At War with Chaff

[paulc]

This is the reason I joined this site but I expect to participate for a long future.

I'm at war with chaff. I can't evacuate it from the drum (IR-12) and I get a lot of it when I dump the roast. I have to wipe the lip and clean the cooling tray after each roast. I get chaff all over the place. This has been going on for several months now. I have to keep the air flow through the drum for nearly the entire roast. This, of course, blows my profile - roasting times are as much as 25 minutes. I do notice that I can evacuate more chaff when I remove the sampler but that increases the roasting time even more.

I know, this sounds like a cleaning problem. But I've been through the entire air flow system and cleaned it all down to bare metal. That, by the way, was no easy job. Lots of knuckle-busting and fingernails that will never come clean. Anyway, Jason at Diedrich seems to be stumped as well. So, I throw it out to all of you. Any thoughts? BTW, this might be a red herring but I sometimes find some chaff particles lying on the sidewalk on a calm day. (no oxidizer or afterburner)

 

[topher]

I had the same issue on a 5 kilo ambex. The exhaust needed a wee bit of help to leave the pipe due to the fact that the distance was to great to escape. I had to add a y pipe half way up my stack and put a fan on it to help push the air flow. Not sure if this makes sense...if it doesn't pm your number and I can try and explain it better....
Christopher

 

[paulc]

Thanks Topher. I did understand you - I may have seen one of your previous posts about it.

This issue has developed over time, which is why Jason and I think it's a cleaning issue. But I don't know what else to clean. From other posts I have learned that some roasters think that the older IR-12 doesn't have enough air movement power. A booster fan might help but the air just doesn't have that far to go - about 15 feet and straight up. And since the problem has developed over time, I'm still thinking it's a cleaning issue. Do you think the impeller or motor might be at issue? I can feel the air moving appropriately but maybe it's not enough.

 

[DirtyDave]

The air flow in many drum roasters is insufficient to evacuate chaff completely from the drum.
Topher's solution seems reasonable.
Too much air flow will reduce the efficiency of your roaster (extended roast times, etc).
So, if you sre going to utilize a booster fan, make sure it has speed control, so you can find that "sweet spot".
Good luck.

 

[DirtyDave]

I strongly suggest to use speed control rather than a damper, to avoid serious maintenance issues (constant cleaning!).

 

[paulc]

Ok, Dave. I'll keep your's and Topher's suggestion of a booster fan in mind as an alternative but I'm not yet convinced this is my problem since it has developed over the last few months. My roast times are already too long. I'll keep at it and if I find any solution, I'll post it.

Thank you, Gentlemen

 

[DirtyDave]

When you do regular maintenance to your roaster, do you thoroughly clean the ENTIRE path, from drum to outlet stack?
Including all interior air passages?
If you shortcut any step, you will experience a degradtion in roaster performance.

 

[paulc]

Yeah Dave, and I appreciate your asking. I also like the concept of a pathway. It's a good representation of where the air comes from and goes to. I did have a thought that not enough air movement was getting into the drum, thinking that the only way air gets in is between the ends of the drum and the roaster housing. I have since found that the air is preheated and enters the drum through passages in the hopper. You also may recall that I mentioned when I started this thread that the cleaning process was a knuckle buster. However, I'm still prepared to discover that I missed something. It really does seem like a cleaning problem.

In any case, I appreciate your questioning me on this. paul

 

[topher]

If you had an afterburner you really could tell if it was a cleaning issue...the temps would tell you right away. If is something that just started I would lean more towards cleaning. I adjust my damper on my roasters to control the heat. I am constantly cleaning and busting my knuckles...last place I worked we were kicking out 80,000+ lbs of coffee a month between a 60 kilo and a 120. We had to tear the roasters apart weekly. You would be surprised how a wee bit of build up can through a wrench into the works! Good luck man!

 

[bprotsman]

I remember those days Topher. Would agree with all the above said.
I had a similar problem awhile back with an IR24 and did the usual maintenance, checked for any airflow obstruction, etc. Ended up upgrading the motor a few HP (needed replacemnet anyways). Sure you know this but as a reminder chaff is easier to blow out of the drum initially (heavier when it gets oily) so dont be afraid to adjust your airflow through the drum a few times early on during the roast. Also when roasting naturals you usually deal with extra chaff so I will adjust airflow through drum several times to blow out. A lot of Diedrich roasters recommend airflow through cooling bin or 50/50 for much of roast but I know when I roast on ours its much cleaner when I play with the airflow through the drum early on. Just thought I would add my 2 cents. Good luck!

 

[paulc]

That's an interesting idea - a new blower motor. I might look into that next. Do you think a new one would have better torque or would it just spin faster? I don't know which I need - maybe both. Would an electric motor lose both with time and use? I had always thought they just sieze.

 

[kanyevil]

Clean it well my friend, otherwise you'll have a fireworks show in your drum !

 

[DirtyDave]

It's not a torque vs HP issue.
Most of these drum roasters utilize 1745 rpm motors to power their "fans".
If you went to separate motors for air/drum rotation/cooling tray, you could use a 3600 rpm motor for the fan.
Control that fan with a variable frequency drive, and you could have a new tool for creating and repeating profiles.

 

[paulc]

DD, thanks, I'll look into that. I don't actually know the rpm rating of the impeller motor. BTW, this IR-12 does have 3 motors.

 

[RichardW]

paulc - we have encountered exactly the same problem on our Diedrich although we are achieving the same roast times and flavors. Did you find a solution?