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alarm deactivate or suppress

Hello everyone,

I have searched a bit about Alarms in DeltaV and suppressing or deactivating them. So in my project, we have some Mobile Units and when we unplug them from the network (or power) we want with a checkbox (in Graphic) to deactivate or suppress the alarms. From what I tested, with suppress the alarms dont show in the Alarms List (but in Suppressed alarm list). 

They are shown though in the Process History. 

So what is better to do, suppress (Opsup) or deactivate and what is the main difference between those two? Also, is it possible that those alarms dont show in the Process History? The reason is that unplugging is a scheduled action and  we dont want to have all those alarms shown in Alarms List and Process History. 

Thanks for your help in advance. 

Loukas Kominis

• 18 Jul 2019 1:05 PM
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2 Replies

• Steve Linehan

  

  • 18 Jul 2019 1:21 PM

  Loukas
  We had a similar challenge on a project a while ago. What we ended up with was blanking plugs that were attached to the cap that the mobile unit was plugged into. We used resistors in the analog circuits and did not need anything for the digitals as they were dry contact, no DO's. If you are using Namur you will need resistors on these also. We also allocated two DI's per plug socket. One had a shunt in the end cap. The other had a shunt in the mobile unit. In that way, we could tell if a blanking plug or a real mobile unit was attached to the plug. Same idea as yours we enabled alarms after the real unit was attached via the graphic and disabled also via the graphic. We had a timer to alarm if the wrong selection was enabled based on actual field conditions.
  The advantage of this was that the channels allocated to the other field plug were not constantly showing up as bad integrity.
  To answer your specific question either is fine. In my opinion, the OPSUP would be better here as the operator is choosing to suppress these alarms.

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• Matt Stoner

  

  • 18 Jul 2019 2:20 PM

  The issue is this is probably a "normal" activity since they are mobile so if you have at least DeltaV v13 you should use the OOS and leave the "Suppression" (OPSUP) only for the operators and abnormal suppressions. There are some alarm management modules that may help you do this with logic and info can be found here: www.emerson.com/.../deltav-ve2136 and go under the Training and Demonstrations (Specifically the Alarm Flood Module that is described in the White Paper in the zip file).
  
  Another method is to make all the alarms conditional so it has to be in the proper "State" to alarm so you just change the state to be something like Connected or Not Connected and the alarms only work if Connected. You could/should also set the Suppress Reason so it is very apparent why the alarm(s) are Suppressed (i.e. Suppressed as Not Connected Unit, Suppressed by Logic for Not Connected Unit, etc)
  
  If you use the Enable/Disable of the Alarm this will work but just be aware that some tools in the product will no longer "help". For example you can view a Difference Report for the alarms where it will tell you where current alarms are different than the configuration but I wouldn't think this would be good if you are manually setting the Enable/Disable. I would discourage using this method as it is hard to find where these are and know if it is in the correct state or not.

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