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Intrepretation of a brand new butterfly valve signature from Valvelink

Dear All

We have a brand new butterfly valve with fisher DVC6200 PD positioner. Attached is the signature we have taken from Valvelink for this valve assembly. Can you please help me interpret it as it does not look normal.

Secondly, the blue line represents the signal from close to open or open to close?

Regards

• AMS
• ValveLink
• signature
• DVC6200

Shaiq Bashir

• 4 Sep 2024 4:12 PM
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1 Reply

• Ron Hager

  

  • 11 Sep 2024 2:46 PM

  It looks like tuning rather than mechanical. I can’t see much because the graph shown is limited in any detail but look at the increasing stroke (Blue line) and see all the hash from seat to stop. Now look at the return line (red), no hash and looks to be pretty smooth if it was mechanical we would see hashing on both the increase and decreasing stroke. Since this only appears on the increase I’d say your proportional gain is a bit too hot.
  
  Dynamic Error Band looks normal as pie and so does the drive signal but I see drive signal above the 80% threshold, I suspect it’s calibration may be a little on the high gain side too. Combine both high gains, I/P and tuning and you get a jumpy device just as you see.
  
  I can see this is a rotary valve but what I can’t see is…
  
  Actuator type – this appears far from linear it looks like a flat sheet diaphragm actuator, a 2052 or something else?
  Actuator size – How big is this actuator
  Pressure targets – what’s supply pressure
  Tuning – letter tuning set or expert tuned?
  Diagnostic setup – no notes or details about the valve structure
  Packing – high load packing or is this just TFE single, no data to reference
  Expected friction – what’s the expected breakout and running torque for this assembly?
  
  Do you have the export file for this diagnostic? I might be able to really pin something down if I had more data and would able to manipulate the graphs. Try reeling in the tuning to something a bit slower and see if that calms the hashing down

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