Pressure in still - how much is too much?

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wishbone77
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Pressure in still - how much is too much?

Post by wishbone77 »

I have spent a lot of time reviewing this forum and haven't found a thread that answers this question sufficiently enough for me so I thought I would post this new/old question to all the the old timers and new timers for comment.

I own and use a prebuilt milk can still that I purchased from Mile Hi Distilling, it is well built and reliable. I never over fill the milk can (2/3-3/4 full) and always double filter/strain any grain mash that goes into the pot. I've never had any issues with this still, however the most stressful and scariest part of this hobby is heating this "pressure cooker" until I see my first drop of distillate. I have read and followed the basics of safe distilling in terms of pressure (don't overfill, slow heating, avoid any seals, etc)., but I am hoping to hear some real experience, stories and specific advice on how to minimize this most dangerous part of this hobby.
Thanks in advance!
My daddy he made whiskey, my granddaddy he did too
We ain't paid no whiskey tax since 1792
You'll just lay there by the juniper while the moon is bright
Watch them just a-filling in the pale moonlight.
- Bob Dylan, "Copper Kettle"
BayouShine
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Re: Pressure in still - how much is too much?

Post by BayouShine »

Unless you have a blockage somewhere in the vapor path, there shouldn't be any pressure build up. Part of building a still safely is leaving a part of it open to the atmosphere.
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Re: Pressure in still - how much is too much?

Post by jb-texshine »

You shouldn't have any pressure in a pot still. With a thumper there's a tiny amount. Due to the submerged down tube. Steam rig has a bit more. There's a old post by Myles "pressure safety valves" that has some pertinent info also reading through the steam distilling section may answer a few questions about pressure. Suffice to say that a potstill should be open to atmosphere and not have any valve that can be shut to allow pressure buildup. Especially if not distilling on grain. Always blow thru or visually inspect for blockage before running and run with a minimum of solids and you shouldn't have to worry abouut it. Checking each seal And solder joint every 15-20 minutes for vapor leaks is a necessary safety practice IMO though.
Proper size pipe and tubing (3/8"id min) helps prevent clogging that can cause pressure buildup also.

Its a good thing that you are safety concious though, it could save your life!
Jbt

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NZChris
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Re: Pressure in still - how much is too much?

Post by NZChris »

If you are looking for a pressure switch to shut the still down on over-pressure, 1 PSI should be safe enough, but don't take my word for it, do your own research.
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Kareltje
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Re: Pressure in still - how much is too much?

Post by Kareltje »

You already minimized the most dangerous part.
It is said the adding a bit of butter or vegetable oil will prevent or lessen foaming.
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Re: Pressure in still - how much is too much?

Post by Pikey »

Sell yourapparatus and go buy a bottle - or else learn !
StillerBoy
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Re: Pressure in still - how much is too much?

Post by StillerBoy »

Pikey wrote:Sell yourapparatus and go buy a bottle - or else learn !
Who elected you to whip this member.. not all members have the ability to learn at the same rate..
If you don't like his question, don't post.. no need to put him down..

Mars
Last edited by StillerBoy on Mon Mar 06, 2017 6:05 pm, edited 2 times in total.
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joeymac
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Re: Pressure in still - how much is too much?

Post by joeymac »

Depends on the still design. A potstill with an ample worm or leibig diameter should be well under 1psi. A reflux column operating efficiently with fluid bed up near the condenser head will build a minimum of about 1psi for every 28-30 inches of vertical column length. Even with an open column top, it's unavoidable physics.

I assume you've got a thermometer probe somewhere near the highest point in the vapor path? yank it out and rig up a simple u-bend manometer to it if your curious.

Another neat thing I suppose you could try if you're positive you know what your boiler ABV% is and you have an accurate thermometer and you know what the barometric pressure is... just read the temperature of your vapor. A known mixture of ethanol will boil at a particular temperature given a certain pressure. For example, azeotrpic water-ethanol boils at 78.1 degrees celcius with zero head pressure applied. However if your thermometer reads 89.2 degrees celcius and you know you're boiling a water-ethanol azeotrope.. then you must boiling into about 7.3PSI head pressure.

PS: Don't put azeotrope ethanol in your boiler... it's dangerous. You'll have to find some charts with reasonable boiler mixtures.
"Woe to those who are heroes at drinking wine and champions at mixing drinks" - God (Isaiah 5:22)
So evidently, God wants us to drink our whiskeys single barrel and our Bourbons neat.
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shadylane
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Re: Pressure in still - how much is too much?

Post by shadylane »

@ Wishbone77
As Joeymac pointed out, a simple manometer will let you see what the boiler pressure is
It can also protect the boiler from over pressure or a vacuum.
If there's only a condenser between the pot-still boiler and the atmosphere.
There should never be more than around 1 inch of water pressure. That's slightly less than .04 psi.
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shadylane
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Re: Pressure in still - how much is too much?

