Vapor pipe diameter for hobby sized, multi column still

I am in the process of designing a modular, hobby sized still with a 15.5 gal boiler and 2-3 4” diameter columns, and curious about what size copper tubing I should use for the vapor paths. Since the larger size copper pipe gets pricey fast, I was curious what people thought would be the minimum diameter that would not cause issues with this size system. Even on commercial stills, it looks like 1-2” is common, could I get away with say ¾” copper without back pressure or flow restriction? Thanks in advance!

Comments

  • You are talking about side mounted columns?

  • The easy answer to this. Your condenser should contain the smallest vapour path in the system. It is also what you should design first as it is related to the power available. Design the condenser and then make sure that the rest of the vapour path is bigger.

  • Also reconsider copper for the down side of the vapor path. Copper good on up side, not so much for downside.

  • from what I have read +1

  • @Myles said: The easy answer to this. Your condenser should contain the smallest vapour path in the system. It is also what you should design first as it is related to the power available. Design the condenser and then make sure that the rest of the vapour path is bigger.

    Myles I find this a bit confusing. Can you say that again?

    @brewsmith, considering we use 2" diameter vapor supply piping for 8" and 12" diameter columns, I would say that 3/4" diameter vapor supply piping is generally fine.

    StillDragon North America - Your StillDragon® Distributor for North America

  • curious what is the disadvantages to copper on the down side of the vapour path

  • edited January 5

    Copper particulate is more or less poison. Copper on the down side my allow an unwanted amount of copper in the finished product. Kinda why you never see finished product stored in copper vessels. Better on the up side of the vapor path to minimized the likelihood of coming over in finished product.

    Though it is a very traditional material and widely used without incident,,,doesn't mean it's not harmful in a measurable way.

    StillDragon North America - Your StillDragon® Distributor for North America

  • @Smaug said: considering we use 2" diameter vapor supply piping for 8" and 12" diameter columns, I would say that 3/4" diameter vapor supply piping is generally fine.

    Agree 1000%

  • edited January 6

    @Smaug said: Though it is a very traditional material and widely used without incident,,,doesn't mean it's not harmful in a measurable way.

    Indeed! Using copper in the down path causes global warming!

    I'm more like I am now than I was before.

  • edited January 6

    Retard lol!!!

    StillDragon North America - Your StillDragon® Distributor for North America

  • My original setup had copper on the upside and downside, and I used to get blue crystals separating out in the tails after they'd been standing for a while. Presumably these were copper sulphate/sulphite, neither of which I want to risk getting into my final product. So I changed the downside to stainless steel, and now I don't get the blue crystals.

  • It’s the copper you can’t see that’s the problem.

  • so a copper product condenser is a no no , any body have a link on this info . thanks

    tim

  • all sorts of links, here is one.

  • Learnt me a new word from that - patinated. Makes since, just never seen patina in that form before. Too cool for school! Thanks Coth!

    I'm more like I am now than I was before.

  • @Smaug said: Myles I find this a bit confusing. Can you say that again?

    Sorry for the delay. Yes, and easiest with an example. Product condenser with 7 x 15 mm ( 7 x 1/2 inch) inner cores. Inner dia 13.6 mm cross sectional area is 145.3 mm square.

    Total vapour CSA is 7 x 145.3 = 1017.1 mm square.

    The closest equivalent is 42 mm tube that has an internal CSA = 1425.3 mm square.

    So the smallest tube in the vapour path - just before the condenser should be no smaller than 42 mm or 1.7 inch. From there back to the boiler it should get progressively bigger.

    If you make the tube before the condenser smaller than the total area of the vapour cores you only do one thing. You increase the vapour speed before it enters the condenser. You can cope with this, but it means that you might need to increase your coolant flow rate or decrease the coolant temperature.

    The condenser should be optimized for your boiler power. That PC with 7 x 15 mm cores if it were 500 mm long - is in the ballpark for about 7 kW.

  • I would imagine the sizing of a vapor tube would be based on the potential back pressure generated in the kettle, and not the cross-sectional capacity of the condenser.

    We can't diss Bernoulli here, while the vapor speed will increase in a smaller diameter pipe, it will immediately slow once it hits the larger cross-section of the condenser. Conservation of energy.

  • edited February 12

    The biggest argument about copper product condensers usually relates to ethyl carbamate. If you have enough copper in the ascending path the copper in the product condenser is irrelevant. Any precursors to ethyl carbamate are removed before the vapour gets anywhere near the condenser.

    There is a reason why some of the still manafacturers (e.g. Carl and Holstein) use both copper catalysers at the top of the vapour path and copper product condensers.

    Here is some more reading material.

    pdf
    pdf
    Copper in pot stills.pdf
    2M
    pdf
    pdf
    ethyl carbamate.pdf
    134K
  • edited February 13

    @grim said: I would imagine the sizing of a vapor tube would be based on the potential back pressure generated in the kettle, and not the cross-sectional capacity of the condenser.

    We can't diss Bernoulli here, while the vapor speed will increase in a smaller diameter pipe, it will immediately slow once it hits the larger cross-section of the condenser. Conservation of energy.

    I don't think this is valid. There is minimal back pressure in any tube that is open to atmosphere. Have you noticed much increase in boiler pressure on any pot still? There might be some if you are using plates but the maximum pressure increase in the boiler will be due to the total height of all the tray depths added together.Probably minimal.

  • My sixpence worth, 7x15mm is too large. Go for smaller diameter. Even smaller than 12mm OD.

  • @richard I wasn't proposing 1/2 inch cores although many folks use them and bigger. It was just an illustration. I personally use 12 mm for shotguns and have 10 mm in my own coiled liebig.

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