Run off problem, grain husks and particles near end of run off

[J.Scholb]

We have an interesting problem with our new brew system. After about 75% of the wort has been collected in the kettle we start to see grain husks and grain particles in the site glass. Whereas at the end of the 40 minute vorlouf and the first 75% of the run off the wort was clear and free of particles. It gets really bad if the flow gets really slow or we stop it. It's enough grain to be concerned about.

Pertinent Information:

• We gravity flow the wort from the MLT to the Kettle, with no wort grant in-between.
• We target a 90 minute run off, collecting 180 gallons.
• The flow of the run off slows from about 2.5 GPM to about 1.5 GPM as the liquid level in the kettle rises.
• The MLT screens have a 0.025" gap
• We crush the grain to 0.065". We have used a 3 roller mill (at 300 rpm) and a 2 roller mill (at 500 RPM) with the same result.
• When we clean the MLT there is a lot of grain and particles left under the false bottom.
• Our mash is 1.2 qt/lb, but we have a 35 gallon underlet that is not included in the calculation. Total water is 500 quarts to 300 lbs of grain and we don't count the underlet (water under the false bottom), so it's 360 quarts/300 lbs of grain = 1.2 qt/lb.

We have tried the following options:
1) added a strainer to just collect the grain husks and particles, but the strainer got full and slowed the flow and then even more grain came out of the MLT.
2) a faster run off, but still had the problem near the end.
3) longer vorlouf. Wort looked very clear, but still picked up grain near the end
4) switching from a high rate vorlouf to a slow rate, see some more grain when slowed and it clears, but then still have the problem at the end.

We are thinking of adding a wort grant to give us better control over the flow rate out of the MLT. However, it feels like the root cause is the, crush, grain bed or the MLT screens. And anything down stream is not solving the problem.

Any insight would be helpful.

[Todd Hicks]

Wort grant or manomater is always needed in my opinion.

For such a small system, manometer might be very easy to install. Be sure to have a fitting to control flow and take samples and a site glass to view the clarity of wort.

40 min or vorlauf seems excessive. Might try cutting it down to 10-15 minutes.

If you put in the grant, you could always put a strainer basket in it during trouble. And also use it as a hop back.

[irishod89]

A couple of thoughts.

1) Try and keep a your runoff speed from slowing down at the end---solved by using a grant and pump like you already addressed

2) Check your sparge volumes. How much water are you currently sparging with?

Good luck,

Ryan

[spetrovits]

I will second a grant. Even a SS homebrew pot that you flow into the top and out of the ball valve will help control flow rates. But the real problem would seem to be your crush. While some flour/particles will accumulate under the MLT false bottom, there shouldn't be so much that it starts sloughing into the drain well before you're done running out. I recommend buying or borrowing a set of ASTM sieves to fine-tune your mill. It worked wonders for us, moving us from 69-73% efficiency to just over 80.

Also, you should increase your sparge volume, so you can stop sparging when you reach your boil volume, leaving the stuff under the false bottom undisturbed. We used to run out until we nearly emptied the space under the false bottom, but got some of that crud in our kettle if we weren't careful.

Finally, you could consider installing a short standpipe in the MLT outlet. An SS or PVC pipe with an O-ring, pressed into the outlet, raises the outlet above the actual MLT bottom, and the flour/particles slough into the sides of the standpipe and not into your kettle. You just have to account for the extra sparge volume, as some liquid will be trapped in the MLT until cleaning, when you pull the standpipe out.

Hope this helps.

[J.Scholb]

Run off problem update

We brewed yesterday with a wort grant. We kept a constant flow during the vorlouf and then started the run off at exactly the same rate. We started sparge soon after and kept the same rate. It was actually easier to operate with the grant because we could set one valve and pump speed and maintain the liquid level on the grain bed.

Well, at about the same time as before, 125 gallons out of 185, the grain started dumping out of the MLT. literally dumping out. At least a few pounds collected in the grant. We stopped the run off and went back to vorlouf. In about 15 minutes it cleared up again and we ran off the remaining wort, but stopped a little short because it was more diluted by the sparge.

So what can cause the grain bed to stop working? This wasn't a stuck mash since there was no loss of flow. Is the hot sparge heating and diluting the wort, making it much more easy to flow and allowing the grain bed to expand and drop particles?

Should we increase the run off rate as the wort heats and gets less viscous? What do other brewers do, is your run off at constant rate?

[Mike Elliott]

We brewed yesterday with a wort grant. We kept a constant flow during the vorlouf and then started the run off at exactly the same rate. We started sparge soon after and kept the same rate. It was actually easier to operate with the grant because we could set one valve and pump speed and maintain the liquid level on the grain bed.

Well, at about the same time as before, 125 gallons out of 185, the grain started dumping out of the MLT. literally dumping out. At least a few pounds collected in the grant. We stopped the run off and went back to vorlouf. In about 15 minutes it cleared up again and we ran off the remaining wort, but stopped a little short because it was more diluted by the sparge.

