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Kamal:
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<div>Disclaimer: I am retired and have not received a paycheck for 5 years. As a result, you cannot trust/accept anything I say without independently verifying it with someone that is still up to date. </div>
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<div>But, a few comments:</div>
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<div>1. CGA (Compressed Gas Association) produces a document numbered G-13 related to the handling and distribution of Silane. Many, but not all codes, refer to that and use their recommendations as standards. Last I knew (double check this …) Silane was NOT
required to be secondarily contained. </div>
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<div>2. For low pressure gases such as DCS and BCl3, I would be remiss if I did not tell you that Steve Paolini at Harvard (AKA The Equipment Dood) would STRONGLY recommend the use of sub-atmospheric regulators to avoid the need for heating these lines to
prevent condensation. While I never had a chance to specify/buy/work on such a system, I would ABSOLUTELY explore that option. Heating gas lines is never fun!</div>
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<div>3. For the chlorinated gases such as Cl2, BCl3, HCl … and maybe their brominated brethren … you used to be able to run them in a single-wall line of Hastelloy (AKA C-22) instead of double walled 316L. Note: this may no longer be true … don’t trust my word.
The downside is that Hastelloy tubing makes 316L look cheap … although single-wall Hastelloy may be comparable to double-wall 316L. But, if you do have to heat lines, heating single-wall is a LOT easier than trying to heat double-wall. Also, orbital welding
of Hastelloy takes a completely different program than they use for 316L. A good welder will have that program ready to go. Beware, however, if they say “It looks like stainless … how hard can it be?”</div>
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<div>Best of luck!</div>
<div><br>
<div dir="ltr">John
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<div>Sent from my iPhone</div>
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<blockquote type="cite">On Sep 14, 2020, at 6:02 PM, Nathanael Sieb <sieb@4dlabs.ca> wrote:<br>
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<p>Hi Kamal,</p>
<p>We used electropolished SS for all of our high purity gas lines. Double wall was used for all toxics, including Cl2, BCl3, and SiH4. The sheath is exhausted through the gas cabinet so we can sense any leaks. I believe that it is a combination of welded
and bends depending on the area. We didn't end up heat wrapping any of the lines.</p>
<p>Our worksafe code doesn't appear to specify double-walls, but as far as I know it is best practices.</p>
<p><a class="moz-txt-link-freetext" href="https://www.worksafebc.com/en/law-policy/occupational-health-safety/searchable-ohs-regulation/ohs-regulation/part-06-substance-specific-requirements#SectionNumber:6.116">https://www.worksafebc.com/en/law-policy/occupational-health-safety/searchable-ohs-regulation/ohs-regulation/part-06-substance-specific-requirements#SectionNumber:6.116</a><br>
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<p>I hope that helps!</p>
<p>Thanks,</p>
<p>Nathanael<br>
</p>
<div class="moz-cite-prefix">On 2020-09-14 12:02 p.m., Kamal Yadav wrote:<br>
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<blockquote type="cite" cite="mid:CAOfoCyhT-_sC_xCeG2ncHVMMOLKGF_7hLUxaqvMsNgDWkckfag@mail.gmail.com">
<div dir="ltr">Dear All,
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<div>Another query in continuation for gas tubing-</div>
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<div>3. How does heat trace constraint impact choosing of single of double contained tubing for Cl2/BCl3. Is the heat tracing as effective on double contained tubing as single. Is the need for heat trace tube length dependent.</div>
<div>4. All process gases with 5N or higher purity are with electropolished tubings?</div>
<div><br>
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<div>Thanks,</div>
<div>Kamal</div>
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<div dir="ltr" class="gmail_attr">On Mon, Sep 14, 2020 at 9:43 AM Kamal Yadav <<a href="mailto:kamal.yadav@gmail.com" moz-do-not-send="true">kamal.yadav@gmail.com</a>> wrote:<br>
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<div dir="ltr">Dear All,
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<div>We will be installing SS gas tubing for Cl2, BCl3, HBr, SiH4.</div>
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<div>I have some experience in how industry does it, but wanted to know how different universities do this. From some prior posts, I got to know University of Michigan has co-axial tubing for all these gases and every connector location for these gases is exhausted
as well at their facility</div>
<div><br>
</div>
<div>My queries are: </div>
<div>1. Is this how most of the Universities do it or there are places where these gases are in single tubing [non co-axial or double contained]. </div>
<div>2. Also if you do orbital welding or just bending of the tubes?<br clear="all">
<div><br>
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<div>I have been informed it is based on the fire code of the city or county, but it's not apparent from those documents.</div>
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<div>Thanks for your help.</div>
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<div>Thanks,<br>
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<div>Kamal </div>
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<div>Thanks,<br>
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<div>Kamal </div>
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