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The MV1 valve which is a red box in the back of HR3 will start blinking and close the main recovery path and then it forces helium gas through REG4 (making the horn sound). Closing this valve increases the pressure in the recovery manifold so that PC1 with a spike (usually just to 2 psi or so but less than 4 psi). Building pressure in this space pushes helium to the buffer tank through REG4 and REG3.
Recursive cycles in fault mode:
The Kaeser seems to have its own internal logic that is independent of the top QT ladder logic. The Kaeser run time is regulated by this internal logic under two modes Dual and Quadro. Quadro is the default mode (so anytime we lose power it will like come back in Quadro). The internal timing of these cycles is supposed to be settable in Quadro through the Kaeser interface but we could not find out how to do that. In Dual it's fixed. The HR3 part above the Kasser is also in 'idle' when not under load. It is in idle most of the time that we tried things no matter what the flow was.
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When we actually started trying to liquefy HR3 started running normally on its own. There may or may not be a correlation.