chandra.romel@LIGO.ORG - posted 14:36, Tuesday 16 May 2017 - last comment - 16:18, Tuesday 16 May 2017(36213)
Troubleshooting x-beam manifold pressure discrepancy
[John, Chandra]
More investigation on leak hunt of x-beam manifold. Here's what we're trying now:
- Valved out IP5 & IP6 on x & y beam manifolds to measure rate of pressure rise (looks like x is rising 2-3x more than y)
- Hard closed GV5 & GV7 to confirm no help from adjacent cryopump (no change in rate of rise)
- We found that hard closing GV5 does not change status on MEDM from yellow to red (FRS 8142)
- GV7 hard closed fast at around 20 psi
- GV5 wouldn't hard close at maxed out 80 psi, so we partially re-opened to re-seat the gate. Then it hard closed around 40 psi with a very loud bang
- Valved in x & y beam manifold turbos to trend the pressure drop. Inlet pressures (foreline pressures) before and after valving in:
- Y: valve closed: 5.2e-8 Torr (7.6e-3 Torr); valve open: 9.0e-8 Torr (7.6e-3 Torr)
- X: valve closed: 2.2e-9 Torr (1.0e-3 Torr); valve open: 5.2e-8 Torr (1.0e-3 Torr)
- Note: X turbo is being backed by leak checker equipped with a turbo; Y turbo is backed by scroll only
- Attached is trend so far (log scale & linear scale)
- NOTE that PT-180 was baked by Kyle many months ago when we were investigating why these two new hot cathode ion gauges drift up in pressure while the cold cathode (PT-120) doesn't follow same trend. Do we trust the gauges??
- Chris will refill the three empty He gas bottles so we can resume spraying the tube tomorrow
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In regard to GV5 not showing as hard closed on the medm screen. I looked at the Beckhoff code. It appears that I am just not seeing a change in signal (from 0 to 1) for the closed limit switch. Both the code and documentation agree that this should be LY terminal 2 channel 4. On April 8 2015 Kyle reported that GV5 hard closed (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=17748). I see this in the minute trends (attached). This is the most recent time I can find GV5 being hard closed from the alogs. On April 26 2016 LY was upgraded to Beckhoff (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=26803). I guess we should check the wiring into the Beckhoff chassis?
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From minute trends, the last time that GV5 hard closed is on March 14 2016. https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=26065
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