Ask The Brewmasters

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Michal,

Correct me if I am wrong, but it sounds like you have two concurrent problems: 1) excess flour from the mill into the mash mixer and 2) inadequate mixing keeping a layer of flour on top of the mash.

For #1, I imagine you are just going to have to adjust mill settings and define new grist parameters for your new set up. You should see a very different grist requirement for a mash mixer + lauter tun as compared to a combi-vessel.  I don't know what your LT set up is, but you may want to adjust your overall wort separation protocol accordingly too. Travis Audet's MBAA podcast on the topic was eye opening for us and we made huge changes to our runoffs. 

Regarding #2, we actually faced the same problem and our programmer (from GEA) came up with a creative solution. We don't run our mixer at constant speed during mash-in and rests. Instead, our mixer varies speed between 10 and 25rpm every 60s and this creates a wave action that forces the flour "pancake" down from the top of the mash to adequately mix. I don't know what your controls interface looks like but it should be easy enough to trial. 

Shoot me a note if you want to chat through it more. 

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Michal,

Correct me if I am wrong, but it sounds like you have two concurrent problems: 1) excess flour from the mill into the mash mixer and 2) inadequate mixing keeping a layer of flour on top of the mash.

For #1, I imagine you are just going to have to adjust mill settings and define new grist parameters for your new set up. You should see a very different grist requirement for a mash mixer + lauter tun as compared to a combi-vessel.  I don't know what your LT set up is, but you may want to adjust your overall wort separation protocol accordingly too. Travis Audet's MBAA podcast on the topic was eye opening for us and we made huge changes to our runoffs. 

Regarding #2, we actually faced the same problem and our programmer (from GEA) came up with a creative solution. We don't run our mixer at constant speed during mash-in and rests. Instead, our mixer varies speed between 10 and 25rpm every 60s and this creates a wave action that forces the flour "pancake" down from the top of the mash to adequately mix. I don't know what your controls interface looks like but it should be easy enough to trial. 

Shoot me a note if you want to chat through it more. 

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Michal,

Correct me if I am wrong, but it sounds like you have two concurrent problems: 1) excess flour from the mill into the mash mixer and 2) inadequate mixing keeping a layer of flour on top of the mash.

For #1, I imagine you are just going to have to adjust mill settings and define new grist parameters for your new set up. You should see a very different grist requirement for a mash mixer + lauter tun as compared to a combi-vessel.  I don't know what your LT set up is, but you may want to adjust your overall wort separation protocol accordingly too. Travis Audet's MBAA podcast on the topic was eye opening for us and we made huge changes to our runoffs. 

Regarding #2, we actually faced the same problem and our programmer (from GEA) came up with a creative solution. We don't run our mixer at constant speed during mash-in and rests. Instead, our mixer varies speed between 10 and 25rpm every 60s and this creates a wave action that forces the flour "pancake" down from the top of the mash to adequately mix. I don't know what your controls interface looks like but it should be easy enough to trial. 

Shoot me a note if you want to chat through it more. 

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Michal,

Correct me if I am wrong, but it sounds like you have two concurrent problems: 1) excess flour from the mill into the mash mixer and 2) inadequate mixing keeping a layer of flour on top of the mash.

For #1, I imagine you are just going to have to adjust mill settings and define new grist parameters for your new set up. You should see a very different grist requirement for a mash mixer + lauter tun as compared to a combi-vessel.  I don't know what your LT set up is, but you may want to adjust your overall wort separation protocol accordingly too. Travis Audet's MBAA podcast on the topic was eye opening for us and we made huge changes to our runoffs. 

Regarding #2, we actually faced the same problem and our programmer (from GEA) came up with a creative solution. We don't run our mixer at constant speed during mash-in and rests. Instead, our mixer varies speed between 10 and 25rpm every 60s and this creates a wave action that forces the flour "pancake" down from the top of the mash to adequately mix. I don't know what your controls interface looks like but it should be easy enough to trial. 

Shoot me a note if you want to chat through it more. 

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Michal,

Correct me if I am wrong, but it sounds like you have two concurrent problems: 1) excess flour from the mill into the mash mixer and 2) inadequate mixing keeping a layer of flour on top of the mash.

For #1, I imagine you are just going to have to adjust mill settings and define new grist parameters for your new set up. You should see a very different grist requirement for a mash mixer + lauter tun as compared to a combi-vessel.  I don't know what your LT set up is, but you may want to adjust your overall wort separation protocol accordingly too. Travis Audet's MBAA podcast on the topic was eye opening for us and we made huge changes to our runoffs. 

