
Consult Applications Engineering for your specific condition.
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Gas being used / S.G.
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Gas for which meter is calibrated
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H2
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Cracked
Ammonia
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Methane
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Ammonia
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Gas
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Neon
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Acetylene
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N2 or O2
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Air
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Ethane
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O2
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Argon
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CO2 or N2O
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Propane
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Butane
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0.070
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0.294
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0.554
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0.588
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0.620
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0.700
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0.899
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0.967
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1.000
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1.038
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1.105
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1.520
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1.523
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1.523
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2.007
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Air
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3.78
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1.84
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1.34
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1.30
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1.27
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1.20
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1.05
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1.02
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1
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0.98
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0.95
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0.85
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0.81
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0.81
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0.71
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Oxygen
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3.97
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1.94
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1.41
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1.37
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1.34
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1.26
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1.11
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1.07
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1.05
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1.03
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1
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0.90
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0.85
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0.85
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0.74
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Calculating Conversion Factors
Based on Specific Gravity
Pressure & Temperature Corrections
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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:
• All pressures are in absolute, not gauge
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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:
• All temperatures are in absolute
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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?
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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?
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