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Solution #1

Try not to let the Liqeufier (A) level go up to the upper limit where it will automatically switches to the IDLE mode.
On   we've noticed that this behavior (outlet flow jumps to 71.11slm), happens when the cold-head heaters are ON


Solution #2

  1. Restart the QT-PLC by following the steps on How to restart the QT PLC
  2. Switch LQ-A (only) to  the Run + Manual + Liqiefy mode.
  3. Switch LQ-B also to  the Run + Manual + Liqiefy mode while LQ-A also running.
    If the problem fixed, then do not need to proceed after this step. Ensure the system is in the Operational Configuration
  4. If the problem still exists, then switch both LQs to Run + Manual + Liqiefy mode.
  5. Switch LQ-B (only) to  the Run + Manual + Liqiefy mode.
  6. Switch LQ-A also to  the Run + Manual + Liqiefy mode while LQ-B also running.






On (starting around 8:30 am) for the first time, we noticed that both outler flows FCA and FCB showing 71.11 slm while both liquefiers are on "Liquefy" mode.


We followed the following steps to fix it.

  1. Unplug and plug the communication cables of both outlet flow controllers → Problem was not resolved by this step.
  2. Restarted the HMI screen (in the hall) following How to fix the QT-HMI if its screen got frozen → Problem was not resolved by this step.
  3. Restarted the QT PLC cabinet, following these steps on How to restart the QT PLC → The outlet flows FCA and FCB were still showing 71.11slm
  4. Switched both Liquefiers to the Run + Manual + Liqiefy mode and monitor the FMR
  5. Switched LQ-B (only) to run on Run + Manual + Liqiefy mode → changed the outlet flow to 2,5,10,20,30,40slm and noticed that it is working properly (also confirming the FMR value also consistently changing)→ Noticed that the LQ-B is working fine only when that LQ is running.
  6. Switched LQ-A also to  the Run + Manual + Liqiefy mode while LQ-B also running → Noticed that both FCA and FCB immediately started showing 71.11slm
  7. Stopped both LQs and Switched LQ-A (only) to  the Run + Manual + Liqiefy mode → Noticed that the outflow FCA was 2slm (as same as the set value).
  8. Switched LQ-B also to  the Run + Manual + Liqiefy mode while LQ-A also running → Noticed that the problem with FCA and FCB was fixed.
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