Regarding #2, we actually faced the same problem and our programmer (from GEA) came up with a creative solution. We don't run our mixer at constant speed during mash-in and rests. Instead, our mixer varies speed between 10 and 25rpm every 60s and this creates a wave action that forces the flour "pancake" down from the top of the mash to adequately mix. I don't know what your controls interface looks like but it should be easy enough to trial. 

Shoot me a note if you want to chat through it more. 

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Glen,

I agree with your first point. We tried not running the blades during rest a couple of times this week and could not get the mix going again after doing so, at least from what we can tell from the top and the temp not raising when jackets are on.  We run into the issue of dry pockets between the baffles that seem to carry all the way down the tank.

Our protocol for mashing in currently is 7-9bbls of water as a base and then bringing the grist in after.  The hydrator is running about 90-94gpm while we are mashing in and total grain is about 4000-4500lbs based upon the couple recipes we have ran into here.  We end up with 40-44bbls of water in the mash mixer and then use about 2-3bbls for a flush out after we mashed out.  The later tun has a foundation of 3-4bbls of water, about 1/2" above the screens when we run mash into it.  Does that seam about right for water ratio?  We have tried more and less, but still have not seen better results.

------------------------------
Michal Frankowicz
Head Brewer
Fort George Brewery
Astoria, OR
503-298-3174
------------------------------

Original Message:
Sent: 04-02-2024 12:01
From: Glen Sprouse
Subject: Mash Mixer Designs

Original Message:
Sent: 3/29/2024 1:40:00 PM
From: Karl Ockert
Subject: RE: Mash Mixer Designs

Original Message:
Sent: 3/28/2024 2:30:00 PM
From: Campbell Morrissy
Subject: RE: Mash Mixer Designs

Hey Michal,

Correct me if I am wrong, but it sounds like you have two concurrent problems: 1) excess flour from the mill into the mash mixer and 2) inadequate mixing keeping a layer of flour on top of the mash.

For #1, I imagine you are just going to have to adjust mill settings and define new grist parameters for your new set up. You should see a very different grist requirement for a mash mixer + lauter tun as compared to a combi-vessel.  I don't know what your LT set up is, but you may want to adjust your overall wort separation protocol accordingly too. Travis Audet's MBAA podcast on the topic was eye opening for us and we made huge changes to our runoffs. 

Regarding #2, we actually faced the same problem and our programmer (from GEA) came up with a creative solution. We don't run our mixer at constant speed during mash-in and rests. Instead, our mixer varies speed between 10 and 25rpm every 60s and this creates a wave action that forces the flour "pancake" down from the top of the mash to adequately mix. I don't know what your controls interface looks like but it should be easy enough to trial. 

Shoot me a note if you want to chat through it more. 

------------------------------
Campbell Morrissy, PhD
Director of Brewery Operations
pFriem Family Brewers

Original Message:
Sent: 03-27-2024 13:29
From: Michal Frankowicz
Subject: Mash Mixer Designs

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

------------------------------
Michal Frankowicz
Fort George Brewery
Astoria OR
(503) 298-3174
------------------------------

Hey Glen,

I agree with your first point. We tried not running the blades during rest a couple of times this week and could not get the mix going again after doing so, at least from what we can tell from the top and the temp not raising when jackets are on.  We run into the issue of dry pockets between the baffles that seem to carry all the way down the tank.

Our protocol for mashing in currently is 7-9bbls of water as a base and then bringing the grist in after.  The hydrator is running about 90-94gpm while we are mashing in and total grain is about 4000-4500lbs based upon the couple recipes we have ran into here.  We end up with 40-44bbls of water in the mash mixer and then use about 2-3bbls for a flush out after we mashed out.  The later tun has a foundation of 3-4bbls of water, about 1/2" above the screens when we run mash into it.  Does that seam about right for water ratio?  We have tried more and less, but still have not seen better results.

Hey Michal,

Correct me if I am wrong, but it sounds like you have two concurrent problems: 1) excess flour from the mill into the mash mixer and 2) inadequate mixing keeping a layer of flour on top of the mash.

For #1, I imagine you are just going to have to adjust mill settings and define new grist parameters for your new set up. You should see a very different grist requirement for a mash mixer + lauter tun as compared to a combi-vessel.  I don't know what your LT set up is, but you may want to adjust your overall wort separation protocol accordingly too. Travis Audet's MBAA podcast on the topic was eye opening for us and we made huge changes to our runoffs. 

Regarding #2, we actually faced the same problem and our programmer (from GEA) came up with a creative solution. We don't run our mixer at constant speed during mash-in and rests. Instead, our mixer varies speed between 10 and 25rpm every 60s and this creates a wave action that forces the flour "pancake" down from the top of the mash to adequately mix. I don't know what your controls interface looks like but it should be easy enough to trial. 

