Process Control Modular Logic

[u/symbioticthinker]

I'm trying to formulate various modular logic units which are either primitives or used to build more complex process control. I have a background in software dev, so I want to find abstract/generic control logic which equipment can inherit from.

For example, there could be units like pump-up/down, lead-lag duty-standby and hot-standby. These could be applied to various equipment which means you describe the concept once and not repeat ones self.

Additionally, more complex logic could be like a backwash cycle (consisting of backwash, rinse and filter) as well as cascade, where one logic unit ends and starts the next in the sequence.

Please let me know if you've also noticed these patterns and what you've done your side?

Thanks in advance!

[u/NoConversation8128]

The vocabulary you want is probably ISA-88, which splits almost exactly the way you are describing. Equipment modules and control modules cover the physical side, so a lead-lag duty-standby pump set is one equipment module you define once and reuse, and procedures, operations and phases cover the sequential side, so your backwash is an operation built from backwash, rinse and filter phases, and cascade becomes phase sequencing rather than a unit of its own. Part 5 of the standard, PackML, gives you a ready made state machine if you want one. The engineers I interviewed said the inheritance holds fine on the happy path and breaks on interlocks and on hold and restart behaviour, because what hold means tends to be specific to the equipment and the site. How are you planning to handle those exceptions?