If required, set constraints on properties

You can configure individual constraints governing the behaviour of property profiles in the Constraints page.

Two types of constraints on properties are supported in Assay:

• Global Constraints. Global constraints govern the default behaviour of properties throughout Assay in the absence of any other property constraining information. Global constraints on properties may be set up and managed on a property by property basis using the Property Manager. See Configure your properties.

• Local constraints. Local constraints govern the behaviour of properties within a particular crude assay. They override any corresponding global constraints that would otherwise be applied to the property. However, they apply only to the individual assays in which they reside. Thus, for example, a local constraint specifying a monotonically increasing sulphur profile for a crude will not affect the behaviour of the sulphur profiles of other crudes in the database, although any global constraints on the sulphur profile will. Local constraints provide you with significant additional flexibility and control over property profiles and distributions that would otherwise not be available.

Local constraints are embedded in the crude assay being worked up, so that they may be remembered within generated crudes, even after they have been saved to the database. However, they are created and managed at the point at which an assay is being worked up within a Generation module.

Tip: You can also activate a number of predefined constraints on multiple properties by selecting the corresponding check boxes in the Multiple Property Constraints pane at the bottom of the page.

The behaviour of local and global constraints when creating a new crude description from within a Generation module is determined as follows:

• When beginning a new generation from scratch, the default property constraints are applied. In this case the local constraints and global constraints for the properties of the crude will be the same.

• When copying or importing a crude to a Generation module, constraints are copied across with the crude if these are present in the crude assay. In this case, for these properties, the local constraints may differ from the global constraints.

• When copying or importing a crude to a Generation module, default property constraints associated with the Property Manager are applied provided no constraints are present in the crude assay. In this case the local and global constraints for the properties of the crude will be the same.

  Note: In addition to constraints, you can also use guide points to have control over individual properties.

  

  To add a constraint for a property, select the property from the Properties pane on the left hand side of the constraints page. Click the Add button to open the Constraint Editor dialog.

  In the constraint dialog, select an effective boiling point range and temperature scale for the constraint. Then select an appropriate type of constraint:

• Value between: Enter maximum and minimum values to ensure the value for the property remains between the selected range. You can set the units for this range from the associated drop down list.

• Value fixed at: Enter a value to ensure a fixed value for the property. You can set the units for the fixed value from the associated drop down list.

• Monotonically: Select increasing or decreasing to ensure the value for the property never decreases or increases, respectively.

To add the new constraint, click OK. The new constraint is added to the list of constraints for the property given in the Constraints pane.

To cancel adding the constraint, click Cancel. You are returned to the Constraints information page proper.

To edit a constraint, either double click on it in the Constraints pane, or select it and click the Edit button at the bottom of the pane. This opens the Constraint Editor dialog box.

To remove a constraint for a property, select it in the Constraints pane and click the Remove button at the bottom of the pane.

Once constraints on a property have been configured, they will be applied in all subsequent operations involving the fitting of profiles for that property in the current assay.