Emerson Exchange 365

Advice for Isolation of AI and AO channels

Hi, looking for deltav users advice and experience when it comes to having to isolate a field device connected to either an AI or AO.

We've just had a scenario where an old m-series 1 AO card had its field device isolated for a few months. the isolation was made on the hazardous side of the field barrier so the deltav channel was still connected to the field barrier. during this time the AO channel has constantly been switching between open circuit and healthy, resulting in over 1 million alarms in the past 30 days. as our hardware alarms are low priority, this wasn't annunciated on the operator workstations as per deltav standard configuration and has gone unnoticed until we observed our alarm KPIs for area A.

When other users of DeltaV I/O have to isolated field devices, what do you do?

Do you disable the I/O channel? Fit end of line resistors? Take alarms out of service?

Any advice would be much appreciated

Stuart Jolley

• 26 Nov 2020 7:41 PM
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2 Replies

• LaurentB

  

  • 26 Nov 2020 7:56 PM

  Hi, I also had same experience. Open loop is re annunciated at each scan time. It’s looks like a bug because alarm should appear only one time... Global Service Center didn’t get us a clear answer.
  As workaround you can disable IO or close the loop with a resistor.

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• Stuart Jolley

  

  • 26 Nov 2020 8:39 PM

  In reply to LaurentB:

  Thanks for the reply. When we open circuited the loop between the deltav card and the field barrier, the open circuit status remain active and the re-annunciation stopped. it was only when the deltav channel was connected to the barrier that the open circuit kept re-annunciating. almost feels like the type of barrier isn't compatible with deltav

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