Boka insufficient cooling?

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Re: Boka insufficient cooling?

Postby still_stirrin » Sat Jan 19, 2019 8:59 am

Scrubbies are good and probably better than marbles at efficiency. But they’re more expensive and hard to clean...you have to boil them in a pot of water to clean the oils and crap off/out.

Marbles are the easiest to load and unload...just pour them in gently. And clean up is easy too, I pour them into a bucket of hot water and let them soak. Then drain and pour into an old pillow case to dry. Ready for the next use any time.

Now SoCD likes scoria and I would too. Very economical and easy to source (local garden shop) but you need to break the chunks to a good size to fit your column. They’ll be dusty when you get them so they need a good rinse before use. Scoria has a very good surface roughness and is somewhat insulating (not a good heat conductor) like glass marbles. So, it works very well as packing. Cleaning it would be a little like the scrubbies, that is you may need to boil it in a pot of water.

Bottomline, marbles were cheap and easy to source (Hobby Lobby). They’re easy to fill and remove. And they’re easy to clean and dry. And...they produce good results, if you can match them with the appropriately sized system...column diameter and height...for the product you expect to produce.
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Re: Boka insufficient cooling?

Postby paddy1000111 » Sat Jan 19, 2019 9:22 am

Hmm maybe worth a go at some point. The SS scrubbers are inconvenient for pretty much everything. What difference does the packing have in a still? As in, what is the noticeable difference? Also, how do you get on with cleaning them? Do you put them in the oven and burn off any off flavours?

*edit* That last post clears up all the questions! I will have a think about the rock. I went with SS scrubbies because they were cheap. I bought 108 stainless steel pot scrubbers for about £8 from my local restaurant wholesaler/cash and carry. They are a little bit smaller than the normal supermarket ones but for the price I put one inside the other as they are structured like hair scrunchy type things.
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Re: Boka insufficient cooling?

Postby OtisT » Sat Jan 19, 2019 10:37 am

Glad you got it working Paddy.

I recently switched from mesh to raschig rings which like marbles or rock has much more mass than mesh. One difference I noticed immediately was that the added mass causes the still to react slower. Not a problem, just something to be aware of. Takes a lot longer to reach eq, power adjustments are not noticed immediately, etc. So, even with minor adjustments to heat, cooling, production rate you need to allow a lot more time for the change to propagate through the system.

As an example: When the boil first starts with mesh the column gets hot at the top in just a minute or so. With heavy packing, it takes many minutes for the heat to climb to the top. Same on the other end. If you shut off power on mesh, production stops immediately. With more mass, it keeps producing for a bit. I’ve only been using a 2’ packed section and the reaction time difference is big. Reaction time would be even more so with a taller packed section.

Overall, I prefer the rings to the mesh.

Again, congrats on the successful run. :thumbup: :thumbup: Otis
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Re: Boka insufficient cooling?

Postby kimbodious » Sat Jan 19, 2019 2:20 pm

You’ll need to correct the ABV reading for temperature; the alcometers are usually calibrated to be accurate for liquid at 20C. If your output was hot your final ABV will be less than what you observed.

High ABV on its own does not mean that your product is fine. Heads has high ABV and can ruin your product if you haven’t been able to isolate it in your run. You’ll only find out when you smell and taste your product at the time of making cuts.
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Re: Boka insufficient cooling?

Postby paddy1000111 » Sat Jan 19, 2019 3:22 pm

Thanks otis! Maybe I will have to try them. Previously I have used stuff like baking beads but didn't get on with them. I'll get used to the scrubbies first but let's face it, a still is never complete!

I completely agree kimbodious, the only reason I was talking about the abv is because I couldn't get much higher than 73-75 with the previous coil at about about 1800w. That's 73-75 with the distillate hot too for comparison. I'm now getting 95-96 at the same temp

I've ordered the bits to make a cooling arm so when that is all together next week it should make readings a lot more consistent/reliable.
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Re: Boka insufficient cooling?

Postby ShineonCrazyDiamond » Sat Jan 19, 2019 7:55 pm

I used this. No need to break up. They are perfect size.

https://www.amazon.com/gp/aw/d/B00E56EP ... asin_image
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Re: Boka insufficient cooling?

Postby paddy1000111 » Sun Jan 20, 2019 4:52 am

Thanks, I may get some and see how it goes. Partially because I am interested in the difference but also being able to say my product is distilled through Hawaiian Volcanic rock will just sound awesome at parties :lol:

What size is your reflux column and how much did you buy to fill it? I will be filling 30" of 3" tube with it.
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Re: Boka insufficient cooling?

