jason.oberling@LIGO.ORG - posted 10:27, Wednesday 12 October 2016 - last comment - 13:24, Wednesday 12 October 2016(30451)
TCSy Chiller Topped Off and Flow Alarm Reset
I added 250mL of water to the TCSy chiller this morning, bringing the reading on the scale from 4.5 to 9.0.
In addition, the TCSy CO2 laser tripped out this morning on a flow alarm. Peter and I reset the laser box (key off, then key on) to clear the alarm and restart the laser. Cheryl had trended the flow channel for the CO2 laser and indeed the flow dropped to zero and recovered (I don't have the trend, perhaps Cheryl will post it later). Maybe an air bubble working its way through the system?
That's a bit concerning and not something that I believe we've seen (other than on this one system recently). Certainly possible that it's an air bubble. We'll need to watch this because if the flow sensor causes it to trip out then we will start having down time on the laser. Are there any bubbles visible in any of the tubing or do you think these are getting trapped at some high point in the system? The highest point overall should be up at the chillers, but there will be other local high points such as on the table.
The trend suggests that the flow rate only went to 0 for 3 seconds then made its way back up. Bubble does sound reasonable.
There look to be some regular dips in flowrate, perhaps also bubble related. Might be easier to see in non-trended data how long and deep these dips are.
I took a 30 second full data trend from the trip, also including the interlock signal. As can be seen the flow rate is not at its usual value of ~3.0 gpm for approximately 10 seconds. Interestingly, the interlock does not trip until the flow has been below nominal for ~3 seconds. Is this the expected behavior of this interlock?
There is a low pass filter on the input, so yes that's expected behavior. I am surprised that it goes negative though - this should be linear in current from the flowmeter which makes me think it can't go negative without the flowmeter running backwards.