vernon.sandberg@LIGO.ORG - posted 10:29, Monday 03 October 2016 - last comment - 12:13, Monday 03 October 2016(30170)
TCS Chiller Status and Fill Report
Gerardo and Vern
TCS-X: Full no water added, 3.9 gal/min, 20.0 deg C.
TCS-Y: found water level to be 6.6, added 750 mL to raise gauge to 8.6, 4.0 gal/min, 19.8 deg. C. Unusual fill pattern, first 500 mL showed no sign on gauge then suddenly the gauge ball droped to 5.0 and climbed with the addition of the last 250 mL of water.
Noticed the icons on the two chiller control panels were different. TCS-X displayed horizontal bars. TCS-Y displayed chevrons pointing up.
I'm guessing that the TCS-Y symbols are related to the fact that this laser tripped right when you guys were refilling the water for some reason (9:45am).
Yes this is normal. Means that the chiller is heating with the arrows pointing up (or cooling when pointing down) so that the water is at the setpoint of the chiller
At Richard's request, I inspected the inside of both TCS tables, and found nothing, no drips and no sign of water, the tables are dry.
I inspected TCSY first, then TCSX.
Also, apparently both Gerardo and I, separately, walked the length of the piping and found no leaks.
Attached is this morning's story of laser power.
It looks like there is a small increase in temperature on the laser which causes a power output increase from the laser. Following that the laser trips off, and the Guardian code then starts trying to relock the laser.
We'll need to think about the right way to get Guardian to "see" that the laser has tripped off - we should get it to check the laser error channels. Anyway that's why the temperature of the chiller has those steps in it.
I'm not sure how sensibly Guardian will react if you just restart the laser without restarting Guardian. The reason I say this is because it typically takes ~30mins for the laser to come into thermal equilibrium during which time Guardian won't be able to lock it. Also while Guardian is hunting for a locking point it will occasionally be stepping the chiller temperature (as shown in the chart) which may in turn increase the time taken for the laser to reach an equilibrium temperature. This logic isn't well baked in to the current Guardian code which at the moment locks the laser when it is reasonably stable (ie after 30mins of running unlocked).
I'm thinking the anomolous note Vern mentions in the first post on this thread is the culprit for the laser trip: The indicator float bobbled way low and then rose while they were filling. So, I think an air bubble pushed out from under the filter and dropped the level briefly, thus triggering a low water level trip.
This adds to my thought that maybe the mystery water "loss" issue is actually not a water loss at all, but an air loss. Maybe we didn't fill the chiller all the way up when we found the chiller dry on Wed, and we are still "topping it off'. as I pointed out last week, the indicator goes/stays low after you push air out from under the filter. Today, I played with this more and was again able to bleed more air out from under the puffy filter fabric which then left the indicator low. I had to fill another 225mL just in playing with it. Attached are pix of the X and Y filter while water is running thru. Note how the Y filter fabric is being pushed up towards the surface of the water, while the X one has more of a trough down the middle? (Use your imagination, it is much more obvious when standing over it and pushing it around with a gloved hand or hose tool).
They added 1.3gal (5L) on Wed when they found it dry. We've added ~a gallon (3800mL) since then, in small ~500mL batches. I'm looking up the capacity of the chiller...
The chiller reservoir volume is listed as 7.2L (1.9 gal).
We've added ~5L plus ~3L since Wed - given some error bar on these plus a little reasonable amount of bubble bleeding, we might find that the indicator reading settles out at "full". That's one theory anyways...
We have inspected the tables, the piping and the chillers 3 times since last Tues and cannot find any loss of water.