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Thread: LAGER Brewers- help with temperature targeting

  1. #1
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    LAGER Brewers- help with temperature targeting

    so we have some 4 and 5 bbl fermenters. dual zones, but thermowells only have them at the top of the cone just below where it meets the body. the temp differential between what we get out of the sample valve and what the controller shows is about 5.6F on the 4bbls with both zones cooling during first week of fermentation.

    upon discussions here we were advised to stop using the cone and just cool with the upper jacket. so we tried it in our 5bbl with no cone cooling and the differential there was actually worse, +/- 9.6 to 12.1, averaging 10.5F. now i assume the sample port will always be a few degrees higher since it sits in a hole in the jacket, but an average differential of 10.5F seems like alot.

    at first glance it appears that using only the jacket zone and not the cone made the problem worse. so maybe thats not a great idea. easily fixable. but i cant add thermowells at the top to monitor the beer up there. im stuck with one thermowell.

    so i either target my temps for the cone as we've been doing up to now, or i switch gears and try and target the temps at the top of the beer.

    for instance, if my numbers in the 4bbl vessels say there's a 5.6 degree differential, maybe i lower my target(cone) temp by only 2-3 degrees from where i'd really want it. (some of the difference being attributable to the sample port location outside the jacket)

    if the 5bbl stays at a 10 degree differential, then maybe i undershoot my target temp by more like 5-6-7 degrees to keep the beer on top from getting too hot.

    anybody who regularly deals with lagers want to chime in here with an opinion-? (remembering that i only have a cone thermowell, and two jackets) i feel like the bulk of the beer is in the top jacket and should get the temp targeting, but lager yeast does seem to floc early and settle down low. which makes me a bit worried to ignore it, and cooling it too far could stall things.

  2. #2
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    Are your temperature probes calibrated? Lager or Ale brewing, it should make no difference on how the tank cools. Lower ABV beers will be more likely to freeze up on the side walls if your glycol temps are too low. First things first, calibrate your tank probes to an alcohol or mercury in glass thermometer, then take your temps. You also have to run a considerable amount of beer through the sample ports to actually cool them down, if your ports are in the middle of a jacket, the jackets are helping with this. So with the bottom jacket off, I bet the ports are warmer than with it on.

  3. #3
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    the glass/mercury thermometer was broken when i was there last. for now, the probes are calibrated based off the same digital thermopen that is measuring the samples- so while the exact temp may be off, the differential still exists.

    i've instructed the assistant to do big pulls off the sample valves to try and mitigate the issue with jacketing, but when i'm not there who knows what he actually does when he records measurements. but now that you mention it, i think the sample valve is down towards the bottom 1/3 of the main jacket. makes sense that it'd be warmer than usual with the cone turned off. i can have him turn on the cone and see if that narrows the differential down just to confirm it.

    if i had a thermowell in the top half i could compare those temps to the final fusel/ester profile and decide what changes to make. but with only a bottom temp reading, i'm in the dark about the actual temp up top. and my assumption is that since most of the beer is in the top of the tank, that's where most of the fermentation is taking place, and therefore thats where i should be most concerned about the temps.

    so other than popping the top and dropping a probe down into my beer, what other way do i have to get an accurate idea of what the temperature is in the top half of my tank? i cant really think of anything else...

  4. #4
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    During active fermentation, a cylindroconical tank has a pretty good convection, the temperature should be pretty consistent.

    Don't know what it says about your assistant brewer, but if you can't trust him to do things right when you're not there, I would find another assistant.

    As far as calibration goes, when was the last time you calibrated the probes with the thermapen? They can both drift away from each other over time. Another thing to look at is make sure you have some sort of thermal paste in the thermowell with your probe, if not you will get inaccurate readings. I brew lagers year round, never had any issues here with the yeast dropping early. Ferment is around 55, warm to 60ish for a D rest, then crash. We only see a temperature drift of 2F or so out of the sample port, but we have to pull a pretty big sample and it warms up quickly. I would suggest that you calibrate your temp probes every 6 months, or more if they are problematic, then rely on that temperature to be your guide. Make adjustments up or down on your ester profile on that number. Measuring beer out of the tank is never going to line up perfectly with what the probe in the tank says. We also brew larger, 20bbl batches, so this may also be an issue directly related to your tank sizes.

