Foxboro DCS Control Strategy – Alarm Considerations

The manner in which the AVEVA Batch Management System implements alarming provides several alternatives as to how you can implement an Foxboro DCS Control Strategy. The following is an overview of these designs.

• One equipment entity (unit, connection or segment) is represented by one compound.

  In this case, each equipment entity (unit, connection or segment) has a corresponding compound in the Foxboro DCS Control Processor.

  Solution: Use either the LOOPID parameter or the equipment allocation approach.

• One equipment entity is represented by multiple compounds.

  • Exclusive Use

    In this case, there is more than one compound used to control the equipment entity. There is typically one lead compound with the same name as the equipment entity and other exclusive use compounds whose logic is used by the lead compound as required. In this situation, the exclusive use compounds can only be used by one and only one lead compound. Alarms generated in the exclusive use compound should be associated with the batch that has allocated the equipment entity that is associated with the lead compound.

    Example: A filter can be used by either Reactor_A or Reactor_B, but only one reactor at a time can use the filter. When the filter is being used with Reactor_A, filter alarms must be logged to the batch that has allocated Reactor_A. If the filter is being used with Reactor_B, then the alarms must be logged to the batch that has allocated Reactor_B.

    Solution: The LOOPID approach must be used. When Reactor_A is allocated the Batch ID is written to the LOOPID of the Reactor_A lead compound by AVEVA Batch Management with Foxboro DCS components. When the filter is used, the Batch ID should be written to the LOOPID of the compound, so if alarm occur in the filter the correct Batch ID is used.

  • Shared Use

    In this case, there is more than one compound used to control the equipment entity. There is typically a lead compound with the same name as the equipment entity and other compounds whose logic is used by the lead compound as required. In this situation, the shared compound can be used by more than one lead compound simultaneously. Alarms generated in any of the blocks within this shared compound should be associated to both batches if both lead compounds are using the shared compound.

    Example: An example of this is a heat exchanger that can be used by more than one reactor simultaneously. When the heat exchanger is being used by Reactor_A and Reactor_B, heat exchanger alarms should be logged to the batch that allocated Reactor_A and to the batch that allocated Reactor_B.

    Solution: AVEVA Batch Management with Foxboro DCS components does not support this situation. Batch alarms can only be associated to one equipment entity; but, not to multiple equipment entities.

  • One to One Usage

    In this case, there is more than one compound used to control an equipment entity. There is typically a lead compound with the same name as the equipment entity and other dedicated compounds whose logic is used by the lead compound as required. In this situation, the dedicated compounds are always used by the same lead compound and are never shared. Alarms generated in any of the dedicated compounds should be associated to the batch that has allocated the lead compound.

    Example: A Filter is used by only by Reactor_A. When the filter is being used with Reactor_A, filter alarms should be logged to the batch that has allocated Reactor_A.

    Solution: Either the LOOPID or the equipment allocation approach can be used. If the equipment allocation approach is used, then at least one equipment entity tag (Reactor_A) must be linked to an Foxboro DCS filter tag (Compound:Block.Parameter).

• Multiple equipment entities represented by one compound

  This approach is desirable if there are many connections or segments in a system and Compound are limited. In this situation, one Compound has many Blocks each representing a Connection or a Segment. Alarms generated in any of the Blocks should be associated with the Batch that has allocated the Connection or the Segment.

  Example: A manifold has many connections and many segments. A compound is dedicated to the manifold and each connection and segment has an associated block. Any block alarms should be associated with the batch that has allocated its associated connection or segment.

  Solution: Either the LOOPID or the equipment allocation approach can be used.