When defining batch processes, it is best to apply a top-down/bottom-up design approach. Begin at the top of the physical model and work downward, defining boundaries (process cells, units, etc.) and the specific equipment within each boundary (vessels, pumps, headers, valves, etc.). Once physical entities are identified, work upward from the bottom of the procedural model to define the actions that each piece of equipment and unit will perform.This model supports an iterative design process that helps identify reusable objects. The benefit becomes apparent when a process is undergoing initial designs, perhaps for budgeting purposes. Usually at this point, Piping and Instrumentation Diagrams (P&IDs) are not available and preliminary designs are based on Process Flow Diagrams (PFDs). Because equipment specifics are still undefined, automation designs are developed at a high level.Later, when P&IDs become available, the S88 model and its support for top-down/bottom-up designing makes expanding the details of the preliminary design easier. Additionally, the iterative design approach is well suited for achieving the true objective of object-oriented programming techniquesidentifying reusable software objects.The CIP process from concept to practiceFor many of us, a top-down/bottom-up iterative design approach, identifying class-based entities, and developing reusable objects, makes a lot of sense. But it is harder to understand what this approach looks like, and it is helpful to have a practical example.Clean-In-Place, or CIP, is a process frequently used in pharmaceutical and biotech manufacturing facilities to ensure that process lines, vessels and reactors are free of inorganic and organic contaminants. At the laboratory scale, equipment can be cleaned manually, but in large-scale production processes it is impractical to disassemble equipment and transfer lines to clean individual components. Instead, this must be done by sending cleaning solution through the process path, or CIP circuit, without disassembly. This introduces unique design challenges.Within flexible manufacturing facilities, other factors complicate CIP. Because process connections frequently change, it is necessary to identify, track and clean the multitude of possible product transfer paths from upstream to downstream vessels, and to supply CIP solution from a few shared CIP sources to a number of process units distributed throughout the facility.Even with preconfigured modules and efficiency tools, automating CIP activities and finding a solution that is easy to use, validate and maintain remains a challenge. Defining the boundaries and responsibilities of the various elements is a key step. There are several suggestions to keep in mind when defining boundaries:
- Seek identical or very similar entities
- Identify unique and one-of-a-kind entities
- Select several smaller objects, which provide more flexibility than a few large objects, and are easier to develop, validate and maintain.
- Think beyond each VMs physical boundary
- Consider requirements one at a time
- Apply an iterative design process.
SAMPLE EQUIPMENT STATES Dirty Default/initial state. Completion of CIP will automatically transfer the state to Clean. Clean Indicates CIP is complete. May start the clean timer. If the clean timer expires, the state changes to Clean Expired. Clean Expired Indicates clean timer is expired. CIP must be repeated to return the state to Clean. In-Use Indicates that a batch has started. If a Phase Hold occurs, the state transitions to In-Use Hold. Upon batch completion, the state transitions to Ready for Transfer. |
- Inlet headers (sources) are to be tracked by upstream (provider) equipment
- Destinations are to be tracked by downstream (receiver) equipment
- CIP VMs will track everything in between the source and destination.