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Running operations in parallel in a unit procedure

Hi,

Currently, I'm working in a plant that has configured the operations in a unit procedure (UP) in series, then if the UP goes to hold, on return from hold it uses a setup EM to put all the EMs on the unit back to the states they were in before going to hold.

I would rather have operations in parallel, and then when restarting from hold let each operation manage the restarting logic for their subordinate modules.

Is there a reason to run all the operations in series?

Any information would be much appreciated.

Colin 

Colin Horgan

• 9 Jun 2020 3:06 PM
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4 Replies

• vmvmhatre

  

  • 9 Jun 2020 5:10 PM

  In your current recipe which is Unit Procedure there are two operations in series ( I assume both operation contains separate phase class instance). So these two phases are loaded in series (First phase from first operation and and then second phase from second operation) on a single unit.
  Then you are mentioning second recipe structure of having two operations in parallel which is also valid recipe structure. but in this recipe, two operations (hence two phases on same unit) will be running in parallel.
  
  Can you provide more information how second approach will help in improving restart behavior ? are these both process phases ?

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• Colin Horgan

  

  • 9 Jun 2020 7:27 PM

  In reply to vmvmhatre:

  Thank you for your reply, much appreciated. Both operations contain a separate phase class. Currently, if a phase goes to hold on the unit, then it snapshots the last state of each EM on the unit and puts them back to that state on restart. The hold logic is common for all phase classes. I would rather have the phase just control it's subordinate EMs. For example, the Agi phase controls the Agi EM and the Temp phase controls the Temp EM etc. Then you could run agi phase in parrellel with temp phase.

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• Youssef.El-Bahtimy

  

  • 15 Jun 2020 3:44 PM

  In reply to Colin Horgan:

  The topic of EM ownership and operational serial/parallelism are unrelated. You need to update your phase logic to only acquire and reset the EM state of EMs that need to be acquired by the phase, not all EMs on the unit. Remember though, that a phase may have the specific focus of a particular activity, but it may need to acquire EMs cumulatively to support previous activities. For example, if you start temperature control, then move on to some monitoring phase, that monitoring phase will need to interact with the temp control EM potentially.
  If you need to run things in parallel, that's purely a feature of how your process needs to be designed for efficiency, etc., but segmenting the ownership of EMs by phase function is necessary in either serial or parallel setups.

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• Colin Horgan

  

  • 18 Jun 2020 10:20 AM

  In reply to Youssef.El-Bahtimy:

  Hi Youssef,
  
  Thank you for your reply, very much appreciated.
  
  The project I am working on currently runs all operations in series, however, it uses a Setup EM for when returning from hold to put all EMs back to the state they were in before the phase going to hold. In this way, the phase, i.e. monitoring phase commands the setup EM to setup when returning from hold, then the Setup EM drives all subordinate EMs such as temperature, pressure, and agitation back to the state they were in before going to hold. I don’t think this is the correct implementation. I prefer the way you have suggested where the phase cumulatively acquires EMs to support previous activities. Are there any references examples of unit procedures configured with series and parallel operations?

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