Chaff fire planning

[NorthSouth]

I roasted a new batch of coffee today. It had a huge amount of chaff.
Near the end of the roast, I saw smoldering chaff, glowing red (no flame).
Luckily no harm was done.
It made me realize how ignorant I am as to what to do in the event of a real chaff fire.
I would really appreciate hearing how other people plan for this possibility.
How do you prevent your roaster from being destroyed either by the fire or by your attempts to extinguish it?
Thanks in advance for your insight.

 

[John P]

chaff fires are not fun, however roasters (for the most part) are contained environments. Immediately shut down blower, heat source, roaster to cut off airflow/oxygen which will keep the fire going. Turning off fuel source and roaster (if IR or similar) goes without saying.

In most cases you can just let it burn out and you will be fine. If it's just in a collector, water quenching is fine, no need to over do it.
Always clean out your chaff collector before roasting. I've learned it's a good thing to do!

 

[Mr.Peaberry]

Hi John,

Aren't most roaster fires due to poor maintenance/cleaning of the equipment? How likely is a chaff fire in a roaster that had been thoroughly cleaned before the roast? Would it be accurate to say that the likelihood of a roaster fire increases with the number of roasts between cleanings? OR...is there also a random element to it as well, as in a batch of bean with more than average amount of chaff?

 

[John P]

Mr. Peaberry,

You hit the nail right on the head.

I would think the vast majority of fires are due to the frequency of cleaning between roasts. I've experience 2 fires in ten years of roasting. One was small and due to an inordinate amount of chaff in the small number of roasts I did, the other was a bit more dicey, but manageable, and entirely my fault.

Also, if someone happens to roast on the darker side of dark, lots of oil production and that sorta stuff, it would make sense to clean the ducting as a regular course of maintenance. A fire in the ol' exhaust stack would not do wonders and would likely frighten the neighbors.

When it comes to roasting, cleanliness IS godliness.

 

[expat]

Seems like I often say, 'Do what John says'. I've had two chaff fires too. Both were in the piping between my roaster and chaff collector. Shutting everything down as John described killed the fires. So keep your roaster very clean and keep a fire extinguisher handy just in case things get out of hand somehow and spread beyond the roaster.

 

[topher]

NorthSouth...you wouldn't happen to be roasting on a smaller roaster say 2.5 to 10 kilo? If it has an internal chaff collector it is what it is...they have earned the name as a firebox. Keeping clean is key as everyone else above has mentioned. I would definitely have a water source near by. I am partial to hoses..but I also have a water extinguisher. Water is easier to clean up...unlike chemical. If it is a small amount of chaff a small spray bottle works like a champ! I have had some doozies! Some my fault...well more like my boss not allowing time for maintenance. Others not my fault. Electricity going out when running 3 machines at once is a nightmare!

 

[Mr.Peaberry]

Oh lord toper...that is the "one arm paper hanger" scenario of the roasting world! How often does a power outage occur? You need to hit your boss up for a backup generator. Tell him to look on PublicSurplus.com for a steal on a used generator.

Peaberry

 

[topher]

This was my past place. We ended up buying a huge back up generator. My "brilliant" boss bought one big enough to run everything in the 40,000 plus sq ft warehouse. Oh wait...everything but the a/c. Can you imagine cranking out 100,000 lbs of coffee a month and no a/c?? Luckily it never came to that.

 

[NorthSouth]

Thanks for the advice everyone.
One suggestion of cutting off the heat and airflow makes sense, unfortunately my Toper Cafemino only has a single switch for drum rotation as well as the fan.
I can turn off the burner and shut the damper from the roasting drum, but if I switch off the fan and drum rotation, the drum might warp.
While I fully agree with cleanliness, the problematic roast I encountered was solely due to the vast amount of chaff it produced.
I always empty the chaff collector immediately after each roast.
I have already decided to roast less quantity for this specific bag of beans.
Any further suggestions very welcome.
Clearly I haven't been safety minded enough.
I really liked the spray water bottle idea from topher.
Thanks again.

Now a new (related) question:
How do you know if you are having a chaff fire?
With the exhaust venting outside and only a tiny sight window into the roasting drum, it is perfectly possible to have a fire in the exhaust stack without knowing.

 

[topher]

You will smell it. I am assuming you are roasting a natural coffee..My Sumatra has a loads of chaff. Good news is your roaster is small so the fire can't get too big. You say you clean your chaff collector out after every batch. How do you do this with an internal chaff collector? I have a lever in my external cyclone chaff collector. It is awesome! If I want to clean it out I just push in the lever and it cuts the cyclone in half so I can vacuum it out without cooling it down. In the past it sucked! I would push it to 18 batches and then cool it down, vacuum it out as quickly as possible and then heat it up again..insanity. Best was once I cooled down the roaster opened the chaff collectors door and there wasn't any chaff. There was just a little bit of grey ash...lol. Maybe you wont smell the chaff fire after all. Sorry that probably didn't help your concern.

 

[mbristol22]

In a sealed chaff collector, it is difficult to tell if you are actually having a fire until it is too late. One thing to monitor is heat spots in the metal from the inside. You can take the chaff can out and look inside the collector. Depending on how many bells you want your roaster system to have, I have seen water quench systems incorporated into the chaff collector monitored by a thermocouple that would run back into the plc or hmi running the roaster. This would require some modifications to the programming.

 

[NorthSouth]

I have to admit a quench system triggered by a thermocouple sounds very good.
Being a simple guy though, I think I will mount a thermocouple to the inside of my chaff collector and keep an eye on the readings during the roast.
A high temp will trigger the quench system (me with a squirt bottle of water).

Thanks for the replies.

 

[Bradleysteenkamp]

We've set the chaff on fire a few times on our Joper 25kg. Every time it is because we didn't follow the alarm that goes off every hour (4 batches) and a super hot particle falls into the chaff bin and sets it off. So, always follow the recommended cleaning!

Having said this, the chaff bin on the Joper has a shut off valve and we simply close that to starve the fire of oxygen and it very quickly goes out. Then it's just a simple case of removing the bin and cleaning it out. The metal is very solid and it is built to with stand a fire. This is one of the reasons why I'd personally never buy a roaster with an internal chaff collection system. I like having the primary fire risk completely isolated from the rest of the machine. Feels much safer!

 

[Boss99er]

I actually had my first chaff fire (smolder) this past weekend. I roast on a 5KG Ambex and I got this fire after my 3rd roast for the night. I normally clean up every 3 roasts......but apparently my last batch (a natural Brazil that is extra chaffy) was too much to wait. All I had to do was pop off the side cover and mist with water. Luckily I had semi-prepared for this so had a water bottle on hand. The smell though.....that was the worst part. There was no "wondering" if I might have a fire. Ha ha. Smoldering chaff is pretty gross smelling.