So what can cause the grain bed to stop working? This wasn't a stuck mash since there was no loss of flow. Is the hot sparge heating and diluting the wort, making it much more easy to flow and allowing the grain bed to expand and drop particles?

Should we increase the run off rate as the wort heats and gets less viscous? What do other brewers do, is your run off at constant rate?

Lewis and Bamforth recommend gradually increasing runoff rate during the sparge in order to a) maximize extract, b) minimize extraction of tannin near the end of runoff, and c) keep the bed from collapsing early when wort viscosity is high.

I also suggest loosening your mill with the aid of sieves and increasing your sparge volume.

Something I do on every troublesome recipe (stuff with lots of wheat or rye, as well as high gravity beers) is add plenty of rice hulls and gently rake the schmutzdecke (dirty layer) that forms after vorlauf. Sometimes the flour can blind the bed and cause cracking and junk falling through.

[TheCarolinian]

Can you give us more details about your sparge? Also, give us more details about temps of both mash and sparge as well as volumes for both.

[TJC]

manufacturer

who built the brew house? I've experienced this issue before with the dreaded PUB systems that use gravity to run off with no grant.

[Todd Hicks]

What is the runoff wort gravity when it turns to mud? If it is low enough to have captured your wort, you may not want to continue lautering the mud. Top off with water. Adjust mash with a little more base malt.

How is the mash ph? Wort ph during lauter? Take a test at each barrel moved.

Have you tried another grain supplier for a test batch? At one time, I used Munton's pale malt and it always ran off muddy at some point. Wort settled after boil and the beer was just fine though. Briess 6-row Munich malt also gave me fits before also when used in very high percentage. The fix for both was to ass a bit of wheat malt. Even though cloudy runoff, the beer fined in the kettle just fine and the end beer was great.

[J.Scholb]

Brew Update

Well it happened again. At about 50 gallons of run off out of 185 gal, we again started to see grain in the site glass. We quickly stopped the sparge and went back to vorlouf. The grain wasn't as bad this time, but there was still a surprising amount of grain in the wort grant. It cleared up after 15 minutes of vorlouf. Unfortunately, going back to vorlouf dilutes the wort and we had to stop the run off short to hit the gravity.

The changes we made for this batch were:
1) less fine crush on the grain mill
2) added rice hulls
3) Smoothed out the top of the mash
4) was very careful to start the vorlouf slow and then keep a constant rate
5) made sure the distributor was evenly spraying the liquid and not digging holes with too strong of a spray
6) made sure the sparge water was not too deep over the grain bed

While we can mitigate this problem by going back to vorlouf, we are pretty confused as to how the grain bed can fail on us so early on in the sparge.

Any other ideas?

[Todd Hicks]

You could try batch sparging in three 2bbl lauter runs. That would prevent oversparging as you will be collecting all of the liquid each time. Could even try a vorlauf each time. You will lose about 5% efficiency though and will be time consuming.

[J.Scholb]

We just brewed again with a thicker mash, 1.0 qt/lb to try an get a better grain bed to keep the flour from coming out during the runoff. The same problem happened at exactly the same time during the Sparge. Grain and flour came dumping out into the wort grant. We went back to vorlouf and it cleared right up in about 15 minutes.

Could the problem be too thick of a mash and the distributor not circulating the Vorlouf to the outer parts of the grain bed? Then during sparge, with a 1" liquid level, these outer areas are washed and the grain comes out, just like at the beginning of the vorlouf. This would explain why going back to vorlouf for only 10 to 15 minutes clears it right back up. There are no signs of air, floating or burping that would be upsetting the grain bed when this problem happens, nor is there excess vibrations or slamming of the manway door.

I attached a picture of the vorlouf. With a thick mash it's pretty clear the outer sections are not being sprayed by the distributor. Do you think this is the problem?

For next time, we're going to try a thinner mash and see if we can get the distributor to spray the outer parts of the grain bed too.

[BeachBrew]

Runoff Level to Low

I think I see the issue. Try keeping the mash liquid level at least 2 inches above the grain bed. You could be putting too much pressure on the bed.

[J.Scholb]

We're going to try more mash water and see if we can get better distribution to the outer areas of the grain bed. Our vorlouf was taking about 45 minutes to clear up and this may have been caused by the poor distribution. So if more water, a liquid level and better distribution helps, we should see it clear up in about 15 minutes.

Any other thoughts?

[J.Scholb]

Update

We increased the mash water to 1.5 qt/lb and had much better results. We only saw a little grain all the way up until the last 10 minutes of the run off. It started to break down and get cloudy, but it was much better than before. We forgot to use excess sparge water so it ran out near the end. For next time we will have enough sparge water to keep doing the sparge until the runoff is complete.