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High Vacuum Piping Help

  1. Jun 27, 2015 #1
    Hello all,

    I have a Varian M4 diffusion pump that has a 6 inch diameter opening at the top, is it okay for me to connect that to a reduced size opening like just 2 or 3 inches diameter so that I can use a smaller valve? I am only trying to pump down a cubic foot or two sized chamber. I am trying to lower costs by going with a smaller valve because big gate valves are extremely expensive.

    I'm assuming this would only result in slower pump down speeds? What are the consequences of doing this? I would prefer a right angle valve connecting the pump to the chamber
  2. jcsd
  3. Jun 27, 2015 #2
    see take a look at this system thats commonly posted on here, it reduces diameter from the diffusion pump up to the chamber, i truly doubt that there is much consequence to what I am planning, however if the angle valve idea is truly inhibiting and laminar flow of a straight valve would make a huge difference, then please let me know

  4. Jun 27, 2015 #3


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    If you're just pumping the chamber to high vacuum with no processing gas flows it will have a small effect on the ultimate base pressure in the molecular flow region where the kinetic effects of the mean free path of the gas molecules is important for pumping. The valve size will be less critical to pumping speed if there are no angles to the diffusion pump from the chamber.
  5. Jul 8, 2015 #4
    Thank you for the info, ended up getting a gate valve instead of a right angle valve. Glad to know it will have higher performance because of it.
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