[Dsg-halla_gas] GEM Gas Rack - problem with leaks

[Marc Mcmullen]

Hi Chuck,

Thanks for the update. A leak test may be the way to go before connecting to the system, Jack might want to weigh in on that.

The connections are 1/4", so what ever 1/4" you want to use should work. The chassis uses a soft Tygon tube internally.
If Jack decides to leak test the panels, I would make sure the tubes connecting the flow meter valve panel to the chassis are disconnected, as your leak test pressure may exceed the rating of the sensors (see diagram below) or tubing in the chassis. The tubing may just pop off of the sensor (internally of the chassis) or the sensor may break. Most likely nothing will happen as long as the output push-loks on the front panel are not blocked off. It should just bleed to atmosphere...but that all depends on the pressure, I suppose.

Please feel free to check out our documentation on the chassis and system, here is the link to that chassis so you can get a sense of the internals.

l<https://www.jlab.org/div_dept/physics_division/dsg/presentations2/Hall%20A%20GEM%20Gas%20Flow%20Sensor%20Chassis.pdf>ink<https://www.jlab.org/div_dept/physics_division/dsg/presentations2/Hall%20A%20GEM%20Gas%20Flow%20Sensor%20Chassis.pdf>

Also here is a diagram of a single channel so you can see the flow path with pressure ratings for all the components in-line. I believe you are going to replace the Nylotube 12 from the manifold to the input of the Dwyer RMA. Let me know the part number of the tube you decide to go with and I will update the diagram on our end.

[cid:8f3515ee-506c-41be-b01c-9c305c86d4c3]

Please keep us informed on the progress by emailing the dsg-halla_gas at jlab.org mailing list. I will add you to the list this morning.

Regards,
Marc
________________________________
From: Chuck Long <mlong at jlab.org>
Sent: Tuesday, December 22, 2020 9:05 AM
To: Marc Mcmullen <mcmullen at jlab.org>
Cc: Rathnayake, Anuruddha (adr4zs) <adr4zs at virginia.edu>; Jack Segal <segal at jlab.org>
Subject: GEM Gas Rack - problem with leaks

 Hi Marc,

 Seems that a number of 1/4NPT quick connect fittings in the gas rack are leaking, I had one on the manifold pop out and would not seat under pressure. I replaced that one but then found (3) more, might be a combination of the stiffness of the nylon tubing combined with the sharp bends pulling it to one side.

 In all the other gas setups in the EEL cleanroom for the UVa GEMs we are using polyethylene tubing, we might need to rebuild the panel and replace the nylon tubing.

 Also would like to mention the flowmeters on the low flow side are not sensitive enough for the desired setting of 75cc/min, the lowest setting is 100cc/min. We might need to replace these with one where 75cc/min falls somewhere in the middle of the range.

                                                                                                       -Chuck
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