aLIGO LHO Logbook

LHO VE (CDS, VE)

patrick.thomas@LIGO.ORG - posted 18:31, Friday 16 March 2018 - last comment - 08:52, Monday 19 March 2018(41048)

Verbal alarms high vacuum alarms

Verbal alarms just reported high vacuum alarms at BSC2, BSC7, HAM6 and PT245. I can understand the ones at HAM6 and PT245 (CP4), but I'm not certain about the ones at BSC2 and BSC7. Is this due to the change in verbal alarms code [alog 41046]?

Comments related to this report

patrick.thomas@LIGO.ORG - 18:36, Friday 16 March 2018 (41049)

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Minute trends for last 30 days.

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trends.pdf

kyle.ryan@LIGO.ORG - 20:10, Friday 16 March 2018 (41050)

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I don't see any reason why we should be getting any alarms from the Corner Station.  PT110, PT120 and PT170 shouldn't be alarming at current pressures.  

I don't know what the alarm levels are currently set at for the Y-mid station (PT210, PT245 and PT246) but we are monitoring regularly from home due to the fact that we are currently baking out CP4.  I think that Chandra's intention was for Dave B. to have recently increased PT210's alarm threshold from 5 x 10-8 Torr to 1 x 10-7 Torr.  This was so as to reduce potential nuisance alarms resulting from the Y-mid pressure rising as CP4's temperature slowly increased to its eventual maximum of 130C (Sunday?  Monday?).

thomas.shaffer@LIGO.ORG - 08:52, Monday 19 March 2018 (41055)

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The threshold in Verbal for all vacuum chambers, except for HAM1 & HAM6, is set at 7e-8Torr. We are definitely above that for all of the alarmed chambers so the alarms make sense. I currently have the vacuum alarms to repeat every two hours if they are still in their alarm condition. This seems to be a bit much, but I erred on the cautious side with data taking operations in mind.

Since this is creating alarm noise while we are venting, and the vac crew has their own alarm systems in place, I will drop the threshold until we are back under normal operations.