[dsg-hallb_dc] DC CO2 mix 2?

[Marc Mcmullen]

Hi Mac,

Hall A uses a BGA-244 binary gas analyzer on the GEMs.

Marc

https://www.thinksrs.com/products/bga244.html

________________________________
From: Mac Mestayer <mestayer at jlab.org>
Sent: Friday, July 1, 2022 2:37 PM
To: Brian Eng <beng at jlab.org>; Morgan Cook IV <mcookiv at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>; Florian Hauenstein <hauenst at jlab.org>
Subject: Re: DC CO2 mix 2?

Hello Brian and all;

We don't have an instrument that directly measures the Argon CO2 mixture, correct?
We just measure the input flow rates with the mass flow controllers, right?

Are there good instruments available which can measure mixture ratios?

Mac
________________________________
From: Brian Eng <beng at jlab.org>
Sent: Friday, July 1, 2022 2:31 PM
To: Mac Mestayer <mestayer at jlab.org>; Morgan Cook IV <mcookiv at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>; Florian Hauenstein <hauenst at jlab.org>
Subject: Re: DC CO2 mix 2?

Hi Mac,

No safety issues to the chambers or people, that's what the bubblers (detector) and relief valves (people) are for.

The mix will be off, but probably not significantly, due to the buffer tank size. However, that depends on how long the flows aren't what is expected.

Since changing the pressure range won't help if it really is a differential pressure issue I've put the multiplier to zero temporarily to bleed off flow from the tank faster without filling it once it has dropped down some more I'll put it back to the default.

________________________________
From: Mac Mestayer <mestayer at jlab.org>
Sent: Friday, July 1, 2022 2:26 PM
To: Morgan Cook IV <mcookiv at jlab.org>; Brian Eng <beng at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>; Florian Hauenstein <hauenst at jlab.org>
Subject: Re: DC CO2 mix 2?

Morgan;

I just got this, but in the future cc me and Florian directly.

Is the mass flow controller working correctly now?   ... was its failure due to a pressure drop?  ... and do we know the cause of the pressure drop?

Do we know the mix ratio in the chambers?

I suppose any malfunctions will not affect chamber safety from over-pressure, right?

We have recently developed a procedure to directly correlate the chamber time to distance correlation with atmospheric pressure.  This parameterization won't work the same for different mix ratios.

If there is no safety issue (to people or to chamber gas bags) then let's discuss this in detail next week.

Mac
________________________________
From: dsg-hallb_dc <dsg-hallb_dc-bounces at jlab.org> on behalf of Morgan Cook IV <mcookiv at jlab.org>
Sent: Friday, July 1, 2022 2:09 PM
To: Brian Eng <beng at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>
Cc: dsg-hallb_dc at jlab.org <dsg-hallb_dc at jlab.org>
Subject: Re: [dsg-hallb_dc] DC CO2 mix 2?

well, hopefully it survives the weekend. Thanks.

Y'all have a good weekend
________________________________
From: Brian Eng <beng at jlab.org>
Sent: Friday, July 1, 2022 2:08 PM
To: Morgan Cook IV <mcookiv at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>
Cc: dsg-hallb_dc at jlab.org <dsg-hallb_dc at jlab.org>
Subject: Re: DC CO2 mix 2?

Done.

https://logbooks.jlab.org/entry/4009546

Note that this change won't survive a power cycle of the controller.
________________________________
From: Morgan Cook IV <mcookiv at jlab.org>
Sent: Friday, July 1, 2022 1:57 PM
To: Brian Eng <beng at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>
Subject: Re: DC CO2 mix 2?

Yeah, I think it's a pressure differential issue. It looks like the pressure differential between the CO2 tank and the mix 2 buffer tank isn't enough. For some reason the  CO2 tank isn't building pressure as it should.
Can you lower the fill mix 2 fill points from 80-100 psi to 70-90 psi?
________________________________
From: Brian Eng <beng at jlab.org>
Sent: Thursday, June 30, 2022 12:52 PM
To: Morgan Cook IV <mcookiv at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>
Subject: Re: DC CO2 mix 2?

If I had to guess there was probably an issue with the zeroing. Best is if you can valve off both up and downstream of the MFC prior to zeroing, but at a minimum one of the sides needs to be valved off. Since I don't have the PI&D in front of me I don't know what's possible offhand.

These don't normally have such high flow when the valve is closed.

________________________________
From: Brian Eng <beng at jlab.org>
Sent: Thursday, June 30, 2022 12:39 PM
To: Morgan Cook IV <mcookiv at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>
Subject: Re: DC CO2 mix 2?

Right now Mix 2 seems fine.

There seems to be issues with the mix 1 CO2 MFC. The valve is all the way closed but it still thinks there is ~6 l/min flow.

________________________________
From: Morgan Cook IV <mcookiv at jlab.org>
Sent: Thursday, June 30, 2022 12:15 PM
To: Brian Eng <beng at jlab.org>; Marc Mcmullen <mcmullen at jlab.org>
Subject: DC CO2 mix 2?

Hey Y'all,

When y'all get a minute, can you take a look at the DC mix 2 system? There is some new, strange behavior with the Mix 2 CO2 flow. It seems that when both Mix 1 and Mix 2 are calling for full flow, i.e filling the buffer tanks, there doesn't seem to be enough flow through the Mix 2 CO2 mfc.

This morning when I came in, the Mix 2 CO2 mfc was at 100% open with a zero/negative flow. They only way I got Mix2 CO2 to flow was to turn off Mix 1 completely, then Mix 2 seemed to work correctly. Reducing both the Mix 1 set pt and HTCC rotameter seemed to allow some CO2 to flow through Mix 2, but even then, then mfc creeps open to 100% to try and maintain the required flow.

The CO2 was filled a couple of days ago, and the tank and line pressure are a bit low but I can't quite figure out why only Mix 2 CO2 is affected. I did re-zero all the Mix mfcs but I don't think it changed anything.

Thanks,
Morgan

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