[dsg-hallb_htcc] HTCC gas pressure

[Youri Sharabian]

Hi Brian,

Yes, I agree with you, we need to check oil level and fix possible leaks.
The leaks that I expect currently do exist are most likely along seems of the HTCC  Entry and Exit windows. Even since differential pressure is very low the force acting on windows are high enough to tear off edges of attached windows especially for the Exit window due to its large dimensions (about 9 feet of diameter). We had to "glue"/attach the windows from outside only because windows were last parts to install after completion of light collection geometry checks.

Youri

________________________________
From: Brian Eng <beng at jlab.org>
Sent: Tuesday, January 4, 2022 9:20 AM
To: Youri Sharabian <youris at jlab.org>
Cc: Denny Insley <dinsley at jlab.org>; dsg-hallb_htcc at jlab.org <dsg-hallb_htcc at jlab.org>
Subject: Re: HTCC gas pressure

Ambient stopped being so unstable once the storm finished passing through which is why the pressure in the detector seems better now. The faster the change the more it will show up in the detector, that's just inherent to the setup itself, not something wrong.

While oil does evaporate, so checking the level is definitely an easy thing to look at, the rate within the bubbler should be quite low especially at the temperatures it is at.

A leak is still more likely, which is of course harder to isolate since it can be anything past the MFC (fittings, tubing, detector itself, etc).

________________________________
From: Youri Sharabian <youris at jlab.org>
Sent: Tuesday, January 4, 2022 8:30 AM
To: Brian Eng <beng at jlab.org>
Cc: Denny Insley <dinsley at jlab.org>
Subject: Re: HTCC gas pressure

Hi Brian,

All right. Let me meet Denny Insley first to decide when we can run HTCC gas leak checks. If leaks will be possible to fix and, as I expect, pressure is back to what we had before (i.e. about 0.14 iwc) than after that probably would be the best time to look at the alarm limits. Thanks God right after we had our conversations yesterday the pressure in the system since then is stable and shows considerably smaller fluctuations.
I'll keep you informed.
Thank you for your time.
Regards,
               Youri


________________________________
From: Brian Eng <beng at jlab.org>
Sent: Monday, January 3, 2022 1:23 PM
To: Youri Sharabian <youris at jlab.org>
Cc: Amrit Yegneswaran <yeg at jlab.org>
Subject: Re: HTCC gas pressure

Hi Youri,

I won't be on-site so an in person meeting won't be possible.

Since there is a passive backup installed (the rotameter) I would suggest to just loosen the alarm limits (at least while this storm rolls through the area) as there shouldn't be any danger of not having flow to the detector.

________________________________
From: Youri Sharabian <youris at jlab.org>
Sent: Monday, January 3, 2022 1:04 PM
To: Brian Eng <beng at jlab.org>
Subject: Re: HTCC gas pressure

Dear Brian,

Thank you for your response. Yes, of course change of the atmospheric pressure coases corresponding changes of the differential pressure in the HTCC. The problem was that these changes were unexpectedly large. I do agree with you that before we had about 0.14 iwc, but now we observe only half of that. I do not think anybody was changing any oil level but new gas leaks are very possible and need to be checked. The rotameter was installed and is being used to mitigate possible power outage. I have used it yesterday just to increase the CO2 flow rate. The pressure went up of course but still I am receiving minor low pressure alarms (even when the pressure is about 0.06 iwc). I need to make decision what to do. I would like to ask you for a meeting with you in your office, please.
Please let me know if you have additional time for that and when if it is possible.
Thank you very much.
Regards,
                  Youri

________________________________
From: dsg-hallb_htcc <dsg-hallb_htcc-bounces at jlab.org> on behalf of Brian Eng <beng at jlab.org>
Sent: Monday, January 3, 2022 11:32 AM
To: dsg-hallb_htcc at jlab.org <dsg-hallb_htcc at jlab.org>
Subject: [dsg-hallb_htcc] Fw: HTCC gas pressure

Youri,

I've forwarded this email to the mailing list so we can get some more eyes on it.

The issues with the instability recently are due to ambient pressure changes (see the HTCC recent.png image). While the ambient pressure normally does fluctuate, it doesn't normally fluctuate so much within those changes, which is why the pink line is "bolder" for the past few days. I'm not sure what there is to do about this other than flowing even more and forcing it to bubble constantly.

Another thing I noticed is that the detector pressure is lower than it used to be (see the HTCC history.png image). I don't know if this was a simple oil level change and is expected or if maybe there is a leak somewhere so the amount being flown isn't actually getting to the detector (or even the detector itself leaking). Also since there is a rotameter in parallel there is additional flow that can't be tracked.

As far as the gas system itself it's doing what it's being asked.

________________________________
From: Youri Sharabian <youris at jlab.org>
Sent: Monday, January 3, 2022 10:15 AM
To: Brian Eng <beng at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>
Cc: Denny Insley <dinsley at jlab.org>
Subject: HTCC gas pressure

Dear Brian and Marc,

Last several days I am receiving HTCC minor pressure alarm notifications on my cellphone. Yesterday on Jan 2 I have increased CO2 gas flow rate on the rotameter from 7-8 l/min to 10 l/min in order to reduce sensitivity of the detector to fluctuations of atmospheric pressure. But the gas.stp Graph shows very large fluctuations of the differential pressure in the detector (from 0.1 iwc to 0.04 iwc) which I consider as unusual although weather currently is also very unstable. But the pressure changes are very large and rapid.
Please, I would like to ask you to look at the data including for last couple of days and let me know your opinion on explanation what is going on in general.
Today during regular Hall B meeting I have reported my observations regarding HTCC gas pressure problems. I have suggested that we need to run tests to find possible gas leaks and also check performance of regarding pressure sensors. I asked Denny Insley to meet to decide what needs to be done in the hall. Of course without your opinion not much can be done at all. I am ready to meet withyou in your office at any time to get help from you. I think that would be very important to understand what needs to be done.
Thank you very much for your response in advance.
Best regards,
                       Youri

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/dsg-hallb_htcc/attachments/20220104/42bb06ed/attachment.html>