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  • Usiing rakes during lauter/runoff

    Hi,

    We have a mash/lauter tun and were wondering about the potential benfits of using the rakes during runoff. Anyone doing this? Any comments?

    thanks,

    e

  • #2
    Using Rakes During lauter/runoff

    Absolutely DO NOT use rakes during lauter/runoff. The primary purpose of the lauter is to separate clear wort from the mash by allowing the grain husks to act as a natural filter bed. Using rakes during lauter or runoff is contrary to this purpose because it disturbs the husks and releases the particulates that are trapped there as the wort recirculates through the mash. Further, the rakes will cause the husks to break up into smaller pieces, increasing the particulates present in the wort and increasing tannin extraction as a result. If you are forced to use the rakes due to a stuck runoff, let them turn for one rotation only, just enough to get the runoff going again.

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    • #3
      ProStarter is absolutely right. Using the rakes will negate the whole purpose of the lauter. Those rakes can be used once or twice during the mash PRIOR to vorlaufing if necessary to break up dough balls in the mash and stuck mashes. They are also handy for clearing out the spent grains AFTER all wort is collected. Good luck.

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      • #4
        not absolutely correct.

        rakes in a properly designed lauter tun are supposed to prevent channeling/ lift compacted grain beds. In larger breweries they are able to raise and lower them. When the flowrate slows down and the differential pressure across the filter bed rises, rakes are started slowly at a high cut. The level is gradually lowered to keep the lauter flowing. Haze/ turbidity is monitored in the wortstream and the lautering is stopped then it goes beyond a setpoint. They then refloat, raise the rakes up, let it settle and continue running off.

        When it is grain out time a plough is moved around by the rake system to push the spent grain out. Smaller systems often run in the reverse direction, and the ploughs then rotate to push the grain out.

        Read Wolfgang Kunze to learn more.

        Depending on the size of your brewery, i would say < 25Hl don't bother with rakes, < 60Hl don't bother with lifting rakes.
        in the case of small systems, the rakes may be so disruptive of the grain bed that they cause cloudy wort at any speed. in that case, it is probably best to run off until lautering slows down. stop runoff, rake, refloat grain bed, let settle and then continue runoff. Find a way to make your system to work.


        British single step infusion mash tuns generally don't have rakes and are much simpler in operation and more common in small microbreweries. Read Hough Briggs, Stevens and Young.

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        • #5
          Lots of misconceptions here.


          The rake is there for a reason. Actually several:

          1. Speed up the lautering process

          2. Increase extract

          3. As an aid to get a little better mixing during pumping over the mash to the lauter tun, when you have a stuck mash and during spent grains discharge.


          During lautering, it has been my experience that you can leave the rakes turned off, but if you can adjust the height of the rakes I don't see why you can't use them just fine.
          The rakes are used to decrease differential pressure if it goes too high and it is used quite alot during sparging to increase the amount of extract to the wort kettle.

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          • #6
            Rakes are only required to be fitted to lauter tuns if the grist is too fine and or has had all the air beaten out of it during mashing, typically during a separate mashing in vessel, with heating and a stirrer. I have worked with traditional mash tuns producing 800 hl of wort for 4.5% beers – no rakes, 95 - 96 % extract efficiency – though admittedly with long turn round times.

            Providing the grist is reasonably coarse (see HB&S for example grist profiles), during mashing in to a mash tun, the grist is mixed and wetted thoroughly with water, and a fair bit of air is entrained in the mash, allowing it to float and maintain porosity. As soon as you use a mixer of any sort to help mash in, you knock out the air, and the bed sits on the bottom of the tun, and is fairly impervious, and may need raking to help increase the bed porosity.

            The problem is that someone in their wisdom, a long time ago, decided that mash tun isothermal mashing systems needed rakes, presumably because the mashing in system used a simple water spray and no mixing baffles, instead of having mixer rakes like a Steeles masher. So the mash had to be mixed in the tun to break up the lumps. Having done this and knocked out all the air, rakes were needed to increase the porosity of the mash bed.
            Subsequently, this seems to have become a common, and in my opinion, bit of bad, (not just poor, but bad) design. I have removed the rakes from a number of small breweries because they create more problems than they resolve.
            Most (well every picture or real life example) I have seen of small mash tuns with rakes have far too few rakes, so cannot possibly increase the porosity evenly across the grain bed, are not height variable and so create good porous beds, and are far too fast, which helps to destroy the bed.

