[Dsg-rich] Follow up to RICH N2 flow loss last night

[Tyler Lemon]

Hi Marco,

My answers are inline below:

From: Marco Mirazita <Marco.Mirazita at lnf.infn.it>
Sent: Friday, June 7, 2019 8:42 AM
To: Tyler Lemon
Cc: dsg-rich
Subject: Re: [Dsg-rich] Follow up to RICH N2 flow loss last night

Hi Tyler,
thank you for this update and for your intervention.
I have a couple of comments though.
1) Bob says that the N2 valve was off. What does it mean? That someone
manually closed it?
Yes, someone closed manually closed the valve. I don't know if it was at the RICH N2 panel or someplace else, but the effect was the same that N2 flow was lost to RICH from the main Hall B supply dewar.

2) From your analysis, we know that the valve was closed on June 3rd,
then the backup system came into operation  and worked for 3 days, but
we got an alarm only when also the backup system died. It means the N2
system worked for three days in an unsafe mode without any warning. We
got an alarm only when it was "too late" and the flow dropped to zero.
Fortunately, you, Bob and the jlab crew fixed the problem quickly and
most likely the aerogel didn't suffer any damage, but for the future I
think the alarm should be sent out when the primary system fails, while
the backup must ensure enough time time to fix the problem.
We plan on implementing an alarm on the N2 backup pressure transducers to let us know when the backup supply is in use.
We'll have to look at the values we saw during the loss of N2 to determine what measurements will be alarmed.

Best regards,
Tyler
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