[Hallb-engineering] [Revised Logentry] Hall B Solenoid 4K supply relief valve lifted

kashy at jlab.org kashy at jlab.org
Fri May 21 09:10:03 EDT 2021

Logentry Text:
Calvin e-mailed me this morining after hearing an RV in Hall B lifting.
I found TP8611 (thermometer on RV8611) at 273K. It normally runs 288K and droped to 276 at approximately 6pm yesterday 5/20.
At the same time the 4K supply pressure got rather unstable. oscillating between 2.66 and 3.29 atm. (this should NOT blow this RV its setpoint is 6 atm!) The peak pressure could have been higher and epics did not record it.

I increased the MajorAalarm trip level from 273 to 282K and we will get the alarm to be on the ON-Call pager . 

Denny will make sure ALL Helium relief valves in the Hall will have their temperature sensors go to the pagers/emails.

After talking to Chris Perry, it seems that Hall C is also seeing unstable. Chris said that cryo has a temporary setup for the SL that is being returned to the purifiers and it is likely causing the instability. Looking closer, it seems that the instability is causing the cooldown valve to open too. The direct cause of the relief valve opening is likely warm supply flow getting into the supply U-tube (which has a check valve on its inlet bayonet) and heating the liquid/supercritical gas which can't easily get out through the supply valve EV8611JT, this then causes a real pressure spike where there are no pressure sensors and blows the RV.

Chris went to JLab and put the warm return from Hall B on the ESR compressors until the CHL gets to a normal operational state.

We will monitor the stability and return the controls back to normal to see if the root cause was the issue with CHL operation.

Once we are stable too, we should lower the Min of EV8611JT_Min loop back down from 60 to the normal value of 45.

We will monitor this RV closely to see if it needs to be replaced.


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/3877611
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