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Thread: Slow Runoff Issues

  1. #1
    Join Date
    May 2018
    Location
    Charlotte, NC, USA
    Posts
    2

    Slow Runoff Issues

    Hey folks,

    We’re a new brewery here in Charlotte, NC and have been open for about 2 months now. We’re brewing on a 10bbl two-vessel system from ABE and are happy with everything for the most part. However, we’ve been having some occasional issues with runoff and I was hoping to get some perspective/advice on what we may be doing wrong.

    Basically, we conduct our mash as normal and then vorlauf through our wort grant before running into the kettle through the same grant. We always do our best to start the runoff for the vorlauf into the grant slowly so as to not pull on the bed too hard at first and will then speed it up a little once we have a good flow. Vorlauf normally goes perfectly fine with no real issues but has been taking approximately 25-35 minutes to achieve clear enough wort without grain pieces still in solution. This seems like it could be a possible cause…

    Once runoff to the kettle starts is often where the issue begins. It’s interesting because we usually slow the wort pump down to a lower speed than what we’re using to vorlauf but the wort level in the grant will gradually drop to the point that we’re getting a trickle into the kettle because the wort feeding into the grant isn’t flowing as fast as the wort into the kettle. We haven’t fully stuck a mash yet (knock on wood) but we basically have to stop the pump, close the kettle-in valve and then let the grant slowly fill back up before starting the pump and opening the kettle-in valve again. The other day we literally had to do this for the entire amount of wort in the MT which, at roughly 15 gallons in the grant at a time, extended the brew day considerably.

    We use rice hulls for brews with any significant portion of wheat, oats, spelt, rye, etc. but for all barley brews we normally don’t. We checked the crush out of the mill and auger with a rotap and we are on the course side, so logic tells us the grain crush shouldn’t be the issue either. We have used some rice hulls in all barley brews and haven’t had this issue, and we’re sort of okay with just adding rice hulls to every mash as they aren’t too expensive. However, we don’t feel like we shouldn’t have to do that.

    We also don’t normally do a mashout rest in the MT as the steam jackets are hard to control, so we turn the jackets in the BK on once we reach a certain level and let that temp rise halt enzymatic activity. We know that heating the wort in the MT thins it out some but again, this just isn’t an easy thing to accomplish without potentially overheating the entire mash.

    We’ve pulled the plates out in the MT to inspect the plumbing and underlet ring and have no clogs there. We’ve tried eliminating the potential causes but are not having much success.

    Sorry for the lengthy post but I’m just looking for anything we might be missing or should be doing differently. The beers have been turning out well, which is the most important thing but we sure would like to avoid adding a couple hours to our brew days if we don’t have to…

    Any help is welcome and appreciated! Cheers!

    Ben Dolphens
    Divine Barrel Brewing
    ben@divinebarrel.com

  2. #2
    Join Date
    Dec 2013
    Location
    Danielson CT
    Posts
    101
    What is the shape of your MT? If it's taller and thinner you'll likely need rice hulls no matter what

  3. #3
    Join Date
    Oct 2002
    Location
    Chesterfield, UK
    Posts
    1,800
    I would try two things. Firstly, don't bother vorlaufing for so long and so fast. I know lots of people will disagree and say you should have completely clear wort before running into the kettle, but trying to get them so bright can leasd to exactly the sort of problems you are having. In running large mash tuns and lauter tuns, the vorlauf is normally not more than about five minutes, and the volume transferred is sufficient to take the weak worts from under the plates to the top of the mash. Any mover volume is wasting time when it comes to large operations, and like it or not, they produce good quality beer - never mind that it might not taste like your favorite beers. The flow rate for vorlauf shouldn't be any more than first wort runoff flow rate - you are currently trying to filter comparatively viscous wort at such a high flow rate you are pulling the grain bed down, and almost certainly pulling so much fine material through you have to recirc for the time you do simply to clear it, but at the same time compacting the bed dramatically.

    In summary - slow you vorlauf flow rate down drastically, to no more, or only VERY slightly more than your first worts run to kettle. Only vorlauf enough to transfer slightly more volume than the volume under your plates. Take your time about the first worts flow rate to kettle and only start to ramp up flow rate as your sparge progresses - you can even run at completely constant flow rate - no problems, possibly better. And don't worry too much about a few bits of grain going through (I know plenty will try to shoot me down for that).

    If that fails, to work completely, then coarsen your grind a bit. I have worked with five foot deep mash beds, without rice hulls, so if you have decent malt, rice hulls shouldn't be necessary.

    If you are beating your mash up with mixers - don't - they aren't necessary in a mash tun. A mash mixing vessel supplying a lauter tun or mash filter - yes, but not an isothermal mash in a lauter tun.
    dick

  4. #4
    Join Date
    Feb 2016
    Location
    San Francisco, CA
    Posts
    88
    I work on a system not unlike yours, 8 barrels, gravity from MLT to grant, then pump to recirc or kettle. We basically do what dick murton suggests, with good results. We run into the grant slowly during vorlauf (no faster than when sending it to the kettle, anyway), and we finish vorlauf and start sending the wort to the kettle after ten minutes, rain or shine.

