Gas Meter Compensation
Use the Gas Meter Compensation calculation to provide a compensation of actual gas volume based on the difference between measured flow, flowing conditions, and design conditions of an orifice meter.
The compensation calculation is made according to the following equations.
Where:
Vg = Actual gas flow calculated at flowing conditions (compensated actual flow).
Vgd = Actual gas flow calculated at design conditions (uncompensated actual flow).
Vs = Compensated standard gas flow.
Tgas = Actual flowing temperature of the gas.
Td = Design flowing temperature of the meter.
Tr = Reference temperature.
Pgas = Actual flowing pressure of the gas.
Pd = Design pressure of the meter.
Pr = Reference pressure.
MWd = Molecular weight of the meter at design.
MWgas = Molecular weight of the gas at flow.
zgas = Compressibility factor of the gas at flowing conditions.
zrgas = Compressibility factor of the flowing gas at flowing conditions.
zd = Compressibility factor of the meter at design conditions.
zrd = Compressibility factor of the design gas at reference conditions.
Note: All pressure and temperatures used in these formulas are absolute.
EXAMPLE: Gas Meter Compensation
A meter data sheet has the information listed in the following table.
Meter Data
| Parameter | Value |
|---|---|
| Base or Reference Temperature, Tr | 60 °F |
| Base or Reference Pressure, Pr | 14.73 psi |
| Flowing Temperature (design), Td | 76 °F |
| Molecular weight | 7.92 |
| Flowing pressure (absolute, design), Pd | 211.7 psi |
| Compressibility factor, zd , zrd | 0.9993 |
Air has a molecular weight of 28.9625 and a compressibility factor of 0.99959 at reference or base conditions. The material being metered has a molecular weight of 8.95 and a compressibility factor at flowing conditions of 0.9788 and at reference or base conditions the compressibility factor is 0.9992. The flowing conditions are 100 °F and 204 psi (absolute). The meter reading is 1510.5 MMscf/d, which corresponds to 117.46 MMacf/d. Question: what is the compensated flow rate for the flowing conditions?
Vgd = 117.46 MM aft3/d
Tgas = 100 ºF = 559.67 °R
Pgas = 204 psi
MWd = 7.92 lb/lbmol
MWgas = 8.95 lb/lbmol
zgas = 0.9788
zrgas = 0.9992
Tr = 60 ºF = 519.67 °R
Applying the equations listed above, the calculated value for the compensated flow is the following.
Vs 1407.46 MMsft3/d
See Configuring - Gas Meter Compensation for details on how to configure this compensation.