Baffled Inventory Method
The Baffled Inventory method keeps the inputs and outputs separate until the end of each time slice.
In a Baffled Inventory, after all the original contents of the inventory are flushed out, the Composition Tracking analysis creates an event at the time when the original contents are removed. Before the event, the composition of the output flow is the same as the original composition of the inventory. After the event, the composition is the same as the new composition of the inventory, which is the same as the input to the inventory.
Baffled Inventory Method Example
An inventory initially has 2000 bbl 50%A:50%B. There are three time slices during the accounting period. During time slice 1 a quantity of 2000 bbl 40%B:60%C enters and 1980 bbl are extracted. During time slice 2 a quantity of 1000 bbl is extracted and 3000 bbl 33.3%B:66.7%C enters. During time slice 3 1000 bbl are extracted and 500 bbl 100%A are added. The minimum tracking level is set such that any compositions less than or equal to 10 bbl are removed. The packet number signifies the order the packets entered into the inventory.
The calculation procedure is described below.
- Assume that materials have the same composition as the time slice start composition.
- Calculate the percentage of each material in the inventory. If any materials/packets are below the minimum tracking level, then for the last time slice push these out first.
- Multiply the composition percent by the transfer quantity leaving for each product during the time slice.
- Subtract the quantity of each material from the columns in the calculation table.
- Add the quantities of each material entering the inventory to the calculation table in new columns to the right, using the next available packet number.
- At the last time slice, check columns to see if any are below the minimum tracking level. If there are, then redo the time slice by flushing out these materials first.
- Re-index all packet numbers.
The results are illustrated in the tables below.
Inventory has an opening volume of 2000 bbl and a starting composition of 50%A:50%B.
The Col 1, Col2, …column syntax is: Packet number.; material; quantity (bbl)
Initial Inventory Reading
| Inventory | Col 1 | Col 2 |
|---|---|---|
| 101 | 1;A;1000 | 1;B;1000 |
Time Slice 1 After 1980 bbl Output
| Inventory | Col 1 | Col 2 |
|---|---|---|
| 101 | 1;A;10 | 1;B;10 |
Time Slice 1 After 2000 bbl Input of 40% B:60% C
| Inventory | Col 1 | Col 2 | Col 3 | Col 4 |
|---|---|---|---|---|
| 101 | 1;A;10 | 1;B;10 | 2;B;800 | 2;C;1200 |
Time Slice 2 After 1000 bbl Output
| Inventory | Col 1 | Col 2 | Col 3 | Col 4 |
|---|---|---|---|---|
| 101 | 1;A;5 | 1;B;5 | 2;B;404 | 2;C;606 |
Time Slice 2 After 3000 bbl of 33.3% B:66.7%C
| Inventory | Col 1 | Col 2 | Col 3 | Col 4 | Col 5 | Col 6 |
|---|---|---|---|---|---|---|
| 101 | 1;A;5 | 1;B;5 | 2;B;404 | 2;C;606 | 3;B;1000 | 3;C;2000 |
Time Slice 3 After 1000 bbl Output
| Inventory | Col 1 | Col 2 | Col 3 | Col 4 | Col 5 | Col 6 |
|---|---|---|---|---|---|---|
| 101 | 1;A;3.8 | 1;B;3.8 | 2;B;303.4 | 2;C;455.3 | 3;B;751.2 | 3;C;1502.5 |
Time Slice 3 After 500 bbl input of 100.0% A – Ending Result
| inventory | Col 1 | Col 2 | Col 3 | Col 4 | Col 5 | Col 6 | Col 7 |
|---|---|---|---|---|---|---|---|
| 101 | 1;A;3.8 | 1;B;3.8 | 2;B;303.4 | 2;C;455.3 | 3;B;751.2 | 3;C;1502.5 | 4;A;500 |
The inventory has an ending volume of 3520 bbl and a composition of 14.3%A:30.1%B:55.6%C