  5. #5
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    The issue is in fact tank design. 20bbl should have at least 3 if not 4 jackets, and i assume a thermowell at cone and one in the main cylinder. My issue is i only "know"the temp in the cone. which begs the question- what about the top?

    As these brews are happening in baja im trying to get this sorted asap. Tossing a batch sucks, but doing it after a 1000 mile round trip drive is worse. Trial and error is getting painful. As for the quality of help- Finding someone with even homebrewing skill was a challenge. Pro experience doesn't exist yet down there. Which iswhy im hoping for a bit of insight to our particular situation to speed the process along.



    Probes checked vs pen within past month. Thermo paste in thermowells. And equipment changes arent on the table for now.

    so how about a hypothetical- if you were stranded on a desert isle and only had one temp probe/rtd/etc to run your glycol- would you put it in the cone or up in the main cylinder body?

  6. #6
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    I have never seen a 20bbl FV with more than two jackets.

    As mentioned cylindroconicals have good convection by design. Unless you have actually had a bad batch, I think you are probably worrying yourself over nothing.

  7. #7
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    The question is simple- desert isle....cone or body?

    Not sure what part of "1000 mile round trip" "mexico" and "tossing a batch" makes you think this is some philosophical debate. Im looking for help to try and sort our issues, "dont sweat it" doesnt cut it.

    Thanks in advance to any constructive advice.

  8. #8
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    I have seen probes in various places on the tank, usually in the cone just above the lower jacket, but also in the body of the tank between the upper and lower jackets. I have never noticed a difference between the two in terms of the progress of the beer or it's quality. That includes scaling 2bbl batches up to 30bbl where the probes were in different places on the tank. Desert isle answer; it doesn't really matter in the end.


    You stated that the issue was tank design and that a 20bbl tank should have 3-4 jackets, I replied that I have never seen one that had more than 2, and that as was mentioned before cylindroconicals have good convection by design. I asked if you actually had a batch you have had to dump, you didn't answer. I was not trying to have a philosophical debate, I was giving you a simple answer. I have been doing this for a long time, nearly 30 years, and from what I saw you seemed to be over thinking the situation and borrowing trouble. Now, if you HAD already dumped a batch because it was bad, then there would be need to look into what caused the problem.

    The people answering here are legitimately trying to help and want you to succeed. We have all had trouble at one time or another, we get it, there is no need to get defensive.

  9. #9
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    Few points- we had a few 20bbls tanks with 3 jackets, they exist. The very post that you replied to states that we tossed batches, after 1000 mile trip to baja. And you didnt answer my question, cone or body, you dismissed it with a "dont sweat it" reply. So yeah, i got pissy. Seems like an offhand, not paying attention, non-helpful jackass reply.

    Now when you come back with a reasoned and fleshed-out/explained answer like the one directly above i can appreciate that, even if i still dont agree with your answer.

    If you are in AL, imagine driving 1000 miles round trip to brew somewhere past the border at brownesville or laredo. And thats in addition to your normal 9-5 routine. Takes you away from home and family. Gas. Time and effort. Missing weekends with your 1 yr old because you gotta fill those tanks. Hopefully that explains why a "dont sweat it" reply is borderline offensive.

    I appreciate your second post. So maybe you humor me here for a moment- you have a fermenter with a cone thermowell and a main body thermowell, but you only have one temp probe. Where do you put it?

  10. #10
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    Having dealt with both cone and body thermal wells I have seen no difference between the two, so from my experience it doesn't make a difference and neither is clearly superior. If I had to make a choice it would be on the cone for no other reason than it would allow for a situation in which the temp were being measured at a lower point in the tank. This could be an issue if you are using your Unis as actual Unitanks (fermenting in and packaging from) or using a cylindroconical as a brite tank and packaging from it in increments. In these cases you could measure the temp at a lower volume.

