S/S bokabob inline still design question

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S/S bokabob inline still design question

Postby nuddy » Sun Jun 08, 2008 10:45 pm

I've been reading for the past few weeks or so about still design, i've opted for a still like this one viewtopic.php?f=17&t=7093&p=6750908&hilit=bokabob#p6750908, however im making a few changes to it, im making it all out of stainless. I'm planning on making a column and boiler that will take multiple heads, one for LM and another later on once i make it for VM. The condenser is able to be taken out of the head aswell, therefore swaping between the two. Currently ive made the condenser, have a 1/2 keg looking at me wanting a nice flange put on it. However one thing im not to sure about it the venting for it. I understand that it's required to stop pressure building up, however having a hole open to the atmosphere doesnt that allow vapour to escape. How does this affect it during 100% reflux conditions while waiting for it to equalise?

For the LM type head, from the above link, how critical is this vent hole? am i able to put a pressure valve in instead? If anyone can shed some light on this it would be much appreciated :)

I also have a few questions about the heating of the boiler but i will leave them for the moment until i play around with it a little.
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Re: S/S bokabob inline still design question

Postby HookLine » Sun Jun 08, 2008 11:50 pm

Yes, you absolutely MUST have a vent hole or very reliable pressure release valve. The valve can be a simple as a hole with a 100% natural cork plugged in it (but make sure the cork is situated so that it can't hit you in the eye if it pops out!)

I prefer a permanently open vent hole instead of a pressure release valve, as a vent hole can't go wrong.

The vent hole goes above the reflux condenser. If the reflux condenser is doing its job properly it should be condensing all the vapours coming up the column, even during 100% reflux, and so there should not be any vapours getting past the condenser to leak out the top. Some columns don't even have any cap at all on top, just the in/out lines of the reflux condenser sticking out.

Why do you want two different reflux heads (LM and VM)? They both do the same job, so one is enough.
Last edited by HookLine on Mon Jun 09, 2008 1:59 am, edited 1 time in total.
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Re: S/S bokabob inline still design question

Postby nuddy » Mon Jun 09, 2008 1:58 am

Cheers Hookline, i've gone for the open vent on top, after the condenser, ill post some progress pictures when i get home.

HookLine wrote:Why do you want two different reflux heads (LM and VM)? They both do the same job, so one is enough.


I wasnt to sure how the LM incline would work, and figure i change my mind and tinker with stuff all the time that i'd be better off making it easier to do. I've heard that vapour management where u control the amount of vapour that leaves the column then heads down a condenser think its called a leibeig?? is alot easier to control. Whereas the incline bokabob is alot more sensitive to temperature changes. Correct me on anything if i've confused it. But i'd like to eventually make it a fairly self regulating distiller in regards to temp control. Which one would be better suited to this?
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Re: S/S bokabob inline still design question

Postby HookLine » Mon Jun 09, 2008 2:23 am

I have only used a vapour management (VM) column, and it sits rock steady right through the hearts cut, all the way to the tails. My understanding is that the liquid management Bokabob slanted plate is a bit more sensitive to the temperature of the coolant and hence the reflux condensate, but they are still excellent columns. I have not heard any complaints about them, and you shouldn't go wrong if you choose that design, or the 2 cups Bokabob.

Check the photos of my VM (and also the vent hole in the condenser cap).

The stability of the heat input, the quality of the packing, and the height of the column (ie the height of the packing in the column) are also major factors in how well a reflux column works. More stable heat input, better quality packing, and greater packing height gives better results. (For packing heights up to about 1500-1800 mm, after that you start running into diminishing returns)
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Re: S/S bokabob inline still design question

Postby Hawke » Mon Jun 09, 2008 3:17 am

I run a 3" Boka slant plate with 48" of packing. Once it reaches temp and the column hits equalibrium, it stays rock steady through the hearts. Cuts are very sharp. If I'm going for max purity, I get 94.5% at around 1/2 litre an hour with a very small tails portion.
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Re: S/S bokabob inline still design question

