[Dsg-mvt] News about Isobutane MFC

[Marc McMullen]

Hi Maxime, 

I have been running argon through the c4h10 mfc which was removed from the mixing system. It is not functioning properly after hours of purging. We will need to replace it. I'll contact MKS today to see if they will repair it. We need to buy at least two more (~$1600 per), because I believe the mix 1 c4h10 was not acting properly and was exposed to condensed gas during the same time, although to a lesser extent. Testing shows that the valve will no longer seat, so that if there is any pressure (10-15psi) the mfc will flow 35 - 50 sccm. If I close off the argon valve at the regulator, the flow bleeds off, so I believe it's leaking through the internal valve seat. If the mfc is mechanically isolated from gas, it measures no flow, so the sensor seems to be ok. So a repair of the internal components may be the fastest way to have a second perfectly running mfc (4 week lead time on purchase). 

The other focus needs to be on insuring the gas will not condense in the mfc. You should address this with the system owner (Bob) and tech (Todd) on the best way to keep the gas > 70degF. Although the mfcs are specified to operate down to 50F, the gas may condense due to the small amount of flow. The mfcs are sized correctly. So unless there is an objection I will request the same size. 

We may also consider going with an mfc which may have a better recovery from this kind of issue. I read an article on a different brand which may provide some solution in the future. 
http://www.alicat.com/alicat-blog/products-and-services/liquid-in-a-gas-flow-controller-how-bad-is-it-doc/ 

Finally, I have requested a status update from the premix vendor. When he responds I'll forward the info. 


Marc McMullen 
Physics Division 
Detector Support Group 
7738 


From: "mdefurne" <mdefurne at jlab.org> 
To: dsg-mvt at jlab.org 
Sent: Tuesday, December 19, 2017 11:26:33 PM 
Subject: [Dsg-mvt] News about Isobutane MFC 

Hi Marc, 

What is the schedule for the mixing system? Let me know if you need 
anything or think I could speed up one or two things. 

We are on the last premix bottle. We have to be ready for January 12th 
with either the gas mixing system or premix bottles (when will the ten 
bottles delivered?). 

Cheers, 

Maxime 

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