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Condensation dripping from chaff collector... is this a problem?

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  • Condensation dripping from chaff collector... is this a problem?

    Hi there,

    This question is for those of you with commercial drum roasting experience. I have noticed that when its raining or excessively humid outside (60%+) that nasty looking brown water drips from my chaff collector. This only occurs during the drying phase of the roast (from drop to approx 160 degrees C) and that when the air damper is more fully opened the dripping ceases. The source of the moisture is not in question... it is obviously coming from the beans. My question is... will this moisture end up messing up my roaster? Will it rust out the cyclone or possibly even cause long term problems for the roaster as a whole? Is there anything I could do to attenuate or even eliminate the problem or am I simply worrying over nothing?

    FYI... the machine in question is a 1.2kg/batch stainless steel drum roaster 2 x 1500W electric heating elements. The chaff collecting cyclone appears to be made from regular old steel.

    All feedback appreciated.

  • #2
    Re: Condensation dripping from chaff collector... is this a problem?

    Is there that much moisture in the coffee?

    Ive never had this experience, my chaffs over a period of 26 years roasting have always been "bone" dry.

    But I have never used the kind of roaster you are using.....have you asked the advice of the supplier/ manufacturer of your machine? Also of course, im not on the coast with high humidity.

    Be aware that despite the kind of airflows you get in a coffee roaster a certain amount of chaff sticks and lines the piping between the drum and the cyclone & over time it solidifies into a crust and can eventually catch fire, but in my experience that is over a great deal of time and many kilos roasted. Occasionally open up the piping and take look.

    I imagine your cyclone would eventually rust out but how long is a piece of string....it could be tens of years, and if you clean the chaff at the end of every day of roasting you will keep an eye on its condition, and wont leave moist chaff sitting in there "indefinitely".

    Also have you tried roasting with flue butterfly valve (or whatever your machine uses) in such a position as this does ont happen. Does it rsult in too quick a ramp up, is the resulting roast time too quick, and is the cupping quality of the coffee affected and if so, is it a bad thing????? Try different ways, always log results, see what happens.

    Dont need answers to these questions, just annunciating some thoughts out loud to help you get your own thoughts around this.

    Rgdz.
    Attilio
    very first CS site sponsor

    Comment


    • #3
      Re: Condensation dripping from chaff collector... is this a problem?

      The only time I have ever experienced such an issue as you describe was when I first received my roaster and the beans that I bought to season the drum (Cheap and nasty) were a little too cheap and nasty and must have gotten wet at some point. 

      I did 2 roasts with those beans, threw them in the bin and have never had that problem again. 

      I am not saying you have crap beans, they may have been exposed to moisture at some point though? 

      That is the only experience that I have had with the dampness you describe.

      Attilio is correct as usual and I clean out the pipe work between my cyclone and my roaster after every 5 or 6 roasts.

      More often than is probably needed but the build up does clog up the pipe work over time and you should check it as the moisture will make it worse.

      I get some rain water in the bottom of my cyclone after heavy rain due to the open top design of the flue but I wipe the bottom out with a rag and the heat from roasting soon dries it up. I have not noticed any rusting of the inside of the cyclone though.

      Comment


      • #4
        Re: Condensation dripping from chaff collector... is this a problem?

        What Ive noticed on 3 different brands of commercial drum roasters (US, Turkey and German) is only initial moisture when heating the equipment up at the start of any roasting - in the first 5-10 mins - usually more apparent the colder the environment temp.

        After these few "drops" or "beads" of moisture (call it condensation), in the roaster (typically around the sight glass and dump chute) it evaporates in 5-10 mins once the cyclone and all flue equipment is warm to hot.

        Have never experienced moisture in or around the roaster or flu once roasting has started. Even the "baked on" chaff in the linings of the cyclone and flu seem to absorb any initial condensation and then dry out very quickly.

        If you have adequate heat at the drop point (start) and you are reaching turning point within 2:30 to 3:00 mins on full charge (or earlier on partial batch sizes), then its hard for me personally to imagine that beans inside the roasting drum would create visible moisture unless there was a specific issue with insufficient thermal energy (heat) or airflow within the roaster, cyclone or flue - there may be something wrong with the design or installation of the cyclone/flu combination.

