Project: Biopharmaceutical filtration automation - October 4th
October 4, 2005
The UF (ultrafiltration) skid instrumentation includes flow meters that transmit a pulse signal where each pulse corresponds to a volume of liquid that has passed through the measuring element. We had previously assumed that these signals would not be used by the application, as we have never used this type of signal in biotech applications. That was a bad assumption.
The customer is requesting a totalizer control module that counts pulses. We already have a totalizer module that integrates a rate signal over time. We developed the new totalizer over the past week. It was not a significant effort since much of the existing totalizer code was reused. Also, because our control modules are largely a collection of reusable subroutines, new modules can be quickly created as long as the functionality can be achieved with existing subroutines. The USC module explained in last week's post was one that required new functionality. We are code complete with the new USC and doing some internal testing. We'll test it more extensively when we finally get the HMI set up and we can start running equipment modules from a user interface.
Speaking of the HMI– we finally have all the hardware for the entire HMI system. The SCADA server has also just arrived (maybe a small celebration is in order). Our developers are deep into UF equipment module development, so HMI setup will wait until they are code complete. The UF equipment modules are currently 30% code complete and should be 100% in two more weeks.
We have not received customer approval of the MF (microfiltration) design– something that makes us increasingly uncomfortable over time. We have incorporated the few comments previously received. I suspect we simply need to remind the customer and the approval will be received shortly thereafter.
The UF design was submitted two weeks ago– something I neglected to mention when it happened. We have, as yet, received no comments on this design. The comments on the MF skid design were few and we expect even fewer for the UF design because they are so similar. We are pushing to get comments or approval of the UF design within two weeks to keep the project moving forward.
The design of cross PLC communications was modified this past week. Originally, the system design included a ControlNet network specifically for PLC-to-PLC communications. The information passed between controllers includes signals for module interlocks, sequence permissives, and handshaking between units when material is passed from one unit to another. Because of the obvious safety issues involved with this type of communication, ControlNet was selected over Ethernet because of the deterministic nature of ControlNet communications. However, the customer has notified us that the ControlNet network will be replaced by a dedicated Ethernet network due to system design and installation constraints outside of our control.
In addition to normal project updates, I'll provide a few more details of the nature of a deterministic scan, how this differs in control systems, and how it can be achieved through application implementation if not provided by the system vendor.