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Heating and cooling with the same jacket

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I'm looking at jacketed tanks to use for mashing grain, and looking for opinions on alternating steam and cold water through the same jacket for heating/cooling. I've visited other distilleries where this is being done, but I'm worried about stressing the steel with big swings in temperatures. Am I just being paranoid, or should I also be looking for a separate heat exchanger for cooling?

The tank I'm currently considering is used surplus from a pharmaceutical company made by a reputable fabricator, and rated for 50 psi on the jackets.

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You're not being paranoid. Although this seems to be a regular (if not "common") practice in distilleries, I have seen...with my own two eyes...the damage that can be done using this practice.

Now, if a tank is specifically manufactured to use this process, I'd not be opposed. It's just that most dimple cooling jackets I've seen on pharma, brewery, and dairy tanks are simply NOT safe to use with steam...and the tack welds that hold them to the inner wall do not have full penetration (on purpose). I've seen thin dimple jackets pull loose just from rapid glycol temperature change, and channel type jackets are even more delicate.

Running glycol or cool water in a steam jacket is slightly less bad. Steam jackets by nature are more robust. I have seen serious crevice corrosion in a steam jacket that had cooling run in it...it had not failed, but it was going to!

Part of the problem is the crash cooling that people like to do to speed up their process. I'd have no issue with running 80 or 90 F water in a steam jacket to bring mash down to pitching temp, but running 17, 27, or even 40 F water or glycol is asking for trouble.

If you are going to do this, make sure you install a few doohickeys. You don't really want cold cold water running down your steam trap and condensate line, so plumb your valve and cooling bypass in before the trap. Because you are going to bypass your steam in line, there will be no pressure relief. I'd plumb in a 1/2" npt fitting into my jacket that has a good ball valve and then a triclamp fitting to a PRV...opening this after you turn off steam and before you turn on cooling will ensure that no over pressurization or vacuum will damage the jacket. Heat stresses will still get the welds, but a steam jacket should take that with little problem.

I would also passivate inside the jackets once a month. There's no way to inspect that area until it fails. I suppose you could use a borescope, but few of us want to invest in that.

If pharma equipment is that available, get a jacketed tank, run cooling in it all the time, and pump your hot mash into the cooled tank. Then you can mash again right away. Use the cooling tank to ferment in, or just pump the mash at pitching temp into whatever you want to ferment in. Potentially cheaper than modifying and plumbing in a dual purpose tank, and you increase your throughput. The other advantage of this is that once you have pumped the mash into the cooler, just move your input hose, and recirculate your mash in the cooling tank to cool it even faster. That is essentially what I did using jacketed totes.

Even better, use a Heat Ex!

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"I would also passivate inside the jackets once a month." - Natrat. I was planning on running my 200 gallon kettle as described above. The thing is incredibly heavy duty so I'm not too concerned it will be damaged but I hadn't considered doing a passivity cycle on in. Have you done this before? Maybe just run a low concentrate citric acid wash in it and let soak for a couple of hours?

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kckadi, that should be fine, for 304 or 304L, the cycle should be something like 10% citric acid by weight, heated to 150F for 30 min (or 20% nitric for 30 min at 120F)

Check the ph on your boiler water/steam as well as your cooling water. Sometimes it will be reasonably acidic, but more often it is not. And after checking my notes, I see that I really only passivated the jacket about 3 times a year (I don't remember being that lazy!)

Maybe what we need is someone to make a mash tun with a steam jacket around the bottom and the dish, and a glycol jacket around the top third, separated by a few inches of insulation.

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Maybe what we need is someone to make a mash tun with a steam jacket around the bottom and the dish, and a glycol jacket around the top third, separated by a few inches of insulation.

my mash tun has a steam plate on bottom and cooling jacket on sides... similar to this guy:

http://www.kothe-distilling.com/newsite/additional-equipment/mash-tanks

seems like a lot of work/cleaning/fittings to use/create a dual

purpose jacket..

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Mine is not the same as the one in the drawling, but same idea. I think mine was made/sold by Kothe previously and they changed suppliers or manufacturers or something like that and now what they show on there site is not exactly the same.. Mine was purchased used.

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The jacket mash cool will require more chilling HP or at minimum a larger water reservoir than a external heat exchanger.

I use 50F chilled water for the heat exchangers I specify and a 500 Gal mash gets crash cooled in 1 1/2 hr. One client up North has added a drycooler and isolation exchanger to cool in the winter with a 1000 gal water reservoir and hasn't turned on the chiller yet (who knows when with the cold they've been having!).

Some energy saving ideas for you to consider.

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Mine is not the same as the one in the drawling, but same idea. I think mine was made/sold by Kothe previously and they changed suppliers or manufacturers or something like that and now what they show on there site is not exactly the same.. Mine was purchased used.

Hey HedgeBird,

I've seen them so far only from Kothe. Can you share the manufacturer?

Does anyone know if there's someone in the US making a similar style mash tun?

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The name-plate on the mash tun fell off ages ago, but the matching dish-bottom fermenters say Speidel on them. All the tanks have DIN (European Thread Standard) fittings.

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Any steam jacket should be 316 grade stainless steel, 304 will stress crack in time, you might get enough service life that it is not a problem, but it will fail, not a question of if but when. I agree that thermal shocking is a big concern, you should de pressurize the steam jacket and allow time for the jacket to cool. Transitioning from warm to cool to cold water will reduce the strain. Not sure I understand the comment about repeated passivations, it typically takes a welded repair or other sanding / grinding to remove the passivation layer.

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I am also curious about this passivation step. The citric acid "renews" the metal surface like it does to copper? there is a build-up we are trying to avoid or are we strengthening the metal? I would love to learn more about this. Regular maintenance is always a good idea I just want to understand what exactly it is doing

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https://wine.appstate.edu/sites/wine.appstate.edu/files/Diversey_PassivationofStainlessSteel.pdf

We are removing iron exposed by wear and exposing chromium so that it can form a protective oxide layer. This oxide layer renders the steel 'passive' to further corrosion until it is damaged again. Oxidation takes time, so passivation is best done with a large time gap (at least overnight) between completing the acid cycle and using the equipment.

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