Data reconciliation with user added boundaries/linear constraints

You can define the boundary conditions and additional linear constraints for measured and unmeasured flows in AVEVA Production Accounting. The term “linear constraint” is a type of constraint implemented by the Smart Constraint feature of AVEVA Production Accounting. Constraints are considered linear when they are used to balance just mass or just volume (not both simultaneously).

Examples of constraints are as follows:

• Boundary condition: 0 =< FC001 =< 100

• Additional linear constraint: FC001 = 0.75*FC002

Where FC001 is an unmeasured flow, and FC002 is a measured flow.

In the case of a boundary condition, you can define the minimum/maximum flow rate using the AVEVA Production Accounting GUI. The GUI passes this information to DR Solver engine as follows:

If you define the Min/Max constraints of the flow, these minimum flow rate and maximum flow rate act as boundary constraints when running data reconciliation.

Maximum handling

• If the reconciled value is above the maximum flow rate, the data reconciliation step sets the reconciled value to the maximum flow rate and then runs overall data reconciliation again.

Minimum handling

• If the reconciled value of a flow after running data reconciliation is below the minimum flow rate specified for it, the data reconciliation step sets the measured value of the stream to zero and then runs the overall data reconciliation steps again.

Note that the handling of minimum constraints is not entirely like the handling of maximum constraints, because reconciled values that fall below the minimum are not set to the minimum, but rather to zero. AVEVA Production Accounting does this because this approach is more likely to model reality. Normally, in processes, if the reconciled value is below the specified minimum flow rate, it means there was actually no flow, not some small amount of flow at the minimum value.