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<p>The MFC stopped working although the heat tape was heating the
isobutane pipe all along (The pipe was hot enough to slightly
burn). Is it possible that the exit pipe of the MFC must also be
heated to prevent the isobutane from condensing on the other side
of the MFC? <br>
</p>
<p>Cheers,</p>
<p>Maxime<br>
</p>
<br>
<div class="moz-cite-prefix">Le 14/12/2017 à 17:39, Marc McMullen a
écrit :<br>
</div>
<blockquote type="cite"
cite="mid:53e28c3c-ed43-2b7a-6148-fbf45c270993@jlab.org">
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<p>Hi Max,</p>
<p>I am not recommending the use of c4h10 in the new mfc until I
can prove the old one can be dried out or we get a new one, it
is the spare and we don't have another in that range. Tomorrow
I'll submit an order for a replacement. <br>
</p>
<p>The liquid had to be isobutane, it evaporated as it was exposed
to air. Todd is looking into improvements to the thermal tape.
Isobutane needs to be above 70F to keep it from condensing. Todd
also may be able to set up a test for mixing Ar/C4H10. But the
owner/da may have to look into that first.<br>
</p>
<p>Marc<br>
</p>
<br>
<div class="moz-cite-prefix">On 12/14/2017 4:46 PM, mdefurne
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:eeab20c9-32c2-ce01-c4a9-2727d174d948@jlab.org">
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<p>Hi Marc,</p>
<p>Just for curiosity, when will you try the death test, the
test with isobutane? :P<br>
I am also very curious about this fluid seen by Todd. Liquid
isobutane? Unlikely considering the temperature of the MFC,
no?<br>
</p>
<p>Thanks again for investigating this issue.</p>
<p>Max<br>
</p>
<br>
<div class="moz-cite-prefix">Le 14/12/2017 à 16:25, <a
class="moz-txt-link-abbreviated"
href="mailto:mcmullen@jlab.org" moz-do-not-send="true">mcmullen@jlab.org</a>
a écrit :<br>
</div>
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<article id="node-577429" class="node node-logentry
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<header class="node-header">
<h1 class="node-title"> <a
href="https://logbooks.jlab.org/entry/3504568"
rel="bookmark" moz-do-not-send="true">MVT Mixing
System C4H10 Mass Flow Controller</a> </h1>
</header>
<div class="date-vitals">
<p class="author-datetime"> Lognumber <a
href="https://logbooks.jlab.org/entry/3504568"
class="lognumber" data-lognumber="3504568"
moz-do-not-send="true">3504568</a>. Submitted by <a
href="https://logbooks.jlab.org/user/mcmullen"
moz-do-not-send="true">mcmullen</a> on <time
datetime="2017-12-14T16:21:07-0500"
pubdate="pubdate">Thu, 12/14/2017 - 16:21</time>.
</p>
<table class="field-vitals">
<tbody>
<tr>
<th>Logbooks: </th>
<td><a
href="https://logbooks.jlab.org/book/hbmvt"
moz-do-not-send="true">HBMVT</a></td>
</tr>
<tr>
<th>Entry Makers: </th>
<td>mcmullen, jtewing</td>
</tr>
</tbody>
</table>
</div>
<div class="logentry node-content">
<p>We purged the mix 2 C4H10 mass flow controller with
Argon this morning (venting to atmosphere). During
the disconnection Todd saw a small amount of liquid
drain from the mfc. It responded to flow set points
routinely above 150sccm. Below that value the flow
was between 90 - 100sccm, with the internal valve in
the closed position. The mfc was then zeroed by the
manufactures procedure, which specifies that is
isolated from flow. The procedure went as standard,
however once the Argon supply was opened, the
~90-100sccm flow returned. Proper operation below
150sccm was not achieved.</p>
<p>The gas pad temperature reading was > 50F. The
RTD was being read from inside the enclosure. The
MFC temperature reading was ~32C. Both of the
reading were within operating specs for the mfc.</p>
<p>Around 1pm we swapped it out for the spare, which
tested perfectly in the lab.</p>
<p>Once online we were able to flow Argon to the mfc
low limit of 13.9sccm at the set full scale
(1390sccm). Even a little below that, the mfc did
not become unstable until < 10sccm. We then ran
the mix 2 system with both mfcs, still venting to
atmosphere. Again no issues with either mfc, as long
as the C4H10 mfc set point was > 10sccm.</p>
<p>Tomorrow I will test the bad mfc in the lab to see
if I can dry it out with either N2 or Ar.</p>
</div>
<div class="attachment-box"> </div>
</article>
</div>
</div>
<br>
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<br>
<pre wrap="">_______________________________________________
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</pre>
</blockquote>
<br>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Marc McMullen
Detector Support Group
757-269-7738</pre>
</blockquote>
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