Postby nuddy » Mon Jun 09, 2008 5:14 am

heres a few pic of the condenser and head, has the two slanted plates in it, still have a few little things, gotta put the temp probe hole in etc.
Image
Image
Was gonna try do a double helix condenser but my attempt failed miserably, instead went with the easier option. What direction of water input will be more benificial, cold water coming down the straight then flowing back up the condenser towards the top, or cold water coming down the condenser then exiting via the straight??
Image
Image
the vent hole
Image
a quick question about this pic, ive used plumbers thread tape to seal the brass fittings, is there a downside to this?? i know u guys use flour paste etc to seal and was wondering whether this thread tape will leach anything detrimental?? cant remember brand or type off top of my head.
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Re: S/S bokabob inline still design question

Postby HookLine » Mon Jun 09, 2008 6:31 am

Nice welding. Pity you don't live nearby. Did you have to float the 2" threaded nipples when welding them onto the column, or are they tight fits to start with?

What is the vertical distance between the plates?

The vent hole is good, a little bigger wouldn't hurt.

All those brass connectors! Maybe a touch overkill, I would have just taken the copper condenser tube straight through the stainless cap.

Did you de-lead the brass connectors?

a quick question about this pic, ive used plumbers thread tape to seal the brass fittings, is there a downside to this?? i know u guys use flour paste etc to seal and was wondering whether this thread tape will leach anything detrimental?? cant remember brand or type off top of my head.


Oh dear. Let's see if I can answer this without stirring anything up.

The rule on this forum is NO PLASTICS IN STILLING, (except HDPE plastic for fermentation containers). That is a very good rule that everyone here agrees with. More or less.

Plumber's tape is made from a kind of plastic called PTFE (commonly known as Teflon). PTFE is a special case in plastics, it has some unique properties, particularly high resistance to degradation from a very wide range of chemicals in a wide range of temperatures. There is an argument on this forum over whether PTFE in sustained contact with hot, high strength alcohol vapours releases any undesirable chemicals into the alcohol that we make to drink.

Some use PTFE for various seals on their still, some only use flour paste, natural cork, or sometimes oak wood.
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Re: S/S bokabob inline still design question

Postby nuddy » Tue Jun 10, 2008 12:57 am

HookLine wrote:Nice welding. Pity you don't live nearby. Did you have to float the 2" threaded nipples when welding them onto the column, or are they tight fits to start with?

The welding was a little rough and rushed, im still learning to tig, but every little bit helps. The 2" threaded toe nipples did float but i ended up getting the hammer and vice on to the pipe and expanded it till it was a nice fit. As can be seen by the multitude of small dint marks towards the ends. Doesn't look as pretty but a little more functional.

HookLine wrote:What is the vertical distance between the plates?

Vertical distance is roughly 3/4 of an inch.

HookLine wrote:Did you de-lead the brass connectors?

De-lead the brass, no i didnt, how do i go about doing this?

Now about the heating i spoke about in an earlier post, ive done a little reading around and am going to settle on using two electric elements to heat the boiler, one large one and a smaller one. Once it gets to temp kill the large one and control the boil with the smaller element. I went to an electrical supplier and found a vast array of heater elements, but what i was unsure of was that wattage to get. Also they didnt have anyway to control the power to the small one. I can get a 3600W element for roughly $25 aus. So that takes care of the large element, but im unsure of what to do about the smaller element that i plan to control. Reading the triac, diac thread i got a little lost and decided to go with something a little easier (haven't done much with electronics). Since i want to control the temp, i was thinking of getting a catering hot water urn and pulling it apart and using the variable control dial and element on it. Is this feasible? Do these maintain a temperature by reducing the power, or by simply turning on and off?

The boiler is a 50L 1/2 keg roughly 400 diameter by 500 high. Given what ive said above, can someone provide better insight into the required wattage needed to bring a wash roughly 25-30L to boil in a short amount of time (30mins?), then be able to maintain it with a smaller element. Any advice, suggestions etc would be much appreciated.
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Re: S/S bokabob inline still design question

Postby HookLine » Tue Jun 10, 2008 1:36 am

De-lead the brass, no i didnt, how do i go about doing this?


