Project: Biopharmaceutical filtration automation, August 30, 2005

By Control Engineering Staff August 31, 2005

August 30, 2005

No HMI hardware has arrived this week either, so development of the user interface must remain on hold.

However, work continues on equipment module design in parallel with equipment module development. We expect to complete the first pass design on all equipment modules by next week. The design will then be given to the customer for review. It is normal for the customer to request a few changes with their review, but we expect these changes to be functionally minimal. Again, we have been developing equipment module code without an approved design document to stay aligned with the project schedule.

Speaking of schedule, we have received a modification to the project schedule. Originally, we planned to complete our software by the end of September for factory acceptance testing (FAT) at the skid vendor’s site in mid-October. The newly scheduled FAT date is in mid-December. However, we plan to keep our schedule unchanged. We don’t expect to need the extra time for developing the application software.

There have also been recent developments around the design for equipment status software. Biotech applications require exacting standards for cleanliness. Equipment internals must be cleaned and sterilized after each batch. A new batch cannot be started unless there is a high degree of confidence that the process is free of foreign material and microorganisms. Equipment that is cleaned is often marked “CLEAN” with a physical sign hung prominently for all to see. Manufacturing instructions often instruct the operator to verify a piece of equipment is marked CLEAN or STERILE or some other such status before proceeding with the instructions. If not properly marked, an operator will clean or steam the equipment before further processing.

Many in the industry now look to the automation system to track the processing status for a piece of equipment and to provide automatic time-based expiration of various states. This functionality has been added to the project scope. We implement this functionality through a control module called a unit status controller (USC) that provides a logical status for any piece of equipment that may have a unique and independent status. The end user has defined status for 4 distinct states:

  • In Use—after start of a production recipe until recipe is finished;

  • Post Use—after a production recipe has finished until cleaning recipes have finished successfully;

  • Post CIP Hold—after CIP or SIP recipe is finished successfully or until a timer expires. Upon timer expiration, the status is switched back to Post Use; and

  • Post SIP Hold—after SIP recipe is finished successfully and the previous status was Post CIP Hold. This status also has a timer that, when expired, automatically drops the status back to Post CIP Hold unless that timer has expired and the status is then dropped to Post Use.

This is a simplified version of the state logic, but it explains the primary functionality. The code will be developed as a state machine within the control module. States may be set by sequences—equipment modules or recipes—or by an operator from the HMI with sufficient security access. Expiration timers and the transition logic will be contained within the USC control module logic.

Until the HMI hardware arrives, we’ll continue to work on equipment modules and develop a first draft of the equipment module design document for submittal to the client.