In the 17 years that I've been roasting coffee, I've never had a drum fire. I like to think that this is because I take cleaning and maintenance seriously and don't engage in risky behaviors that can easily cause a fire, but the truth of the matter is that I've also been lucky. Perhaps the closest that I've come to a drum fire was in the story that I tell in the latest episode of 60 Second Coffee Tips.
While some manufacturers have been transitioning to direct drive systems on smaller machines, it's still fairly common to see roasters where a chain or belt is used between the motor and the drum. On these machines, you'll often find a couple set screws that are essential to keeping that drum spinning. If they come loose, the key connecting the sprockets to the drum axle can slip out. The chain and sprockets will still move, but that motion won't be transferred to the axle and the drum will stop spinning. If there's coffee in the drum when that happens, chances are good that this coffee will ignite and you'll have an annoying roaster fire to put out before you can get back to roasting coffee. It can take a long time to put out a roaster fire and you're not going to be able to sell that batch of coffee so it's better if you can just prevent that fire from happening.
I don't think I've ever seen checking set screws called out in a roaster manual as a recommended piece of preventative maintenance. I certainly hadn't considered it before the screws came loose. Fortunately, there are other maintenance tasks that are commonly recommended that involve opening the back of the roaster. If you have bearings that need lubrication, chain tension that needs checking, or removing an exhaust pipe for cleaning, that's a great time to take a few extra seconds to check that those set screws are nice and tight. This is the sort of problem that doesn't really develop suddenly so as long as you're aware of this failure mode as a possibility it's easy to prevent this problem from reaching a point where it becomes dangerous.
While you should certainly do everything that you can to prevent roaster fires, you should also expect that you will eventually have one and plan for that. If you don't know how to handle a roaster fire, it's easy to make things worse. Make sure that you have everything that you need to put out a fire, have plans for dealing with fires in the various parts of your roasting system, know when it's appropriate to call in professional fire fighters, and review your all of this regularly so that when you do experience a roaster fire you'll remain calm and take the appropriate action to extinguish that fire and bring your roaster back into normal operation.
I hope that everybody (aside from that one person who hit the dislike button on last week's episode) is enjoying this new weekly series of tips for people who work in coffee. I intend to keep it going for as long as I can remain motivated to stick to this weekly release schedule or until I run out of good tips that I think can be meaningfully shared in one minute. I've gotten some questions from people who want to know how they can help keep this series going, so here are some things that would help.