Do a search for "treating brass" there should be plenty of stuff, it has been talked about quite a few times.

Since i want to control the temp, i was thinking of getting a catering hot water urn and pulling it apart and using the variable control dial and element on it. Is this feasible? Do these maintain a temperature by reducing the power, or by simply turning on and off?


No good, they just slowly cycle on/off and don't give a constant even boil, which is critical for stilling.

I control the power on my still element with a zero switching triac module that you can buy from RS Components (Product Code: 489-3424). Works brilliantly but you have to wire it into a box and the total parts cost is about $130. It is a big advantage being able to fine tune your power input for both reflux and pot stilling.

I have a single 2400w element in my 50 litre stainless keg boiler. It takes about 70-90 minutes to bring 40 litres to the boil, starting at about 25-27º C. So double that power (4800w) will bring it to the boil in about half the time.

One reason I chose 2400w is that I can plug it into any standard power outlet in Australia (or New Zealand), with no risk of overloading the circuit. The only downside is that it takes longer to come to boil. If one of your elements is going to be 3600w, then make sure you have a 15 amp power socket to run it from, and use a 15 amp cable to connect it up.

I recommend getting an Incaloy coated element, they are much tougher and are about the same price as tin coated or plain copper. Also, if they have them, get the low density version of the element, they put out the same power but spread over a larger surface area, which helps prevent scorching if you have any solids (like grain, fruit, etc) in the wash.

Make sure your boiler is well insulated, makes a fair bit of difference to boil up time and overall power costs.
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Re: S/S bokabob inline still design question

Postby nuddy » Tue Jun 10, 2008 6:35 am

HookLine wrote:I control the power on my still element with a zero switching triac module that you can buy from RS Components (Product Code: 489-3424). Works brilliantly but you have to wire it into a box and the total parts cost is about $130. It is a big advantage being able to fine tune your power input for both reflux and pot stilling.

Thats pretty much what im after, had another look thru ur pictures at the box u made up, and decided to build one. Is 2400watts the most u can run thru a 10amp power socket? If so, i'll use two 2400watt elements, one running straight from a wall socket (help bring to boil), while the other will run thru the triac box (control once boiled). Also with your box, i noticed you have a fair few airholes, does it create a fairbit of heat the triac module??
Hookline, your a wealth of information and its greately appreciated :)
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Re: S/S bokabob inline still design question

Postby HookLine » Tue Jun 10, 2008 7:05 am

Yes, 2400 w is the most you can (legally and safely) get from a single power point in a standard power circuit (in Aust and NZ).

If you are going to run both 2400 w elements at the same time then plug them into different power circuits (not just different power points). Most houses have at least two separate standard power circuits.

When you are bringing the wash up to the boil using both elements, just plug them straight into the power sockets, by pass the controller completely, no need for it to be in circuit just for full power.

The module has to be mounted on a heat sink (and you need heat sink paste). That box is aluminium, which is a good heat sink, and the ventilation holes help keep it cool. But I also have a small 6" desk fan I sit right next to the controller when it is on and that keeps it real cool.

Glad to help out.
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Re: S/S bokabob inline still design question

Postby nuddy » Wed Jul 16, 2008 12:11 am

After an extended hiatus (end of uni semester, exams, quit my job etc etc etc) im back, the still has moved along slowly, have the boiler nearly ready to go, just need to put the heater elements into it. Have to delead the brass still, but have all that is required to do so.

Now one thing i dont have ready is the triac controller, that one u linked me to hookline looks good but i dont have the money at the moment to splash out on it. So what i was planning on doing, is to get my first wash or two down, then put these thru a few stripping runs to get myself a collection of low wines. Then store these low wines until i can get the triac controller to do the spirit run. Is this feasible? Do low wines keep well, what the prefered method of storage?

