Specification Tolerance

This window is used to select the tolerance basis and value for a Generalized Specification in various unit operations.

Default Tolerance

PRO/II defaults the specification tolerance to the bases and values selected in the Default Unit Specification Tolerances window, which can be accessed through the Input / Flowsheet Tolerances menu item.

Relative Tolerance

The formula used to calculate the relative tolerance is :

| P calculated - P specified ) / P specified | , where P is the parameter.

The calculations to meet the required specification value proceed until the tolerance calculated using the above formula is less than or equal to the given tolerance value. Note that the tolerance value should always lie between 0 and 1.

Absolute Tolerance

The formula used to calculate the absolute tolerance is :

| P calculated - P specified | , where P is the parameter.

The calculations to meet the required specification value proceed until the absolute difference between the specified and calculated values become less that or equal to the given tolerance value.