For liquid flow meters
- Last UpdatedFeb 28, 2025
- 3 minute read
Symbols commonly used in the liquid flow compensation equations
|
Symbol |
Name |
Description |
|
CLVF |
Corrected (also known as “compensated") Liquid Volume Flow Rate |
Flow rate re-corrected to standard conditions by AVEVA Production Accounting |
|
MLVF |
Measured Liquid Volume Flow Rate |
Observed flow rate corrected to standard conditions by plant instrumentation (using design flowing density and design density) |
|
MFD |
Measured Flowing Density |
Observed density at observed operating conditions |
|
MD |
Measured Density |
Observed density corrected to standard conditions |
|
MT |
Measured Temperature |
Observed temperature (at operating conditions) |
|
MP |
Measured Pressure |
Observed pressure (at operating conditions) |
|
DFD |
Design Flowing Density |
Presumed density at design operating conditions |
|
DD |
Design Density |
Presumed density at design standard conditions |
Corrected Liquid Volume Flow Rate:
Or, if a K value has been specified:
The Measured Flowing Density is not directly obtained from measurements but is back-calculated from the Measured Density by using a VCF (Volume Correction Factor).
VCF(Density, T, P) is a function of the operating temperature, pressure and the density of the material at the base temperature. The volume correction factor is calculated as follows:
…where Cpl is correction factor for the effect of pressure on the liquid and exp(x) = ex and ΔT is the difference between the operating temperature and the standard base temperature (60 °F), and A is the coefficient of thermal expansion at standard conditions, calculated using the following equation:
… where Fp is compressibility factor ( a = -1.99470, b = 0.00013427, c = 793920, d = 2326; based on density kg/m3 at 60 °F) and ΔP is the difference between the operating pressure and the standard base pressure (0 psig)
The equation used to calculate A is a function of the type of material (e.g. gasoline, diesel, etc.) and its density. K0, K1 and K2 are constants and are also a function of the type of material and the material’s density.
The constants K0, K1 and K2 are fixed at:
|
Material type |
Density range (kg/m3) |
K0 |
K1 |
K2 |
|
Crude Oil |
610.6 – 1163.5 |
341.0957 |
0 |
0 |
|
Products |
> 838.3 |
103.8720 |
0.2701 |
0 |
|
787.5 - 838.3 |
330.301 |
0 |
0 |
|
|
770.4 - 787.5 |
1489.067 |
0 |
-0.0018684 |
|
|
610.6 – 770.4 |
192.4571 |
0.2438 |
0 |
|
|
610.6 |
341.0957 |
0 |
0 |
|
|
Lubricating Oil |
800.9 – 1163.5 |
0 |
0.34878 |
0 |
This volumetric correction factor (VCF) calculation is based on the method of API Chapter 11.1 Volume Correction Factors.
For example, the condition of FC001 liquid stream is as the following.
• Design Density : 0.879 SG
• Design Temperature : 154 C
• Design Pressure : 11.7 kg/cm2G
• Measured Density : 0.8947 SG
• Measured Temperature : 173.6 C
• Measured Pressure : 9 kg/cm2G
You define the design values at Design Data tab.
You use compensation by checking the Compensation checkbox and get the measured values from the tags.
And the compensated flow rate is calculated as volume correction factor is 0.983763.