Shoot me a note if you want to chat through it more. 

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hi Michal, can you go into a little more detail about what you're seeing with "decent turnover"? A rule of thumb I was given once for mash mixing was to aim for the mash to be spinning just fast enough to generate a slow roll but not so slow that the mash settles. With that in mind, I'm curious how rapidly your mash is mixing at 40 RPM.

Also, I'm guessing you already looked into this but I'm still curious: have you done a sieve analysis of the grain coming out of your mill?

One last thought: I've found that manufacturers are a great resource. If you haven't already, I would suggest reaching out to them!

Nassim

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Nassim,

Our mixer is designed to pull down in the middle and up the side walls.  Decent turnover for us is like you described, just enough moving to keep it from settling/ stopping.  That would be at about 35rpm.  We need it at 40rpm to mash in or raise temp because it will just settle if we do not have it moving that fast.

We ran sieve tests before the install of the mixer and all was in spec.  I have not run one since, but we have been trying a coarser grist with no better results.

I am currently working with the manufacturer on this, but was looking for outside information since they are telling me to just speed it up even faster and the design is not the issue.

Michal

Hi Michal, can you go into a little more detail about what you're seeing with "decent turnover"? A rule of thumb I was given once for mash mixing was to aim for the mash to be spinning just fast enough to generate a slow roll but not so slow that the mash settles. With that in mind, I'm curious how rapidly your mash is mixing at 40 RPM.

Also, I'm guessing you already looked into this but I'm still curious: have you done a sieve analysis of the grain coming out of your mill?

One last thought: I've found that manufacturers are a great resource. If you haven't already, I would suggest reaching out to them!

Nassim

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hi Michal,

Do you have a picture you can post of your current mash tun setup?   

You can try to run the mash mixer at a higher speed when heating up the mash for good heat dispersion.   Keep the mixer running for 1-2 minutes after you get to your step temperature to allow the steam jackets to cool down but then turn off the mash mixer completely for the rest.   Especially with the added baffles in your mash tun, this will get rid of a lot of extra shear you might be seeing, we eventually removed all the baffles in our old mash tun because of this shearing but we also changed our mixer design at the same time, it really depends on your mixer blades.  Our newer blades are a twisted style so it spins the mash off the blades and helps mix with less shear, see attached pictures of some different blade versions.   

 If you don't feel comfortable completely turning off the mash mixer during the rest, then go to a really slow speed during your mash rests just to keep the mash from settling.  Or a do a hybrid step where you just bump the motor for a few minutes every 5 minutes during your rests.    You may find at lower temperatures that the mash settles too fast to the bottom so the mixer may need to stay running all the time at lower temperatures, but as the starches convert and the mash thins then you can get away with longer non-mixing times so it may take some experimentation on what works best.  

As Karl mentioned, I would also check the rotation of your mixer blades.    Even though it's not great to be pushing the mash down into the tank bottom, on one of our old mixer blade designs the incorrect rotation worked better than the correct rotation due to a poor blade design.  

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Below is a photo of the mixer.  We just tried a mash in with upward flow and after about 75% of the mash in, we stopped getting any rotation and the grain sat on top.  I do believe this is the right direction, but the blades are too short for this, or the baffles stick out too far.

We did run a mash earlier today with slowing down to 30% during rests, and it was definitely better, but still had a nice cake in the lauter that caused some severe channeling.  We notice that if we turn off the mixer in the mash, everything seems to float up, as far as we can tell of course.  All of this would be so much easier if we just had a glass mash mixer to see what was going on.

Hi Michal,

Do you have a picture you can post of your current mash tun setup?   

You can try to run the mash mixer at a higher speed when heating up the mash for good heat dispersion.   Keep the mixer running for 1-2 minutes after you get to your step temperature to allow the steam jackets to cool down but then turn off the mash mixer completely for the rest.   Especially with the added baffles in your mash tun, this will get rid of a lot of extra shear you might be seeing, we eventually removed all the baffles in our old mash tun because of this shearing but we also changed our mixer design at the same time, it really depends on your mixer blades.  Our newer blades are a twisted style so it spins the mash off the blades and helps mix with less shear, see attached pictures of some different blade versions.   

 If you don't feel comfortable completely turning off the mash mixer during the rest, then go to a really slow speed during your mash rests just to keep the mash from settling.  Or a do a hybrid step where you just bump the motor for a few minutes every 5 minutes during your rests.    You may find at lower temperatures that the mash settles too fast to the bottom so the mixer may need to stay running all the time at lower temperatures, but as the starches convert and the mash thins then you can get away with longer non-mixing times so it may take some experimentation on what works best.  

