VM Experts...help please

[Kenster]

Hi..i have read the 'how to run a VM ' several times and it all relates to a 2'' system. I dont know how to calculate what a 3'' should do.
Does anyone run a 3'' insulated VM. As i am just starting to play with my new build, what sort of collection rate should i be aiming for with a 1200 packed column...1 to 1.5lit per hr for 2'' is kind of recommended...should i just try to achieve this or should i aim for a greater volume. The whole idea of going 3'' was to increase thru put rate... or am i just kidding myself?
TIA...Ken

[Zak Griffin]

3" should be significantly faster mate. I've never run a VM, but your best bet is going to be running your rig and seeing where it is happy. Crank the heat up until quality drops, them back it off until you're holding azeo.

Have you got any pics? We haven't seen many VM builds around here for a while!

[Kenster]

Zak...thx for the speedy reply...the build link is in another post...The Humble T500... has all the pics.
Except for the coldfinger, which i will upload to this post (as i was too slack to get it when the others were taken)

[Kenster]

COLDIE.jpg

The Condenser...My first(and last) attempt at braizing the bottom...gave up as i just couldnt get enough heat out of the Map gas.
450mm over 1'' ... 8mm and 6mm winding.

[stilllearning]

Mate that's a very tidy looking condenser, nice handiwork.

[WTDist]

I was looking at the exact same thermometer the other day 8-}

Are you doing single run ken, or low wines?

Not sure who it was, maybe Hardy :think: maybe not, its been a while, I think he had a 3" boka before the bubbler and had it going about 3l/h on low wines. I think the T500 would go about 1.7l/h on single run and decrease as run progresses. from my experience, I had it spraying out of my still on low wines with the T500 that much that even the parrot over flowed. this was cause my column flooded and i think it was going 3l/h or faster on low wines.

have you tried low wines yet? that is where the real magic will happen :handgestures-thumbupleft:

[toil]

My VM produces a nice product at 3 L per hour. For a VM increased column diameter gives more speed however you will also need more power to run it compared to smaller diameters. I would agree that for a high quality product you need to do strip runs prior and then fill the boiler with low wines at 40% for the VM run.

[Kenster]

Thanks for the feedback guys...appreciate it.
I have a heap of (T500) product @ 90% which i will try to 'clean up' via low wine dilution.
3 litres per hr... i think i just got wood.

[TheMechwarrior]

For a 1200mm column on a 3" still you are really restricting the performance at 16 column diameters in height.

For a VM still designed to produce neutral the optimum range is 20-30 column diameters for your height so your minimum really should be around 1500mm if you want to get the most out of your 3" column diameter.

A height of ~1838mm is roughly equivalent to the purity that would be achieved on a 1200mm 2" column for example.
A 1200mm 3" column will give roughly the same purity as a 783mm 2" column, all other variables being what they should be.

To get the purity you want you'll be running at a much higher reflux ratio so your output rate is going to be reduced.
If you want the speed and the purity you have the option of running an offset second column and feeding from the top of one into the bottom of the other, not sure if you have height restrictions limiting you to 1200mm? If you don't, go for the 1800mm-2100mm range.

Hope I haven't confused you.

Cheers,

Mech

[WTDist]

Good info there, i agree if you can go higher go higher. Its what i plan on doing height not restricting

[Kenster]

Mech...that is some sensational advice..appreciate it.
You are dead right...ran yesterday and could only get 1 lit per hr. wide open. (94% at 13C) happy with purity...shit collection rate.
I thought that it may have been due to insufficient heat/power as i run the std T500 element and thought that if i cranked it up it should spit out more, as i have a 2.5kw element on order.Obviously not. The Boka, however(as it is a combo) just goes great, very quick and reasonable ABV (about 1 to 2 less).
I get what you say about the height but do you think that throwing more heat into it may help because i really dont want to rebuild.
Worst case, i Bok will do just nicely.