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2 Roll vs. 4 Roll Mill

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  • 2 Roll vs. 4 Roll Mill

    Besides the obvious, I can't seem to find any information about the difference between 2 roll, and a 4 roll miller?

  • #2
    2 roller mills are very typically used in most smaller scale breweries. A 2 roller has one set of rollers which takes care of separation of the husks and extract. Conversely, a 4 roller mill is usually used in larger scale distribution breweries due to its ability to increase extract yield by around 2%. The way it accomplishes this is because a 4 roller mill can crush the extract in malt to a finer degree (increasing surface area exposed during mashing) in the second pair of rollers after the initial roller pair.

    It usually is economically prohibitive to have a 4 roller mill versus a 2 roller mill if you aren't brewing a lot of beer.


    • #3
      A real 4

      Also, not all mills with 4 rollers are 4 roller mills. They are just two two roller mills stacked. Imo you have to be brewing tens of thousands of barrels before this matters .
      Larry Horwitz


      • #4
        if you are running a 10/15 bbl system or less, and brewing 2-3 times per week it probably does not matter much.

        Also, if you doing a British style single step infusion mash it makes less sense, since this relies on bigger floating particles, deeper beds and well modified malt.

        For production breweries making 5000+ BBL/a it begins to make sense.

        Generally, if you get a better mill, you will get better extract, your lautering will work better and you will extract less undesirable components from the grain, polyphenols, silicates, lipoxygenases. I believe that steps in brewing are all interrelated, and doing a good job in the brewhouse will lead to better fermentation, conditioning, filtration, processing and ultimately better quality beer and shelf life. In a larger brewery this becomes more important.

        Thus when you are making more beer, the better mill will pay for itself in terms of better extract, time saved every brew in brewhouse and cellar, and better quality and shelf life of final product.

        I bought a 4 roller Buhler LEFA mill and am really happy with it.

        Generally how it works is that the first set of rollers have a spirally fluted roller. (instead of straight cut grooves along the roller they spiral around it somewhat) this encourages the grist to break apart without grinding the husk to shreds. The first roller gap is set to just crack the kernels open.

        The second set of rollers can be set tighter to break up the starchy endosperm and make it more accessible to the strike water and allow the mash to access all of the insides. This will allow for more rapid and complete mash conversion and better extraction in the lauter tun. The husks are sometimes screened out to bypass the rollers, but if they pass through the second rollers, they are thinner, and will fall through the gap. The second gap should not be set too small as to make flour anyway.

        Maintaining intact husks, and properly breaking up starch is the benefit of a 4 roller mill.

        I use chain disc conveyors to more gently deliver the malt to and from the mill, so you can use your mill to crush the malt rather than your augers. In other threads there is also talk of low speed/ low shear mash transfer pumps for similar reasons.


        • #5
          2 Roll vs. 4 Roll Mill

          Difference between 2 pair and 4 pair RMS mill was about 2k. I am not sure if top pair was spiral cut or not. I decided for 2 pair and RMS mill is doing fantastic job.


          • #6
            A four roll mill only really makes sense if it is fitted with sieves to separate out the parts you don't want to send through the second set of rollers. 2k doesn't sound anything like enough to incorporate all the gubbins associated with sieves. A local brewery to me changed from pre-ground to a simple 2 roll mill and got nearly 20 % improvement in extracts, and more consistent runoff times (I think part of this, but only a small part, can be attributed to increasing the beta glucanase addition). A local uni got involved in helping out. They currently achieve about 100% efficiency, which I still can't quite believe, in spite of having double checked the figures for a number of different brews.

            So, as said elsewhere, a good two roll mill will probably work effectively up to I would guess 50 hl brewlengths. Certainly a couple of the local breweries around here of that sort of size use 2 roll mills. And when setting up a 4 roll mill, it really helps to have access to a properly set up (i.e. for brewery grists, not farm or bakers type gradations) grist shaker system.