chandra.romel@LIGO.ORG - posted 16:51, Monday 11 April 2016 - last comment - 09:28, Tuesday 12 April 2016(26533)
GV 5 & 7 open
Kyle, Chandra Opened valves that were soft closed a week ago. GV 7 needed 40 psig. GV 5 needed 45 psig to open. Attached is plot of pressures on either side of each valve before and after opening. Before we realized to pump the gate annulus after a week, we had already set pressure against pistons to 20 psig, shifting gate slightly and releasing annulus gas into beam tube.
Images attached to this report
Comments related to this report
The take away from this observation is that O-rings of GV5 and GV7 must have been in full contact with their sealing surface whilst soft-closed, i.e with 5 - 10 psi applied to the top of their pistons. This is as intended. Had they not been in full contact, the gate annulus volumes would have been pumped by the adjacent vacuum volume(s) and no gas release would have occurred when the gates where stroked open. Typically we would have "burped" the un-pumped gate annulus volume into the rest of the annulus piping before opening the gate valves. In summary, soft-closing GV5 and GV7 does provide protection to the Beam Tubes.