[Dsg-ft] [Dsg-mvt] MVT MFC Heaters

Wed Jan 3 11:59:01 EST 2018

Hi Amrit, 

As far as initial operating parameters, the following is a good starting point; 

1. C4H10 gas temp, 75-80F 
2. C4H10 gas inlet pressure to MFC, 20 psi 
3. Pressure control 12-15 psig 
4. ALL MFC temp, 75-80F 

The Argon and CF4 gas lines at the MFC input and output should also be heated and insulated in order to properly maintain MFC temp. The MFCs and piping must be sealed to prevent C4H10 condensation due to the cold ambient air. The MFC mounting plate should be thermally insulated from the steel rack it is mounted in. This would be a good start. 

The current MFC and piping layout is problematic for temp control. This layout should be re-designed keeping the following priorities in mind; 
- make it easy to insulate 
- make it easy to heat 
- minimize the gas line length between the MFC and gas cylinder pressure requlator 
A layout similar to my original concept along with some additional considerations for the heat tape and insulation would cover these priorities. 

George 

From: "Amrit Yegneswaran" <yeg at jlab.org> 
To: "Marc Mcmullen" <mcmullen at jlab.org> 
Cc: "rossi patrizia" <rossi at jlab.org>, "Bob Miller" <rmiller at jlab.org>, "dsg-mvt" <dsg-mvt at jlab.org>, dsg-ft at jlab.org, "Todd Ewing" <jtewing at jlab.org> 
Sent: Tuesday, January 2, 2018 7:50:42 PM 
Subject: Re: [Dsg-mvt] MVT MFC Heaters 

hi george, 
thanks for the excellent explanation about the saturation curve, it is most useful. 
since we, the dsg, have chased our tails on this issue for quite a while, i suggest that you come up with a set of conditions for the gas, temp, and pressure something like; 

    1. gas temp T gas >70F 
    2. gas inlet pressure P in : 20 psig<P in <25psig 
    3. gas oulet pressure P out : 15 psig<P out <16psig 
    4. MFC temperature T MFC : 50F<T MFC <122F 

once these conditions have been met we can see how we can work the interface software and controls. 

marc and brian, 
as for the seals, i understand nothing. 
sounds like mumbo jumbo to me. 
what is the difference between the two seals? 
can you please explain, i'm not an expert in this matter. 
why should kalrez be better? 

also, brian and marc, check with george with regards to the gas system, especially with regards to matters like vapor pressure saturation curve, condensation temperature, etc. etc. before you fire off e-mails. 
for DSG, t here is only one expert on the gas system and that is George, you guys might be close but no...remember "a good man know his limitations". 

in any case, I think we have been futzing around with the MVT gas system for way too long and it isn't even on my books? 

so marc and brian prepare a simple talk for tomorrow's meeting. 
i really would like to know how you plan to resolve this matter and when you plan to call it quits. 
amrit 

From: "Marc Mcmullen" <mcmullen at jlab.org> 
To: "Bob Miller" <rmiller at jlab.org>, "Brian Eng" <beng at jlab.org>, "Todd Ewing" <jtewing at jlab.org> 
Cc: dsg-mvt at jlab.org, dsg-ft at jlab.org 
Sent: Tuesday, January 2, 2018 3:48:02 PM 
Subject: Re: [Dsg-mvt] MVT MFC Heaters 

Bob, 

We will monitor the enclosure temperature overnight, you may want to 
make an adjustment to the enclosure temperature control we have seen it 
peak at 54F and then drop to below 46F before the cycle started again. 

We spoke with Steve Rockwood from MKS, he says there may be issues with 
the Viton seals, and suggests using Kalrez as a possible alternative. We 
are waiting for his final suggestion/report. 

Once Todd has the CF4 hooked up we can test that MFC. As far as the 
C4F10 MFC, the operating range is 10C - 50C, anything outside of that 
and the unit will not perform to spec. We have seen that with the DC 
MFCs when the temperature in the Gas Shed dropped below 50F. 

The gas vapor pressure is specified to be 30psi @ 70F. Until we can get 
the system stable to these numbers, we risk the operation of the MFC. 

Marc 

On 1/2/2018 2:17 PM, Bob Miller wrote: 
> Hey Marc and Brian, 
> 
> Todd is working on the heaters and insulation for the MFCs. The heat 
> tape was limited to 5% by George. Todd has increased it to 20% and 
> will monitor the inside temperature and adjust the heaters as 
> necessary. The heaters will turn off when the thermostat reaches 
> temperature anyway. The heat tape is rated at 144 watts, so I am sure 
> it will be able to heat the MFCs. 
> 
> Todd will also connect the CF4 bottle. 
> 
> Regards, 
> 
> Bob 
> 

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

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