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Re: [new_distillers] needle valve size - 3/8 or 1/4 or 1/8 does it matter?

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  • Bob Bourne
    Gotcha. Thanks Mike! BB. ... From: Mike Nixon To: Sent: Saturday, March 01, 2003 2:33 PM Subject: Re:
    Message 1 of 10 , Feb 28, 2003
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      Gotcha. Thanks Mike!

      BB.
      ----- Original Message -----
      From: "Mike Nixon" <mike@...>
      To: <new_distillers@yahoogroups.com>
      Sent: Saturday, March 01, 2003 2:33 PM
      Subject: Re: [new_distillers] needle valve size - 3/8 or 1/4 or 1/8 does it
      matter?


      A bit of head of liquid. Mount the needle valve so that there are a few
      inches of liquid above it, eg in a feed tube. This increases the pressure
      differential across the valve and that overcomes any tendency of the valve
      to "stick" due to surface tension or a stray bubble. All sizes need this as
      when the valve is almost closed, they all offer a very small area through
      which liquid can pass. The diameter of the feed tube doesn't make any
      difference ... it's just the distance above the valve that does.

      Mike N
      ----- Original Message -----
      From: Bob Bourne
      To: new_distillers@yahoogroups.com
      Sent: Saturday, March 01, 2003 4:15 PM
      Subject: Re: [new_distillers] needle valve size - 3/8 or 1/4 or 1/8 does
      it matter?


      Give it a bit of head to work on Bob. Those small needle valve can be
      erratic when surface tension or a small bubble gets in the way.

      Sorry Mike, not quite clear on what you mean here?

      Are you saying 3/8 OK, 1/4 OK maybe, 1/8 dodgy bubble prob?!

      BB.


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    • mwmccaw <mwmccaw@yahoo.com>
      The size of the needle valve CAN matter - depending on how much power you are putting into the boiler. snd whether or not you wish to strip as well as rectify
      Message 2 of 10 , Mar 1, 2003
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        The size of the needle valve CAN matter - depending on how much
        power you are putting into the boiler. snd whether or not you wish
        to strip as well as rectify with your setup.
        For example - a kw of power will produce somewhere between 35 and 80
        ml/min of condensate (depending upon ABV). Check the capacity of
        your needle valve wide open (with the same liquid head you will have
        when installed). If the valve cannot pass as much liquid as the
        still will produce, then it is too small!
        There is quite a bit of variation between different needle valves of
        the same nominal size.
        The other difference you will see between the sizes is that the
        bigger the valve, the touchier it is at the extreme low end of its
        flow capability. You need to find the best compromise between
        maximum capacity and low-end controllability.
        Cheers,
        Mike McCaw
      • BOKAKOB
        1/4 - yes 1/8 - too small if it exists Bob Bourne wrote:The inline reflux column I m working to (Nixon) calls for a 3/8 needle
        Message 3 of 10 , Mar 1, 2003
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          1/4 - yes

          1/8 - too small if it exists

           Bob Bourne <bourne@...> wrote:

          The inline reflux column I'm working to (Nixon) calls for a 3/8 needle valve. Can I use a 1/8 or 1/4 instead? Bob.


          I can be wrong I must say.
          Cheers, Alex...



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        • Mike Nixon
          BOKAKOB wrote: Subject: Re: [new_distillers] needle valve size - 3/8 or 1/4 or 1/8 does it matter? 1/4 - yes 1/8 - too small if it exists Bob Bourne
          Message 4 of 10 , Mar 1, 2003
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            BOKAKOB wrote:
            Subject: Re: [new_distillers] needle valve size - 3/8 or 1/4 or 1/8 does it matter?

            1/4 - yes
            1/8 - too small if it exists
             Bob Bourne <bourne@...> wrote:
            The inline reflux column I'm working to (Nixon) calls for a 3/8 needle valve. Can I use a 1/8 or 1/4 instead? Bob.
            ==================================
            Alex is right, for the size of still most of us use, for reasons given earlier by Mike McCaw ... the size needed to be able to cope with whatever your still is capable of producing.  I had assumed that factor to be self-evident when I said that any size would serve. 
            I personally use a 1/4" with my LM rig (the 1/4" needle valve is a common item for gas fittings here) and find it works very well.  However, I do not use that rig for stripping, so the valve only has to be able to cope, at the most, with 20% of the total that the boiler/column/condenser produces.  A 1/8" needle valve is getting pretty small, but would work fine for a small, low power rig. 
             
            Mike M's rule of thumb should help you decide on the maximum flow rate you can expect: "a kw of power will produce somewhere between 35 and 80 ml/min of condensate (depending upon ABV)"  Use those figures if using the rig for stripping as well as purification, but divide by 5 (7 and 16 ml/min/kw) if the rig is used for purification only. 
             
            His advice about control of small flows should then help you decide on the best size for your purposes: "the bigger the valve, the touchier it is at the extreme low end of its flow capability", so use the smallest valve you can get that can cope with the maximum flow rate you expect.
             
            Fot the best of both worlds, use a T-junction and mount a large needle valve in the bottom line and a small one in the side line.  The procedure to use with this arrangement should be obvious.
             
            Mike N
             
             
            Mike N
             
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