[Dsg-mvt] MVT gas pressure regulation issue

[Guillaume CHRISTIAENS]

Hi Bryan,

Thanks a lot apparently it did the trick by going back to 50%.

Bob installed a thermostat for the MFC after we had these temperature 
alarms.

Thanks again

Guilllaume


Le 14/04/2018 à 20:20, Brian Eng a écrit :
> Sorry for the multiple emails, last one before I find some dinner...
>
> Looks like there is still MFC temperature alarms https://logbooks.jlab.org/entry/3560796
>
> Maybe the heat tape needs to be adjusted lower again?
>
> ----- Original Message -----
>> From: "Brian Eng" <beng at jlab.org>
>> To: "Guillaume CHRISTIAENS" <guillaum at jlab.org>
>> Cc: "DEFURNE Maxime" <Maxime.Defurne at cea.fr>, dsg-mvt at jlab.org, "Francesco Bossù" <fbossu at jlab.org>
>> Sent: Saturday, April 14, 2018 8:16:29 PM
>> Subject: Re: [Dsg-mvt] MVT gas pressure regulation issue
>> By the way, there is a limit to this multiplier since we can't let the MFCs go
>> below their minimum flow. It could probably be higher than the current 50%, but
>> won't be able to be something like a factor of 10. I'd be surprised if we could
>> get it to more than 2-3. FYI, the minimum value for the C4H10 MFCs is ~2 sccm.
>>
>> Again, raising the demand flow would allow for a larger multiplier.
>>
>> However, in theory you want the smallest possible one in order to make the
>> changes in flow as infrequent as possible (which is why the DC is 20%).
>>
>> ----- Original Message -----
>>> From: "Brian Eng" <beng at jlab.org>
>>> To: "Guillaume CHRISTIAENS" <guillaum at jlab.org>
>>> Cc: "DEFURNE Maxime" <Maxime.Defurne at cea.fr>, dsg-mvt at jlab.org, "Francesco
>>> Bossù" <fbossu at jlab.org>
>>> Sent: Saturday, April 14, 2018 8:08:29 PM
>>> Subject: Re: [Dsg-mvt] MVT gas pressure regulation issue
>>> Hi Guillaume,
>>>
>>> Sorry for the late reply, I saw the email, but didn't have access to a computer
>>> until now.
>>>
>>> The current factors are to reduce/raise the flow by 35% of the demand value (see
>>> this entry: https://logbooks.jlab.org/entry/3544160)
>>>
>>> I've put them back to 50%, even though that value seemed to work fine for quite
>>> a while (since 4/6).
>>>
>>> The mixing system is doing what it is supposed to, the 20 psi number was for
>>> safety and it should set the multiplier to 0 to stop flow.
>>> We can raise this number as well if your system can handle it, but it shouldn't
>>> ever get that high to begin with.
>>>
>>> I see mix 2 is over 15 psi as well, which means it has the same issue, but just
>>> isn't effected as much.
>>> I suspect this might be because the temperature inside the MFC enclosure is 95F,
>>> which is much higher than I recall seeing in the past.
>>>
>>> If the pressure is still is an issue even with the increased multiplier, one of
>>> the things you can try doing is raising the flow on the MVT/FTT doing so will
>>> make the difference between the demand flow and mixing flow higher which should
>>> make the changes faster.
>>>
>>> ----- Original Message -----
>>>> From: "Guillaume CHRISTIAENS" <guillaum at jlab.org>
>>>> To: "Brian Eng" <beng at jlab.org>, "Marc McMullen" <mcmullen at jlab.org>
>>>> Cc: "Francesco Bossù" <fbossu at jlab.org>, "DEFURNE Maxime"
>>>> <Maxime.Defurne at cea.fr>
>>>> Sent: Saturday, April 14, 2018 5:22:11 PM
>>>> Subject: MVT gas pressure regulation issue
>>>> Dear all,
>>>>
>>>> Sorry if you received a duplicate message about this subject. I had an
>>>> issue with my first mail and wasn't sure it was sent.
>>>>
>>>> So we have an issue with pressure regulation for mix 1.
>>>> Pressure reached 20 psi and don't want to decrease, it oscillate between
>>>> 19.99 where flows are reduced (by a factor 2 I think) and 20.00 where
>>>> flows are 0.
>>>> However it seems that the flows scaled by this factor 2 is not enough to
>>>> decrease the flows today, I guess because of temperature changes.
>>>>
>>>> Since factor 2 doesn't seem to be enough, do you know how we can change
>>>> this factor to 4, 5 or even maybe 10 ? Can we do it remotely ?
>>>>
>>>> Thanks
>>>>
>>>> Guillaume
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