[Hallb-engineering] [New Logentry] Hall B Cryo event

[gopinath at jlab.org]

Logentry Text:
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Hall B buffer Dewar saw a pressure spike of 0.12 atm at 9:21 am which the system recovered from in the next 10 mins without any issues.

Investigation began in to finding the reason for this spike through the afternoon. Cryo (Brendan) was contacted to see if they had seen any anomalies on the ESR side - none was reported. He mentioned changes in the Torus LHe reservoir level leading up to the pressure spike. 

Upon further investigation under Dave Kashy's guidance, we found that the LHE level (LL8120SC) in the Torus dewar dropped below the setpoint around 9:12 am (87%), causing the valve (EV8115JT) to open and increase level to 94% by 9:20 am. At this point the valve throttled the flow which saw a rapid drop in the 4.5K flow (CFI6711B) to the hall from 7.52 g/s to 5.16 g/s in 50 seconds. This caused the pressure (PT8512) to build up 4.5K supply line to Hall B and also was seen in the Buffer dewar (PI8210).

Similar rate and limits of valve actuation and the increase in the LHe level have been seen before BUT did not cause the drastic change in flow rate and pressure spikes. Further investigations are being conducted which includes checking solenoid & buffer dewar condition during this spike. We will continue to monitor these signal over the weekend.

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This is a plain text email for clients that cannot display HTML.  The full logentry can be found online at https://logbooks.jlab.org/entry/4278785
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