Stuck mash/Sparge issues.

[Truman42]

Howdy brewers,

Ive been having ongoing issues with my system with stuck mash issues where my grain bed compacts like concrete whilst recirculating through my herms. Here is what Ive looked at so far.

1. Grain crush, around 1mm with 80 rpm motor, so not too fine.
2. False bottom, Keg King style domed stainless FB which others use without issues.
3. Setting grainbed by closing return valve off at start of recirc. Even if Ive left this just cracked open I eventually get a stuck mash, it just takes longer to get there.
4. Using rice hulls. This helps for most brews of around 1.070 up to 25 litre batches. But if I go over this even rice hulls dont seem to help. Ive recently been doing 80 litre batches, topping up MLT to near full then sparging over and over again to get 80 litres into my fermenter with a Sg of 1.076 but I still kept getting a stuck mash even with a shit load of rice hulls thrown in, and had to stop recirculation and let it rest.

A fellow brewer has suggested that it may be my mash tun design. I use a 50 litre keg but its the taller narrower style keg as opposed to the stouter CUB style kegs. And because of this my grain bill is taller and narower so the weight of the bill may be compacting down onto itself.

So do any of you use a narrow style 50 litre keg for your MLT with a KK false bottom and approx 1mm grain mill gap? if so do you have any issues with stuck mash/sparge? I could test the theory out by using my HLT as my mash tun next brew as this is a CUB style keg so is shorter but wider. But if no one else seems to have issues then there goes that theory I guess and its back to the drawing board.

 

[Cocko]

So, it is during recirculation - As in, out of MT through HX and back to MT?

If so, what is your grain to water ratio in your MT?

 

[Online Brewing Supplies]

Howdy brewers,

Ive been having ongoing issues with my system with stuck mash issues where my grain bed compacts like concrete whilst recirculating through my herms. Here is what Ive looked at so far.



A fellow brewer has suggested that it may be my mash tun design. I use a 50 litre keg but its the taller narrower style keg as opposed to the stouter CUB style kegs. And because of this my grain bill is taller and narower so the weight of the bill may be compacting down onto itself.

I also would be looking at the mash tun max capacity and probably be looking for a Falsie that covers the whole bottom area.
Nev

 

[Spookhud]

I use similar set up I get problems when using wheat and more than 10kg of grain I think my bed depth is to deep was thinking changing mash tun dimension to get 8-12 inch max depth

 

[Camo6]

Like Cocko asks, is it while recircing with a pump? If so what pump do you use and what rate are you recircing at Truman?

I changed my sparge arm recently to a blichmann auto-sparge (terribly dull looking thing h34r: ) and found this had very little resistance to flow compared to my old setup. I was used to running the Kaixin at full pelt but now have to throttle it right back to stop a stuck mash.

A full tooheys style keg does sound like a lot of grain compacting on itself though.

 

[MHB]

Two things that come to mind, based on having used a very similar MLT for several years.
1/ not all "1mm" cracks are created equal. some mills will give a good crush at 1mm, some throw lots of fines that will cause trouble. You are looking for dethatched but not shredded husks and a kibble of malt that lets wort pass through and around it easily.
2/ the speed you are drawing down at or the amount of wort you are recirculating, if its too fast the grain bed will pull, try slowing down the flow rate.
3/ a combination of 1 & 2.

There are other things to take into account, as mentioned your L:G ratio, if there isn't enough water in there it can be an issue.
The mash tun capacity, you don't say how many Kg of malt you are putting in there but to make 80L of 1.070 wort we have to be talking around 17Kg which is pushing the limits for a 50L MLT. That sort of feeds back into the L:G and the bed depth both mentioned above.

I did a brew two weeks ago that had 26Kg in a 75L MLT and it was a shit of a brew day, that's about the same volume to grist relationship you have, and it was painfully slow. Still got 80% efficiency in fermenter but it was a seven hour brew day and no fun was had by anyone.

Mark

 

[razz]

Only thing not mentioned yet Truman is the tube that connects your falsie to the tap. Is it something like silicon or plastic that can compress under weight of grain or vacuum from pump?

 

[dago001]

I had similar issues when I swapped my mills over. My old mill (homemade one) set at 1.0 mm was fine. With the millmaster I am now out to 1.5 mm. Anything less and I get too much flour. So a brew day for me now involves mash in and turn the pump off for the first rest at 55. Start pump and herms and away I go. Water to grain ratio of 3.2l/kg. No more stuck mashes. the pump is still pulling down the grain bed, as when I turn it off to swap over to the HLT, you can visibly see the grain bed lift. I'm happy enough with this. as it lets me run the pump (march pump) at full flow.
Hope this helps you, as it drove me bonkers until I got it right.
Cheers
LB

 

[Truman42]

It is during recirculation, MLT to herms and back to MLT. I use a March pump and my water to grain ratio is usually what beersmith defaults too. I think around 3 litres per kg. I use a ball valve on the MLT return to throttle it back to a very slow flow in some instances but it still gets stuck and stops all together, just takes longer to do so. My MLT drains from the bottom under the false bottom and through an elbow. (keg has bolts for legs) so no issues with the hose collapsing.

When I did my 80 litre batch it was a grain bill of 16 kgs and the MLT was full to the top with water. (I added sugar to get the gravity I needed) but Ive also had issues with smaller grain bills too.

I was confident my grain crush was not too fine, lots of grain husk particles, and if I increase my gap size to 1.5mm I end up getting very poor efficiency, down to 60%.

The 80 litre batch aside I will try a 4:1 ratio next time and see how I go. Also my falsie is an inch diamater less than the MLT so maybe I need to increase this as well.

Thanks for the replies gents.

 

[MastersBrewery]

not mentioned, at mash in allow a 5 min rest before starting the pump, this allows the grain to absorb and expand before setting the bed.

MB

 

[pk.sax]

What they said, besides - don't recirc during the protein rest, stir. Start pumping for the next step/s. I used to have all sorts of dramas with grain bed compaction but no problems past the protein rest.