Post by shadylane »

joeymac wrote:Depends on the still design....A reflux column operating efficiently with fluid bed up near the condenser head will build a minimum of about 1psi for every 28-30 inches of vertical column length. Even with an open column top, it's unavoidable physics.
Sorry Joey but your mistaken :oops:
The only way a 28 inch tall column could have 1 psi is for it to be totally flooded.
During normal operations, the column would only cause the boiler pressure to rise an additional .05 psi or there abouts
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Re: Pressure in still - how much is too much?

Post by joeymac »

True. I should have said "maximum possible" ... not minimum pressure. Even then, you're pretty screwed at that point anyways. But I'm not so sure the pressure is super low either. When looking at some of the fluidized bed or aquatic environment information, especially the glass column videos, there's several inches of liquid held in the top and bottom of the column. It probably wouldn't be too hard to get 20" of fluid entrainment into a 42" column. Although it's not pure liquid at rest either either, it's quite bubbly and dynamic.

The quickest way to get a close guess would be to subtract the boiler volume when at full equilibrium from the original boiler charge, multiply that volume by the liquid density to get the mass of fluid entrained in the column and divide that mass the by the column area.
(V1-V2)*Density/Area = Boiler pressure.
"Woe to those who are heroes at drinking wine and champions at mixing drinks" - God (Isaiah 5:22)
So evidently, God wants us to drink our whiskeys single barrel and our Bourbons neat.
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Re: Pressure in still - how much is too much?

Post by StillerBoy »

wishbone77 wrote: however the most stressful and scariest part of this hobby is heating this "pressure cooker" until I see my first drop of distillate.
The best way to over come the stress and the fear you experience at the start of a run is to make yourself a check list, and walk through it just before you fire up.. then trust the check list, and after a few runs, it will become second nature..

I trust you drive a vehicle, and have no second thoughts about how dangerous driving is.. driving a vehicle is the most dangerous activity we all do with no second thought about it.. we just put the key in and away we go.. yet thousands of people are killed every year..

Stilling is so much safer because you are always in control of the operation..

Enjoy the experience of still, not the fear..

Mars
" I know quite certainly that I myself have no special talent. Curiosity, Obsession and dogged endurance, combined with self-criticism, have brought me to my knowledge and understanding "

– Albert Einstein
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Re: Pressure in still - how much is too much?

Post by Pikey »

Ok Wishbone, firstly may I apologise for my post earlier - it was out of order. :oops:

I suppose it can be quite scary sitting there for an hour or so, hearing all sorts of hissing and creaking and not knowing what the F*** is going on.

Let me explain my way - I've never had the slightest issue apart from the first time when it was a bit of a step into the unknown.

Firstly it is not a pressure cooker - Look at it as a kettle. There is a little pressure inside, or else the "steam" wouldn't come out but that's all and it is small.

I use two thermometers. One strapped to the outside of the pot using a bit of wire tied fairly tighly around the pot. This tells me what the temperature inside the pot is to within a degree or so and I can watch the temperature going up. I know that when the temp gets to around 165, it's not going to be long and I start thinking about turning the cooling water on. Around 176 (Actually about 178 F on mine) the head temperature starts to rise - [The other thermometer is poked through a cork in the top of my column, but could equaly well be strapped on as before] The head temperature rises quite quickly once it starts and now you know for certain the "Steam" is getting through, so there is no blockage. When the head gets to 165 I am expecting the first drops any moment and they invariably start soon after. These are the Foreshots and a few degrees more, the stream gets steady and I take the first 100ml into my fire starter bottle. The next part is the heads and then come the Hearts, followed by the Tails and I switch off when my head temperature gets to 212 ish. The temperature in your kettle at this stage will still be quite a way below "boiling" point of water.

Keep notes - I've just looked at mine to look up these temperatures and I know it takes me just under an hour to get my warm up phase done. [My temps are in degrees C and I've converted them for you, so they may not e exactly right, butt they'll do near enough.]

Use my system, you will know exactly what stage you're at at any time and the fear will evaporate ! You can take joy in the clear crystal likker filling up your jars instead!

I hope that helps 8)
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Re: Pressure in still - how much is too much?

Post by StillerBoy »

Pikey wrote:Ok Wishbone, firstly may I apologise for my post earlier - it was out of order.
Pikey.. Thank you :thumbup:

Mars
" I know quite certainly that I myself have no special talent. Curiosity, Obsession and dogged endurance, combined with self-criticism, have brought me to my knowledge and understanding "

– Albert Einstein
wishbone77
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Re: Pressure in still - how much is too much?

Post by wishbone77 »

Thank you all for the replies, Mars is the man (although I think you called me slow :crazy: ). Pikey, LOL but excellent point about the kettle concept. Love the concept of the manometer.

