Emerson Exchange 365

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CONTROLLER OR BAY SUPPLY OR PID LOOP ISSUE

Hi My Name is Sami  ...within the span of 22 days we observed same issue that all pid loops relates to pressure and flow goes open wrt there acting where as temperature and level dont show a change due to slow response

We have two controllers

Controller 2 ( load percentage 14) related cards AO are working fi9 and found no  change

Controller 1 (load percentage (23%) related cards AO are problamatic but dere is no system issue as per the events ( Manually done the cards redundancy check and controller redundancy check and all are working fi9)

(Issue time span is to0 small (10-20 seconds) that when reach to field everything get normal and only trend help to identify loops )

Remedies which i have done

Unresolved issues resolved ( alarms which were not  configured)

power supply check ( and its redundancy) = All Ok

bay supply voltage check

If same thing occur again then what next i have to do ....Problem is critical for our plant as it may create column pressure xv pop up  yet i m observing it on regular basis

Sami Uddin

• 12 Oct 2015 6:55 AM
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14 Replies

• Maarten van der Waal

  

  • 12 Oct 2015 7:55 AM

  2 possible causes I can think of:
  1. Software revision of controller or IO cards may not be up to date (requires partial shutdown of related equipment to update unless you have redundant cards)
  2. AMS is doing a too long stroke in valve testing.

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• DBacker

  

  • 12 Oct 2015 11:59 AM

  In reply to Maarten van der Waal:

  Have you trended SP, PV and OUTPUT? Is the output at the card not matching the output shown on the trends/faceplate? I'd apprecaite your patience, I'm having trouble understanding your issue.

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• Sami Uddin

  

  • 13 Oct 2015 4:23 AM

  In reply to Maarten van der Waal:

  Thank You Mr Maarten van der Waal for suggestions ...we have redundant cards and we dont have AMS license it was one year license and its been 6 years.. version of delta v is Version 7...

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• Sami Uddin

  

  • 13 Oct 2015 4:30 AM

  In reply to DBacker:

  Mr DBacker thank you for the reply...yes i have trended  it is matching for instance if it is vaccum loop the sudden problem which occur made that controller to Failed to Open PV showing the vaccum going towards coarse yet sp remains the same ..dese type of acivity happened in pressured and flow looops as both loops have fast response  nd did not find any change in level and temperature loops...from my end i have checked ( written in question) nd yet observing on daily basis...all in all ... all control valves acted as failure and AO have redundancy as well ...

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• Sami Uddin

  

  • 13 Oct 2015 6:17 AM

  In reply to DBacker:

  Mr DBacker SP.PV.AND OUTPUT r matching.. card value with trend but in field output is failure ....PCV loop detected PV increasing it tries to adjust out put wrt setpoint here the question is how PV increases answer is in field Control valve was closed as it is failed to open nd thus the pressure starts to increase but when we see trend output reacts accordingly wrt to pv to adjust it ...nd dis happen in all AO cards of One controller ...in field we checked the air pressure and everything related to it ...we found everything ok...on the other hand it mite be AI card which is creating confusion so m checking AI as well but wat i get till now is all loops related to pressure nd flow reacted very fast while loops related to level and temperature did not reacted ....
  Cards verified different control valves are in different card ..diff instrument values are in diff ai cards....

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• James Beall

  

  • 13 Oct 2015 3:11 PM

  In reply to Sami Uddin :

  Sami,
  If the PID's actual mode goes to Manual during the problem, it is likely an input (AI) problem. If it is a problem on yh

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• James Beall

  

  • 13 Oct 2015 3:16 PM

  In reply to James Beall:

  Sami,
  If the PID's actual mode goes to Manual during the problem, it is likely an input (AI) problem. If the it goes to IMAN, it is a problem relared to the PID output circuit (AO). If it is the AO circuit, is the HART enabled on the AO? If HART is enabled but there is a loss of HART communication, the AO won't operate with the default settings. Let me know what you find out.
  James

