NGL, LPG Calculations Extension
In order to report inventory positions and for custody transfers purposes, NGL and LPG volumes are reported at base temperature and its corresponding saturation pressure. However, actual temperatures are most probably different from the base temperature. For this reason, users at the plant are required to perform volume correction factors computations related to this difference in temperature. This extension calculates the volume correction factors (CTL) only attributed to temperate. This means that if pressure is significantly higher than the saturation pressure, a correction factor (CPL) has to be used, but this correction is not covered by the standard followed within this extension. Specifically, the CTL calculations used are those described in the Manual of Petroleum Measurement Standards, Chapter 11 – Physical Property data (ASTM Technical Publication [Stock No. PETROLTBL-TP27]; GPA Technical Publication TP-27). Currently the sequence of calculation is limited to support Table 24E of the mentioned standard.
In addition, this extension can be used to calculate vapor volume correcting factors (VCF) of mostly propane fluids in pressurized vessels.
Inputs
| Input | Description |
|---|---|
| Specific Gravity | The Relative Density of fluid at a base temperature (in any Specific Gravity UOM). |
| Temperature | The Temperature of the fluid (in any Temperature UOM). |
| Material | An Attribute of the material. |
Outputs
| Output | Description |
|---|---|
| VCF liq | The Volume correction factor that converts liquid volume at a temperature to the equivalent liquid volume at the base temperature. |
| VCF vap | The Volume correction factor that converts vapor volume at a temperature to the equivalent liquid volume at base temperature. |
Volumes for liquefied petroleum gas (LPG) are generally stated at a fixed base temperature and saturation pressure. As most volume transfers occur at temperatures and pressures other than standard conditions, volumes are adjusted to standard conditions through the use of volume correction factors (VCF). This guide covers the NGL and LPG calculations data reference, which computes only the temperature related correction factors for NGL and LPG in:
The results of these calculations are used to convert the LPG Vapor and Liquid Volume (at actual conditions) to a Liquid Volume at base temperature.
Note:
VCF is used to calculate equivalent 60 °F (base temperature) volume of the combined NGL or LPG liquid and vapor in a vessel
- Vapor_Volume_60 °F = Volume_Vapor * VCF_Vapor
- Liquid_Volume_60 °F = Volume_Liquid * VCF_Liquid
- Total_Volume_60 °F = Vapor_Volume_60 °F+ Liquid_Volume_60 °F