Grain Bed Pulling Away From Lauter Tun Walls?

[brewingnewbie]

it seems everytime i brew while sparging the grain bed seems to pull away from the lauter tun walls. i'm not really sure if its letting solids through (
i dont think so) but just wondering why its doing this. when the other brewers brew i dont recall seeing it happen.

i got a slow runoff. dont start it off too fast. i figure its probably something to do with pulling a vacuum?

any thoughts?
happen to anybody else?

[beejay]

I believe this usually happens when the grains aren't in suspension. Try keeping the water liquor level slightly higher than the grain bed so they are loose. A good trick is to cut the mash bed up a little during run off. Not sure what scale you're working at. If it's on a homebrew level cut a grid into the mash bed as you run off. Keep the knife slightly above the false bottom and gently cut across the bed every few inches in a grid pattern. If on a larger scale you can use your mash paddle. On even larger systems some people run the rakes rased above the false bottom during run off.

slow and steady wins the race and gets you better efficiency

[brewingnewbie]

the liquor level was definitely above the grain at all times.
had horrible efficiency too!
gonna try everything over tommorow. i've heard that slicing the bed can help, but i was always worried about disturbing it too much...i'll try that tommorow.

[Natrat]

hitting sides

I've seen sparge nozzles or balls that let water hit the sides of the tun and run down the sides. That will cut away the sides and cause the bed to look like it's "leaning in." You may have to adjust your sparge ring/nozzles/ball/shower.

I've also seen excessive condensation do this in a very cold brewhouse...the steam from the sparge condenses on the cold tun walls and runs down.

Last of all, on one tun with a very low screen, I've seen the grain bed just lift off of the screen, and then fall, lift, fall as the grant pump loped. It destroyed the edges of the bed, and runoff was awful. Found out the pump was undersized and that the sparge piping was bigger than the grant piping. It started during recirc and got worse. If you hear your pump "loping" this might be the problem.

hope that helps a bit...

Nat

[gitchegumee]

I've had this happen often; seems to be equipment/technique specific. It happens every batch at my current plant, but haven't had it happen at a few other places. I believe it may be due to loss of solids in a fairly firm & structured grain bed. Grain loses ~ 70-80% of its dry mass in the tun. Perhaps when this happens, the bed shrinks a few percent. The result would be a slightly smaller cookie. Bigger tuns would crack through the middle as well as pull from the sides. This will provide a preferential path for sparge water and you'll lose efficiency. So, stir the top half of your mash every 5-10 minutes so that you can fluff & redistribute the grain. You won't get turbid wort if it's done right. And it's not hard to do right. Good luck!

[Moonlight]

If I stir my mash too much it makes all the fines settle on the top of the bed, blinding the bed and causing cracking like you mentioned. Less stirring could help. Rice hulls could also solve it, Perhaps even a coarser grind would work.

[billiebyrd]

The facility that I was previously at had a large diameter lauter with a shallow bed and this would occur from time to time I agree with gitchegumee Running your rakes every so often during the runoff always fluffed the bed and kept it against the wall. Our bed was never blinded by this and our wort always stayed crystal clear with an efficiency in the 90% range. Happy brewing.

[Sulfur]

lauter

Do you have only one source from the Lautertun? If only one and in the center, and you lauter too fast, I suspect it could suck the bed away from the walls and into a V shape. You do want some suction, just not so much that it will cause this to happen. Either slow down the lautering, or keep the speed the same but increase the resistance via finer milling, more load etc.

[dick murton]

The bed is simply blinding. You should never compress the bed so much it pulls in from the sides

You may need to slow down the runoff rate, particularly at the start with strong worts and no sparging

I suggest the opposite of making the bed finer as this will increase the likelihood of the bed blinding

Coarsen the grist will reduce the risk of blinding

Don't rake too vigorously which will stir the bed up and may cause the fines to rise to the top

Rake enough to break the bed up. The trouble is, you need plenty of rakes, and from what I have seen of brewery LTs, many do not have sufficient to break the bed up evenly without destryiong the bed

Runoff rate should equal the sparge rate ance you have started sparging.

The point about the number of runoff points is absolutely correct - more or less the more runoff points the better. I have quotes of > 1 runoff pipe per m2.

You may need to go back to the mash mixer (I am assuming you have a separate mash vessel) and the pump you use to transfer. If you are using a bog standard centtrifugal pump - change it - NOW, as it will be trashing your mash and producing masses of small particles. Mono pumps work well

[jailhousebrewer]

If I stir my mash too much it makes all the fines settle on the top of the bed, blinding the bed and causing cracking like you mentioned. Less stirring could help. Rice hulls could also solve it, Perhaps even a coarser grind would work.

I recently tightened up my mill gap and in the next batch found the grain bed pull away from the wall of the lauter tun. I also noticed some cracking of the bed that wasn't occuring before. The grain bed was much tighter and I noticed a large amount of clumping, though the clumps were not void of water like in a dough ball. Effeciencly actually went up in that brew.

[Sulfur]

lauter

I mentioned increasing the load or milling finer because although counterintuitive it has helped in my case. Certainly if you mill too fine, or increase the load beyond the limits of your Lautertun, then you will increase the tendency to get a stuck mash. I've experienced better lautering with increased load up to a point. I've had the clearest runoffs with my biggest beers due to the great filtration of the bed, but they are also long runoffs. So there's always a give and take. On a "normal" strength beer, I have noticed that occasionally fluffing the bed helps, as does a thicker mash.

[kai]

Don't rake too vigorously which will stir the bed up and may cause the fines to rise to the top

Rake enough to break the bed up. The trouble is, you need plenty of rakes, and from what I have seen of brewery LTs, many do not have sufficient to break the bed up evenly without destryiong the bed

Hi Dick,

Do you have or is there a rule of thumb for the ideal rake setup per lauter tun size?

[dick murton]

I'll have to get back to you on that. It seems to depend on the shape of the rakes as well as the speed of raking. I haven't got my info with me at present, and haven't used it recently, hence the black hole in my head. I'l try and find it later tonight

Cheers

[kai]

Don't go to too much trouble, I would assume on a practical level that if the bed is being destroyed then one would see very cloudy runoff and inconstencies in runoff gravities... neither of which happens when I take the rakes out for a spin...

But I do always like reading stuff.

[dick murton]

Info I have been using is 3 + rakes per square metre lauter tun floor area

Raking speed equivalent to 12 rakes / square metre / hour

The number of rake is based on the Briggs design, so with Steinecker / Huppman type there are about 50 % more in number, because each rake is narrower and disturbs the grain bed less. However the raking speed still relates to the briggs style

The key to speed is not to push the bed round or disturb the bottom of the bed which casue grain carry through, but still be fast enough to break the bed again before it starts to blind