Petroleum Liquids Formula
The CygNet Line Pack engine calculations for petroleum liquids comply with the API standards published in the following standards document: Manual of Petroleum Measurement Standards, Chapter 11 — Physical Properties Data, Section 1 — Temperature and Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products, and Lubricating Oils. Adjunct to: ASTM D 1250-04 and IP 200/04. Measurement Coordination October 2002. May 2004. Addendum 1, September 2007.
Depending on the variables the user configures to be calculated, appropriate calculations are made and the results are written out to the various Line Pack points. As the formula used to calculate estimated line pack volume for petroleum liquids is very complex, the following describes the calculation steps in a simplified manner.
See the following subsections below for more information:
- Assumptions
- Calculation Flow Diagram
- Calculation Steps
- Formula Inputs Reference
- Formula Outputs Reference
Assumptions
The following inputs must be provided to perform all calculations:
- Observed density
- Observed temperature at which observed density was measured
- Observed pressure at which observed density was measured
- Either a single pair of inlet and outlet temperatures, or multiple temperature values at different points on the pipeline segment
- Either a single pair of inlet and outlet pressures, or multiple pressure values at different points on the pipeline segment
- Standard temperature at which the liquids line pack volume will be calculated
- Standard pressure at which the liquids line pack volume will be calculated
- Liquids commodity type or thermal expansion factor at base condition (60°F and 0 psig)
- Pipeline segment volume based either on the segment’s configured length and diameter or a user-configured volume
- Optionally provide inlet and outlet Maximum Allowable Operating Pressure (MAOP), or provide multiple MAOP readings at different points on the pipeline segment
Also see Formula Inputs Reference below.
Calculation Flow Diagram
The following diagram shows a graphical representation of the flow of calculations for the petroleum liquids line pack formula.
|
Click the thumbnail to see |
Calculation Steps
Step 1
Using the API 11.1 Observed to Base formula, calculate Base Density with inputs: Observed Temperature, Observed Pressure, Observed Density, and Commodity Group (or Alpha 60).
| Intermediate Output | Description |
|---|---|
|
ρ60 |
Density at base conditions 60°F and 0 psig |
Step 2
Calculate the Average Temperature, Average Pressure and Average MAOP for the pipeline segment using selected formulas on Temperature, Pressure, and MAOP readings at pipeline segment (inlet and outlet, or multiple).
| Intermediate Outputs | Description |
|---|---|
|
T,a |
Average Pipeline Segment Temperature |
|
P,a |
Average Pipeline Segment Pressure |
|
MAOP,a |
Average Pipeline Segment MAOP |
Step 3
Convert from Base to Average conditions using the API 11.1 Base to Alternate formula with inputs: Average Pipeline Segment Temperature, Average Pipeline Segment Pressure, Base Density, Pipeline Segment Volume, and Commodity Group (or Alpha 60).
| Intermediate Outputs | Description |
|---|---|
|
CTL,a |
Volume correction factor due to temperature at pipeline segment average conditions |
|
CPL,a |
Volume correction factor due to pressure at pipeline segment average conditions |
|
FP,a |
Scaled compressibility factor at pipeline segment average conditions |
|
CTPL,a |
Combined volume correction factor due to temperature and pressure at pipeline segment average conditions |
|
ρ,a |
Density at pipeline segment average conditions |
|
V60 |
Volume at base conditions (60°F and 0 psig) |
Step 4
Convert from Base to Standard conditions using the API 11.1 Base to Alternate formula with inputs: Standard Temperature, Standard Pressure, Base Density, and Commodity Group (or Alpha 60).
| Intermediate Outputs | Description |
|---|---|
|
CTL,s |
Volume correction factor due to temperature at standard conditions |
|
CPL,s |
Volume correction factor due to pressure at standard conditions |
|
FP,s |
Scaled compressibility factor at standard conditions |
|
CTPL,s |
Combined volume correction factor due to temperature and pressure at standard conditions |
|
ρ,s |
Density at standard conditions |
Step 5
Calculate Line Pack Volume and Line Pack Mass.
