[Dsg-rtpc] MFC change

[Marc Mcmullen]

Hi,

DSG has installed a 500 sccm mass flow controller on the rtpc gas panel. Using the HeCO2 premix, the max flow is 580 sccm.


Marc
________________________________
From: MADHUSUDHAN POKHREL <mpokh001 at odu.edu>
Sent: Thursday, June 27, 2019 11:14 AM
To: Marc Mcmullen
Subject: MFC change

This is the forwarded email.

> On Jun 27, 2019, at 9:23 AM, Bill Crahen <wcrahen at jlab.org> wrote:
>
> The supply orifice is okay for the new 500 sccm requirement. You folks can replace the MFC- please let me know what the new part number is for the component spreadsheet. When you finish testing, you might consider a detector "autopsy" to find your leak- permeation would only be a very small portion of what you are losing, and I would think a leak this bad would affect the new detector performance if it is susceptible to the same issues. FYI-  hall D's forward drift chamber is ~ 2 meters long, 1 meter in diameter and has ~100 orings ~ 1meter in diameter, and only flows 100 sccm with good bubbles. Your leak is large.
>
> On 6/27/2019 9:01 AM, Jiwan Poudel wrote:
>> Dear Bill,
>>
>> Current prototype is the old one from eg6 experiment, and we expect the new detector better one. We are hopeful that it won’t leak as much as the current prototype.
>>
>> But because of the helium, there is a bit more leakage from the detector compared to other heavy gases! Perhaps, small fraction of helium permeates through the detector surface as well.
>>
>> Thank you,
>> Jiwan
>>
>>> On Jun 27, 2019, at 8:24 AM, Bill Crahen <wcrahen at jlab.org> wrote:
>>>
>>> to do this I will have to re-visit the orifice sizing for the supply bottle. My question to you is where is the gas going? It goes in, and presumably is all supposed to come out the exhaust line, unless you have bad leaks. 200 cc leak rate is a MAJOR leak! Do you expect this for the new detector?
>>>
>>> Incidentally- please add Bob to the distribution list in future, he is the hall engineer.
>>>
>>> On 6/26/2019 7:48 PM, Jiwan Poudel wrote:
>>>> Dear Bill, George and Carlos,
>>>>
>>>> During the eg6 RTPC test at EEL building, we were able to get bubbles from bubbler for ArCO2 gas with a flow rate of around 233 sccm which generated a pressure of 0.11 inches of water in the RTPC exhaust line. However we could not get any bubbles for HeCO2 as the pressure inside the RTPC could not get more than 0.05 inches of water, with the maximum allocated flow rate(233 sccm) for the MFC1. Without the exhaust of the gaseous mixture, we could not get signals because of the larger concentration of CO2 inside RTPC.
>>>>
>>>> For the current prototype, we want to go higher flow rate (we operated the RTPC at the flow rate of 410 - 450 sccm for HeCO2) to observe the difference for HeCO2 mixture. So it would be better to replace the MFC1 to the range of 500 sccm.
>>>>
>>>> At ODU meeting today, we agreed that there is no harm by changing MFC1 to 500 sccm. We don’t want to reach 400 sccm also, if lower flow rate works for us.
>>>>
>>>> Could you please let me know if you have any objection? In any case, how could we proceed to change the mass flow controller?
>>>>
>>>> Thank you,
>>>> Jiwan

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/dsg-rtpc/attachments/20190627/14e14479/attachment.html>