VM design check and questions

[Henri]

Hi all,

I'm building a VM still, and I would really like to ask some last minute questions, before I start cutting the
expensive parts. Other comments are also greatly appreciated.

Here's a crude drawing of my design (made in mspaint ):


My questions correspond with the numbers in the picture.

1) Distance between top of take-off and the reflux-condenser. My notes say this should be about 50mm, is this correct?

2) Distance between top of packing and take-off. Should there be any?

3) Packing height. I've calculated 51mm (inner diameter) * 24 = 1224mm packing height. Is this correct? Will it hurt to use more, or is it just a waste?

4) Distance between top of boiler and bottom of packing. Does this even matter?

5) Drop before product condenser. How long should this part be?


thanks for your help,
Henri

[astrangebrew]

Heneri,
You got it right
1 50 mm is good
2 50 mm is good here as well
3 1224mm almost exactly the same as mine (I'm 12mm shorter - height of ceiling was my restriction)
4 a little room is good (mine is about 75mm) just in case you have some foaming
5 doesn't matter, mine drops about that but I swung mine back towards the column to minimize the offset weight

other: try to minimize the distance between the Tee and the valve
There is a calculator on the parent site for the product condenser but I really overbuilt (I had the material and room).
700mm - but there is a benefit, the distillate comes out as cold as you water going in, in my case about 12C (12mm inside 18)
Insulate the column and boiler. I used 3 layers of Refectix, duct tape and velcro - worked great.


SB

[rad14701]

+1

Looks good, Henri...

[plonker]

Agree with astrangebrew, however, I have found 5 to be important. It seems that the longer the drop to the condenser, and the larger the pipe, the more the collapsing vapor creates a suction. This can make it hard to dial in just the right reflux.

Having said that though, the other thing I have found is that the more heat you put in to the boiler (providing your reflux condenser can take it), the less important how open the gate valve is.
More heat = more reflux = easier cuts and more output. If I run my boiler flat out, 16000 BTU across two burners, I can run my VM with the 1" gate valve wide open.

Cheers

[squidd]

Hi all,

I'm building a VM still, and I would really like to ask some last minute questions, before I start cutting the
expensive parts. Other comments are also greatly appreciated.

Here's a crude drawing of my design (made in mspaint ):


My questions correspond with the numbers in the picture.

1) Distance between top of take-off and the reflux-condenser. My notes say this should be about 50mm, is this correct?

2) Distance between top of packing and take-off. Should there be any?

3) Packing height. I've calculated 51mm (inner diameter) * 24 = 1224mm packing height. Is this correct? Will it hurt to use more, or is it just a waste?

4) Distance between top of boiler and bottom of packing. Does this even matter?

5) Drop before product condenser. How long should this part be?


thanks for your help,
Henri

Henri,

Is there a VENT at the top of your reflux condenser ??
EXTREMELY IMPORTANT for safety.

squidd

[Henri]

Thanks for your advice all.

I've started cutting and sawing. This is what I have put together so far.



Reflux condenser could be prettier and shorter I guess. I have some tube left, I might give it another try
The brass is another thing I'm not too happy about. I seriously think there are NO copper adapters or unions anywhere in Europe.

I will start on making the flange tomorrow, but I want to wait till my keg comes back from the welding shop before I do any soldering.

Henri

[HookLine]

1) 30-50 mm seems fine.

2) Depends on the exact column design. But generally for VM you need some kind of turbulence happening at the take-off port so that it is easier for the vapour to turn down into the take-off arm. Using a reflux centring ring, or little bit of twisted 1/4" tube, sitting on top of the packing, with the top of the packing about 50 mm below the take-off port, seems to work.

OTOH, my packing sits level with the bottom of the take-off port, but I also have a reducer/reflux collar above the take-off port, at the bottom of the reflux condenser, and that set-up also seems to do the job.

3) 1224 mm is good, and other 300 mm will not hurt, but past that and you are running into seriously diminishing returns, and probably starting to hit your ceiling as well.

4) Yes, it certainly can. You need a gap to allowing for bubbling and foaming of the wash/low wines. Typical rule of thumb is to only fill a boiler 4/5 for low wines, and maybe 2/3 for washes, especially molasses and grains.

5) More is better, but it is not a critical design feature. Most would use 250-400 mm.


What is the size of your take-off port?

[airhill]

Henri

On 4 it may be wise to push the packing up about 1" from the boiler entrance point and check it after every run.

[HookLine]

Oops, slightly misread question 4. I have my packing flush with the bottom of the column, but do not fill the boiler all the way up, so there is a gap between the packing and the surface of the liquid in the boiler.

[airhill]

Hook

One of the reasons I suggested 1'' was the fact I cannot see the boiler connection in the pic. Even if space is left in the boiler, if the connection is a constriction or packing is too tight or it moves down (I flush mine out with a hose from the top followed by boiling water) I found I could get destabilisation of the column temps.
I theorised it was reflux competing with rising vapours but I could be full of shit

[Henri]

3) 1224 mm is good, and other 300 mm will not hurt, but past that and you are running into seriously diminishing returns, and probably starting to hit your ceiling as well.

OK, the column is now 1.35m. Ceiling is high enough to allow for a longer column and I have plenty of copper pipe, so maybe I should have made it longer. But I guess this length will be fine.

What is the size of your take-off port?

The take-off port is 28mm, I have a 54x28x54 fitting.


Henri

[astrangebrew]

Just remember - don't make the column so high you need a step stool to reach the valve <GRIN>

...Now if I could just find a valve with a remote control so I didn't have to get my lazy butt out of my chair...

SB