            So if you have a mash mixer, then you will almost certainly benefit from having properly designed rakes, at a good density to ensure effective cutting, and for optimum performance, automated. If you don't have separate mash mixer & LT, and use simple isothermal mashes, then you shouldn't need rakes
            dick

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            • #7
              We have went from 40 hl trad. Infusion mash system to a separate mash tun and separate lauter tun system 80hl with rakes and knifes. Not able to lift rakes. We do not use rakes during lautering. We get lower efficiency compared our old system. Lautertun is about 345 cm diameter. Is it common to use rakes and knifes slowly during sparging/lautering? Maybe we can crush a bit finer. Rakes are about 20mm above screens. We have a sloped bottom in lauter tun so we need to add 800 liter water prior to pump in mash from mash tun.

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              • #8
                In a traditional mash tun, the mash floats due to entrained air, which along with the coarser grind used allows the bed to remain relatively porous.

                With a separate mash mixer and lauter tun, the grind is normally finer, and the air has been driven out of the mash during mash mixing and mash transfer, and as a result the mash does not float but simply sits on the plates. To help maintain the porosity of the bed, a mash mixer / lauter setup generally requires use of rakes to assist wort run off.

                Ideally you should have rakes that are height adjustable, but since you haven't, you will simply have to work with what you have. Typically the rakes are used to help level the bed during & just after mash transfer, stopped during the early stages of wort runoff, and run as the differential pressure starts to climb. The speed of rotation depends to some extent on the number and design of rakes. In a large LT, typically the height would be varied at different times of the runoff cycle. The speed of raking will vary according to suppliers rake design, numbers of rakes, grind, bed loading, speed of runoff and sparge philosophy used, so all I can suggest is that you run them and see how you get on with it. If you have a VSD, make sure the rakes are not turning so fast that the bed gets dragged round with it - so just below that point.

                It might also be worth considering coarsening your grist to help improve bed porosity - the coarser the particles, the better the runoff. A fine grind is only beneficial if you get more extract, and or better quality extract in the time permissible than you would with a coarser grind. So if you have made the grind finer to suit a typical large LT grist, then try reverting back to a MT grist and see if that helps.
                dick

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                • #9
                  Thanks Dick. Our first runnings are calculated to about 1090 but we do not exceed 1076. So it can also be a bit of a dilution problem if circulation runs at the walls of LT and do not mix in mash bed. Circulation tubes enter LT towards inside wall.

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                  • #10
                    use a fishtail spreader to reduce this problem
                    dick

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                    • #11
                      I used to work with a 20 bbl system that had rakes that would lift. I would spin the rakes as slow as possible in the top 2" of the grain bed. This seemed to stop any channeling of water and once I started vorlaufing I never had to rake the bed at all. I am now on a smaller system that I am unable to lift the rakes so my procedure now is to stop the run off, re rake the bed and then reset and continue my runoff. I have found if I dont re rake the bed water finds its path of least resistance and channels the same way thru the grain bed thus lowering my OG.
                      Mike Eme
                      Brewmaster

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                      • #12
                        We have now understood that rakes leave about 20 cm of mashbed to the side walls unstirred during transfer to LT. These 20cm of mash gets much thicker compared to the rest (central part) of mash. So after stirring during settling/lautering, these 20cm falls towards center of mashtun leaving a great channel towards wall of LT. Tomorrow we will weld two more knifes going close to wall. We will see if it improve efficiency.

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                        • #13
                          We have now understood that rakes leave about 20 cm of mashbed to the side walls unstirred during transfer to LT. These 20cm of mash gets much thicker compared to the rest (central part) of mash. So after stirring during settling/lautering, these 20cm falls towards center ofLT leaving a great channel towards wall of LT. Tomorrow we will weld two more knifes going close to wall. We will see if it improve efficiency.

                          Skickat från min SM-A310F via Tapatalk

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                          • #14
                            Any Improvement?

                            Originally posted by ironbrew View Post
                            We have now understood that rakes leave about 20 cm of mashbed to the side walls unstirred during transfer to LT. These 20cm of mash gets much thicker compared to the rest (central part) of mash. So after stirring during settling/lautering, these 20cm falls towards center ofLT leaving a great channel towards wall of LT. Tomorrow we will weld two more knifes going close to wall. We will see if it improve efficiency.

                            Skickat från min SM-A310F via Tapatalk
                            Did the extra rakes solve the problem? We're having similar issues on our new 25hl system at the minute.

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                            • #15
                              Originally posted by THL View Post
                              Did the extra rakes solve the problem? We're having similar issues on our new 25hl system at the minute.
                              Yes. With these extra knifes we can stir all out to the wall. Practice is now as this:
                              After filling LT. Rest 20 minutes
                              Cirkulation 20 min or until we get a clear and strong wort
                              Lauter until wort is 5 cm under mash surface
                              Sparging lautering as fast as possible without getting to high differencial pressure.

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