Dephlegmator safety issues

[Brendan]

I found this in an American Distilling Institute paper on whiskey distilling...

I was unaware that there were any pressure dangers running a plated column with dephlegmator...does anyone understand this issue and are able to elaborate on the possible safety concern please?

"During the distilling process the distiller must be very careful not to over- cool the dephlegmator/pre-condenser. Doing so with a non-safety equipped system will cause the alcohol to condense quickly and possibly collapse the still. All distilling systems should be equipped with a pressure and vacuum safety valve. In a safety-equipped system, over-cooling of the dephelgmator/pre-con- denser will only result in stopping the flow of spirit from the condenser and will avoid disastrous results."

And if your answer is just to run warm water from the product condenser through the dephlegmator, well these excerpts are on the same page...

Some systems use the warmed water exiting the condenser to cool the dephlegmator/ pre-condenser. Although this can save some water, by using colder water and slowing down the flow exiting the dephlegmator/pre-condenser, finer control of the purity of the spirit can be achieved.

Clean sweet spirits can be obtained by running a “cold still.” This is accom- plished by keeping the head temperature of the still under 180oF. This is done by running a significant amount of water through the dephlegmator/pre-condens- er cooling the top portion of the column which will increase condensation and thereby allowing greater reflux.

It almost seems contradictory...running the dephlegmator cold could cause disastrous results, but then to run it cold for cleaner sweeter spirits!!?? :wtf:

[Rumdrinker]

Sounds like a load of shit to me with a well designed hobby sized still.
How would a cold Dephlegmater result in the still collapsing?
It should be the equivalent to putting it in to full reflux which any well designed still should be able to handle.
Only time it could pose an issue would be if you built a multi plate column out of paper thin material & run under sized down comers so it would flood completely, but surely if you are building a bubbler you would know better......
Did you find this info on a web site advertising the "safety systems" for sale?

[Brendan]

No mate, this is a paper by the ADI on artisan whiskey distilling.

http://www.distilling.com/PDF/chap11.pdf

Definitely for information, not sales propaganda.

My only thoughts on this never being mentioned is maybe a small vacuum can be created and on a commercial sized still, this could be substantial to the material used...I wasn't sure by "collapsing" if they meant the distillate on the plates...or the wall of the still actually physically collapsing.

Obviously the former would not be a concern at hobby size...

[bt1]

I reckon technically there is minor issue here

sure when a vapour collapses back to liquid there would be a corresponding pressure drop. We expect this.

Two issues to consider, copper if you check the Australian copper handbook has a significant burst pressure rating but imploding can be estimated I guess.

The other point is the process is almost perpetual in that the reduced pressure would be equalized by the incoming/uprising vapour....it's not a stand alone or cyclic collapse, replenish type arrangement.

I venture to suggest but don't have the figures to confirm, that sight glass fracture would likely occur first imho....to be confirmed here.

On still close down yeh sure we get suck back and pending on restriction this may be a small risk...This was covered with relief valve posts many months ago.

bt1

[Sam.]

Quickly looking over that paper and they are talking about 80 gallon up to 250 gallon stills. That is huge.

Assuming they are running pretty big diameter columns then.

I guess if you had no water running through the deflag, then pumped ice cold water into it when its up to temp then there would be a fair vacuum created.

Still not sure about it collapsing the actual still. May have happened to someone somewhere once with a real thin copper still?

Don't reckon its much of concern on hobby sized and the quality of Australian copper. :handgestures-thumbupleft:

[Kimbo]

Dont forget that the Dephlagmator allows the still to be vented to the atmosphere, so any sudden drop in pressure will result in air being sucked back from the outlet. Air/vapour will always follow the path of least resistance ;-)

[crow]

yeah was just thinking, unless they had a non return valve somewhere past the RC (why would you) then this would simply not be able to happen even with a massive column of the thinnest copper and a 3/8 outlet the pressure wouldn't alter but a few degree's and then in a lot less than a second would equalize
Sorry but I'd have to say Myth Busted

[Brendan]

Great post bt1 :handgestures-thumbupleft: I like your thinking...

I gave this idea credit as it was published by the ADI, so there would have to be some merit to possible dangers.

I can only assume that the pressure drop created in a commercial sized still can be considered significant enough to design safety measures, and is not for our concern at hobby sized setups. :-B