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I see no problem with using Swagelok compression fittings at those pressures. If I was to design the system though, I would specify VCR connections because of the extremely low dead volume in the interface. It isn't as though compression fittings can't handle
pressures into the 1e-8 range but the more compression fittings that are on the chamber could lead to slower times to get to your specified pressure because of the two-ferrule design where gas molecules take a little more time pumping out.</div>
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I would also use only stainless steel tubing. If you decide on braided stainless hoses for your connections, beware of the fact that when you do helium leak checking, the helium permeates the Teflon liner and will cause migraines while testing.</div>
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One very important tidbit is to avoid pipe threads on a vacuum chamber if your process calls for pressures at 1e6 or lower.</div>
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I cannot provide the specific information in your 4 questions since my response is based on my experience with Many different vacuum systems over decades.</div>
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Hope this helps,</div>
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Equipment Dood</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> labnetwork <labnetwork-bounces@mtl.mit.edu> on behalf of Yongkui Tang <yongkui.tang@iota.bio><br>
<b>Sent:</b> Saturday, April 5, 2025 1:00 PM<br>
<b>To:</b> labnetwork@mtl.mit.edu <labnetwork@mtl.mit.edu><br>
<b>Subject:</b> [labnetwork] Swagelok tube fitting for high vacuum systems?</font>
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<p class="x_MsoNormal">Dear Labnetwork,</p>
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<p class="x_MsoNormal">We are converting a generic quartz vacuum furnace (5e-3 Torr) into a somewhat higher vacuum one (1e-5~1e-6 Torr base pressure without gas load) and are deciding on the inert gas line fittings. In the old setup, we used Swagelok tube fittings
(the ferrule compression type) on plastic tubing -- not ideal but worked fine for the mTorr-range pressure. For the new system, we are unsure if it’s necessary to invest in a gas line with all Swagelok VCR or VCO fittings, or simply replace the plastic tubing
with stainless steel one. I couldn’t find any vacuum rating for the Swagelok tube fittings except from this
<a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__www.reddit.com_r_engineering_comments_2m2pk9_has-5Fanyone-5Fused-5Fcompression-5Ffittings-5Fswagelok-5Fon_&d=DwMF-g&c=WO-RGvefibhHBZq3fL85hQ&r=-H4Z_jeDfTYjnKPXor15vLwzBllmg8gFrb9m_k9OGks&m=zkFMd_gbT4hyVRgvUYR2Yr96AAIHMMIOSxlkJSiR6zn-_kbvxeo7_lEN6qNM9ug1&s=QMIqIK3OchJnaSGNlYLNn0Uy85TFc_VI1dg8sIIQpEk&e=">
Reddit post</a>, in which a Swagelok salesman claimed that these fittings are rated to 1e-6 Torr, along with two anecdotal experiences claiming to reach 1e-7 and 1e-8 Torr, but no further details were given.
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<p class="x_MsoNormal">Does anyone use Swagelok tube fittings for their vacuum system whose base pressure is at 1e-5~1e-6 Torr pressure? If so, could you please share some information:</p>
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<li class="x_MsoListParagraph" style="margin-left:0in">Chamber volume. </li><li class="x_MsoListParagraph" style="margin-left:0in">Turbo pump volume flow rate.
</li><li class="x_MsoListParagraph" style="margin-left:0in">Number of Swgelok tube fittings in the setup. </li><li class="x_MsoListParagraph" style="margin-left:0in">If available, any leak testing data would be extremely helpful!</li></ol>
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<p class="x_MsoNormal"><b>TL;DR</b>: Would you recommend against using Swagelok tube fittings (the ferrule compression type) for the vacuum system at 1e-5~1e-6 Torr range?
</p>
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<p class="x_MsoNormal">Many thanks,</p>
<p class="x_MsoNormal">Yongkui Tang</p>
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