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Re: Procedure to handle a two valve system?

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  • jrrymiller
    What you are trying to avoid is exposing the hot DP oil to the air. You should continue to pump through the DP until you are sure the oil is cool. You can
    Message 1 of 3 , Apr 1, 2008
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      What you are trying to avoid is exposing the hot DP oil to the air. You
      should continue to pump through the DP until you are sure the oil is
      cool. You can tell by the increase in pressure as the oil cools. The
      roughing pump will not pull oil out of the cool DP. If it could then it
      surely would when the DP is hot. The reason to keep pumping while the
      DP cools is to prevent the DP oil from backstreaming into the chamber.

      Keep looking for that valve.

      Jerry Miller


      --- In VacuumX@yahoogroups.com, "henry_3507" <kmnhij@...> wrote:
      >
      > I wonder what the procedure is with the valves when i want to open
      > the chamber? I have seen a couple of tips on the net but they doesnt
      > really add up for me. I have seen some descriptions on a two valve
      > system that say that after the heating element is turned off to the
      > diffusion pump so should the roughing pump be on all the time with
      > the roughinh line to the diffusion pump fully open until the
      > diffusion oil is cool enough to vent the chamber and not until then
      > close the valve to the roughing pump.
      >
    • henry_3507
      Thanks for the answer. No i didnt mean that the roughing pump could draw out oil of the diffusion pump or any air get into it i ment the opposite that the DP
      Message 2 of 3 , Apr 3, 2008
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        Thanks for the answer. No i didnt mean that the roughing pump could
        draw out oil of the diffusion pump or any air get into it i ment the
        opposite that the DP could draw out oil from the roughing pump. Because
        when the DP starts to cool so would the roughing pump be exposed to say
        10e-6 Torr since the roughing port on the DP would be exposed to the
        vacuum in the chamber, and that is what concerns me a little.

        Regards Henry



        --- In VacuumX@yahoogroups.com, "jrrymiller" <gandamiller@...> wrote:
        >
        >
        > What you are trying to avoid is exposing the hot DP oil to the air.
        You
        > should continue to pump through the DP until you are sure the oil is
        > cool. You can tell by the increase in pressure as the oil cools. The
        > roughing pump will not pull oil out of the cool DP. If it could then
        it
        > surely would when the DP is hot. The reason to keep pumping while the
        > DP cools is to prevent the DP oil from backstreaming into the chamber.
        >
        > Keep looking for that valve.
        >
        > Jerry Miller
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