What would be be best way to approach this, Im thinking of using both elements (2400 watt types) continuously during the strip, and just collecting everything after the first 150ml.
How critical is the temp when doing stripping runs? Can i just leave them both on and have the collection valve fully open and collect away?

i'll grab some pic's of the still within the next few days to post up,

cheers, nuddy
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Re: S/S bokabob inline still design question

Postby HookLine » Wed Jul 16, 2008 12:57 am

nuddy wrote:Now one thing i dont have ready is the triac controller, that one u linked me to hookline looks good but i dont have the money at the moment to splash out on it. So what i was planning on doing, is to get my first wash or two down, then put these thru a few stripping runs to get myself a collection of low wines. Then store these low wines until i can get the triac controller to do the spirit run. Is this feasible? Do low wines keep well, what the prefered method of storage?


Yup, they keep forever, in a glass or stainless container, a (clean) beer keg is good. Plug the top with a large cork, or wrap several layers of aluminium foil over it and tie it on tightly.

nuddy wrote:What would be be best way to approach this, Im thinking of using both elements (2400 watt types) continuously during the strip, and just collecting everything after the first 150ml.
How critical is the temp when doing stripping runs? Can i just leave them both on and have the collection valve fully open and collect away?


Yup. Turn it on flat out, as long as the condenser can cope with it. Collect everything up to 98ºC.

Don't worry about foreshots, etc, on the first run. Take them out on the second run (the spirit run).

If you have two elements, you can get away without a controller. Have one element 2400 w, and the other 1200 w. Run them both for stripping, and then switch to the 1200 w only for the spirit (reflux) run. (Put the 1200 w lowest down the boiler.)

If you plan to run the boiler as a pot still then you can connect both elements in series and that will give you a combined output of 800 w.

You still don't have the fine control a controller will give, but it should work quite well.

Make sure there is ALWAYS enough liquid in the boiler to cover the active element/s.

The lower down in the boiler you can mount the elements, the better.
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Re: S/S bokabob inline still design question

Postby nuddy » Thu Jul 02, 2009 11:09 pm

holy old thread revival batman

ok I'm back, have done more work on the still, slowly....very slowly putting it together

Updates,
Have got myself a temp controller, was gonna build a triac controller, but ran into a mate who built me a temp controller. Its basically a box with a fancy array of wires and switches with a dial on the front, and a temp probe (i have question on its placement later on). It bascially works like a commercial urn used for boiling hot water but with alot stricter tolerances, +- 0.5 degrees. (will put pics up when i can)

Now Ive got two heater elements, 2.4kw and 1.8kw that will bolt into two flanges that im welding to the boiler.
Image
Image

flange
Image

boiler
Image


ill be placing them as low as i can. however i have a problem with sealing them. They came with two rubber boots that fit perfectly between the element and flange
Image
Image
Image
these seal water tight, however they are rubber :(

ive machined the surface of the flange to form a solid fit but the element has a less then an idea surface to seal to.
My only options i can see are to turn up a substitue boot out of nylon.
Is there any other way to seal these? bear in mind that these elements will be removed to wash the boiler out, so it will have to be removable and faily durable.

Now the question about the temperature probe. Where would be the best place to put this. I have a thermometer placed at the take off point already. Am i better off putting the probe in the bottom of the boiler where is will regulate off the wash temp. Or place it up next to the take off point, where it will be the heated vapour doing the regulating?

pic of the still together, take off point is the shiny piece sticking out just down from the top.
Image

cheers nuddy
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Re: S/S bokabob inline still design question

Postby muckanic » Sun Jul 05, 2009 11:04 pm

nuddy wrote:ive machined the surface of the flange to form a solid fit but the element has a less then an idea surface to seal to.
My only options i can see are to turn up a substitue boot out of nylon.
Is there any other way to seal these? bear in mind that these elements will be removed to wash the boiler out, so it will have to be removable and faily durable.


