Emerson Exchange 365

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Manual output selection for multiple PID blocks

I am working on an application where I have 2 PID outputs to a single control valve.  I'd like to manually select the PID block that will be in service and have the other PID block track.  I found this thread from 2014 that discusses some different ways to do this by building the logic manually.  I was just curious if any new solutions have been built into DeltaV V13.  It appears the CTSEL block still does not have the capability to manually select the output.  I have not found any other blocks that provide this capability so I'm assuming I just will need to build the custom logic but I thought I'd check to see if I'm missing something.

https://emersonexchange365.com/products/control-safety-systems/f/deltav-discussions-questions/4105/operator-input-to-control-selector-function-block

Asher Mertz

• 17 Oct 2019 1:21 PM
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5 Replies

• Matt Stoner

  

  • 17 Oct 2019 1:32 PM

  The new block is in v14 and called the Enhanced Control Selector (ECTLSL) and has this ability but yes you will still need to build the custom logic in v13.

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• Asher Mertz

  

  • 17 Oct 2019 2:43 PM

  In reply to Matt Stoner:

  ok, that is good to know. Thank you!

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• Jason.Brumfield

  

  • 6 Dec 2019 3:59 AM

  In reply to Matt Stoner:

  Can you utilize an input selector block with the PID outputs as the input and the out of the selector routed to the AO block?

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• Matt Stoner

  

  • 6 Dec 2019 4:46 PM

  In reply to Jason.Brumfield:

  The output value selection part would work but the back calculations that are needed to tell the supplying PIDs that the output value being sent is being selected, not selected or rejected is NOT supported by the block. So if you use that block you will have to generate these back calculation statuses with logic (which if you have to do that just might as well write all the selections logic) which is what a lot of people have done.
  
  The back calculations (value and status) are very important to prevent bumpless transfer and windup so this shouldn't be ignored or treated as trivial. That other call linked above I should a quick example and the logic to get this accomplished but mentioned the logic should using 208 instead of the pictured 204.

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• Jason.Brumfield

  

  • 7 Dec 2019 4:30 AM

  Matt, I have not had a need for this application previously, but it intrigued me.  I tried a couple of things and I came up with the below logic that appears to work to me with no custom bkcal programming needed and it allows bump less transfer.   These could be 2 separate modules, but I put the 2 PID blocks in one for simplicity of display.  I just utilized the Remote Output functionality for the PID that was tied to the actual AO.  When PID2 is in anything but Remote Out then PID1 is IMAN but tracking the AO so when it returns to control it is bump less. When PID2 is in Remote its output tracks the PID1 output so that it is bump less when it is returned to control as well. It seems to work as is overly simple so I am curious if I am missing something.  Thanks for stirring my curiosity.

  

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