    Regarding the 1000 miles and dumping beer, you didn't specifically say you DID dump it. The comment "Tossing a batch sucks, but doing it after a 1000 mile round trip drive is worse." can be read as a hypothetical, something to be avoided, not necessarily something that had happened and I was trying to get clarification on that.

    What did you detect wrong with the beer that caused you to dump it? What yeast are you using? Are you confident in your assistant's sanitary procedures? What is your SOP for fermentation progress? (times, temps, etc)

  11. #11
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    You might find this interesting. The paper's objective is not the same as what you're talking about, but there are some interesting measurements on the temperatures within the CCV that might answer your question:

    http://onlinelibrary.wiley.com/doi/1....tb00596.x/pdf

    A couple points I thought were interesting:

    1. Temperatures vary significantly within the CCV (~8-10F). This should be obvious, because you're cooling only at the side wall. Temperature differences cause convection, which is critical to keeping the beer mixed and as isothermal as possible.

    2. You can see from the thermal images that there is significant temperature variation as you go in to the center (e.g. a longer probe at the same height will read a higher temperature). So it's not just about what height you measure at, but how long the thermowell is.

    3. There is a separate convection occurring in the bottom zone of the cone that interacts with the one coming down the side walls. The two currents interact at the interface between them. This is caused by the density inversion of water; at 4 degrees C (~39F), water is at it's maximum density. Above 4C, the cylinder cooling jacket chills the water, which moves down the side wall. When the water in the cone is cooled below 4C, it's density decreases, causing it to RISE along the cone sidewall, not fall. It meets the warmer water coming down the cylinder side, and both flows divert to the center of the vessel. The cone is cooled more, I suppose, because of the greater cooled surface to volume ratio.

    My conclusion:

    A. The warmest area of the fermenter is in the upper part of the CCV, but it's not uniformly warm. If you're mostly concerned with keeping the maximum temperature low, I'd put the probe higher up. If you're worried that the conical section is getting too cold under this situation, then I'd turn off the cone jacket (or throttle it).

    B. You can't ever get the top and bottom to read the same without mechanical mixing. If they were the same, there would be no convection, and no mixing. A very large CCV might need mixers. At least, in the wine industry they use them...I've fixed a bunch of them in my life. I haven't worked at any breweries with fermenters anywhere near that big. But it doesn't matter in your case. No matter where you put the probe, the tank performs the same way. If you've lost beer due to high temps in the upper part of the vessel, then control for a lower temperature, even if it's below optimal--you have to have faith there is beer you're not directly measuring that is warmer than your temperature gauge says.

    Finally, that paper lists a few good resources:

    1. Kunze, W., Fermentation and maturation in cylindroconical tanks. In: Technology Brewing And Malting, International Edition, VLB: Berlin, 1999, pp. 366–394.
    2. Gross, P., Programme for dimensioning the cooling areas at cylindro-conical tanks. Brauwelt Internat., 1998, 16, 152–155.
    3. Ishiguro T., Mizutani S. and Kuwahara K., Numerical analysis of cooling mechanisms in cylindroconical lager tanks. Tech. Q. Master Brew. Assoc. Am., 1997, 34, 164–170.
    4. Andrews, J.M.H., Temperature profiles in dual purpose tanks. Ferment, 1997, 10(5), 309–316.
    5. Takamoto, Y., Saito, Y., Kawanishi, K., Axisymmetry-breaking in a transient cool-down process of water in a vertical cylinder through maximum-density temperature. J. Phys. Soc. Jpn., 2002, 71(10), 2439–2444.

