Recirculation issues with same crush

[PirkDiggler]

My system is set up as a homemade, all electric Brewmagic with keggles and all so I have been recirculating for years. I've done 30+ lbs of grain on a 12" domed false bottom at 1.25qt/lb with no sticking. My biggest improvement in efficiency, consistency, and not having to worry about my mash element has been moving to a coarse crush.

For my base malts I tend to crush around a .060 (inches) and I've found that most specialty malts and wheat will slip right through that so I reset it back to around .050-.055(in) for those.

Coarse crush sounds counter intuitive, at least it did to me, but I promise if you are doing a full recirc, it will improve your mash. Just be sure to keep 1-2" of liquid on top of the grain bed, run your pumps at 100% without throttling valves and stir maybe once or twice per mash, then sit back and enjoy pain free, 80%+ efficiency mashes.

 

[rudylyon57]

Rotameter works great for this.
View attachment 410060

I've found that my max achievable flow rate without sticking depends on how deep the bed is.

Few other things:
-Malt conditioning has been mentioned. This will help keep your husks more in tact. Even 1oz of water from a spray bottle makes an enormous difference. Also keeps the dust down. 1-2% as mentioned i think is more than needed and just gums up the mill rollers.

-Milling slower is better. A variable speed drill with an adjustable trigger knob lock is great.

-If you have a sight glass in the tun it will indicate the pressure across the bed. Use this as a guide for when you're going too far.

-Dough in low, i target 131 and give it time to hydrate the starch. This prevents dough balls from forming.

-I picked this one up from low oxygen brewing, but it would also work great for normal brewing - underlet the mash. In essence you fill the tun from the bottom up, which displaces air and fills the gaps between the grain slowly. This combined with the dough in at 131 makes a big difference. You still need to give it 1 really good stir in the beginning though.

Getting a stuck mash, from experience, is dependent on a lot more than just mash thickness.

From years of brewing on my recirculating system with grain bills up to 30 lbs in a 1/2 barrel keg with a V screen false bottom and a 500 micron stainless steel filter over it, here's what I can tell you:

The crush of the grain can change based on moisture content of that harvest. How well you get rid of dough balls during mash in makes a large difference. The total pressure on the false bottom makes a large difference.

The first one you can address with malt conditioning, it helps a lot.

The second I solved with a 20 ft/lbs motor driving a custom made stir rake.

The third issue depends on the vacuum of your pump during recirc (obviously not as bad during sparge), and the surface area of your false bottom vs the total weight of your mash (water and grain together). If the pressure on the false bottom gets too high you will get stuck, be it which ever of those variables you are messing with. Your surface area of your false bottom is pretty fixed I bet, same with its filtration, so lets bypass those.

If you add too much water from the top you can actually cause a stuck mash/sparge because you've increased the pressure pushing down on the bottom of the grain bed too much. Too thick of a mash and the proteins all conglomerate into a hard cylinder and you get no flow as well. General rule of thumb is that you should have 1-2 inches of water above what the grains resting height would be (easy to measure at sparge, hard during mash). Too much vacuum from your pump and you can cause a stuck mash as well.

To address all this in my system I've found the standard 1.25 quart per lb to be a good thickness, I put a gate valve on the output of my pump to prevent it from pulling too much vacuum, I always condition my grain, always use rice hulls with large amounts of wheat and/or rye but dont put the rice hulls through the mill, stir WELL during grain in adding the grain to already existing water, not the other way around, and then I maintain a decent stir speed during the entire mash, and give the mash 10 minutes of no recirc or stir before sparge while sparging at a hotter temp (168 or so) (note I fly sparge). Also note I mill at .029

With that combination of changes to the system I have had neither a stuck sparge nor mash in over 3 years brewing once a month with everything from a 18lbs grain bill up to a 30 lbs grain bill.

When dealing with a stuck mash/sparge the best way I've seen to deal with it is with what is called an "under-let". This is when you push water up into the mash tun from the bottom to lift the grain bed. If your system is not designed to be capable of doing that I suggest you change it so it can, it makes a huge difference when trying to deal with a stuck mash/sparge.

Hope that helps.

Excellent information folks. Not my thread, sorry, but some useful stuff here. My fist step is to fixture up a "sight glass/manometer" to measure, and most importantly control, pressure across grain bed.