Displaying report 1-1 of 1.
Reports until 17:05, Tuesday 06 September 2016
LHO VE
kyle.ryan@LIGO.ORG - posted 17:05, Tuesday 06 September 2016 - last comment - 10:59, Wednesday 07 September 2016(29506)
Manual over-fill of CP3 not required 
No overfill required today as we had an LN2 delivery and I had to reduce the LLCV %open from 21% to 18%.  

~1635 - 1700 hrs. local -> I visually confirmed that CP3's exhaust line was frosted - dewar vapor pressure at 20 psi.  

Next overfill to be Friday, Sept. 9th.
Comments related to this report
kyle.ryan@LIGO.ORG - 10:59, Wednesday 07 September 2016 (29515)
Link 

So I screwed up (I used to keep a tally of these occurrences but it has become too impractical)!  It wasn't until after the LN2 delivery was underway (done?) that I realized that I hadn't proactively reduced CP3's LLCV %open value so as to avoid over pressuring CP3's LN2 reservoir.  As I have now demonstrated, we are vulnerable to this on delivery days.  Recall that while CP3 is in "Manual" fill mode, we have defeated any ability for CDS to close the Fill Valve (aka LLCV) as a response to overpressure.  As such, we are completely reliant on Vacuum Personnel awareness.  

Gerardo suggested that I notify he and Chandra when LN2 deliveries get placed to lessen the likelihood of this happening again.  John suggested that we leave open the exhaust check-valve bypass-valve and not rely on "Vacuum Personnel awareness" - that is why he gets paid the big bucks!  I will open the bypass valve the next time I am at the Y-mid - Brilliant!
Non-image files attached to this comment
Displaying report 1-1 of 1.