Dear forum members,
Please share if you had a similar experience with an FFAO block not accepting CAS mode.
We had an issue with one of the Flow loops where the PID drives the FF AO block (a fieldbus actuator from Rexa, XPAC Actuator). The FF AO block at the output of PID should be in CAS mode to work properly, however it is not accepting CAS mode and shows up OUT OF SERVICE MODE. This issue has begun after the potentiometer on this actuator has been replaced with a similar POT due to maintenance. This valve has a local control where we are able to stroke it properly from Rexa control unit. Also, we are able to stroke it with a hand help communicator locally. However, we are not able to control it from the DV. What could be the probable cause for this behaviour?
Any suggestions and discussion is greatly appreciated!
Thanks,
Have you checked the device status in explorer to see if they requested mode in inservice? you might also need to do the calibration on the new actuator as you said you changed it so that deltaV knows the characteristics of the new actuator (IE counts for the full travel ect.)
In reply to wpettit@fce.com:
Thank you wpettit,
Yes, we checked the device status, it was good. As a part of troubleshooting, we re-calibrated the pot too, but the actual mode is still in OOS. We asked instrument people to manually change the valve position in the field and we found that we are able to read the current valve position when we diagnose the valve tag with AMS through DV. It's just that the FFAO won't accept CAS mode (target mode) in Control Studio online.
In reply to PolarWind:
I have had a few instaces when the field bus cable was removed I had to decommision the device and then commision the device for it to start working again correctly. Before that I would suggest going to the controller card in explorer drill down to I/O ... associated H1 card ... port ... device click on the actuator and then in the right window right click on the transducer block and select status and look in the block error tab / alerts / mode / and other tabs and see if there are any errors that jump out at you and take you in a direction to finding the issue.
I had an issue like this. I solved it by setting the FFAO block's target mode to Auto in AMS. From DeltaV it was not possible.
In reply to István Orbán:
Thanks for the feedback. We decommissioned and re-commisioned the device back to the port, however we ended up with OOS mode only in the DV. I will look at other settings mentioned above once again.
@István Orbán, thanks for your comments. You are right, it worked with AMS. Still trying to understand how it works with AMS but not the DV. This FF AO block should be in CAS mode (Target) for the PID loop to work as the FFAO block receives CAS_IN from the upstream PID block.
When you mentioned that you were able to solve this situation, are you able to bring FFAO target mode to CAS finally in the DV? Appreciate your response.
Hi Polarwind,
had similar problems, just can´t rememeber how we solved it
Propably we did what @István Orbán said
Here is something from BOL:
"PID Block's Actual Mode is Stuck in IMAN When a PID block is the upstream block of a cascade pair, it will go to IMAN as its Actual mode when its downstream partner, (an AO block for example), is not in CASCADE preventing the PID from closing the cascade. Putting the AO block in CASCADE mode usually causes the PID to leave IMAN and return to its Target mode.
Note Some devices' AO block will not go into CASCADE mode if AUTO is not enabled in the Permitted mode. The Permitted mode can be changed only in Control Studio in edit mode.
Additionally, be sure that the PID's BKCAL_IN is connected to the downstream block's BKCAL_OUT. Failure to make this connection can result in the PID's Actual mode going to IMAN."
"Use Valid Channel AssignmentsFieldbus Input (AI) and Output (AO) function blocks must have a valid channel number for device signals. When you configure a fieldbus AIand AO block, you must set the channel parameter to a valid number or the blocks will remain in OOS mode. Refer to the device documentationand to the Valid Units and Channel Values for Fieldbus Devices topic."
Niklas Flykt
Klinkmann Oy
Key Account Manager safety products
nikfly@gmail.com
In reply to Niklas Flykt:
Make sure the mode of the Resource block is also Auto, if not the mode of function blocks will be OOS
It could be that this is done automatically by the EDDL wizard ("method") in used in device dashboards. Human centered design.
In reply to Jonas Berge:
Dear all, thanks everyone for the valuable comments. This issue appeared due to a faulty instrumentation in the valve. We were able to solve the issue when E&I changed the faulty fieldbus (electronics) component within the valve itself. Once the change is made, the PID loop went to AUTO and the FF AO block achieved CAS as its target mode without any modification needed from automation.
Rexa? Really? I like their hydraulic actuators but I don't see them having a registered product at fieldbus.org and I can't find any DD's on the DeltaV website either. How did you get this to work in the first place?
In reply to John Rezabek:
Dear John,
I am new to DeltaV and I could get more information from E&I. But a priliminary search in Fieldbus website fetches the details of Rexa XPAC actuators.
www.fieldbus.org/index.php
I see a link for downloading DD file too.
Okay, thanks it was under "Koso". I searched both for Rexa and nothing came up.
Thanks all for the comments!