Reports until 22:30, Sunday 27 December 2015
LHO VE
kyle.ryan@LIGO.ORG - posted 22:30, Sunday 27 December 2015 - last comment - 08:46, Monday 28 December 2015(24505)
CP3 manual overfill
2150 hrs. local 

Overfilled CP3 manually -> I prefer the new procedure of opening the LLCV bypass valve 1/2 turn ccw then partially opening the exhaust check valve bypass valve to minimize back pressure.  Once LN2 is observed flowing out of the exhaust (~2 minutes), closing the LLCV bypass valve then closing the exhaust check valve bypass valve - in that order.  This should reduce the maximum exhaust pressure.

NOTE:  I did not open the instrument air pressure regulator bowl drain to check for dryness tonight, i.e. change the air pressure at the CDS controlled solenoid valve but nevertheless, the CDS MEDM "START/enable STOP/disable" indicator went from green to red again and I had to re-enabled it - why?  Manually filling the 80K pump using the above method only changes the 80K pump exhaust pressure and should have no effect on the instrument air. 

Gerardo is scheduled to do the next CP3 overfill exercise sometime before 5:00 p.m. hrs. local tomorrow, Monday.
Comments related to this report
john.worden@LIGO.ORG - 08:20, Monday 28 December 2015 (24511)

The air solenoid is disabled when exhaust pressure exceeds the setpoint which I believe is 10psi. So manually filing is indeed tripping this air valve. Reminder to us - we should ask Dave to move the exhaust pressure over to CDS for trending.

kyle.ryan@LIGO.ORG - 08:46, Monday 28 December 2015 (24512)
Yes, you beat me to it.  I realized this driving home after making this entry.  This is reason enough that it should be standard practice to utilize the check-valve bypass circuit when overfilling.  Also, I will include this as a "mitigation" to the the Vacuum Hazard Analysis.