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7139Re: [new_distillers] needle valve size - 3/8 or 1/4 or 1/8 does it matter?

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  • Mike Nixon
    Mar 1, 2003
      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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