Novice Inquiry re: Potential Pressure Buildup

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scorpion3367
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Novice Inquiry re: Potential Pressure Buildup

Post by scorpion3367 »

I recently assemble a Bokakob Mini Still based on the plans at learntomoonshine.com (not sure if I can post a link) which I am preparing to break in with my first run once the wash is ready in a few days.
That said, I have some safety concerns in terms of pressure buildup as it seems to me that with the column being sealed at the top (according to these plans - a 1-1/2" end cap is to be soldered on) as well as the base (sink drain assembly), aside from the 1/4" needle valve and perhaps the thermometer port, I can see the potential for pressure to build up inside the still. Are my concerns justified or am I missing something that is inherent in the design of this particular unit? I did originally post the same inquiry in the Welcome Center as part of my introduction (incorrect move on my part I might add - my apologies) and cuginosgrizzo was kind enough to respond and indicated that the Bokakob Mini Still is not supposed to be closed on top. This obviously makes me wonder why the plans were modified to include the addition of soldering an end cap on top of the column. I guess at this point i'm wondering if I should err on the side of caution and remove the end cap prior to breaking in this still?
Thanks in advance to any of the more experienced members of this forum for their time and effort in setting the record straight for me. Hate for my first run to also be my last!
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der wo
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Re: Novice Inquiry re: Potential Pressure Buildup

Post by der wo »

A boka definetely has to be open over the reflux coil! Same all other LM and VM designs.
Either don't use a cap or drill a hole in the cap.
This design is on our parent site too:
http://homedistiller.org/equip/designs/reflux_plan" onclick="window.open(this.href);return false;" rel="nofollow
http://homedistiller.org/image/mini_explained.jpg" onclick="window.open(this.href);return false;" rel="nofollow
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rad14701
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Re: Novice Inquiry re: Potential Pressure Buildup

Post by rad14701 »

scorpion3367, my guess is that those plans were modified because I know for a fact that there wasn't a soldered cap on the original plans, if there was a cap at all... Not sure anyone would clean their reflux column if it was hermetically sealed... We recommend at least a 3/8" vent hole if you use a cap... The reflux condenser needs to knock down 100% of the vapor produced so no pressure should be present and vapor leaks would be an indicator of improper adjustments, like not enough coolant flow or too much power input... And truth be told, some reflux columns actually suck some ambient air into the top of the column so the vent is doubly needed...

Go ahead and post a link or PM it to me as I like to see where people get their information from just in case there are other issues they may not be aware of... And if this is the original design it would benefit from a longer packed column...

Edited to add: Search around here because there are lots of Bokakob dual slant plate topics here in the forums... Some of which explain suggested modifications...
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rgreen2002
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Re: Novice Inquiry re: Potential Pressure Buildup

Post by rgreen2002 »

Welcome scorpion... you got some great advice from some damn smart folks up there. A little humble advice I might add.... take whatever that learntomoonshine website has to offer with a grain of salt. It has a nice "flashy' look to it but as I skim the sections I see a lot of things that are not complete. A good example is the fact that they don't tell you the Boka has have a releif on top of the column... either be open or if you use a cap a vent hole has to be drilled.

Another important thing is that you don't get the whole story over there. Nowhere in any of the still build threads did I see the REQUIREMENT of how to clean your newly built still. The information is quite incomplete.

I can see how you ended up here at these forums (and that is the best thing that ever happened to that website and you) since about 50% of the "information" comes from here.. the other 50% just seems to be missing...

I'm glad you landed here... and settle in because you will find everything....EVERYTHING you need for the hobby right here. Stay away from you tube and other "fancy" sites like the one above and you will be making quality product in no time. I recommend clicking the links below in my signature to get the best experience you can.

Good luck, be safe.
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Pikey
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Re: Novice Inquiry re: Potential Pressure Buildup

Post by Pikey »

We had a little discussion on the vent in Bokakob a few weeks ago scorpion. It seems that the vent or open top is essential It is Not an option.

http://homedistiller.org/forum/viewtopic.php?t=64039

There are many other threads on building bokakobs which I'm sure will say essentially the same thing, but with the valve shut, a boka is effectively a sealed gas cylinder and if you apply heat, then your fears are completely well founded. :shock:

I too would like to see that link, if you can post it ?

[Edit - extremely well done for thinking about the situation and querying what looked wrong to you. That's the way forward in this hobby where we have to take responsibility for our own decisions and actions 8) ]
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Danespirit
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Re: Novice Inquiry re: Potential Pressure Buildup

Post by Danespirit »

Pikey wrote:We had a little discussion on the vent in Bokakob a few weeks ago scorpion. It seems that the vent or open top is essential It is Not an option.

There are many other threads on building bokakobs which I'm sure will say essentially the same thing, but with the valve shut, a boka is effectively a sealed gas cylinder and if you apply heat, then your fears are completely well founded.
The vent hole is absolutely MANDATORY on any still that potentially could be sealed off from the atmosphere...! (A vacuum still is the exception)
You want a still...not a pipe bomb with hot flammable vapor.
As the still comes to temperature, some uncondensable gasses are the first to ascent in the column and displace the air within.
Obviously, they eventually have to go somewhere, so has the air...that would be the aforementioned hole at the top.
A Bokakob is a LM reflux still and will only deliver a good result when you are able to bring the column into equilibrium (stack the contents in layers defined by their weight).
You won't be able to accomplish this unless the vapor can move around in there and gradually replace the other gasses.
I know a lot of novices are reluctant regarding that hole or even running the still without a cap.
They fear the vapors will escape....well..they won't as long as there is enough cooling in the RC to knock down the vapor.
Remember...Ethanol is liquid up till 78 C, so if your RC is colder than that you're good.
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