Emerson Exchange 365

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Nuisance modbad alarm chatter

How to prevent Modbad alarm chatter. What is the correct approach to relieve the board operator of multiple instrument failure alarms that flood in from a single instrument at its threshold limits?  Currently the board operator does not have Suppression capability, but that is now under discussion, is suppression the only way to handle this nuisance flood of alarms for a single instrument?  Currently  we are on Ver12 DeltaV and the board operator does not have alarm bypass or the ability to sim IO.

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• 18 Aug 2017 3:17 PM
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3 Replies

• Milton Pollard

  

  • 18 Aug 2017 3:42 PM

  It looks like some sort of dynamic alarming is required in this situation. Please refer to the following whitepaper: www2.emersonprocess.com/.../DV_WP_Advanced_Alarming_Modules.pdf

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• Petrisky

  

  • 18 Aug 2017 4:53 PM

  can you increase alarm hysteresis?

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• Matt Stoner

  

  • 18 Aug 2017 5:36 PM

  Daryl,
  
  You could add a condition block in the module(s) with the condition expression being "'^/BAD_ACTIVE.CV' = TRUE", time duration of 5 secs (or some time you find appropriate) and then modify the MODULE_ALM to point at the OUT_D of the new condition block instead of the BAD_ACTIVE (I think that is what you have).
  
  This would help remove the nuicences that are spikes but if it the module(s) are alarming and staying there for some time, you will need to address those with some sort of dynamic alarming that Milton suggests or another method like State alarming depending on the state of your process.

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