Problems using aluminum vessels for electric brewing system?

[ecbrewer]

I'm to the point in building my electric brewing system (single-tier, aluminum square tubing, 2 x march pumps, 2 x 240v 5500w elements) where I need to pick up the 3 vessels (hot liquor tun, mash tun, and boil kettle). I've been looking around at retailers for pricing and other electric brewing systems for direction. Most often I've noticed the use of stainless steel (stock pots or converted sanke kegs) or hi-temp food-grade plastic in a few. I think I'm going to avoid plastic... I wouldn't mind using stainless steel, but when comparing the prices for 3 x 60 qt vessels in stainless vs. aluminum, there's a bit more incentive to buy aluminum - $$$$$$$. I realize the issues with cleaning aluminum - no caustic - and the need for passivation or build up of the oxide layer... I don't have any issue with either of those because I don't use caustic to clean (nothing quite like elbow grease and a good sanitizer) and I don't mind any downtime required to rebuild an oxide layer as I don't have time to brew more than once a month, if I'm lucky (work + school + 4-month-old).

So, to the question:

Does anybody know of any reason to avoid using aluminum vessels in an electric brewing system? Might there be any galvanic reactions during the heating in the HLT or kettle? Any information is GREATLY appreciated. Thanks!!

[seanhagerty]

Not sure about the vessel. I wouldnt have any real problems with using/getting one. I would have a problem with making my stand out of aluminium tubing. I would be concerned about the heat and weight applied to this thing, and whether or not it would be able to handle it.

Just my thoughts

Sean

[ecbrewer]

I would have a problem with making my stand out of aluminium tubing. I would be concerned about the heat and weight applied to this thing, and whether or not it would be able to handle it.

I chose aluminum tubing for the stand for three reasons:
1. Cost
2. Corrosion resistance
3. Strength to weight ratio

Since I'm only using electric heating elements and not propane, the maximum heat resistance required for the stand is 212F - actually lower than that considering the radiant heat from the boil kettle will be lower given the heat transfer from the boil kettle will not be 100% efficient. At 8.33 pounds per gallon and a maximum batch size of 20 gallons, the maximum weight on the stand will be 500 pounds of liquid (3 x 20 gallons) + 80 pounds of grain + 60 pounds of pots (3 x ~20 pound vessels) = 640 pounds. Adding in another 60 pounds for miscellaneous weight - pumps, plumbing, wiring, the occassional rested pint = 700 pounds... My cousin (machinist and fabricator) and uncle (building structural engineer) estimated the stand (as it's designed) should handle at least 1200 pounds. My brother was in town for Halloween and we both sat on it (~280 + ~320 pounds) while we sampled some beers and talked about the future production brewery - not a wince from the stand.

[Brandt]

I am a big fan of aluminum. I say go for it. As you pointed out, it has a great strength/weight ratio. I don't know about the metal, but in oxide form, aluminum is highly refractory and has a higher deformation point than iron. You make kilns out of this stuff. However, I've watched a soda can burn in a smallish campfire, so I don't know.

As for electric, I don't see a problem with any reactions. You're not electrically charging the water/wort so it shouldn't make a bit of difference what you make the kettles from. A heater is not the same as an electrode, right? Sorry I don't have any definitive answers but my gut says your plan will work fine.

[nathan]

cost-wise, why not consider converting kegs? If you use weldless fittings and do it yourself on a cheap keg, you could get a sturdy vessel for cheap.

[Thirsty Boy]

Your aluminium is going to be fine - but I am a little concerned about your elements. 5.5kw is going to boil the shit out of 5 or 10G of wort, it might not be too much for 20... but you said you were looking at 60qt pots.. which suggests to me 10G batches and 5.5kw is going to be way too much without some way of throttling the heat output.

I've watched 2 x 2400W elements boil a 16-17G volume and we had to turn one of them off once the wort got up to a boil

TB

[ecbrewer]

Your aluminium is going to be fine - but I am a little concerned about your elements. 5.5kw is going to boil the shit out of 5 or 10G of wort, it might not be too much for 20... but you said you were looking at 60qt pots.. which suggests to me 10G batches and 5.5kw is going to be way too much without some way of throttling the heat output. I've watched 2 x 2400W elements boil a 16-17G volume and we had to turn one of them off once the wort got up to a boil

Yeah, thanks for the heads-up... I am going to use a PID w/ thermocouple and SSR to control both 5.5kw elements (HLT & BK) so it won't be running at full power constantly - only enough to maintain the temp/boil. I decided on 80 qt stainless because I'm going to use stainless fittings and those come into direct contact with the vessels which would make those more susceptible to corrosion from galvanic reaction. Plus, I won't have to worry as much about maintaining the passivity of the vessels... It's just money at the at end of the day and I'm not going to be buried with it...

[Thirsty Boy]

yeah - I figured you would be controlling it - but just to play devils advocate and either annoy you because you already know this stuff or, maybe save you some trouble.

Are PIDS and SSRs the right control solution in this situation?? My understanding is that they don't throttle the power density in a way that will gve you control over your boil vigor. After all.. it all going to be at 100°C (give or take a tiny bit) boiling hard or boiling soft... all still at 100°C. So whats the PID going to control?

I know that you can set-up certain types of SSR with a manual dial type control.. (I am sort of guessing / remembering someone elses set up here) I think its basically a rheostat that alters the voltage across the SSR which in turn alters how much electricity it lets through - thus controlling your element.

So a PID / SSR is great for controlling an element in a way that maintains a set temperature - say 78°C in your HLT... basically switching the element on and off quickly and in a cleaver way that avoids over/undershoot - BUT in the kettle situation... what temperature are you going to set it at? At 100C it'll be all 5.5KW till you hit the 100 . . then it'll just sit on 100 and basically not boil.... so you set it to 101 or 102 and its going to try with all its 5.5kw to get there and it never will because boiling water is at 100C no matter how vigorously its boiling. So what you need is a "throttle" for your element that isn't Dependant on temperature to regulate the output. Like the rheostat (thingy) I talked about before.

Like I said, sorry if you already know all that stuff - you probably do - but if you didn't, I hope its helpful.

TB