[Kurt]

I am thinking about making a tun for fly sparging 25-30 lbs of grain at a time.
I have a 15gal Polyethylene (#2)  jug 13.5 in dia. x 25 in tall.
is that to tall a height to width ratio?

[69franx]

Seems small for that much grain with 1.5 qt per pound, your awfully close to full on 30# of grain. I don't have any idea in ideal height to width though


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[narvin]

I am thinking about making a tun for fly sparging 25-30 lbs of grain at a time.
I have a 15gal Polyethylene (#2)  jug 13.5 in dia. x 25 in tall.
is that to tall a height to width ratio?

I think the size is okay.  30 lbs of grain and water at 1.5 qt/lb is ~ 13.5 gal. Palmer says that a pound of dry grain takes up 42 fl. oz, so the grain bed itself would be 9.8 gallons, or 16" deep in your tun.  This is deep enough, since deeper gives you more uniform lautering, but not too deep to cause problems.

I'd be concerned about the PET though.  I see references to 140F being the maximum working temperature that's considered safe for food applications.

[kramerog]

I'd be concerned about the PET though.  I see references to 140F being the maximum working temperature that's considered safe for food applications.

#2 is high density polyethylene, not PET.  Should be fine for mashing.

[Kurt]

Thanks a lot guys, Very helpful!
Now I will make the false bottom  and a gimbal mounted insulated box, so it will be easy to empty.
Kurt

[Kurt]

Kramerog, your spot on below is from the sanitary design web site. I should have put the HD in my original post to avoid confusion.
If anyone is interested these nice sturdy containers are common at many dairy farms for free.(they get acid for cleaning milk lines in then need to dispose of them. You just have to cut the top off.
Cheers,Kurt   
HDPE or High Density Food Grade Polyethylene plastic has an amazing temperature range, and is considered safe for short periods up to 248°F (120°C) or for long periods up to 230°F (110°C.)

[narvin]

Cool, my mistake.  It looks like a good choice for a mash tun.  If you need to mash more grain, you can always go down to 1.25 qt/lb.

[biertourist]

I believe typical German lautertun design is a 3:1 width to height ratio.

-You're more in the English system 1:2 width to height MLT range with that.
Are you looking to create a dedicated lautertun vessel that just makes sure that run-off is fast?


Adam

[biertourist]

Just to clarify, in case my question isn't clear:

British / Modern American breweries normally use a single vessel that acts as a combination Mash Tun / Lauter Tun, called an MLT.  They have deeper grain beds and take longer to run off but enable you to have a single vessel instead of a separate mash and lauter vessel and they take up CONSIDERABLY LESS brewery floor space than a dedicated lauter tun and cost considerably less than a dedicated lauter tun. These vessels are in the 1:1 to 2:1 height to width ratio range. (Remember that commercial breweries do not do continually recirculated mashes; a couple of minute of recirculation to clarify at most; continually recirculated mashes are home brew inventions and generally favor greater width and large % open area false bottoms.)

The German brewing system normally utilizes a steam-fired "mash mixer" that can both heat the mash through temperature steps and includes stir motor and arms to continually stir the mash.  -This (stirring) enables conversion to proceed faster; these "mash mixers" are normally considerably taller than they are wide.  -Then they transfer to a dedicated lauter tun which is generally 3 times wider than it is tall.  The lauter tun includes a sparge ring to let in hot sparge water and rotating rakes and knives that operate on a programed schedule but can be overridden by a human operator.

The dedicated lauter tuns can dramatically increase brewery output as the lauter / sparge process generally is the bottleneck in brew house throughput (and therefore totally brewery output if the rest of the brewery is optimized and sized appropriately). They allow the runoff and sparge to proceed faster than in a much deeper Mash Mixer or MLT and the rakes can further speed things along by preventing the bed from compacting too much and getting a stuck sparge. More raking == cloudier wort but faster throughput.

Lautertuns are a fixture in many mega sized breweries regardless of what country they're in. -The even higher-end, higher efficiency and higher throughput option is a "mash filter" that physically squeezes the mash through tiny holes in a filter membrane; it's again generally used in mega lager breweries where efficiency is everything and malt is milled into flour (mash filters can get over 100% extract efficiency (even higher than laboratory conditions)).


-Its within this context that I asked my question.  If you were talking about a dedicated single vessel MLT and not a dedicated lauter tun then disregard my previous post.


Adam

[Stevie]

Some large breweries do use a separate lautertun. It allows for much faster turnover when using smaller systems to fill larger tanks. I know Lagunitas new system operates this way. There system is German made, so that might explain why.

[narvin]

Ratio is important, but at the homebrew level so is the absolute depth.  I don't think a grain bed of a few inches will work well regardless of the height/width ratio of the tun.  12-18" will work fine, in my experience.  Lauter time is also less important at the homebrew level since things don't scale linearly -- liquid volume increases much faster than grain bed surface area as system size increases.

[biertourist]

Ratio is important, but at the homebrew level so is the absolute depth.  I don't think a grain bed of a few inches will work well regardless of the height/width ratio of the tun.  12-18" will work fine, in my experience.  Lauter time is also less important at the homebrew level since things don't scale linearly -- liquid volume increases much faster than grain bed surface area as system size increases.

Yep thanks for adding that.  A really good point.

Recirculation can help when your grain bed depth gets a bit on the low side, but I agree you're better off to plan for at least 12".


Adam