    Regards,
    Mike Sharp

  12. #12
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    wow. thanks mike. thats a ton of info. hopefully it might give some insight into smaller tanks, i know alot of the research papers address larger production sizes. lots of reading to do.

    i checked this weekend, and all probes/thermometers/etc were within 1F of each other, based on glass mercury thermometer. thermowells reach about 8" into tank, about same as any other tank i've seen. one thing to note- the glycol trunk line is made from 1.5" pvc, which seems large given we've only got 5 tanks on it, at 4 and 5 bbl capacities. possible the pressure isnt high enough to get good flow on the upper jackets? gauge typically shows about 10psi.

    mr guitar- you are correct. although intimating strongly that was going on, technically i did not say we dumped a batch. bygones? i do appreciate the advice. as to your questions-

    the tossed batches were dumped for various reasons. unstable baja power supply was causing our temp controllers to reset themselves to the factory default of 68F. (took a while to figure that one out) three batches tossed. wired a small battery backup power supply in circuit to controllers. our glycol unit shut down once. two batches. unit repaired.

    most recent batch was tossed after a pvc shutoff valve cracked and leaked glycol all over the place. beer was up to 78F by the day after pitching. another 12 hours before things were fixed and brought back down to temp. oddly i didnt get any fusels or esters. some folks detected a slight fruitiness, possibly esters, but i think more likely the hop interplay. the most prominent note to me was a cross between a wet paper/soapy flavor upfront to middle, and then finish with nice citrusy hops. dead yeast i assume.

    we cant use my favored lager yeast as the guys down there are very much in the homebrewer-to-probrewer transition phase. lots of teaching to do, i dont trust them yet to keep a culture going in good health. so i settled on a dry yeast that i could live with, saflager 189. it likes a bit warmer temps than most other lager yeasts, low esters/sulfer, pretty clean and neutral. i've been playing around at home with it to try and familiarize myself with it, but still in the getting acquainted phase. in general, with lagers i like to start at the cool end of the temp range, then at around roughly 50% attenuation start letting it rise to d rest temps and hang there for a while. dry hop for a week or so. crash. etc.

    going to keep using fresh dry yeast for each brew to try and minimize our variables until we get our temp issues sorted. but i would like to institute a schedule for yeast dumping/collecting into the routine so they get used to it. any advice there?

  13. #13
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    Quote Originally Posted by U.K. Brewsmith View Post
    I'd stick it in your ass, mate.
    huh. is that something to do with the metric system?


    you foreigners are weird.

  14. #14
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    We're good, no worries.

    Ok, so the dumped batches were the result of equipment failures/glitches. As a big a pain in the ass as that was, this is actually good news since these are easily addressed issues. Tank configuration regarding glycol and temp probes sounds good.

    I have never used Saflager 189, but have used their S-23 and W34/70 (as well as a number of their ale yeasts) to great success, and actually prefer using them to liquid cultures for various reasons (cost, ease of storage, etc.). W34/70 is the classic Weihenstphaner lager yeast and makes a great beer. I start it at 58 and ramp down to 50-55, depending on the beer, once it kicks off. Ferment out, ramp down to 40 to lager, do forced VDK, then crash. Average strength lager brew to glass in 4 weeks.

    The need for diacetyl rest is questionable. I have not had an issue with any of the lager strains I have used, nor have the majority of my colleagues over the years. Caveat here, as I said I have never used 189. Do you trust your guys to do a forced VDK test? We do them just for piece of mind, but I have never had a lager positive for VDK in nearly 30 years.

    As to yeast harvesting, the method might depend on your situation. Corny kegs are good, provided you trust that the staff disassembles and properly cleans/sanitizes the parts in between uses. A simple manifold of corny keg fittings, tubes, and TC fittings is easy to put together. Harvest the fresh yeast into the sanitized corny keg, make sure it's pressurized, pop it in the cooler. When you are ready to pitch, push it out of the corny into the wort... either directly into the tank or in line as wort flows in. Different yeasts strains are good for different numbers of generations depending on strain, handling, length of storage, etc., but a good rule of thumb to start is 4-5 generations and adjust as fits your situation and results.

  15. #15
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    What is the diameter of your tank? 8" seems pretty far for a 4 or 5 bbl tank. 8" would be good for a 10bbl tank, possibly a 20 bbl, the probe should only reach in 1/3 the radius of the tank to be in the best zone for measurement. If you have a 3' diameter tank, 8" puts you at roughly 50% the radius in, which is a bit close to the center of the tank, which is also the warmest part.

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