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Thread: Mash Temp Variation

  1. #1
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    Dec 2018
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    Chicago, IL
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    Mash Temp Variation

    Hi all, I'm new to the forum as I am new to professional brewing. Quick question. I'm trying to hit certain temps in our steam jacket MLT and my handheld thermometer is ready radically different temperatures throughout the grain bed. If I'm trying it hit 152, I can be up to 170 near the sidewall, 115 near the center on the bottom of the bed, and anywhere in between throughout the bed. Running our mixer like crazy to try to even out the bed temperature and no matter what I seem to have major temperature differences throughout the bed. Is this normal? Any tips or ideas on how to fix this?

  2. #2
    Join Date
    Jul 2004
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    MO.
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    Does your mlt have true mixing paddles or does it just have rakes/knives? Is there anything that causes the mash to move sideways? Sounds like the mash is just spinning in concentric circles, without true mixing.
    An angled baffle on the sidewall can help in the mixing. Or maybe you can think up a mixer blade that can be temporarily attached to the rakes/knives in the mlt.

    Some of the large older mash/lauter tuns used to have knives that could be rotated to help with mixing, and also to help with spent grain removal.

  3. #3
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    Water (and mash) as such is not a good conductor of heat, as you have discovered. It needs to be stirred effectively to distribute the heat.

    The traditional british mash tun for beer brewing may have had grains extraction rakes, but never mixers - if you mix you knock out air from the grains, so it sinks to the false floor plates and tends to blind them - hence the use of lauter tun rakes - which are solely for raking, not mixing. The mash mixing for a lauter tun is carried out in a separate mash mixing vessel, fitted with separate mixing specific paddles and some for of heating, normally steam heating jackets, before transfer to the lauter tun, fitted with rakes purely for maintaining / increasing permeability, not mixing, and usually some form of grains discharge rake / plough.


    The simplest solution is simply to mash in at the appropriate temperature - normally about 65 C, and then leave without any attempt to heat up or mix during the mash stand. With careful selection of materials, you can brew good examples of pretty much any beer - though some (most?) German brewmasters would consider it is not possible to get the finer distinctive flavours created by decoction mashing or to a lesser extent rising temperature infusion mashes.
    dick

  4. #4
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    Oct 2018
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    Lenexa, KS, USA
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    We have been having similar problems with our MLT (I’m with Dick on this - mashing & lautering should be done in separate vessels).
    I’m curious to know who built your kit & if it’s the same people as did ours (ABE).
    The advice we received was to mash wetter especially until the thermowell is covered (we currently use 3.5:1) & spin the rakes faster, so we do that & it has been better, but if we used this ratio on bigger beers, we’re likely to struggle to fit the mash in the tun & have issues with achieving our gravity &/or good extract efficiency.


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  5. #5
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    Carmel, IN
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    The wort has the highest thermal capacity and recirculating that through your bed via some form of vorlauf or pump over is the most effective way of redistributing that heat. Physical mixing of mash grist is less likely to produce a uniform temperature distribution.
    WaterEng
    Engineering Consultant

  6. #6
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    Jul 2004
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    MO.
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    There is a real problem that is being overlooked here.
    The mlt in discussion will work fine for a single temperature infusion mash. But the steam jackets do not function the way one should be able to expect them to. These mash/lauter tuns are not built with an adequate mixing arrangement to be able to use the steam jackets in a proper controlled manner. Adjusting the mash temp a degree or two is a very hit or miss proposition, if it works at all with the difference in heat near the sidewall as versus that in the center. Trying to "mash off" with a rise to 170 degrees is a waste of time and very inaccurate.

    One responder mentioned they are having the problem on ABE equipment. I have had this issue on a Stout/Brewery Automation 8 bbl brewhouse. Chinese equipment that promises to do more than it actually does?


    Yes Dick, having a mash tun to mash in and then a lauter to do the runoff in is a better way to go. Having the ability to do a fast gravity drop from the mash tun to the lauter is better than pumping the mash. Having a separate kettle and whirlpool is good also. But remember these systems are being made for and sold primarily to startup brewpubs with limited space and resources, breweries that are generally not doing multiple brews in a day. It is disappointing to see equipment being sold with what I consider to be basic design flaws.


    They should have been designed with a better mixing arrangement so that the not inexpensive steam jacket would actually be functional and useful. It is a good thing that they do work okay for single temperature infusion mashes.

  7. #7
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    Dec 2018
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    Quote Originally Posted by brewingpro View Post
    There is a real problem that is being overlooked here.
    The mlt in discussion will work fine for a single temperature infusion mash. But the steam jackets do not function the way one should be able to expect them to. These mash/lauter tuns are not built with an adequate mixing arrangement to be able to use the steam jackets in a proper controlled manner. Adjusting the mash temp a degree or two is a very hit or miss proposition, if it works at all with the difference in heat near the sidewall as versus that in the center. Trying to "mash off" with a rise to 170 degrees is a waste of time and very inaccurate.

