VM take off buried in the packing?

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needmorstuff
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VM take off buried in the packing?

Post by needmorstuff »

I am considering buying a 2" column but just noticed that the VM take off is actually in the section where the packing resides? is that sensible? I note that there is another port to put the VM take off higher up out of the packing but why would you even have a VM buried in the packing.

http://destylatorymiedziane.pl/en/reflu ... -lmvm.html" onclick="window.open(this.href);return false;" rel="nofollow

this is the pic i refer to
vm in packing.PNG
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der wo
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Re: VM take off buried in the packing?

Post by der wo »

Not long ago a new member from eastern Europe posted, that the homedistillers in his area believe, that fores are not only produced by fermentation but also while distilling. In theory it's correct (esterification). If in practice it's really tasteable, I don't know.
So it makes sense to collect foreshots at a higher point during the whole run. They use the LM outlet not only at the beginning for the "real" fores, but also during the whole run. Only perhaps 1 drop per 1 or 5 seconds, I don't know. So the packing above the VM branch is for concentrating the fores which are formed during the run.
For the functionality of the VM branch the packing next to it and above is no problem. Interesting to know would be, if they have a collar or something which hinders the reflux to take the VM branch. Or also if the valve is not full bore but reduced bore would solve the problem I think. Or if they need a mesh to hinder the SPP to fall into the branch? Or perhaps the branch aerea is without packing? They have a packing retainer under and above?

And European threaded brass fittings contain a bit lead unfortunately. I recommend to electroplate them inside with copper. You could also tin it. Or delead it with acid (but this is not proven to work). Google search the site with brass and lead. You will find discussions.
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needmorstuff
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Re: VM take off buried in the packing?

Post by needmorstuff »

sadly I have no answers for you.. I did however notice a small bore copper tube poking down from above the spp, I did wonder what it's purpose was

the brass however has pit me off it altogether
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needmorstuff
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Re: VM take off buried in the packing?

Post by needmorstuff »

another thing i couldn't get my head around with the lower vm placement...

the purpose of the sight glass is presumably to monitor the column for flooding (aparently spp is prone to it) well by the time you noticed the column was flooded the flood would already be pissing out the vm takeoff
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BayouShine
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Re: VM take off buried in the packing?

Post by BayouShine »

needmorstuff wrote:another thing i couldn't get my head around with the lower vm placement...

the purpose of the sight glass is presumably to monitor the column for flooding (aparently spp is prone to it) well by the time you noticed the column was flooded the flood would already be pissing out the vm takeoff
Exactly.

Even if you didn't run it flooded, can you imagine the amount of smearing from condensate constantly dripping into the takeoff?
needmorstuff
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Re: VM take off buried in the packing?

Post by needmorstuff »

you can of course run the top vm take off. I just find it strange
Last edited by needmorstuff on Thu Feb 01, 2018 10:25 am, edited 1 time in total.
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Re: VM take off buried in the packing?

Post by BayouShine »

Took another look on the website. There's ports all over that still. Strange for sure.
needmorstuff
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Re: VM take off buried in the packing?

Post by needmorstuff »

better too many than not enough? would need a good supply of ptfe tape
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der wo
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Re: VM take off buried in the packing?

Post by der wo »

Ok, I looked at their website. The small pipe is a reflux return. A good thing. Helps centering the reflux.

And yes, you can attach the VM branch also at the same height like the LM, over the packing and the sight glass.
But in general you will find out soon, when it floods and when not.

But I think you have seen, it's a 2" only. I thought you want to go 3"?

And the brass... I have never seen a commercial reflux still following all hd-rules... IMO every still you can buy needs a bit work.
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needmorstuff
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Re: VM take off buried in the packing?

Post by needmorstuff »

enough people have told me I don't need a 3" still and it is starting to get through to me :-)

I am coming from a 24 x 2" CM and my only real complaint is the speed and me striving for a better product. I was going 3" to improve throughput and for quality.. If what I read is correct a taller column will allow me to run a bit faster than a 24" and the height will also get me better quality.

With regards buy over make, I have no tools and no experience so whilst I love a project the cost of the 2" from those guys is good considering what you get for your zloti.

From looking at their pictures and reading description - the other two ports are for the included temp gauges.
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zapata
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Re: VM take off buried in the packing?

Post by zapata »

I run a still somewhat like this. I can't tell exactly what's going on internally in that one. I assume that VM takeoff is not actually in a packed section but rather the packing ends just beneath it. So far as I understand, a VM takeoff should always be in an empty vapor chamber, not the middle of a packed section.

But mine goes like this from top down:
reflux condenser at the top
LM trap based on one of boka's designs for taking off fores and heads
an upper packed "heads" column
LM trap to route liquid reflux down external to the VM Tee
reducing T with a VM takeoff
packed column
boiler

I do not find the need to run it as derwo describes, and I've seen that the russians do. I don't run a constant bleed off the upper LM, I just count on the in situ produced heads rising up and being trapped and compressed in the heads column. The heads column needn't be too large for this, during VM hearts takeoff the heads column is at perfect equilibrium under 100% reflux so at it's best HETP. I have used both a 10" and a 12" high heads column and guess it's good for about 4 theoretical plates.
Of course it isn't perfect, as I will still catch a percentage of in-situ heads in the VM takeoff, but only in relation to my reflux ratio. So if it's a super slow run at 9:1 reflux ratio, I only take off 10% of any in-situ heads. A faster 4:1 reflux ratio and I'm still eliminating 80% of in-situ heads. I think in-situ generated heads are real, but small, so I'm happy with this less than perfect way of reducing them. From what I infer on the pictured still, it will function in the same way. A lower VM will never be able to fully eliminate in-situ heads, only exclude a percentage of them.

The other effect of the VM takeoff being beneath a packed section is that the back pressure of the heads column forces more vapor through the VM than the ratio of valve opening:column diameter should allow. If you plan for this, it lets one use a smaller valve while still preserving the range of RR possible. This is apparent in that design, but not something I took advantage of in mine where I went with the old reducing Tee to hold my VM takeoff:column ratio at 1:1 without needing a giant valve. With my heads column it means just a tiny crack in the valve is sufficient for takeoff and makes it harder to control. I don't use SPP, but imagine this effect is even more pronounced with SPP than it is with either my scoria or copper mesh.
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