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Vito:<br>
<br>
While I do not profess to be Mr. DCS ... and, some would argue,
being in California I have no right to weigh in on the topic ... I
will share what we have done on our DCS lines. As a qualifier,
however, our DCS runs in single-walled, rather than
double-contained, tubing. We have two DCS lines and each is about
400 feet in length and nearly half of that runs outdoors between our
gas bunker and the main lab.<br>
<br>
We don't run spiral wrap ... we simply run our heat trace along the
length of the line. We do, however, use sticky aluminum tape along
virtually the entire length of the line to try to improve the
thermal conductivity between the heat trace and the actual gas
line. While we believe that is reasonably effective from a thermal
standpoint, it's a real mess to undo if you ever remove the line.
In our case, the line/heat trace/tape assembly is encased by
inexpensive black foam insulation normally used on 1/2" plumbing
lines.<br>
<br>
Here is a low-quality image of what we have with the foam pulled
away:<br>
<br>
<img overflowing="true" class="moz-attached-image"
src="cid:part1.05060902.00090500@stanford.edu"><br>
<br>
Good luck,<br>
<br>
John<br>
<br>
<div class="moz-cite-prefix">On 1/21/2015 9:23 AM, Vito Logiudice
wrote:<br>
</div>
<blockquote
cite="mid:D0E54A9E.55EFE%25vlogiudi@connect.uwaterloo.ca"
type="cite">
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<div>Dear Colleagues,</div>
<div><br>
</div>
<div>We are experiencing an issue with the heat trace on our
Dichlorosilane gas line. The all-welded 1/4" SS line is
encapsulated with a 1/2" SS outer containment line which is
itself heat traced with a single strand of heat trace that runs
the entire length of the coax assembly. The 120 foot line is
insulated as shown in the attached photo. A portion of the
heat-trace appears to have failed prematurely (it was installed
less than one year ago) and we are wondering if the method of
installation may be the cause.</div>
<div><br>
</div>
<div>The heat trace was not installed in a spiral fashion around
the outer 1/2" tube. Rather it was installed in a straight
fashion along its entire length with "heat trace fastening tape"
located every four feet or so. A member of my team has suggested
that such a straight rather than spiral installation may have
caused hot spots (at the fastening locations) which may have in
turn caused the failure.</div>
<div><br>
</div>
<div>I would appreciate hearing from the community on this point:
Are the heat traces around your low pressure gas lines
spiral-wound around the lines or are they installed in a
straight fashion and somehow fastened along the entire length?</div>
<div><br>
</div>
<div>Other insights/suggestions on the proper heat tracing of gas
lines by experts in the field as well as comments on possible
causes of premature heat trace failure are very much welcome and
appreciated. Thank you.</div>
<div><br>
</div>
<div>Regards,</div>
<div>Vito</div>
<div>
<div><font class="Apple-style-span" color="#000000"><font
class="Apple-style-span" style="font-size: 14px; "
face="Calibri"><font face="Calibri,sans-serif">--</font></font></font></div>
<div><font class="Apple-style-span" color="#000000"><font
class="Apple-style-span" style="font-size: 14px; "
face="Calibri"><font face="Calibri,sans-serif">Vito
Logiudice </font>P.<font face="Calibri,sans-serif">Eng.</font></font></font></div>
<div><font class="Apple-style-span" color="#000000"><font
class="Apple-style-span" face="Calibri"><font
style="font-size: 14px; " face="Calibri,sans-serif">Director
of Operations, Quantum NanoFab</font></font></font></div>
<div><font class="Apple-style-span" color="#000000"><font
class="Apple-style-span" face="Calibri"><font
style="font-size: 14px; " face="Calibri,sans-serif">University
of Waterloo</font></font></font></div>
<div><font class="Apple-style-span" color="#000000"><font
class="Apple-style-span" face="Calibri"><font
style="font-size: 14px; " face="Calibri,sans-serif">Lazaridis
QNC 1207</font></font></font></div>
<div><font class="Apple-style-span" color="#000000"><font
class="Apple-style-span" face="Calibri"><font
style="font-size: 14px; " face="Calibri,sans-serif">200
University Avenue West</font></font></font></div>
<div><font class="Apple-style-span" color="#000000"><font
class="Apple-style-span" face="Calibri"><font
style="font-size: 14px; " face="Calibri,sans-serif">Waterloo,
ON Canada N2L 3G1</font></font></font></div>
<div><font class="Apple-style-span" color="#000000"><font
class="Apple-style-span" face="Calibri"><font
style="font-size: 14px; " face="Calibri,sans-serif">Tel.:
(519) 888-4567 ext. 38703</font></font></font></div>
<div><span style="font-size: 14px; ">Email: <a
moz-do-not-send="true"
href="mailto:vito.logiudice@uwaterloo.ca">vito.logiudice@uwaterloo.ca</a></span></div>
<div><span style="font-size: 14px; ">Website: </span><a
moz-do-not-send="true" href="https://fab.qnc.uwaterloo.ca">https://fab.qnc.uwaterloo.ca</a></div>
<div><br>
</div>
</div>
<br>
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