    We do still have grain particles floating around in the grant at this point, but there are very few still being pulled in from the mash when we end the vorlauf. That one grant of slightly grain-particled wort isn't something we worry about, anyway – you know from hard experience what a small fraction of a full batch one grant's worth of wort is!

    To give you some idea of the rates we're talking about, our runoff reliably finishes in under two hours, though not by much – we haven't measured, but a little back-of-the-napkin math tells me we're not running more than 2.5 gallons/minute into the grant. We go even slower than this during vorlauf (very manual system, lots of twiddling butterfly valves to keep everything balanced).

    Been here four months or so, haven't seen a rice hull or a stuck sparge. Don't know how much mash tun geometry plays into it, ours is a little more than half as tall as it is wide.

  5. #5
    Join Date
    Oct 2012
    Location
    Midland, Texas
    Posts
    57
    Question I have is how to fix 'stuck' when this occurs. I stuck a mash last night and there was nothing we could do. Granted, this was to be our first brew on our system as our finalized permits were received on monday and we were legal. Instead, we ended up with wasted malt because the run off rate was terribly slow.

  6. #6
    Join Date
    Jun 2003
    Location
    Anchorage, AK
    Posts
    117
    To hopefully add to Dick and feinbera's posts.

    We run a 15 bbl. mid 90's Specific Mechanical system with surprisingly few miles on it; unheated mash tun/grant/kettle, single step infusion with North American malts. We run it as Dick suggests (from years of reading his informative posts). We vorlauf for 20 mins (~5 min longer than Dick would suggest, but based on sedimentation trials.) We vorlauf and run off at the same rate, ~4.6 gpm. Run off takes a shade less than two hours and yields 17.33 bbl at kettle full. We installed a short standpipe in MT to cut down on solid carryover...our screens are probably a little old and droopy.

    To Ben's original post I bet slowing down a bit will help your situation. I shoot for a ~2 hr run, off setting kettle fill targets and checking them every 15 mins.
    Clarke Pelz
    Cynosure Brewing

  7. #7
    Join Date
    Oct 2002
    Location
    Chesterfield, UK
    Posts
    1,800
    Quote Originally Posted by Mad Scientist View Post
    Question I have is how to fix 'stuck' when this occurs. I stuck a mash last night and there was nothing we could do. Granted, this was to be our first brew on our system as our finalized permits were received on monday and we were legal. Instead, we ended up with wasted malt because the run off rate was terribly slow.
    The traditional answer is to underlet it with sparge water, let it stand for a few minutes to settle a little, vorlauf slowly just long enough to transfer the underlet water back on top and then restart runoff. A small mash tun you could gently, and I mean gently agitate a little at the bottom once you have underlet - the intention being to break up any dough layer created by the fines, let it settle, and recirculate etc etc. Perhaps I have been lucky, but I have never had to underlet, let alone agitate a mash tun at all (lauter tuns with rakes - yes) so I am passing on what I have been told works!!
    dick

  8. #8
    Join Date
    May 2018
    Location
    Charlotte, NC, USA
    Posts
    2
    Thanks for the responses!

    One of the issues with our system during the vorlauf is that if the wort pump isn't running fast enough we sometimes don't get flow back up through the vorlauf arm...which doesn't seem right. I try to run it as slow as I can to get good flow back on top of the bed. We don't have a flow meter on the inlet or outlet valves to and from the grant, so I don't know what that flow rate is. If anyone has a calculation for this I'd love to see it! We will try decreasing our vorlauf times some to see if that will help. I'm not worried about a few bits of grain getting into the kettle. It's impossible to completely prevent this anyway, I'm just trying to limit it as much as I can.

    Our flow rate into the kettle at the start is usually around 10gpm but as the grant level drops it slows down. I prefer to run off at a slower rate anyway, so we will definitely work on slowing this down and holding it around 4-5 gum going into the BK. We've been running off our 10bbl batches at around 45 minutes to an hour, so I'll slow that down some to closer to an hour and a half or more.

    Again, it's' not an every single brew kind of situation but I'd like to reliably count on this not happening. I know stuff happens from time to time and that's understood but one less thing to worry about is always nice.

    Again, thanks to everyone for the advice! Cheers!

    Ben

  9. #9
    Join Date
    Jun 2011
    Location
    Richmond, VA.
    Posts
    431
    By any chance does the system have rakes to cut and lift the bed and are you running it as slow as possible then you are running off?

  10. #10
    Join Date
    Oct 2012
    Location
    Midland, Texas
    Posts
    57
    Quote Originally Posted by dick murton View Post
    The traditional answer is to underlet it with sparge water, let it stand for a few minutes to settle a little, vorlauf slowly just long enough to transfer the underlet water back on top and then restart runoff. A small mash tun you could gently, and I mean gently agitate a little at the bottom once you have underlet - the intention being to break up any dough layer created by the fines, let it settle, and recirculate etc etc. Perhaps I have been lucky, but I have never had to underlet, let alone agitate a mash tun at all (lauter tuns with rakes - yes) so I am passing on what I have been told works!!
    Dick, I am not sure why I did not think of that. Thank you! Being as it may, my mash tun is 100 gallon so it is just a bit too tall to reach the false bottom with the paddle.

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