Build formulas with smart constraints

The formulas in smart constraints are similar to those used in formulas with Smart objects.

Smart constraints take as their input values based on the reconciled values of stream objects. Typically, those reconciled values are actually calculated results from smart objects (used to provide stream component values).

If the stream from which input is obtained is a logical stream, rather than a balance stream, the reconciled value of the stream object in the smart constraint is a calculated value since the logical stream is not involved in data reconciliation.

The values used as smart constraint inputs that come from other object types, such as process, node and tank, are calculated values even though their properties are considered reconciled values.

The classic use of smart constraints is to enforce a component balance.

If you are enforcing a mass component balance, your smart constraint should take, as input, the reconciled mass flow rate or quantity properties from the input streams, such as RecMassFlowrate or RecMassVolume. Note that if you are performing a mass balance, the mass properties are directly reconciled by AVEVA Production Accounting, while the equivalent volume values (RecVolFlowrate and RecVolVolume) are actually calculated values.

If, on the other hand, you are enforcing a volume component balance, then naturally you will take as input the RecVolFlowrate or RecVolVolume values, rather than the calculated mass values.

Whenever one or more of a stream’s properties have been used as input variables in the formula(s) of one or more smart constraints, that stream will be reconciled according to the smart constraint(s) as well as according to the overall material balance constraints. The designation of the solvability of such a stream is differentiated from the solvability of streams that are not used by smart constraints as described in topic Flow solvability.

Note that when the amount of flow on a given stream is fixed for some reason (for example, zero tolerance, out of service, non-measured flow that is provided as an estimated raw value), the solvability designation of that flow cannot be changed by including it in a smart constraint.