[Dsg-mvt] Liquid isobutane between bottle and MFCs

[Brian Eng]

I switched it to Ar purge mode to check that the MFC could close when set to low flow setpoint.
As you saw that MFC probably needs to be zeroed again, but we didn't want to stop the purge to valve it off.

Since all the MFCs that should be flowing currently are I've left it in that mode, feel free to change it back if you want (it will just mean the actual flow won't match the reading).

----- Original Message -----
> From: "mdefurne" <mdefurne at jlab.org>
> To: dsg-mvt at jlab.org, "SABATIE Franck" <Franck.Sabatie at cea.fr>, "VANDENBROUCKE Maxence" <maxence.vandenbroucke at cea.fr>,
> "Aune Stephan" <stephan.aune at cea.fr>, "Todd Ewing" <jtewing at jlab.org>, "Bob Miller" <rmiller at jlab.org>, "Brian Eng"
> <beng at jlab.org>
> Sent: Monday, January 8, 2018 4:24:47 PM
> Subject: Liquid isobutane between bottle and MFCs

> Hello everyone,
> 
> We are currently flushing the lines and testing all MFCs with Argon,
> except the brand new Isobutane MFC on Mix2.
> We opened all valves upstream of the MFCs to have Argon. We changed the
> fraction of Mixture 1 from 90-10-10 to 40-30-30 in order to use equally
> all MFCs. For Mix 2, we set isobutane to 0 and close the upstream valve
> off because we want to protect it.
> 
> So far , Mix1 isobutane MFC provided a good stable flow of Argon. Now we
> will decrease it to try to find the leak flow.
> 
> Also, before opening doing this flushing/testing of all MFCs and lines
> with Argon, we tried to purge the isobutane pipe between the bottle and
> the MFCs... A lot of fluid got out of it!!!! Once we thought that the
> purge was done, we closed the relief valve and then the pressure in the
> pipe kept increasing even if the isobutane bottle was closed... most
> likely due to remaining liquid isobutane turning into vapor in the pipe
> again.
> 
> We should first try to ensure to have no condensation in this part. Test
> is easy and MFC-safe. Just close all valves off upstream of MFCs, close
> the argon pipe and open isobutane one. Then purge the isobutane line and
> see if you have drops out of the relief valve. You have first to clean
> the isobutane pipe. We did this cycle several time whereas the bottle
> was closed and there were still pressure building up in the line.
> 
> I haven t checked the heat tape settings on this one. Maybe it is still
> a few percents. It might need to be increased. But let s wait for
> tomorrow, once all lines and tanks are flushed with Argon down to the
> detectors.
> 
> Maxime
> 
> PS: Who did just switch mode from default to purge? (Around 4pm). It was
> done like this on purpose. In purge mode, isobutane MFC is turned off.
> (And apparently not leaking since flow reads -5.4 sccm... which is good
> news!). But apparently, in purge mode, CF4 MFCs keep running.