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Thread: Grain bed depth

  1. #1
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    Greeneville, TN
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    Grain bed depth

    I have a question concering minimum grain bed depth. What is the concensus on the minimum allowable grain bed depth in a lauter tun to be effective?

    Mike Pensinger

  2. #2
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    West Chester, PA
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    almost no such thing as too little....what size is the tun? i've seen beds as shallow as 10"

  3. #3
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    Apr 2005
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    Cleveland
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    Bed Depth

    Im brewing on a 15 bbl Pub system and im finding out that I need to mash in with over 500 #'s to get a good lauter. Less then that and I send bits and pieces over, sometimes lending an unwanted astringency to my brews. Part of my problem is most likely the crush (fine) of my malt, the lack of a grant and the fact that im not brewing to capacity.

    To answer your question, there is an equation for determining your optimum grain bed depth based on the size of your tun. Check the archives. My preferred depth is roughly 18''.

    Goodluck,

    Shoes

  4. #4
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    Larry,

    I am looking at 6" if I use the Tun that I have found.

    Thinking on the homebrewer midset that seems to be enough for me as long as you have an efficent fales bottom.

    Mike

  5. #5
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    mike,
    how big is the tun (dimensions and rated capacity), how big is your kettle, what type of beer will you be making. 6" is very shallow....doable, but very shallow. If its 6" for a 10 plato wort you might be ok but I'd like to see more like a foot.

  6. #6
    Join Date
    Aug 2005
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    Nashville, TN
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    grain depth

    HI All :

    I'm really surprised that we don't get any reply's from suppliers;
    one would think that replies would help their business???

    My question is: Is there a formula to calculate the grain depth based on
    grain:water ratio; total amount of grist used; diameter/hight of mashtun etc?

    OK suppliers, don't hide......

  7. #7
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    Mar 2004
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    Larry,

    The tun is 96" across and 46" deep.

    My calulations indicate 301 cubic inches of space for each inch of height.

    I am looking at 1500 or so pounds of grain for each batch (say 12-13 plato). The kettle will be a 35 bbl kettle and I will be doing 30 bbl batches. The plan is to size myself so I can do a concentrated boil for a 50 bbl batch in the future.

    One of the ideas I have is to modify the tun to place a cylinder in the center of it and form a sort of donut for the mash bed. I have seen this type of system in Croatia before (in another military life). Seems that I can use this to increase my bed depth and take it out later in life if need be.

    Mike
    Last edited by beermkr; 02-07-2006 at 06:25 PM.

  8. #8
    Join Date
    Mar 2006
    Location
    Germany
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    191

    grain bed calculation

    For a normal lauter tun the height should be around 30 - 40 cm, which results in around 175 - 225 kg of malt per m2 of lauer tun area. Of course, how finely the malt is milled is also important. Whether you drop your mash in from the top or let it in from the bottom also plays a role. Easing it in and not pulling too hard during the lauter process will keep the height where it should be to filter the wort as quickly as possible. Lautering is probably the trickiest part of brewhouse work.
    Last edited by crassbrauer; 03-07-2006 at 10:21 AM.

  9. #9
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    Aug 2005
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    Nashville, TN
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    mash bed height

    Quote Originally Posted by crassbrauer
    For a normal lauter tun the height should be around 30 - 40 cm, which results in around 175 - 225 kg of malt per m2 of lauer tun area. Of course, how finely the malt is milled is also important. Whether you drop your mash in from the top or let it in from the bottom also plays a role. Easing it in and not pulling too hard during the lauter process will keep the height where it should be to filter the wort as quickly as possible. Lautering is probably the trickiest part of brewhouse work.
    Hallo Crassbrauer:
    I think you should be more detailed in youre statement about 30 - 40 cm (12 - 16 inch) for a "normal" lauter tun [I assume you mean mash/lauter tun] and of 165 - 496 lbs per sq mt area. You have to look at small breweries too [we are talking USA], like, for example, a DME 7 BBL system. Take a look at the height to sq mt load, it does not fit what you said.
    Thanks,

    Fred

  10. #10
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    Mar 2006
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    Germany
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    Sorry.

    A two-roller mill and a normal lauter tun: 160 – 185 kg/m2; ~30 – 35 cm
    A six-roller mill and a normal lauter tun: 200 – 240 kg/m2; ~35 – 45 cm

    Conditioning or wetting your malt increases the height, because the husks remain uninjured.

    If you use a Pegasus or some other fancy lauter tun: up to 320 kg/m2; ~55 cm

    I guess with small systems made up of a mash/lauter tun combo, nothing is really very optimal. Not saying that good beer, esp. British ales, can't be gotten out of mash/lauter systems; I brewed on them for a couple of years myself. Some of the 60 – 100 liter pilot systems I've seen in use (even in Germany) have lauter tuns that almost look like stainless steel telephone poles; they’re so narrow.
    The figures I gave can’t really be applied to small mash/lauter breweries, although they're a good point of reference. If your system isn't designed for that kind of grain bed height, then you have to adapt, which is of course part of the fun of brewing. If you throw away a few dollars in extract or spend an extra 30 min lautering, it isn't much of a problem for a brewpub or a small micro. However, in a larger brewery, loss of extract and adding 30 min to each lautering session results in a lot of money, especially one doing five brews a day or more.
    Last edited by crassbrauer; 03-13-2006 at 08:17 AM.

  11. #11
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    Feb 2006
    Location
    Juneau, Alaska
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    I've always heard as a rule of thumb that you want 14 to 16 inches of grain bed depth for lauter tuns, with a minimum of 12 inches being acceptable if you really need it. Otherwise the sparge water can move through the mash too quickly and not extract the sugars efficiently, especially if you aren't raking the lauter bed enough to keep down the cracks in the bed. I have heard that a thinner bed than this can allow more grains to get through to your kettle as well. For increasing your lauter bed depth, you could add a donut to the middle as mentioned in an earlier post, Steinecker did this (see their Pegasus system) and supposedly it gets rid of the "inefficient" inner section of the lauter where the rake knives are cutting the bed at a different rate than the outer edge of the lauter...the bed depth increase is just a result of the design but might work for you and increase your efficiency.
    Cheers!
    Curtis

  12. #12
    Join Date
    Feb 2012
    Location
    Jacksonville, FL
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    40

    Bringing the thread back to life.

    I am in the middle of finalizing my dimensions with my equipment supplier for my mash/lauter tun. I am going to be knocking out a cooled wort volume of 17 bbls. I have the opportunity now to size the system accordingly.

    I have been doing some research and have a few questions/concerns: Using 170kg/m^2 I have determined the area of the false bottom and ultimately the diameter of the mash tun. What I don't know is how this number correlates to grain bed thickness? I have seen milled grain occupies 25-27lbs/cu.ft of volume. Is this value only valid for dry grain for sizing a grist case or does it hold true for grain in the mash tun? In the MBAA's Handbook of Basic Brewing Calculations, they state that grain in the mash tun occupies .084gal/lb.

    I am trying to achieve a 16-17" bed depth for 930lbs of grain, which will be my average weight. I am getting a diameter of 70" which seems a bit large. The most grain I will be putting into the mash tun would be around 1,300 lbs., and the least would be 650 lbs. I would like to ensure that the two extremes have an adequate bed depth.

    It would be great if someone could help me determine what my bed depth would be at 930lbs and how they reached that value.

    Thanks,
    James
    Last edited by NHBrewer23; 06-27-2012 at 05:53 AM.

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