    One responder mentioned they are having the problem on ABE equipment. I have had this issue on a Stout/Brewery Automation 8 bbl brewhouse. Chinese equipment that promises to do more than it actually does?


    Yes Dick, having a mash tun to mash in and then a lauter to do the runoff in is a better way to go. Having the ability to do a fast gravity drop from the mash tun to the lauter is better than pumping the mash. Having a separate kettle and whirlpool is good also. But remember these systems are being made for and sold primarily to startup brewpubs with limited space and resources, breweries that are generally not doing multiple brews in a day. It is disappointing to see equipment being sold with what I consider to be basic design flaws.


    They should have been designed with a better mixing arrangement so that the not inexpensive steam jacket would actually be functional and useful. It is a good thing that they do work okay for single temperature infusion mashes.
    Yes, our system has knives and rakes, no real mixing going on. Seems like mashing thin or just doing single infusion is the answer unless I can get a better mixing system installed. Thanks for the help guys

  8. #8
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    Oct 2018
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    Lenexa, KS, USA
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    Mash Temp Variation

    After we found huge temp variations, I started to use the vorlauf (as suggested above) but found the mash plates were getting blinded, adding to our troubles? So we’ve stopped that & indeed stopped using the bottom heat jacket & now just mash wet, turn the rakes fast when heating the sides & sometimes moving the plough down into the mash to help mixing. Hope it helps.
    Cheers
    Mike


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  9. #9
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    Nov 2013
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    Antigua, Guatemala
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    Preheat MLT

    Couple of quick points - I use a combination of my steam jackets and CIP balls from HLT to THOUROUGHLY preheat my mash tun before mashing in. The jackets are on for only 1-2 minutes and I run about 50-75L of 180deg F water through the CIP to cover the entire false bottom and wait about 15 minutes for steam generated to heat all parts of the rakes and false bottom etc, drain water, then mash in with single infusion strike temp water (158-168F depending on style) while running rakes fairly quickly with plough half way down. The very thorough preheat seems to be the key for me, and don't try to use the steam jackets for anything else, they're useless on these systems IMO.

  10. #10
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    Oct 2018
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    Lenexa, KS, USA
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    As long as it’s a wet enough mash & the rakes are moving fast enough, ours does just about work in achieving temp steps.
    It’s a PITA & in my view not at all the right tool for the job, but it does work.


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  11. #11
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    Quote Originally Posted by mic_mac View Post
    I started to use the vorlauf (as suggested above) but found the mash plates were getting blinded, adding to our troubles?
    If you weren't monitoring the head drop across your mash bed while you were pumping, its quite possible that you were pumping at too high a rate. In general, you don't want to impress a head drop of more than about the depth of your mash bed. With a pump, its easily possible to impress much more than than. By the way, that is the reason that old lauter tuns have gooseneck outlet taps...to limit the head drop that they impress.
    WaterEng
    Engineering Consultant

  12. #12
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    Oct 2018
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    Lenexa, KS, USA
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    The plant has a separate wort grant to limit the pressure, but IME too much mixing &/or too long vorlaufing can cause stuck or slow wort run-off.


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  13. #13
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    Oct 2018
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    Portland, Oregon USA
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    Quote Originally Posted by ASB Anthony View Post
    Hi all, I'm new to the forum as I am new to professional brewing. Quick question. I'm trying to hit certain temps in our steam jacket MLT and my handheld thermometer is ready radically different temperatures throughout the grain bed. If I'm trying it hit 152, I can be up to 170 near the sidewall, 115 near the center on the bottom of the bed, and anywhere in between throughout the bed. Running our mixer like crazy to try to even out the bed temperature and no matter what I seem to have major temperature differences throughout the bed. Is this normal? Any tips or ideas on how to fix this?

    Curious as what size of Mash Tun this is and how many zones for steam?

    Cheers,
    Mike Paladino
    Brewery Design Consultant
    Stout Tanks and Kettles, LLC
    “The Small Brewery Experts”
    16300 SW 72nd Ave
    Portland, OR 97224
    Office: (503) 372-9580
    Direct: (503) 766-3206


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  14. #14
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    Oct 2018
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    Lenexa, KS, USA
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    Mash Temp Variation

    I can’t speak for Anthony but the plant I’ve been talking about is 10bbl, with 2 steam jackets - bottom & side...though for stated reasons, I’ve recently been only using the side jacket.


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  15. #15
    Join Date
    Dec 2018
    Location
    Chicago, IL
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    Same as above. 10bbl, side and bottom jackets

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