Postby ShineonCrazyDiamond » Sun Jan 20, 2019 5:25 am

There's a calculator some where. I have 36" of 2", and it takes 2 quart, which is like a 1/3 of that bag. Have a plan for what the packing is going to sit on. I have one stainless scrubby at the bottom and a cross solder that holds it in.

img20170318_133339 (1).jpg
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Re: Boka insufficient cooling?

Postby paddy1000111 » Sun Jan 20, 2019 5:37 am

Ahh one bag will be spot on then. I need to source the same thing in the UK though. My still head is mounted on the barrel with a 3" to 2" step down with scrubby stuck in the bottom so I should be golden there.

The next issue I have with mine is where I welded the temp on the stainless went above 400'c so the iron has precipitated to the top. I have just stripped everything for a good clean so the taste of the turbo yeast doesn't ruin my next batch and the surface of the welds are corroding now. I have ordered some pickling paste so I am going to passivate the stainless welds before my next run just for lifespan of the unit and to prevent any off flavours. I may do a post on here as a guide as I don't think there is anything on here about passivation with pickling paste post welding and brazing?
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Re: Boka insufficient cooling?

Postby still_stirrin » Sun Jan 20, 2019 7:04 am

paddy1000111 wrote:... the surface of the welds are corroding now...

That’s a concern. I question the integrity of the metalurgy and the weld. Stainless should not be corroding, let alone so soon. More info about your sources please.
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Re: Boka insufficient cooling?

Postby paddy1000111 » Sun Jan 20, 2019 7:50 am

You are right about stainless not corroding, or at least being corrosion resistant when it has a smooth surface finish/polish and has not been heavily heated. It was 304 stainless, all from a UK industrial company so not some unknown Chinese "stainless" and all welded with 304 stainless filler rods. All TIG welded on 100% argon. It's only a flash surface rust on the metal around the weld as opposed to the weld itself where water has been sat. You can see corrosion around the hole too which was actually a braze fitting with no weld whatsoever which shows its the base metal and not the weld.
It's basically caused by the stainless getting above 400'c and the iron and oxides getting exposed on the top of the metal, which is why you get the surface discolouration on metals when heated beyond a certain level. The corrosion is massively increased by the hot, wet and damp environment that the still is obviously in. The bottom picture shows an external weld at 30x magnification with no rusting whatsoever, this is due to the inside of the tube and the boiler barrel not being argon purged prior to welding (mainly because of lack of blanking etc) which leads to oxidisation on the surface. Usually stainless has a surface layer that is a dulled out matt finish.

Stainless steel is protected from corrosion by its passive layer – a thin, impervious surface layer that is primarily chromium oxide. The oxygen content of the atmosphere or of aerated aqueous solutions is normally sufficient to create and maintain (“self-heal”) this passive layer. However, when you add an industrial process to this such as welding, brazing or heavy grinding you destroy that layer and it's not able to self heal because the surface is flooded with iron and oxides formed during the industrial process.

The protective layer can usually be restored by grinding, brushing or polishing the surface to remove the oxides and the surface discolouration that was created, hence why the outside weld shown below shows no signs of corrosion. In the second picture you can see one of the barrel fittings, the ground areas have no corrosion but the uncleaned pitted areas are corroding at quite a rate. You can also see in the first picture an area where I sanded out a scratch left by the drill bit that I used to drill the hole and the drill went a little too far, there is no corrosion on the bare metal area but there is on the areas that got hot from welding and weren't shielded by gas. I, however, can't get inside the still to clean off the surface layer with a wire brush so this is where passivation Gel comes in. It's basically hydroflouric acid that eats the oxides and iron and leaves just the Chromium oxide, re-establishing that surface finish.

Long story short, if the stainless steel has discoloured during brazing or welding and you don't clean off that discolouration, it will annoyingly corrode!


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Re: Boka insufficient cooling?

Postby paddy1000111 » Sun Jan 20, 2019 9:41 am

Just done a quick corrosion test by giving the surface a brush off with a brass brush and de-greased it. I then got some tissue soaked with distilled vinegar and left it on it for an hour. This is the weld that is corroding on the inside. This is the result after an hour in a warm room with a vinegar soaked cloth over it. The third picture shows a mild steel bolt that has had the exact same treatment as the weld for a control. The one on the left has been left in the atmosphere, the one in the right had a vinegar soaked tissue over it and hence corroded.

I think the weld is actually shinier after the vinegar :lol: but this test shows that it is a stainless weld and stainless substrate. The only difference is the weld on the outside was brushed off with a stainless wire wheel and the inside has had no treatment.

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