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• Sami Uddin

  

  • 17 Oct 2015 6:48 AM

  In reply to James Beall:

  Mr James thank you for the response ....we dont have AMS ....HART is enables but how one can check the loss of Hart Communication??...Is dere a possibility of voltage drop are something related to voltage as Everything related to dcs logic end and software end seems fi9 ...in field control valve goes to its failure position and no one has seen it we are concluding it over AI value and pid responded wrt AI value but why AI value changes when everything was normal (trends and events history showing that everything was normal and suddenly value increases but control valve was it position and when it increases value pid responded according to that )we assuming it as failure from field just trying to figure it out whether that field failure related to dcs or not something with voltage

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• Tinh Phan

  

  • 18 Oct 2015 12:19 AM

  In reply to Sami Uddin :

  I have several questions. Since you indicate that you have enable HART, what are you monitoring? Are you using Field_val_pct for control in your AI fb that is connected to your PID? I am just guesting that you may have map your AI fb to a HART digital value that is not what you were expecting. This maybe the reason why you values changing unexpectedly. What is your DeltaV version and the HART device you working with?

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• Sami Uddin

  

  • 19 Oct 2015 7:08 AM

  In reply to Tinh Phan:

  Thank you Mr Tinh Phan for answering and helping ...Delta V version is 7.4 Build 4393...Card class is AI = 8 CHANNEL , 4-20mA , HART , AO=8 CHANNEL , 4-20mA , HART and for both AI and AO i have a description Basic functionality + Redundacy...
  I dont know anything about hart in dcs as far as i m in knowledge that Hart is not used YET help me how to find it so that i can tell you in more detail
  PID BLOCK IO_IN is selected as Field_val_pct

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• Sergio Martins

  

  • 19 Oct 2015 11:11 AM

  Sami I suggest you to delete the PID and AO blocks save and download the module then copy the PID and AO block from another module at where is working ok. Configure de blocks save and download.
  I have found corrupted AO block and this corrected the problem.

  Sergio Martins

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• Ben Bishop

  

  • 20 Oct 2015 7:03 PM

  If HART is enabled on the channels, then a HART error may cause the status of the process variable to change. For an AI HART channel associated with a PID function block, a bad status of the AI will cause the PID to shed its mode to MAN, resulting in open loop control. You don't need to have AMS Device Manager licensed to use HART information in DeltaV. Search BOL for "HART_ERRORS". You may want to have your control logic ignore certain HART errors when calculating the status of the channel. A loss of HART communications is one possibility, often the result of power and grounding issues. Other HART errors might include a PV temporarily outside of the configured limits or a saturated PV. These might not warrant a change in status, you can choose to ignore certain errrors using the HART_ERRORS bitstring options.

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• Sami Uddin

  

  • 21 Oct 2015 7:58 AM

  In reply to Ben Bishop:

  Thank You Mr Ben Bishop ...after detail observations and checks...i found out that non of my AI'S and AO'S are HART enable....HART IS DISABLED IN AO AND AI.....
  checked channel configurations individually i found out that AI are ANALOG INPUT CHANNEL selected and for AO its Disable HART Analog output channel ....
  
  Thank You Mr Sergio ....is dere any way to check corrupted AO Block..??? i have changed 2 loops and implemented it from library and another is copy paste ..if again it happens ill check through trends...but for my knowledge need to know to check corrupted block ..
  
  Important thing is it is happening after 8 years ...in 2007 system was implemented and now this unknown issue certainly appear last month September 2015 and 2nd time with span of 22 days dis month 6th Oct 2015...and i got a chance to work with this system last year ...No modification done ...in my 1 year yet Modification planned from 2016 jan as our plant will be in revamping phase .

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• Sami Uddin

  

  • 5 Apr 2018 6:42 PM

  the issue was of process cooling water temperatures which causes the interlocking to be active due to which these main valves went to there failure issues...after studying trends with different loops whole month finally i was able to intimate the process about the situation and after till date there was no issue

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