Add a logical model to summarize the balance models

Create a new model ("summary") to hold the objects that provide a logical view of this example plant, summarizing the most important values using logical streams.

Create the objects and streams shown above.

These summary objects are all considered to be logical objects, but only streams have an explicit setting that lets you define them as logical streams.

To define the streams as logical streams, check the Logical Flow checkbox in the Detail Info frame of the Information tab on the Stream window. Do this for all the streams in model "summary".

Because their properties are calculated using AVEVA Production Accounting equations, the logical objects are considered Smart Objects. The logical objects have both measured and reconciled values in their events, but those values will be derived entirely from properties of non-logical objects in the "test" and "new_test" models.

To cause AVEVA Production Accounting to populate the measured and reconciled event values, we supply an AVEVA Production Accounting equation as the Default Flow Rate in the Mass or Volume tab of the Design Info. tab. In your equation, you need to specify a reference to either the measured or the reconciled value of a physical object, because AVEVA Production Accounting contains special handling for logical objects that will infer the value to fill-in for the other type of value, as follows:

• If you reference a measured value, such as STREAM(FT001;MASSFLOWRATE), the events’ measured values are set to the physical stream’s measured values and the reconciled values are set to the physical stream’s reconciled values.

  physical measured à logical measured

  physical reconciled à logical reconciled

• If you reference a reconciled value, such as STREAM(FT001; RECMASSFLOWRATE), both the events’ measured values and reconciled values are set to the physical stream’s reconciled values, with the effect that both are equal.

  physical measured à ignored

  physical reconciled à logical measured

  physical reconciled à logical reconciled

The reason that we are able to put equation in the static design info is because the equation itself will never change. However, the numeric result extracted by the equation will differ from period to period, so the results in the events for a given period will always reflect the results in the events of the associated non-logical objects.

Use the equations provided in Table to configure default flows for your logical streams.

Some of the equations are specified as being one value OR another because the desired value can be calculated from two redundant sources of the same component data. You should only enter one or the other. Since the component stream was reconciled using Smart Constraints, we can be sure that the values taken from different parts of the physical model are equal.

When this has been done, you will see the measured and reconciled values of the logical streams are calculated based on the last reconciliation of the physical models.

Add a LOSS logical stream to calculate the loss of the node called summary_node.

The equation of "LOSS" logical stream:

NODE(summary_node;MASSFLOWRATE)-NODE(summary_node;MASSRUNRATE)

You can see that the reconciled value of the LOSS logical stream is exactly the same as the reconciled value of the LOSS_PROCESS stream on balance model "test".

You can also use the following bias values of the other streams in the equation of logical stream.

• BiasMassFlowrate

• BiasMassVolume

• BiasVolFlowrate

• BiasVolVolume

• GasBiasVolVolume

For example, 01FC034 balance stream has 1.2 bias factor.

The measured mass quantity is 3,801.806 ton and bias mass quantity is 4,562.167 ton.

The reconciled mass quantity is 4,674.797 ton.

V_DIESEL_SHIPMENT logical stream has the mass equation of STREAM(01FC034;MASSFLOWRATE).

The measured mass quantity of the logical stream is 3801.806 ton and the reconciled mass quantity is 4,674.797 ton.

If you change the mass equation of STREAM(01FC034;MASSFLOWRATE) into STREAM(01FC034;BIASMASSFLOWRATE), the measured mass quantity of the logical stream is changed into 4,562.167 ton as bias mass quantity.

The bias properties (BiasMassFlowrate, BiasMassVolume, BiasVolFlowrate, BiasVolVolume and GasBiasVolVolume) are very useful by calculating the measured value used in data reconciliation.

If the bias factor is used, it is the bias value. If the bias factor is not used but compensation is used, it is the compensated value. If both bias factor and compensation are not used, it is the measured value.