Inventory Calculation Methods
The following inventory methods are available and are described in more detail below. The "mixing model" is set in an Attribute of each inventory.
- Baffled Inventory Method
- Well-Mixed Inventory Method
- Make-Up-Purge Inventory Method
- Line / FIFO Inventory Methods
- LIFO Inventory Method
Setting the Mixing Model for an inventory
The mixing Model is specified by the mixing Model Attribute of the inventory element. The keyword value in the Attribute specifies the mixing model.
Mixing Model Attribute Key Words
| Key Word | Description |
|---|---|
| Baffled | Baffled Inventory Method |
| WellMixed | Well-Mixed Inventory Method |
| MakeupPurge | Make-Up-Purge Inventory Method |
| Line | Line Inventory Methods |
| FIFO | First-In First Out Inventory Method |
| LIFO | Last-In Last-Out Inventory Method |
Minimum Tracking Level Calculations
The minimum tracking level allows you to eliminate components from the analysis when their quantity becomes insignificant. The definition of “significance” varies, so this is a configurable parameter. Elimination of below-minimum-percentage components is done such that nothing “disappears” or is “absorbed.” Refer to Filling In the Control Parameters Tab for more information about how to set the minimum tracking level.
If the normal calculation procedure for any of the inventory types, except Line/FIFO/LIFO, results in an ending component percentage less than this parameter in any calculation iteration, then one of two actions will happen:
- If the inventory has an output flow during the iteration, the composition of that out-flow is adjusted to force the residual quantity of the component out of the inventory. The offsetting adjustment is made to the largest quantity component in the inventory.
- If the inventory does not have an output flow during the iteration, the composition of the inventory is not adjusted. The quantity of the below-minimum tracking level is maintained despite the fact it is below minimum.
Special Materials
Some materials mix in a special way. The inventory acts either Baffled or Well Mixed unless the special material is added. If this material is added it sinks to the bottom and is the first material to leave the inventory. Hence it acts as a FIFO method for that material as long as the material is in the inventory.
You need to enter the special product material code designation into the Special Material column of the SF_Material table. Note that the column name and the table name are selectable. These are the defaults in the configuration dialog boxes.
Currently, Composition Tracking supports water (special material code = 1) as a special material.
Water is always segregated in the inventory and can only be extracted from an inventory using a transfer with a special material code value of 1. If the transfer is greater than the volume of water stored, then the discrepancy is made up by the remaining inventory.
SF_CompositionTracking
When this column is configured in SF_Material table, it allows to exclude some components or material codes from the analysis results. The materials having this flag = false have following processing:
- Transfer carrying a material excluded by the analysis: in this case, the transfer is kept out from the composition tracking in order to avoid the accounting of this material on the composition tracking results of the destination element (inventory).
- Inventory having an excluded material in the previous composition results: In this case, the material is removed from the initial composition.
This kind of processing surely provides inconsistent results on the inventories (total quantity of the components doesn’t match the reconciled value). In such case, it’s strongly suggested enable the tank normalization option in order to compensate the quantity of the excluded materials. From the point of view of the material accounting, this approach will produce a gain in the components.
Note: When the SF_CompositionTracking column is not configured in the SF_Material table, all the materials will be included in the analysis.
Packets
For several of the inventory mixing methods, the sequence in which materials are added or removed is important to the Composition Tracking calculation. The term “packet” is used to describe the segregation of the sequence in the analysis. Materials with the same sequence index belong to the same packet. You define the sequence index with the 'Composition Tracking Viewer'.