I guess what I had in mind when I posted this thread was hearing some true stories about pressure build up and issues that have occurred to members of this forum (if any). Has anyone actually had a pressure explosion, what were the circumstances and the issues surrounding that incident?

I get puckering during the warm up phase when I question if Ive added too much mash (I'm technically safe, no more than 2/3-3/4 full) and what amount degree of foam is being produced with the concern that the escaping gas from the boiling chamber to the lyne arm maybe getting clogged by foam/too much mash, and that this is where the pressure issue occurs (and where my concerns are). The manometer would have no bearing reading pressure at this position of the still as it would be placed much higher/further along on the still (at level before the condenser it appears).
My daddy he made whiskey, my granddaddy he did too
We ain't paid no whiskey tax since 1792
You'll just lay there by the juniper while the moon is bright
Watch them just a-filling in the pale moonlight.
- Bob Dylan, "Copper Kettle"
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NZChris
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Re: Pressure in still - how much is too much?

Post by NZChris »

This one. The still left the building like a bottle rocket when the bottom seam burst under pressure.
http://homedistiller.org/forum/viewtopi ... 44&t=55616
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Kareltje
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Re: Pressure in still - how much is too much?

Post by Kareltje »

You should not believe all you hear: about half of the stories I hear is not true and I think this also goes for you.

I have had no explosion, but once I had a blow out: a grain mash formed a lot of firm foam, that was blown up on the riser and blew the thermometer up. Luckily, for the condenser had a much smaller diameter and would have been blocked.
Since that time I am more careful in filling my boiler. I start at about half the boiler and then gradually augment the amount.

Some time ago I had sloe in my gin box and this box started leaking a bit. Afterwards I found some kernels got into the riser. I was lucky that a) the kernels did not completely block the pipe and b) the gin box was not screwed, but slipped and taped together, so it could open up a bit.

Indeed: when you are afraid of explosions the part of warming up and waiting for the first drops that prove your still is open, is the most stressing part. To relieve the stress, you can make a safety valve on your boiler and/or make some breaking points in your riser or condenser. With a kind of alarm, if the breaking is not alarming enough. When you react instantly and shut down the heating, there will be hardly any risk of the escaping alcohol vapour.

The very best way to get rid of your fear: go and look to what is your foremost fear. Then you check the possible causes and reasons and you either contradict or counteract these. (In this case: contradict: the system is open to the air or counteract: the system is given a pressure surge.) If you knowledge is not sufficient, enlarge it!!
Then go to the next fear and act as described.
At last an uncertainty will remain. Decide if you want to live with it and act according to your decision: stay of go.
wishbone77
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Re: Pressure in still - how much is too much?

Post by wishbone77 »

Kareltje, thanks for the case reports.

Also found this thread, sorry I missed it when I posted initially
http://homedistiller.org/forum/viewtopi ... =1&t=65072
My daddy he made whiskey, my granddaddy he did too
We ain't paid no whiskey tax since 1792
You'll just lay there by the juniper while the moon is bright
Watch them just a-filling in the pale moonlight.
- Bob Dylan, "Copper Kettle"
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Re: Pressure in still - how much is too much?

Post by Alchemist75 »

Once ever did I run into a pressure issue: I was distilling some botanicals in water and I had the heat cranked up higher than usual. Apparently the lyne arm I was using was a bit too narrow to adequately allow all the vapor to pass quickly enough and the cap of the rig blew off. Thankfully I wasn't distilling ethanol! I learned an important lesson about lyne arm diameter and energy input/vapor pressure that day. The diameter absolutely matters for more than one reason even on a small still.
SOLVE ET COAGULA, ET HABEBIS MAGISTERIUM
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Re: Pressure in still - how much is too much?

Post by Chucker »

I once ran into an overpressure situation that I’d previously shared (and was chastised for) for the edification of all.
I built my rig before arriving at this forum and used a 1/4” copper coil graham condenser mounted vertically. Essentially a compact flake stand. I did so because it was easy enough to wind tightly enough to fit in a 2” tube. It seemed to work just fine as I ran a partial reflux with a vertical shotgun riser. But I occasionally ran in potstill mode with the riser cooling off by reducing the heat input.
One day I just didn’t slow it down fast enough once it started running and it built up enough to blow the cap off. It was not secured and only had a gravity seal specifically for this purpose but what a mess! 10 gallons of boiling beer raining down from all over the shop ceiling. There’s still ample evidence scattered about.
I learned my lesson and increased my condenser coil to 3/8” tubing. I keep it carefully plugged when not in use to keep the mud daubers and spiders out and always blow through it when setting up to be sure it’s clear. To be sure there has to be a pressure gradient to make steam rise through a column and arm assembly but it’s well under 2” WC range. I stuck a magnehelic on it for a couple of runs to check and it may have been even less.
Set it up properly and keep it clear and you’ll be fine.
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