Agitator instead of rakes in Lautertun

[beerbeer95648]

We are commissioning a new 20bbl brewhouse for next year. We have some space limitations so are limited to a 2 vessel system with minimal height. We are forced into a KT/WHP, MT/LT All the mid level manufacturers try to sell us fixed height rakes in a combined MT/LT. I have brewed on systems from 7bbl to 100bl, with and without rakes, and I dont see the use of fixed height rakes. In addition they are including substantial steam jackets on the MT/LT. Like I said I do not see the benefit of fixed height rakes, but do like variable height rakes. But they have a larger price tag. So, we are exploring replacing the rakes with a mash mixer in the LT so we can take advantage of the steam jacket for step program mashing. When talking to Phil Loen at JVNW, he mentioned in passing that they have done that, but I did not get any details. We have thought hard about this, and are working on how to incorporate a plow.

Has anyone done anything similiar. Any issues or concerns?

Thanks

[Crawford]

Mash mixer my first choice

We use a mash mixer on our 15bbl. And mash out with the mixer. Works great! Contact Crawford Brewing Equipment ask for Steve I'll send you a video. www.brewtanks.com

[liammckenna]

Fixed height rakes can be a pain in the ass but can help immensely with grains out.

We have a removable 'plow' blade which can also be dropped into place for mixing (removed for runoff/lautering) or grains out (wearing insulated rubber gloves of course).

Ours is but a 10 hL system, so the plow easily fits in the upper manway. With larger systems, there are many mechanisms to have this 'plow' swing into place or out as needed. Do a google image search on lauter tun rake design to see what I mean.

Also, you'll want speed control on that mixer/rake/plow.

Pax.

Liam

[Ted Briggs]

"Like I said I do not see the benefit of fixed height rakes, but do like variable height rakes."
Id Like to hear your reasoning for this. Also by 'rakes', do you mean knifes to cut the bed or a grain out apparatus? I usualy say "Rakes + Knifes"

[liammckenna]

"Like I said I do not see the benefit of fixed height rakes, but do like variable height rakes."
Id Like to hear your reasoning for this. Also by 'rakes', do you mean knifes to cut the bed or a grain out apparatus? I usually say "Rakes + Knifes"

Variable height rakes/knives can be raised to just cut the top few inches of the bed thus easing the pressure differential across the bed.

Fixed height rakes/knives are often just a few mm off the false bottom. Turning them on at such a bed depth during runoff, even on low speed, can disrupt the 'top-dough' and possibly start the whole bed moving if it is slightly compacted on the plates leading to murky runoff issues.

Pax.


Liam

[dick murton]

You are talking about equipment that should be correctly designed for two very different purposes.

A mixer is required at the mashing stage where you want to carry out a rising temperature mashing profile, or to add and mix in something else, such as an adjunct after the initial mashing in. For best results you shouldn't carry this out in a vessel fitted with a false floor of slotted plates as the mixing process will cause considerable amounts to pass through the slots into the space underneath.

Following the conversion of the grist, the mash is then transferred to the lauter tun, which for best results, then needs to be fitted with rakes. These are used to gently maintain the porosity of the bed, so you get even runoff and good wort extraction.

If you carry out an isothermal mash using well modified malt, then you can simply mash into the mash tun, which is basically the same as the lauter tun, but without rakes, and at the end of the stand, run off the wort. The mash should contain bubbles of air (an anathema to lager brewers in particular I know), which casues the mash to float above the false flooruntil the first strong worts have been run off, and maintains the open porous bed so the sparge can run through it - providing the grain bed is wet at all times. I know lots of people do it, but there is no real need to vorlauf in this case, as the wort should brighten up very rapidly. Vorlaufing is most beneficial when you have a lauter tun with rakes as the mash transfer process in particular allows comparatively large quantities of grist to pass through the slots in the false floor, with deep bed raking, i.e. the rakes virtually sat on the floor stirring the bed up a little more and allowing more grist to was through the slots.

The purpose of the rakes in a lauter tun is to maintain the porsity of the grain bed, which is required because of a combination of finer grind, so less air is retained in the mash, and the previous processes of mixing in the mash mixer and the transfer process, which knocks any final air out of it. Ideally the rakes are height and speed variable, but simple fixed speed with variable height is the minimum, preferably with an automated programme. A simple fixed raking profile will work reasonably well, but the newer fuly automated systems will have flow meters, pressure gauges, turbidity meters etc incorporated to allow high efficiency and fast turnround times with no operator input.

In summary, I think you first need to decide what materials you are going to use, what mashing regime you want, and this will dictate the design.

[dick murton]

I also meant to say that the discharge mechanism can be installed as a separate discharge mechanism in a traditional mash tun, playing no part in the wort runoff operation, or can be installed as either an integral part of the raking mechanism, or again as a completely separate mechanism, purely used for mechanical removal of grains rather than manual digging out.

[gitchegumee]

I've used fixed height rakes/knives in several breweries' lauter tuns with no issues. A VFD will slowly cut the bed to maintain porosity with no turbidity increase during sparge after a quick vorlauf. I've also used these same tuns without engaging the rakes/knives as a control. Efficiency was 1-2% better with rakes/knives as compared to control. Depending on the composition of the grist, the differential pressure rises and lautering slows without the rakes/knives, but the wort was bright either way. The capital cost of variable height rakes/knives is high, as is the maintenance cost. I wouldn't buy this option myself. And I wouldn't consider a plow on a lauter tun unless I was above 25hl. Emptying the lauter tun manually is pretty quick and easy--I've done it routinely on a 60bbl system. I'm not sure if Crawford is advocating a mixer/lauter combination, but I would not. You cannot get great heat transfer from the tun bottom to the grist bulk through the false bottom, and this false bottom is likely to get packed with draff if the bulk is mixed vigorously. Mash mixing and mash lautering are always done separately as far as I know. Never seen it done in one tun before--but I'm sure it's been done. If you have space issues, then think about a 3 vessel system where the mash mixer doubles as your kettle, and your (relatively short) lauter tun (with or without rakes/knives) is above the (relatively short) whirlpool. It's an inexpensive solution to limited space breweries that works very well. Good luck!

[liammckenna]

25 years ago, I worked on a 20 bbl system with a MLT that had steam jackets and a mixer (no rakes). The steam jackets were entirely above the wedge wire false bottom.

We were doing downward infusion mashes with an added mashing off step. The mixer was only on for mashing in and mashing off. Never had any issue with temp differentials above and below the plates.

Grains out on this MLT was particularly easy as the whole thing tipped hydraulically for grains out. I still miss that tun.

Pax.

Liam