As Karl mentioned, I would also check the rotation of your mixer blades.    Even though it's not great to be pushing the mash down into the tank bottom, on one of our old mixer blade designs the incorrect rotation worked better than the correct rotation due to a poor blade design.  

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hi Michal,

Thanks for the picture.  Your mash mixer blade size and the baffles looks just like my first mash tun experiences with a new manufacturer, and it worked about as horribly as yours does.  I agree with others that your blades look too small.   We didn't see the shear you are seeing, but had the same poor mixing results.   I would definitely recommend longer mixer blades or a mixing blade redesign if the manufacturer is working with you to resolve this.   If the manufacturer isn't too excited about a blade redesign you could keep the lower mixer that you have, and have the manufacturer give you another set of blades and mount them higher up on the shaft, about 1-2 feet below the liquid level.  In your picture it looks like the manufacturer already left you another set of mixer blade mounting plates higher up on the shaft so it would be easy to add and test.    It's not a great fix to have doubled up mixer blades but it will help, we did this with our first mash tun design and we were able to make it work for several years until we could retrofit the entire mash tun.   

I also noticed that your baffles are solid welded down the entire length of the vessel, so all of your grain is just slamming into all of these baffles.  The manufacturer is expecting all the grain to move up to the top but the force against the baffles can create a lot of shear in addition to giving you a lot of dead corners that might create poor mixing zones where the grain can't get hydrated.   On our mash tun the manufacturer had designed in several 2 inch wide gaps down the length of the baffles so mash could at least move through and around the baffles.  See the attached sketch of what our first mash tun looked like after we added the second mixer blades.   This isn't an easy fix to add the slots to the baffles now and may not fix all of your problems, but they could plasma cut some holes in the baffles just to help movement and mixing in those areas, and this would also help break up any clumps of grain that aren't hydrated fully yet. 

One final idea is to try to move your mixer blades up off the bottom of the vessel, they look really close to the bottom and that could be restricting good movement around the blades.     

Below is a photo of the mixer.  We just tried a mash in with upward flow and after about 75% of the mash in, we stopped getting any rotation and the grain sat on top.  I do believe this is the right direction, but the blades are too short for this, or the baffles stick out too far.

We did run a mash earlier today with slowing down to 30% during rests, and it was definitely better, but still had a nice cake in the lauter that caused some severe channeling.  We notice that if we turn off the mixer in the mash, everything seems to float up, as far as we can tell of course.  All of this would be so much easier if we just had a glass mash mixer to see what was going on.

Hi Michal,

Do you have a picture you can post of your current mash tun setup?   

You can try to run the mash mixer at a higher speed when heating up the mash for good heat dispersion.   Keep the mixer running for 1-2 minutes after you get to your step temperature to allow the steam jackets to cool down but then turn off the mash mixer completely for the rest.   Especially with the added baffles in your mash tun, this will get rid of a lot of extra shear you might be seeing, we eventually removed all the baffles in our old mash tun because of this shearing but we also changed our mixer design at the same time, it really depends on your mixer blades.  Our newer blades are a twisted style so it spins the mash off the blades and helps mix with less shear, see attached pictures of some different blade versions.   

 If you don't feel comfortable completely turning off the mash mixer during the rest, then go to a really slow speed during your mash rests just to keep the mash from settling.  Or a do a hybrid step where you just bump the motor for a few minutes every 5 minutes during your rests.    You may find at lower temperatures that the mash settles too fast to the bottom so the mixer may need to stay running all the time at lower temperatures, but as the starches convert and the mash thins then you can get away with longer non-mixing times so it may take some experimentation on what works best.  

As Karl mentioned, I would also check the rotation of your mixer blades.    Even though it's not great to be pushing the mash down into the tank bottom, on one of our old mixer blade designs the incorrect rotation worked better than the correct rotation due to a poor blade design.  

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal

Hey Curtis,

Thank you for the great info.  We have tried the second set of blades about a foot below the liquid level and it definitely helped, but we still could not get movement off of the walls unless we increased speed, and that caused a lot of turbulence.  I have not tried the second set with upward flow, but will try tomorrow.

I agree with the slots on the baffles, but also understand how big of a headache that might be for the manufacturer.  Would it it make sense to just cut them completely off and add new ones instead of trying to cut out channels and buffing out the excess material?

