Liquid Meter Compensation
The Liquid Meter Compensation calculation is used to account for differences of the temperature and specific gravity between flowing conditions and design conditions of an orifice meter.
The equation for correcting the metered liquid flow rate for deviations of the temperature and specific gravity from design conditions is as follows.
Where:
V = Volume calculated from chart reading and meter factor.
Vc = Compensated volume.
Gb = Specific gravity of the material used in sizing the orifice at reference temperature (Default 60 F).
Glab = Specific gravity of the metered material at reference temperature (Default is 60 F).
Gf = Specific gravity of the metered material at flowing temperature.
Gfd = Specific gravity of the material used in sizing the orifice at design temperature.
If the specific gravity of the material at flowing conditions or the specific gravity of the material used in sizing the orifice at design conditions is not available, then these can be calculated as follows:
Where:
VCFf = Volume correction factor for the material at flowing conditions (also calculated in this data reference).
VCFd = Volume correction factor for the material used in sizing the orifice at design conditions.
EXAMPLE: Liquid Meter Compensation
A meter data sheet has the information listed in the following table.
Meter Data
| Parameter | Value |
|---|---|
| Base Temperature | 60°F |
| Flowing Temperature | 275°F |
| Base Specific Gravity (Gb) | 0.7443 |
| Flowing Specific Gravity (Gfd) | 0.6324 |
The material being metered is crude oil with a VCF type correction of 1. The meter reading is 1334 bbl/d. Question: What is the compensated flow rate for the flowing conditions?
First calculate the volume correction factors. The VCFd is not needed because the meter data sheet provides both the base and flowing specific gravities for the material used in sizing the orifice meter. These are the following.
V = 1334 bbl/d
Glab = 35 API = 0.8499 SG
Gfd = 0.6324 SG
The VCFf is then calculated using the volume correction data reference with the reference temperature of 60 °F, the gravity of 35 API, and temperature of 296 °F. See section "Material Volume Correction Factor (VCF)." The calculated value of VCFf is the following.
VCFf = 0.88545
Gf = VCFf × Glab = 0.7525 SG
The compensated value is calculated as follows:
Vc = 1274.36 bbl/day
See Configuring - Liquid Meter Compensation for details on how to configure this compensation.