[labnetwork] Swagelok tube fitting for high vacuum systems?

[Yongkui Tang]

Dear Labnetwork,

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 Reddit post<https://www.reddit.com/r/engineering/comments/2m2pk9/has_anyone_used_compression_fittings_swagelok_on/>, 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.

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:

  1.  Chamber volume.
  2.  Turbo pump volume flow rate.
  3.  Number of Swgelok tube fittings in the setup.
  4.  If available, any leak testing data would be extremely helpful!

TL;DR: Would you recommend against using Swagelok tube fittings (the ferrule compression type) for the vacuum system at 1e-5~1e-6 Torr range?

Many thanks,
Yongkui Tang
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