Well if you look on the brewing forums, you will find people using all sorts of liquid gaskets that would make your hair curl. Personally, I would be inclined to circumvent the whole problem by using a threaded element and backnut approach. Elements are usually available in either style, so sealing is only a problem if you have scrounged up secondhand elements from somewhere. God knows why more hot water services don't fail catastrophically, as the rubber boot is all that is holding them in and they don't even employ an internal flange as a fastener. But that then creates the additional problem of sealing up 4 bolt holes. I would only be planning to remove these elements if they got scorched somehow, and would put in another outlet for cleaning. You don't by any chance have a die big enough to cut a thread around the base of the element? Alternatively, cut off the backing plate and braze a threaded nipple in where the wires exit. Or just braze your elements into the side of the boiler and hope they don't pack it in too soon ...

More thoughts. Weld 4 studs into the outside of the boiler and then you don't need the inside flange any more. Flick the rubber boot, cut the element hole a bit smaller, and simply mount a flat washer between the base of the element and the boiler.

BTW, and this is for the assembled, how are folks cutting element holes in stainless? I could see a hand-drill and holesaw approach getting real tedious real fast. I realise folks are using jig-saws and the like for the lid, but what about down in the 1.5" area?
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Re: S/S bokabob inline still design question

Postby DestructoMutt » Mon Jul 13, 2009 1:31 pm

nuddy - how goes things?

first your heating elements - go to your local hardware store, they will have screw in replacement elements for water heaters, they will also have a conversion plate for converting from bolt in to screw in. weld the conversion plate onto your boiler, screw the element in (or use the screw in element and a 1" pipe union welded to your boiler).

second your brass fittings at the top - remove the thread tape, is not needed as all of your vapors should be knocked down to liquid by your condensor, thus no worry about leaks, also, remove the brass fittings and run the copper tubing up through the holes/nipples you so lovingly welded in, again no need for a leak free joint at the cap as all of the vapors will be condensed.

third, your element control - thermostatic control is not good, it is a on/off proposition. you don't want on/off cycling, you want a steady boil, the amount of boiling is directly related to the amount of cooling supplied by your reflux condensor. start boiling a wash, turn on your reflux condensor full, if vapors get past your condensor, turn down the heat applied to the boiler (not off, but down). eventually you will get the heat input equal to the heat removed. the column temperature gradient is not something you can control after you have built your column. it is controlled by a combination of the heat input, the heat removed, column length, column packing and wash composition. you will note that one of those variables is under going constant change during a run (the wash composition). the alcohol content is constantly being depleted, thus the boiling point temperature is constantly rising, hence the column temperature gradient is constantly changing. it is not something you can control and still have a pure product.

fourth, nice work.

PS - when you run for product, don't give short thrift to the equilibrium stage. it really does affect the quality of your output, and the amount of heads you get.
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Re: S/S bokabob inline still design question

Postby nuddy » Wed Jul 15, 2009 4:53 am

DestructoMutt wrote:first your heating elements - go to your local hardware store, they will have screw in replacement elements for water heaters, they will also have a conversion plate for converting from bolt in to screw in. weld the conversion plate onto your boiler, screw the element in (or use the screw in element and a 1" pipe union welded to your boiler).


I'd love to get screw in elements only i havent got the money to spend on them at the moment, or even in the near to distant future :( so im going to have to deal with sealing them as is.

what materials would be suitable to use as a gasket, im thinking of using copper and annealing it, hopefully it will be soft enough to mould to seal.

or failing that i was thinking of using nylon??? does this leech anything undesirable into the alcohol??

what other materials can i use?

DestructoMutt wrote:
third, your element control - thermostatic control is not good, it is a on/off proposition. you don't want on/off cycling, you want a steady boil, the amount of boiling is directly related to the amount of cooling supplied by your reflux condensor.


this is a on/off cycling controller. however it has a temperature probe attached to a temp dial. So i set the dial to wat temperature i desire, it heats until it reaches this then turns off, it restarts once the temperature drops 0.5 degrees below the set temp. i understand this will have lag associated with it, and im gonna have a look at getting it changed to a steady boil set up. but i believe i can still use this to do stripping runs yes??? (just crank the temp and let it run)

cheers nuddy
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