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Thread: Boil Kettle Design

  1. #1
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    Boil Kettle Design

    Having a new Boil Kettle made out of a spare tank we had laying around. The aim is a 7BBL kettle. It will be direct fire, using 2 225,000 BTU propane burners, similar to the HPMAX-2. It will have a 2" bottom drain that will be wrapped in ceramic insulation to prevent scorching. A side port with a racking arm to draw off wort, and a whirlpool return arm. It will have a manway access hatch on the top, which is not currently shown in the drawing.

    Doubts I have are if we should be using a enclosed firebox with those burners or is just heat shielding sufficient? And placement of the flue exhaust, should it be higher up, lower down? I plan to have a baffle plate placed in front of the flue exit to help retain the heat, but not really clear on what form/shape that should take either. Are those burners up to the job? or should I be looking to use a forced air burner? If so what size?

    Attached is the design we have come up with, any feedback or comments would be welcome. All measurements are in metric.

    Name:  BK Design.png
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    Last edited by Wayki; 09-28-2018 at 07:08 AM.

  2. #2
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    I would stay away from this kettle design. A direct-fire kettle should have a sloped bottom, not a dished. The drain ports should come out the side of the kettle and be insulated from the firebox. Having a center drain pipe as shown will be a nightmare for you. The wort trapped in the pipe will become scorched, leading to off-flavors and will ultimately bake sugars inside the pipe to the point where eventually the pipe will become clogged.

    An insulated firebox is necessary for safety, integrity of the stainless, and heating efficiency. Good luck with your search.

  3. #3
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    Quote Originally Posted by NHBrewer23 View Post
    The wort trapped in the pipe will become scorched, leading to off-flavors and will ultimately bake sugars inside the pipe to the point where eventually the pipe will become clogged. .
    Even if we insulate that pipe with Ceramic insulation? I understand the benifits of a slopped base, however the tank we are working with as a base has a dished bottom to start with. The intention is to use the side port with the rotating racking arm to draw off wort, and only use the bottom port for draining the kettle during cleaning.

  4. #4
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    While ago I was interested in building 10 bbl direct fired BK.. at the end financials allowed me to go with steam so I did not realized it but here are some observations I get:

    KETTLE BOTTOM: as said, cone bottom with central drainage pipe can be problem since wort will scorch. I would go with sloped bottom with drain port on lowest point and wort outlet port above it. Slope is 2-5%. You can easily weld hop dam on bottom to prevent hops clogging your HEX if you use BK for whirlpool.

    CLADDING, SIDEWALL: you really want double shield with good insulation and ceramic wool is your best bet due to temperature resistance. Insulation layer is ~3" thick with ~2" space between kettle and sidewall.

    KETTLE TOP, VENT STACK: cone top is good choice since it directs steam to center vent stack. To prevent condensation backing into the kettle you can build condensate drip ring on steam pipe.

    OTHER PORTS:
    - whirlpool inlet (if you don't have separate WP): on 1/3 height, pipe is tangential positioned at an angle of 15°.
    - temperature probe inlet
    - CIP port near the center of top cone
    - vent stack

    BURNER: I would go with forced air burner due to better efficiency. Depending on firebox and insulation somewhere around 300k btu may be ok.

    FIREBOX, FLUE: be sure to insulate firebox and build inspection gate for easily maintenance. Flue is build from galvanized pipes with 8" diameter with damper installed (this is most important part of system since it directly effects burner efficiency). Flue is positioned above burner, try to reduce number of elbows on chimney.


    This is the sketch I made at the time direct fired BK was in my sight, it may help:
    Name:  Direct fired BK.jpg
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  5. #5
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    Thanks, I appreciate the feedback and your design helps a lot.

    I know everyone is saying the centre drainage will cause problems. And I understand the why, however has any one successfully used a centre drainage on a direct fire kettle? I keep coming back to it as that's how our tank is setup.


    Sent from my moto g(6) plus using Tapatalk

  6. #6
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    You can wrap it with ceramic wool, and probably get another line of defense with baffle mounted to protect it from direct flame.
    Depending on style, scorching may not be huge issue since it will add caramel or burn flavor, which could go in line with some beers.

  7. #7
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    That's what I was thinking. Wrapping it in at least 3" of ceramic wool and also some kind of baffle to help.

    Sent from my moto g(6) plus using Tapatalk

  8. #8
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    I may be wrong but I believe stout uses a center drain like this on some of their kettles... my 3bbl kettle from sungood has it but mine is set up for electric heat so its not an issue but I believe they use the same kettles without the element ports for direct fire. I will be using the side port for draining anyhow myself and the center port for filling.
    Last edited by augiedoggy; 10-02-2018 at 05:15 AM.

  9. #9
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    Quote Originally Posted by dark_s View Post
    - whirlpool inlet (if you don't have separate WP): on 1/3 height, pipe is tangential positioned at an angle of 15°.
    Name:  Direct fired BK.jpg
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    Question on this one, the Whirpool inlet is positioned at anangle of 15 degrees? Is that an upward or downward inclination? or am I missunderstanding this?

  10. #10
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    WP inlet is 15° towards the side of kettle, on 1/3 of tank height.
    As far as I know, inlet should me horizontal (neither downward or upward).

  11. #11
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    Ok that makes sense. Gracias

    The tank went off to the welder's yesterday, I'll post something when it's done.

    Sent from my moto g(6) plus using Tapatalk

  12. #12
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    I would say that you should nix the rotating racking arm. Dangerous to be moving it when hot wort is involved, but the big reason is that any intrusion towards the center of the kettle will cause problems with whirlpooling. In a perfect world, the whirlpool kettle would have smooth walls all the way around, no temperature probes, ladders or other devices. Your best bet is to always keep the intrusions to a minimum.

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