        Normally, the flow of hot dry air would have been more than sufficient to carry any excess moisture from beans at a rate faster then the beans can "throw off the moisture".

        As you have electric heat sources, the heat is substantially "drier" than gas fired drum roasters which only adds to the puzzle.

        Yes, your cyclone will rust and depending on the grade of steel and finish, may experience visible corrosion inside 12 months as the process of wet/dry is accelerated with the more extreme impacts applied with roasting.

        Bruce, as you indicated when you open the air damper the problem is less obvious, I think this is the clue to your issue - airflow and allowing this to escape freely (and as quickly as possible).

        Comment


        • #5
          Re: Condensation dripping from chaff collector... is this a problem?

          The roaster manufacturers roasting guidelines advise keeping the air damper completely closed during the drying out phase until the beans yellow and only then opening it half way. I have always wondered about this as it does not allow the moisture from the drying process anywhere to go. The excess vapour/condensation issue only occurs on cool days with high humidity and lower dew points and on such days I have been "cheating" a bit by opening the air damper up a wee bit... say 5-10% open. This helps a bit but, as Attilio pointed up, opening the damper further would probably result in temps ramping up too quickly and changing my profiles considerably. Maybe I should play with the air flow a bit more and see if I can eliminate the vapour while still extending the ramp up as much as possible.

          If things go badly with my current chaff collector, any advice on where I can find someone to help me build a replacement? I have a few mods in mind.

          Thanks for the input guys.

          Cheers,

          Bruce

          Comment


          • #6
            Re: Condensation dripping from chaff collector... is this a problem?

            Sounds to me that the manufacturer is in the roaster building business, not the roasting business.

            The same happens with some espresso machines as well and I keep in mind that they just build and sell them but may not actually be that into coffee.

            Id be ignoring their suggestion and trying some other strategies. In general, there not a lot going for coffee soup and clothes dont dry when its humid...

            Comment


            • #7
              Re: Condensation dripping from chaff collector... is this a problem?

              Bruce,

              My personal opinion - Im not a fan (at all) of closed damper roasting. Some of the US roasters suggest a similar style of roasting to this method, or at least using it to constrict airflow at certain points during the roast cycle.

              Having performed countless cup tests of closed and different amounts of open dampers (primarily in early stages of roast), I can say that closing dampers created taints in the cup - again, this is only a personal conclusion.

              Airflow is very important at all stages of roasting - even the drying phase.

              It could be useful to look at heat variables to control your roast, although electric sources do have considerable lag.

              Suggest performing controlled cup tests.

              Comment


              • #8
                Re: Condensation dripping from chaff collector... is this a problem?

                Originally posted by 232B2A2F222C2F202A273A4E0 link=1301064815/6#6 date=1301130208
                Suggest performing controlled cup tests
                Will do

                Thanks again

                Comment


                • #9
                  Re: Condensation dripping from chaff collector... is this a problem?

                  Originally posted by 083730372A3F2D2D3B5E0 link=1301064815/4#4 date=1301121514
                  The roaster manufacturers roasting guidelines advise keeping the air damper completely closed during the drying out phase until the beans yellow and only then opening it half way.......
                  If things go badly with my current chaff collector, any advice on where I can find someone to help me build a replacement? I have a few mods in mind.

                  Thanks for the input guys.
                  I too disagree and repeat, run some tests and cup your results.

                  Find anyone in the sheet metal industry and they will be able to build you a cyclone esp if they tend to work with heating / cooling / ducting system vendors and installers.

                  Rgds,
                  A.

                  Comment


                  • #10
                    Re: Condensation dripping from chaff collector... is this a problem?

                    Originally posted by 1B2F382E35021E323B3B38385D0 link=1301064815/8#8 date=1301131902
                    Find anyone in the sheet metal industry and they will be able to build you a cyclone esp if they tend to work with heating / cooling / ducting system vendors and installers
                    Cheers

                    Comment


                    • #11
                      Re: Condensation dripping from chaff collector... is this a problem?

                      Bruce, think nothing of it!

                      Barrel, arhhhh shucks mate,.......very much appreciate the kind thought!

                      Regardz,
                      Attilio

                      Comment

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