4" To 6" Upgrade

Current 100L boiler has 5 kW heating and takes around 2 hours to heat up my 4" Dash with 3 ProCap plates. Then around 4.5 hours at 4.4 kW with dephlegmator on pretty strong (cold Scottish water) I get a good steady flow through my cuts taking rum hearts around 81% from a 9.5% sugar wash. So I'm running with vapour speed around 15.9"/sec, right? I figure I want to replicate this as I scale up.

Thinking going with a 380L boiler with around 15 kW heating, this should take around 3 hours to heat up. I'm thinking a 6" Dash with 3 ProCap plates would take around 9.8 kW to run double flow rate through the cuts with the same vapour speed as my old rig at 15.9"/sec, right? But since the boiler volume is nearly 4 times bigger the time from heat up to end of tails will now be double the old rig, around 8 to 10 hours. Is my thinking right?

If I want to run more plates, say 6 or 8, would the total 15 kW give me enough headroom on power to push up the extra plates and maintain the product flow rate?

How many plates would I need on the new rig to make vodka, would 8 be enough and would the headroom of 15 kW of power be enough to push this through the plates with a reasonable product flow rate?

Plates and power, the balance of life!


  • Curious, is there some power constraint you are working under?

  • Hi @grim,

    Yeah I've got space and power limits to work within. I've converted my garage at home to a nano-brewery/distillery, fully HMRC licenced and selling product online and markets. I'm amazed at the quality (as are customers) I'm producing rum at on single pass through 3 plate 4" Dash, wow!

    I put 12 kW solar on the roof last year, but that's only good for 8 months of the year, so working with limitation of single phase mains. The mains will do around 20 kW but I need to leave some for the wife to run the house! I recon 15 kW is a safe limit for the brewery/distillery.

    This upgrade gets production capacity on rum alone into significant figures, with literally no overheads (no rent, rates, etc). As I approach capacity on the upgrade kit the business will be well placed to go for a much larger upgrade, commercial premises, and have the books to raise capital for investment. It's a plan to grow with as low a risk as possible.

    Hence a bigger boiler at 380L than perhaps a 6" column requires, but I can't get the power for 8" and a 380L charge on 6" column will give a nice long run with long clear cuts I think. 380L boiler will never go a miss in a craft distillery. In the sunnier months (in Scotland, don't laugh!), I'll have up to 32 kW to play with depending on house load scheduling, this would let me run the upgrade still and my existing 100L 4" Dash... thinking maybe stripping runs on the 6" then run smaller still as a rectifier to produce vodka (might need to go 4 or 5 plates each on 4" and 6" to hit vodka).

  • It's 380l working capacity. It doesn't mean you have to put 380l in there though......

    Manage your work day by the volume i say.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • edited February 16

    @SLOPEmeisteR Have a look at the calcs page

    I used it to calculate your heat up time for 380l with 15000W & got an answer of around 2.5 hours to get a 10% wash to 90C @ 90% efficiency.


    That page also has a vapour speed calculator ;-)

    IMO the 380l is a perfect match with 8" columns. Remember diameter = speed. As a commercial operation, time = money. Smaller diameter = Longer runs = increased cost and lower production volumes :-(

    I don't know why you say you can't get the power to run an 8". I have a 380l with 4 x 8" plates & use 21kw for heat up but cut back to 14kw for the run.

    Good cuts come down to how you run the rig (eg power input, reflux ratio, timing, if you do a strip then spirit run etc). If you're going to be barrel aging you don't need the hearts cut to be as tight because you actually want a bunch of the congeners in heads (& late tails with rum) for flavour (but you won't get much of that on a sugar wash).

    FYI, adding a few more plates will only take a little extra time to heat up. The longest time is getting the wash up to temp, getting the column to temp is pretty quick once the wash is boiling.

    As you're operating in a pretty cold environment, don't forget you can insulate the boiler & column to improve thermal efficiency & hence overall performance of the rig.

    800 x 356 - 29K
  • If the 4" and 6" both have 3 caps, doesn't it make more sense to jump to 8"? I'd think the 8" would be far more future-proof.

    Get a generator, run it to cut down that heat-up time to an hour or less.

  • Hi @punkin - I hear you on volume/work load! Can always charge less than 380lt, but mostly it'll be a full charge to maximise the capacity and volume output. Maybe smaller charge for trial runs, but I've got the 100lt/4" for that anyway.

    Hi @crozdog - I'd prefer to go 8" if I think the powers enough, commercially it makes sense.

    Heat up time is what it is really, max power available, how long will it take. We all work with that.

    The only metric I have to select the column diameter is vapour speed.

    Looked again at my existing 100lt/4"Dash (3 pro-cap plates), vapour speed is actually 16.03 on the run at 4.4kW. Your running 380lt/8", vapour speed is 12.75 on the run at 14kW.

    I could do 380lt/8", vapour speed at 13.66 on the run at 15kW (leaving 5kW for the house load; max 20kW incoming main).

    I do run my 4" quite hard then at 16.03 vapour speed, I use a good bit of reflux on this to maintain product flow. With 8" running at 15kW the heat to cooling ratio would be changed i.e. less reflux cooling at this lower vapour speed to maintain product flow. Is that the right thinking?

    Really my big concern about going up to 8" was will I be able to power a decent enough flow rate, sound like I can albeit with a lower vapour speed than I'm used to on the 4".

    Also 100lt to 380lt is almost quadruple, 4" to 8" is quadruple area. Roughly speaking then my heat-up/run time will be around the same for the same wash.

    When I say sugar wash I mean molasses, demerara and granulated sugar blend, so there are some interesting things in the heads/tails and I do want to barrel age. Currently ageing on Still Dragon supplied oak woods, done one whisky cask aged for 8 months and it was outrageously good and sold out fast!

  • Vapor speed is more relevant in packed and perf tray columns, not really for bubble caps. With caps, vapor speed might be useful in understanding the maximum power input (before causing entrainment flooding), but because of the high turndown ratio of caps, doesn't really help much on the lower bound.

  • @grim @crozdog thanks for your input. I'm a bit happier now knowing 380lt boiler with 8" Dash Pro can run spirit with 15kW, giving me loads of capacity... for now. Simple dimensions check, if you can help. What's the floor to superstructure opening height on the 380lt boiler? I've got the column (standard 3 plate config) at 1160mm and extra sections at 203mm from the web shop, so can work out what fits!

  • @SLOPEmeisteR said: grim crozdog thanks for your input. I'm a bit happier now knowing 380lt boiler with 8" Dash Pro can run spirit with 15kW, giving me loads of capacity... for now. Simple dimensions check, if you can help. What's the floor to superstructure opening height on the 380lt boiler? I've got the column (standard 3 plate config) at 1160mm and extra sections at 203mm from the web shop, so can work out what fits!

    The single wall is right around 1100 + or - mm tall at the column connection.

    The Electric Jacketed version is roughly 1219 mm + or - at the column connection. The conventional steam kettle should be just about the same as the Electric Jacket.

    StillDragon North America - Your StillDragon® Distributor for North America

  • @Smaug cheers! Just food for thought, what's the single walled 500lt boiler floor to column opening height?

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