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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hmmm,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> Not knowing the watt/foot rating of the trace, my first guess would be that it got too hot under all that insulation. I have never heard of straight vs.
spiral advantages or disadvantages but I would be willing to bet that at the fastener locations, the trace would have
<i>cool </i>spots since the heat is being transferred to the tubing more efficiently.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I quit using heat trace for low vapor pressure materials into vacuum systems years ago, I’m assuming your DCS is being used for LPCVD and that would be a perfect
candidate for running the gas at sub-atmospheric pressures to lower the boiling point. I use this method with all my prone-to-liquify-high-vapor pressure gases and have never experienced a “flooded” MFC since doing so.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Best of luck<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Steve Paolini<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Equipment Dood<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Harvard University Center for Nanoscale Systems<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> labnetwork-bounces@mtl.mit.edu [mailto:labnetwork-bounces@mtl.mit.edu]
<b>On Behalf Of </b>Vito Logiudice<br>
<b>Sent:</b> Wednesday, January 21, 2015 12:23 PM<br>
<b>To:</b> Labnetwork<br>
<b>Subject:</b> [labnetwork] Heat trace issues on DCS gas lines<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black">Dear Colleagues,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black">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.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black">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.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black">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?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black">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.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black">Regards,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black">Vito<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">--</span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">Vito Logiudice P.Eng.</span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">Director of Operations, Quantum NanoFab</span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">University of Waterloo</span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">Lazaridis QNC 1207</span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">200 University Avenue West</span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">Waterloo, ON Canada N2L 3G1</span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">Tel.: (519) 888-4567 ext. 38703</span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">Email: <a href="mailto:vito.logiudice@uwaterloo.ca">vito.logiudice@uwaterloo.ca</a></span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:black">Website: </span><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><a href="https://fab.qnc.uwaterloo.ca">https://fab.qnc.uwaterloo.ca</a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
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