[Dsg-mvt] News about Isobutane MFC

[Marc McMullen]

Hi Bob,

I have contacted Steve Rockwood from MKS, I sent him the P&I diagram and 
details of the situation. As soon as I here back from him I'll pass it 
along.


Marc


On 12/20/2017 11:25 AM, Bob Miller wrote:
>
> Hi Marc,
>
> What did the MFC vendor say about using these MFCs for this application?
>
> Bob
>
>
> On 12/20/2017 11:23 AM, Marc McMullen wrote:
>> 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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>> Dsg-mvt at jlab.org
>> https://mailman.jlab.org/mailman/listinfo/dsg-mvt
>
> -- 
> Bob Miller
> Hall B Lead Engineer
> Jefferson Lab
> 757 269-7867
>

-- 
Marc McMullen
Detector Support Group
757-269-7738

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