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Entry  Thu Jun 11 11:48:43 2020, gautam, Update, VAC, Vac failure vacFailure.png
    Reply  Thu Jun 11 16:14:03 2020, gautam, Update, VAC, Vac failure - probable cause is serial comm glitch TP2_tempGlitch.pngPSL_shutterClosed.pngTP2tempGlitches.pdf
       Reply  Thu Jun 11 17:35:34 2020, gautam, Update, VAC, Pumpspool UPS needs battery replacement 
          Reply  Fri Jun 12 01:23:32 2020, Koji, Update, VAC, Pumpspool UPS needs battery replacement 
             Reply  Fri Jun 12 17:32:40 2020, Koji, Update, VAC, Pumpspool UPS needs battery replacement Screen_Shot_2020-06-12_at_17.22.23.png
                Reply  Fri Jun 12 19:02:52 2020, gautam, Update, VAC, Pumpspool UPS needs battery replacement 
                   Reply  Fri Jun 12 19:23:56 2020, Koji, Update, VAC, Pumpspool UPS needs battery replacement 
                      Reply  Fri Jun 12 19:33:31 2020, gautam, Update, VAC, Pumpspool UPS needs battery replacement 
                         Reply  Tue Jun 16 13:35:03 2020, Jon, Update, VAC, Temporary vac fix / IFO usable again Pumpdown.png
                            Reply  Wed Jun 17 16:27:51 2020, gautam, Update, VAC, Questions/comments on vacuum 
                               Reply  Thu Jun 18 11:00:24 2020, Jon, Update, VAC, Questions/comments on vacuum 
                                  Reply  Thu Jun 18 12:00:36 2020, gautam, Update, VAC, Questions/comments on vacuum 
                                     Reply  Thu Jun 18 14:13:03 2020, Jon, Update, VAC, Questions/comments on vacuum 
                                        Reply  Thu Jun 18 15:46:34 2020, gautam, Update, VAC, Questions/comments on vacuum 
                                           Reply  Fri Jun 19 07:40:49 2020, Jon, Update, VAC, Questions/comments on vacuum 
                                              Reply  Fri Jun 19 09:57:35 2020, gautam, Update, VAC, Questions/comments on vacuum 
Message ID: 15404     Entry time: Wed Jun 17 16:27:51 2020     In reply to: 15402     Reply to this: 15406
Author: gautam 
Type: Update 
Category: VAC 
Subject: Questions/comments on vacuum 

I missed the vacuum discussion on the call today, but I have some questions/comments:

  • Isn’t it true that we didn’t digitally monitor any of the TP diagnostic channels before 2018 December? I don’t have the full history but certainly there wasn’t any failure of the vacuum system connected to pump current/temp/speed from Sep 2015-Dec2018, whereas we have had 2 interruptions in 6 months because of flaky serial communications.
  • According to the manuals, the turbo-pumps have their own internal logic to shut off the pump when either bearing temperature exceeds 60C or current exceeds 1.5A. I agree its good to have some redundancy, but do we really expect that our outer interlock loops will function if the internal ones fail?
  • In what scenario do we expect that all our pressure gauge readbacks fail, but not the TP readbacks? If so, won’t the differential pressure conditions protect the vacuum envelope, and the TPs internal shutoffs will protect the pumps? Except during the pump down phase perhaps, when we want to give a little more headroom to the small TPs to stress them less?

At the very least, I think we should consider making the interlock code have levels (like interrupts on a micro controller). So if the pressure gauges are communicating and are reporting acceptable pressure readings, we should be able to reject unphysical readbacks from the TP controllers.

I still don’t understand why TP2 can’t back TP1, but we just disable all the software interlock conditions contingent on TP2 readbacks. This pump is far newer than TP3, and unless I’ve misunderstood something major about the vacuum infrastructure, I don’t really see why we should trust this flaky serial readbacks for any actionable interlocks, at least without some AND logic (since temperature, current and speed aren’t really independent variables).

I also think we should finally implement the email alert in the event the vacuum interlock is tripped. I can implement this if no one else volunteers.

This might also be a good reminder to get the documentation in order about the new vacuum system.

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