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New Style Bubble Caps - Advice for mixing on plates or sections

edited September 2013 in Configuration

Hi all, need to ask a question or two about the new short slot style of bubble caps vs the older style ones.

Sample of new and old style on bubble plate and side by side attached.

I have 2 sets of bubble plates with the old style bubble caps but with new style short slot downcomers.

I have just received my next order for 2 more sets and these are now with all short new style caps and downcomers.

What are the pro's and con's with the different slot heights and perhaps mixing these in either plates / caps / downcomers / position ?

What’s the best way to run with these, ie what plate should be on the bottom and in what order?

Or do I mix and match then so each plate has 2 or 3 new style and 2 or 3 older types?

And for those who are wondering, @punkin has offered to swap all caps to the one type for me if I want to send them back, plus he did not know they are all unused at this stage either, not bad service eh?

Regards fadge

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  • If the liquid depth on the tray is (for example) 1/4" above the high point of the slot in both cases then there is no difference.

    In theory with a deeper tray depth then the longer slot will work over a wider range of vapour pressures. The greater the pressure, the more of the slot length is actually in use.

    How much difference this makes in reality I would not like to say.

    I would suggest using the longer slots at the bottom of the column, just to cater for a puke scenario. There is a bigger gap for any puke to be forced through, so you are less likely to get a blockage.
    You might even consider shortening every other "comb / tooth / finger" (don't know the correct term) to provide a puke gap. In normal use the vapour will never get down that far.

    It should be less of an issue on higher plates.

  • edited September 2013

    interesting question fadge i to would like to know about the new caps looks like an easy fix

    Is there another thread i have missed?

    @Lloyd, can the old ones be modified if you wanted to change them to the new style?

    what would be the advantage of the down comer having less gap also?

  • edited September 2013

    @Myles is correct. If you have the rare opportunity to mix/match the new and old style caps I think the best is to keep the tall slots on the bottom plates.
    The top plates bubble away furiously while there is less and less action lower in the column. The is normal behavior for any bubble plate still. The taller slots may help there to provide more action.

    This design transition has been many months in the making. The idea is to force the vapor deeper into the plate fluid bed to achieve greater efficiency.

    In the beginning we simply machined copper pipe caps but now we own the tooling to make them from sheet copper.


    More tooling allows us to set the "tooth" or slots of the caps and downcomers.
    I used the shorter slotted caps on the downcomers for the last 2 or 3 thousand produced so there would be more fluid above the downcomer holes and lessen the chance of blowthrough when using higher boiler power.
    All fine except when I noticed the bottom 2 plates were barely bubbling on my Dash with eight 4" plates. Figuring there was a pressure problem I bent down every other tooth on the downcomer and everything was good again.
    So yet another mould (tooling) was made to get what I wanted.


    You can see the progress as we continue to refine the caps and downcomers. The new caps for the downcomers will arrive soon but until then you should bend down every other tooth as shown above if you receive the downcomers with the short slots. It only takes a minute or two but gives you the benefits of faster draining with less back pressure and more fluid above the downcomer holes.

    The bubble cap principle is easier to see when looking at a SD bubble cap sitting atop copper caps used in large 1 meter diameter stills. The slots or teeth are very short.


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  • @Lloyd Thanks for the explanations and information. I will bend my downcomers as shown before my first run with my new system . Will toss up if l will keep a mixture of short and long slot caps.


  • edited September 2013

    That is exactly what is so exciting, that SD is constantly developing and improving products continuously and not just sit still in the boat ..... and can I personally contribute to something that drives development forward, I am proud ... and we all get to take advantage of this by good prices on good and tested products. So hold positions lloyd and Cheers from Sweden its whiskytime.....

    Ps: am wery intressed in the Big caps on the foto, and yours press tools for bubbelcaps but a want a bigget tools for 125x50mm caps.... ;-)

  • edited September 2013

    I don't usually show my failures but this one is classic.


    The tooling was produced to make the exact opposite of what was wanted. :))

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  • Just let us think about it. we can probably think up a use for them. How many have you got? :))

  • edited September 2013

    DIY triangular tooth caps - for those that just must have them!!!!!!


    tri tooth.jpg
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  • Only 5 samples were produced from that mould and the parts were reworked to get the new mould made. Getting happy with the caps and downcomers but still need to experiment with the height of the downcomer. A lot of fluid on the plate is considered a good thing but it also creates back pressure on the lower plates causing them to bubble less. Some of this is normal but I suspect the SD downcomers would perform better if shortened by about 7mm or so. That would also work well with the shorter slots on the new bubble caps.
    Making the downcomers adjustable would add a considerable expense but in my little brain is seems logical that the topmost downcomer would be shorter and the lowermost downcomer would be taller. I could be wrong so I'll need to test this idea.

  • Llyod,I did like the old style adjustable,my brother runs his bubble cap column with them!

    It is what you make it!

  • edited September 2013

    @Lloyd and all, first run on mixed plate bubble-caps, used 2 of the long slot caps/plates on the bottom, 2 new style short slot caps/plates on top. All downcomers are short slot with every second tab bend out as suggested. I think it all went OK

    I've added a video of the run, its just over 8 mins and shows the plates running.

    It also shows me stuffing around and my messy shed, but that's gives me an incentive to clean up after playing with my new toy. My wife has not seen me all weekend, she thinks I have something on the side in the shed!

    After the fores and first 1 Lt my run produced about 9 lL @ 96-95 %, then dropped in % slowly for another 2Lt and I then stopped at that point as it was smelly tails anyway.

    Thanks @punkin for your help in getting this baby for me, I kept adding orders for bits and pieces and he has done great.


  • edited September 2013

    Nice vid fadge,looks like you have it figured,it runs like a champ,and hell that looks neat compared to what my setup looked like a few weeks ago,takes time to get a comfort zone going but you have the area for it! :-c

    It is what you make it!

  • best thing ive seen for ages very ozzy love it cant beat a video love the drip tray its hard to get in the shed at my house believe me oh !!!! area of space for play is up there with the best of them very jealous i need some room!!!! :bz

  • cant see difference but im sure its there Harely said so !

  • Great stuff Fadge, love it when a long term plan comes together. How clean does the output taste when dipping your finger under the parrot?

    have you made cuts yet? looking forward to a product review.

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  • Tan and I were spellbound throughout the entire video. Fantastic, Fadge.
    And thanks @Moonshine for downloading it for me.

    Don't we have a place to group these great vids together? It will get lost here.

  • edited September 2013

    I've given @fadge his own pinned video discussion in Usage:

    Watch fadge use his Dash 1!

    @fadge, keep the videos coming and post them to your video thread! :-bd

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