The picture is a bit deceiving.  The blades are about 18" off of the bottom currently and that is as low as we can get them with this design.  I would like to see them a lot lower since the last 10bbls of mash has no agitation when mashing out and causes a lot of grain to stick behind unless we use a lot of water to rinse out.  All of the mixers I have seen are usually 4-6" off the bottom.  Is that the case for yours?

------------------------------
Michal Frankowicz
Head Brewer
Fort George Brewery
Astoria, OR
503-298-3174

Original Message:
Sent: 04-01-2024 22:04
From: Curtis Holmes
Subject: Mash Mixer Designs

Hi Michal,

Thanks for the picture.  Your mash mixer blade size and the baffles looks just like my first mash tun experiences with a new manufacturer, and it worked about as horribly as yours does.  I agree with others that your blades look too small.   We didn't see the shear you are seeing, but had the same poor mixing results.   I would definitely recommend longer mixer blades or a mixing blade redesign if the manufacturer is working with you to resolve this.   If the manufacturer isn't too excited about a blade redesign you could keep the lower mixer that you have, and have the manufacturer give you another set of blades and mount them higher up on the shaft, about 1-2 feet below the liquid level.  In your picture it looks like the manufacturer already left you another set of mixer blade mounting plates higher up on the shaft so it would be easy to add and test.    It's not a great fix to have doubled up mixer blades but it will help, we did this with our first mash tun design and we were able to make it work for several years until we could retrofit the entire mash tun.   

I also noticed that your baffles are solid welded down the entire length of the vessel, so all of your grain is just slamming into all of these baffles.  The manufacturer is expecting all the grain to move up to the top but the force against the baffles can create a lot of shear in addition to giving you a lot of dead corners that might create poor mixing zones where the grain can't get hydrated.   On our mash tun the manufacturer had designed in several 2 inch wide gaps down the length of the baffles so mash could at least move through and around the baffles.  See the attached sketch of what our first mash tun looked like after we added the second mixer blades.   This isn't an easy fix to add the slots to the baffles now and may not fix all of your problems, but they could plasma cut some holes in the baffles just to help movement and mixing in those areas, and this would also help break up any clumps of grain that aren't hydrated fully yet. 

One final idea is to try to move your mixer blades up off the bottom of the vessel, they look really close to the bottom and that could be restricting good movement around the blades.     

Below is a photo of the mixer.  We just tried a mash in with upward flow and after about 75% of the mash in, we stopped getting any rotation and the grain sat on top.  I do believe this is the right direction, but the blades are too short for this, or the baffles stick out too far.

We did run a mash earlier today with slowing down to 30% during rests, and it was definitely better, but still had a nice cake in the lauter that caused some severe channeling.  We notice that if we turn off the mixer in the mash, everything seems to float up, as far as we can tell of course.  All of this would be so much easier if we just had a glass mash mixer to see what was going on.

Hi Michal,

Do you have a picture you can post of your current mash tun setup?   

You can try to run the mash mixer at a higher speed when heating up the mash for good heat dispersion.   Keep the mixer running for 1-2 minutes after you get to your step temperature to allow the steam jackets to cool down but then turn off the mash mixer completely for the rest.   Especially with the added baffles in your mash tun, this will get rid of a lot of extra shear you might be seeing, we eventually removed all the baffles in our old mash tun because of this shearing but we also changed our mixer design at the same time, it really depends on your mixer blades.  Our newer blades are a twisted style so it spins the mash off the blades and helps mix with less shear, see attached pictures of some different blade versions.   

 If you don't feel comfortable completely turning off the mash mixer during the rest, then go to a really slow speed during your mash rests just to keep the mash from settling.  Or a do a hybrid step where you just bump the motor for a few minutes every 5 minutes during your rests.    You may find at lower temperatures that the mash settles too fast to the bottom so the mixer may need to stay running all the time at lower temperatures, but as the starches convert and the mash thins then you can get away with longer non-mixing times so it may take some experimentation on what works best.  

As Karl mentioned, I would also check the rotation of your mixer blades.    Even though it's not great to be pushing the mash down into the tank bottom, on one of our old mixer blade designs the incorrect rotation worked better than the correct rotation due to a poor blade design.  

Hey Everyone,

We recently installed a new 60bbl prop style mash mixer into are system and are dealing with issues of it creating too much flower and making run off from the later very sticky.  Our current design is 20° broken prop blades that are roughly half the diameter of the tank and sit about 16" above the bottom.  The tank also has three baffles on it to keep it from whirlpooling too much.  What we are noticing is that we have to run the prop at about 40rpm to get a decent turnover in the tank and was wondering if large prop blades would be a better solution to lower the rpm and still keep the turn over, or if we should be just looking for a different design?

Thanks all,

Michal