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<div class="moz-cite-prefix">Maxime,<br>
<br>
See if you can get the people together for a show and tell. I
would be interested in attending.<br>
<br>
Volker<br>
<br>
On 1/10/18 10:18 AM, mdefurne wrote:<br>
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cite="mid:f91e4518-b413-7d5d-bbd7-c426767940da@jlab.org">
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<p>Dear all,</p>
<p><u><b>Before all explanations, I want to emphasize that Maxence
and I are not gas experts. So we are just explaining you
what we did,why we think it seems to be safe to make another
test of the mixing system with isobutane. We decline any
responsability if something goes wrong and final approval to
start using mixing system with isobutane must come from the
JLab staff in charge of it. </b></u><br>
</p>
<p>Last night with Maxence, we did the following procedure:</p>
<p>- Closed all the valves.</p>
<p>- Closed the manometer for the argon supply.</p>
<p>From this state where everything is closed, we opened the valve
in the rack on the isobutane line supply and then filled the
line from the isobutane bottle to the upstream valve of MFCs
with isobutane. The pressure was about 25psi (cannot be more
precise since the heat tape was ON at 15% at that moment... when
heat tape is warming, pressure is increasing in the line). <br>
Then we closed the bottle and left the system in this state
overnight, i.e. all the line insulated with heat tape around at
15% filled with isobutane.</p>
<p>This morning we went to purge the line. To do so, we first open
the relief valve and then we open the one of the valves allowing
to purge with argon the isobutane MFC line. It is important to
first open the relief valve, otherwise isobutane will first flow
in a line which is not insulated and condense within a few
seconds. (you tried it yesterday evening and relief valve was
then spitting liquid and gaz. So 30F with no insulation will
make isobutane condensing quite fast.)</p>
<p>So this morning, only gaseous isobutane was exiting the relief
valve. Apparently it seems that isobutane is not condensing
anymore. And once the relief valve is closed, pressure in the
line stayed at 0 (With liquid in it, I would expect to have some
pressure built in the line). I nevertheless insist on the
"apparently" since the relief valve is not exactly on the
isobutane line.</p>
<p> So, considering all this, I would <u><b>only recommend</b></u>
to start testing the mixing system with isobutane again. But <u><b>final
approval must be given either by a staff of JLab since this
system is JLab responsability.</b></u></p>
<p>If you want a demonstration of the test later today (because
the mail might not be very clear without the rack in front of
you), we can organize it. However, I have not a faintest idea
about what the next test is to ensure that isobutane is gaseous,
except going through one MFC (no need to start using both
immediately and risk to lose both of them).</p>
<p>Finally, 15% for the heat tape seems fine for ~30F. But
temperature will get colder over the week end and next week. We
might consider to run safe, i.e. testing again isobutane state
as soon as we hit a new minimum of temperature.<br>
</p>
<p>Kind regards,</p>
<p>Maxime<br>
</p>
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<p><br>
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