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strange plate behavior

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strange plate behavior

Postby Badger » Mon Feb 25, 2013 3:06 pm

So I ran a batch of jaggery rum the other day and it turned out great. My wife took one taste and started raving about how awesome it was (which never happens). So I'm not complaining.

That said, the still acted a bit strange towards the end of the run and I'm hoping someone can explain what might have been going on:

For the majority of the run, my Dash1 ran smoothly and as it should. The only unusual issue was that the dephleg couldn't knock down the full power, which it normally can. No biggie. I backed it off a bit and things ran smoothly.

In the last 1/4 of the run, though, things got wonky. In the space of about 5 min, my 1st (from the bottom) plate went dry and #2 completely flooded. So much vapor was blowing up from #1 that the overflow couldn't even go down the downcomer. There was probably an inch of liquid above the overflow port! #3 and #4 were bubbling like normal.

I turned the heat down and let things settle and drain. When I turned the heat back up, #1,3,4 plates all resumed bubbling like normal but #2 didn't. It had 1/2-1d" of liquid, at least, but no bubbling action. It probably held this way for a good 20-30 min before it finally started bubbling a bit again. By the end of the run, all 4 plates were operating like normal.

Any ideas on what would cause that one plate to act so differently from the others?

Thanks in advance,
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Re: strange plate behavior

Postby DuckofDeath » Mon Feb 25, 2013 3:12 pm

have you checked your riser holes? they may be the older smaller ones or they could even be blocked.
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Re: strange plate behavior

Postby Prairiepiss » Mon Feb 25, 2013 4:16 pm

When you say it can normally knock down everything. For the same wash and ABV? Or was this wash different then what you normally run? What are you using for cooling water supply?
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Re: strange plate behavior

Postby Badger » Tue Feb 26, 2013 1:23 am

@ DoD: I do indeed have the original SD risers. I'll take the still apart later today and look for obstructions. As the plate worked initially and then again at the end, I suppose it could have become plugged and then unplugged. Strange, though as it was only a sugar wash and didn't puke.

@ PP: While I've never made this exact recipe, I have done other sugar washes of a similar ABV (8%) with no incident. My cooling supply is cold city water I port from my utility sink.

@minime: It's a 5500W element on a 30A/220V so I think my full power should be the full 5500W. Normally, I can get it up to full power, equalize with the dephleg on, and slowly back off the dephleg to get the run going. This time, I had distillate coming across at full power no matter how much water I had running through the dephleg.
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Re: strange plate behavior

Postby DrWho » Tue Feb 26, 2013 3:37 am

Badger wrote:@minime: It's a 5500W element on a 30A/220V so I think my full power should be the full 5500W. Normally, I can get it up to full power, equalize with the dephleg on, and slowly back off the dephleg to get the run going. This time, I had distillate coming across at full power no matter how much water I had running through the dephleg.


It could have been the line voltage fluctuating. I used to have that issue which can be quite troublesome. More so when using a phase angle controller. If you have a DVM monitor the line voltage while running.

???
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Re: strange plate behavior

Postby Monty » Tue Feb 26, 2013 3:46 am

If your dephleg was unable to cope this time unexpectedly and you don't recirculate your water flow, my guess would be a restriction of the water somehow. A citywide water pressure drop, spider's nest in your dephleg :lol: , a too-tight clamp holding your discharge hose back into your sink.

As for the plate function, no clue. Though I will say that I ran a cleaning run of my plates and once found a spider's body tangled up in a downcomer...
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Re: strange plate behavior

Postby Prairiepiss » Tue Feb 26, 2013 4:53 am

You are equalizing your still with 5500 watts? :confusion-confused:
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Re: strange plate behavior

Postby Badger » Tue Feb 26, 2013 6:52 am

Hmmm. If you two raise your eyebrows, I must be doing something wrong. The ammeter in my controller box reads 23-ish amps. To figure out watts, don't I multiply this times the 220v ? If so, that's giving me 5000 and change. Did I screw up the #s somehow? As an English major, I'm used to doing that.

As far as equalizing, I should probably make sure I'm using the right term here. I use it to mean "getting all 4 plates loaded under the dephleg, which is knocking everything down." That's what I've been doing at full power. Then, after 20 minutes or so I start to reduce the water to the dephleg until I get a "pencil-lead-thin stream." I've been keeping the power on full, just for consistency's sake. Should I not be doing that?

Honestly, I'm not too worried about the dephleg and whether it can knock down my full power. I'm more interested in how I can get bubbling on plates 1,3,4 but not #2. Sounds like the consensus (so far, anyway) is that there must be some kind of blockage in the 2nd plate? It's hard to imagine that ALL the bubble cap holes would be blocked. I was getting NO bubbling on that plate but plenty on the plates above and below it.

Thanks for all your thoughts and insight,
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Re: strange plate behavior

Postby Prairiepiss » Tue Feb 26, 2013 7:00 am

Personaly I don't think the second plate is blocked. I think your throwing to much power at it. But I've been wrong before. I would think you would ne netters off somewhere between 3000 and 4000 watts. But I've never ran that setup.

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Re: strange plate behavior

Postby SBB » Tue Feb 26, 2013 8:21 am

Prairiepiss wrote: I think your throwing to much power at it.

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Re: strange plate behavior

Postby Badger » Tue Feb 26, 2013 11:06 am

Ok, I take your collective point regarding power. I'll back it off from now on. I just figured that the more energy thrown into the bottom but stopped at the top would mean more vigorous vaporization, which could only help the purity at the top. If I hadn't overwhelmed the dephleg (again, this was the first time) would it have been a problem otherwise? Obviously, at the other (albeit ridiculous) end of the spectrum, I could theoretically back the power all the way down to the point where the dephleg isn't even needed for equilibrium. If that's not what we're going for (and I don't think it is), then what is the happy medium to aim for (and why)? If I were to try pulling off more liters/hour, wouldn't I need more heat/reflux to keep the plates filled?

So, after your comments, here's my theory as to what happened. Tell me if it sounds realistic: Running it too hot dried up the bottom plate. Now there was a ton of vapor shooting past #1 and heading to #2. As soon as the liquid trap of the 2nd plate's downcomer dried up, vapor just shot up the downcomer pipe as well as all the bubble cap holes, basically allowing no liquid to drain from anywhere. This is the point I noticed things and then turned down the heat. At this point bubble plate #1, which still had a liquid trap, started to function normally again. But all the vapor headed for #2, whose liquid trap was now dry, just bypassed the plate through the downcomer and headed straight up to #3. So until enough liquid dripped down from #3's liquid trap down into #2's liquid trap to fill it, plate #2 remained inactive. Eventually, though, it filled and then plate #2 started functioning again.

[pant pant] Make sense?

Thanks for your patience and wisdom,
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Re: strange plate behavior

Postby troglodyte » Tue Feb 26, 2013 1:52 pm

Your flooded plate is due to the riser vapor holes being too small for the heat your pushing, open them up to 4mm.
as for how your running it, I agree with what the others say, equalize and pull heads slowly with low power, then crank it up.
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Re: strange plate behavior

Postby Badger » Thu Feb 28, 2013 7:35 am

Thanks all. High heat= too much turbulence = bad separation makes sense.

That said, as it was I was getting 92% and no taste variability (after the heads, obviously) through the hearts that I could discern . Now I'm really curious how much real-world difference it will make, flavor-wise. I have one more run of whiskey before I start my grand aging experiments so I'll run it as you recommend and see. As I'll have 6 identical batches (but each with a different plate combination) so I'll be able to do a horizontal tasting that will hopefully provide me with some insight.

Thanks again for your comments,
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