Need Resources and Advice :)

[natedawg]

I'm new to roasting as well as the forum so any resources you can point me in would be just as helpful as any advice you could give regarding our current dilemma.

We have a Probat L12 and have just had our 1st fire after roasting a Brazilian bean.

We've been almost exclusively roasting a Nicaraguan bean that has been cracking at 275 with light, dry chaff. We found that the Brazilian takes on a much different character in the roaster. It won't go above 260 and has a dark, sticky chaff that puts out a lot of smoke. A few days before our fire the cops came by because they thought the building was burning because of all the smoke coming out of our stack.

Any advice yall could give about how to avoid another mishap or any good resources yall could point me toward would be greatly appreciated!

Thanks,

Nate

 

[muzoon]

I have roasted with L12 probat for 3 years now.

I dont believe that the issue is in the beans.

Lets start from the basics:
How often do you clean your roaster and how in-depth the cleaning is done???? (it is important, most of fires are because of dirty machine!!!)
We clean our roaster fully every week (we roast 2-3 8hour days per week). chaff should be removed from chaff collector after every roasting day or before every roasting day. (depends how much you roast during a day).
What about piping at exhaust, at the vent., before the vent, space between chaff collector and cooling tray??? these places are covered with highly flammable soft powdery staff that comes from roasting, if you do not clean that regularly then fire is easy to come AND they influence airflow within the roaster and the taste of beans!
Keep in mind that lots of brazils have more chaff then other latin-american coffees which means you have lot more chaff during the same amount of roasting than other american coffees. which means you may need to clean chaff from the roaster much frequently.

by the way in which part in the roaster You had the fire?

 

[muzoon]

Give us some details of your way of roasting: charging temp, how much coffee at charge, roasting time, airflow lever position?
Coffee is considered specialty?
Moisture level is at appropriate range?

The temperatures You are referring to are in Fahrenheit I believe. If so then the cracking temp is very low.

 

[natedawg]

Thank you so much for your response.

We have been cleaning but maybe not as in depth as we could be. Could you explain what steps you take in your weekly cleaning and what tools you use to do so?

I found out from talking with our owner/lead roaster yesterday that our thermostat is faulty but gives us a reading about 100 degrees below what it should be. It is in Farenheit.

Our fire was in the chaff collector but we made several key mistakes in handling it. First we did not turn off the roaster and second we opened the collector. Fire came shooting out and then got sucked into the drum and went all through the pipes and straight up the smoke stack. It gnarled the smoke stack which is rated at 500 degrees F. So next fire won't be such an incident because we know what to do and won't act in a foolish reflex.

 

[natedawg]

Charging temp is 400 degrees (with the extra 100 degrees added), roasting time is about 17 minutes I think. We usually pull about 30 seconds after second crack. Coffee is definitely specialty. We have our air in the drum until we pull the roast. We don't have any moisture setting on our L12 that we are aware of.

Thanks for your help.

 

[muzoon]

Well, it seems that the fire was 100% a cleaning issue!

Walls of chaff collector and exhaust pipe are covered with previously mentioned powdery/oily stuff that has to be removed from these walls regularly - that´s why the fire was able to reach up to the smoke stack at first place!
Every week we use a brush to remove the sticky powder from all of the mentioned area. I know, it is very uncomfortable to clean chaff collector (you have to put all your hand through the small cleaning hole in front of the roaster in order to get the stuff off the back walls and piping walls that are in the chaff collector). As well you have to lift the cooling tray off the roaster and clean the area beneath it. If you have´nt done it for a while you will see a lots of that highly flammable stuff there.
We remove the bean hopper as well and clean the pipe there too (the pipe from where hot air is sucked into a chaff collector. there you may find lots of BLACK burnt beans too!!!
All the areas where the air flows in the machine has to be as clean as possible at all times so the hot air can easily flow without any disturbance and so the fire could not happen!
Chaff and all stuff that comes from roasting is highly flammable and all the areas where these stuff is flowing (with air) should be cleaned regularly.
How regularly it depends of how much coffee you roast during a week.

If similar fire happens in chaff collector one should not turn machine off (but only gas) but remain it working, airflow should be turned into a cooling bin so the fire would not get extra air which is necessary for fire to burn. Chaff collector front door should be closed.

You hold not think of next fire but to think that there will not be any fire no more
Clean your machine as full as possible and weekly and if needed then every half week. thus you will not have any (potential) fire at all to worry about.

The darker you roast the more oil gets onto surface of coffee and thus more oil is pulled into exhaust system. that meas more sticky flammable stuff on the walls of exhaust system. that all means, again, more often cleaning!

If the temperature sensor is faulty you should change it to correctly working one.
All other stuff seems ok for me, although roast time 17 min. is little too long for us but that is an issue of philosophy of roasting technique.
500 F is too high for charging but as I understand you do that at 400 F actually (we talk about air temp. here right?). Bean temp should not be higher than 390 F or so.

No problem man!