| Outputs | Description |
|---|---|
|
Line Pack Volume (at standard conditions) |
(Volume at base conditions) / (Combined volume correction factor due to temperature and pressure at standard conditions) |
|
Line Pack Mass |
(Line Pack Volume) * (Density at standard conditions) |
Step 6
Convert from Base to MAOP conditions using the API 11.1 Base to Alternate formula with inputs: Pipeline Segment Average Temperature, Pipeline Segment Average MAOP, Base Density, Pipeline Segment Volume and Commodity Group (or Alpha 60).
| Output |
|---|
|
No persisted outputs from this step. But the calculated MAOP Volume at base conditions will be used in the next step. |
Step 7
Calculate MAOP Line Pack Volume and MAOP Line Pack Mass.
| Outputs | Description |
|---|---|
|
MAOP Line Pack Volume (at standard conditions) |
(MAOP Volume at base conditions) / (Combined volume correction factor due to temperature and pressure at standard conditions) |
|
MAOP Line Pack Mass |
(MAOP Line Pack Volume) * (Density at standard conditions) |
Formula Inputs Reference
The Line Pack formula for petroleum liquids uses the following inputs to its calculation.
| Inputs/Intermediate Outputs | Symbol | Description | Units |
|---|---|---|---|
|
Alpha 60 |
a60 |
Pre-calculated 60°F thermal expansion factor (used if Commodity Group not given) |
°F-1 |
|
Commodity Group |
none |
Commodity group type describing liquid (used if a 60 not input) |
N/A |
|
Density, Observed |
ρo |
Density at observed conditions to and Po |
kg/m³ |
|
MAOP, Inlet |
MAOP1 |
MAOP input 1 at the inlet (upstream) end of the pipeline segment |
psig |
|
MAOP, Outlet |
MAOP2 |
MAOP input 2 at the outlet (downstream) end of the pipeline segment |
psig |
|
Pipeline Segment Volume |
Vseg |
Volume of the pipeline segment based either on the segment’s configured length and diameter or a user-configured volume |
MCF |
|
Pressure, Inlet |
P1 |
Pressure input 1 at the inlet (upstream) end of the pipeline segment |
psig |
|
Pressure, Outlet |
P2 |
Pressure input 2 at the outlet (downstream) end of the pipeline segment |
psig |
|
Pressure, Observed |
Po |
Pressure at which the observed density was measured |
psig |
|
Pressure, Standard |
P |
Standard pressure at which density is desired |
psig |
|
Temperature, Inlet |
T1 |
Temperature input 1 at the inlet (upstream) end of the pipeline segment |
°F |
|
Temperature, Outlet |
T2 |
Temperature input 2 at the outlet (downstream) end of the pipeline segment |
°F |
|
Temperature, Observed |
to |
Temperature at which the observed density was measured |
°F |
|
Temperature Standard |
t |
Standard temperature at which density is desired |
°F |
Formula Outputs Reference
The Line Pack formula for petroleum liquids calculates the following output variables as part of its calculation.
| Outputs | Description | Units |
|---|---|---|
|
CPL,a |
Volume correction factor due to pressure at pipeline segment average conditions |
N/A |
|
CPL,s |
Volume correction factor due to pressure at standard conditions |
N/A |
|
CTL,a |
Volume correction factor due to temperature at pipeline segment average conditions |
N/A |
|
CTL,s |
Volume correction factor due to temperature at standard conditions |
N/A |
|
CTPL,a |
Combined volume correction factor due to temperature and pressure at pipeline segment average conditions |
N/A |
|
CTPL,s |
Combined volume correction factor due to temperature and pressure at standard conditions |
N/A |
|
Density, Average |
Density at pipeline segment average conditions |
kg/m³ |
|
Density, Base |
Density at base conditions (60°F and 0 psig) |
kg/m³ |
|
Density, Standard |
Density at standard conditions t and P |
kg/m³ |
|
FP,a |
Scaled compressibility factor at pipeline segment average conditions |
Psi-1 |
|
FP,s |
Scaled compressibility factor at the standard temperature |
Psi-1 |
|
Line Pack Mass |
Line Pack Mass |
lbs |
|
Line Pack Volume |
Line Pack Volume at standard conditions |
MCF |
|
MAOP Line Pack Mass |
MAOP Line Pack Mass |
lbs |
|
MAOP Line Pack Volume |
MAOP Line Pack Volume at standard conditions |
MCF |
|
V60 |
Volume at base conditions (60°F and 0 psig) |
same set of units as Vseg |
