GROUNDS MAINTENANCE

Care and Feed of Your Roasters

by Boyd Guildner
photos by Cheryl Guildner

IN THE COFFEE ROASTING WORLD, one of the most overlooked areas is roaster maintenance. Many roasters don’t realize the benefits of taking pride in their roasting equipment the way they take pride in the proper way to roast a particular bean. Proper roaster maintenance creates consistent roast profiles, ensures coffee quality and prevents some of the most common roasting problems, including roaster fires. The lack of regular cleaning is also one of the biggest reasons for roast inconsistencies.
     As a maintenance person, I often hear roasters say, “I don’t have time to work on the roaster. I have a business to run.” I am always amazed by this comment since without well-running roasters, there is little chance you’re going to have customers to buy your coffee. And if you let your roaster go for too long, you run the risk of a roaster fire where you are not only compromising your livelihood, but other people in your building. As with most things, a little prevention goes a long way.
     Maintaining a roaster is not difficult; it just takes a solid plan and someone who is willing to get the work done. A solid maintenance plan should include removing creosote from ducting and cooling trays, greasing the ball bearings, and cleaning motors, gearboxes and any other moving parts. The chaff should be cleaned out of the chaff collector every three to five roasts, and the whole roaster should be cleaned approximately every 150 roasts. The frequency of roaster cleaning depends on the darkness of your roasts, since darker roasts can create more oils.

Ducting & Cooling Trays

You might notice greasiness when you touch different parts of the machine; this is creosote, and over time, it can be your biggest enemy. Creosote build-up happens two different ways: when the beans are hot in the roaster drum and when they are cooling down in the cooling tray. Motors, gearboxes and cooling trays are affected by the oils in the coffee as the beans transition from hot to cold.
     It is important to keep your airflow (ducting) clean. If ducting isn’t cleaned regularly, creosote will begin to adhere to the sides of ducting, motors and cooling trays. This creosote build-up will not only cause your pipes to shrink (much like arteries with cholesterol build-up), it can also increase the risk of fires. In addition, airflow issues can be seen in increased cooling times. Imagine it as the difference between breathing air normally through your mouth and then trying to breath through a straw—not only do you have to work twice as hard, you’re probably not going to get as much air in through the straw.
     Ducting is comprised of two parts: one that runs the exhaust from the roaster to the cyclone to the afterburner or out of the building and one that runs from the cooling tray to the afterburner out the building. Some roasters utilize the same duct for both processes, while others have the processes separated. Creosote build-up in the ducting happens in two ways as well: hard and heavy creosote build-up from the roasting process and sticky, gummy, oily build-up from the cooling tray. The creosote in the pipes of the roaster is caused by the smoke generated by the mass of the coffee as it reaches its drop temperature. The environment temperature bakes this oil onto the sides of the pipe.
     The oils in the cooling tray pipes are from the thermal mass of the coffee beans transitioning from hot to cold. Since there is no maintained heat associated with the smoke, there is no baking on the pipes. Consequently, you get the sticky oily residue build-up. The creosote in the cooling tray appears softer than its counterpart in the flue pipe but is equally as dangerous. In the cooling tray, airflow can be compromised by beans that get stuck in the cooling tray during the cooling period as well as the oils from the coffee as it cools. By keeping the holes on the cooling tray clean, you minimize the amount of airflow restriction.
     It is also important to clean the fan on the motors (blow them out with air) to get rid of any oily build-up on them. When the motors are dirty, they have to work harder and hotter, which shortens their life expectancy.
The stir flex motor is another place to keep on eye on. It is prone to creosote build-up, since the beans are dropped into the cooling tray hot and have a greater time and closer contact with the stir flex motor as the beans cool.
     There are many products available to companies to keep your roaster clean. You need some type of cleaner that can be washed off of the cooling tray, motors and gearboxes.
     The tubing (steel pipe part of the roaster) or flue pipe (insulated) should be cleaned with brushes to keep the creosote out of the pipe. If you have stainless steel tubing, you should use a stainless steel brush. Likewise, mild steel tubing requires a mild steel brush.
     For complete cleaning for your ducting, you can buy rods or chains, depending on how your ducting is run. The rods attach to your brush and you take all the ducting apart and clean each piece and reattach with either silicone or clamps depending on your tubing. On the brush with chains, you can have one person on the top of the tube and one on the bottom with the brush in the middle of two pieces of the chain. Each person pulls the brush from one end to the other. This allows for thorough cleaning without having to take everything apart. While cleaning, you should also look for any compromises in the ducting to make sure that there are no places where carbon monoxide could leak.

Bearings

It is important to clean the ducting and cooling tray and to grease the bearings. By greasing the bearings both front and back, you will keep them from seizing to the shaft that runs through the drum of the roaster. While bearings are wearable and need to be replaced as the roaster ages, greasing will help prolong their life.
     Grease is also where a lot of people get confused. You should always use the roaster manufacturers’ suggested grease in your roaster. The higher the temperature rating on the grease, the more protection you have in the bearing. If the temperature rating is lower, then your roaster operating temperature greasing intervals need to be increased because of the loss of the grease in the bearing.
     If you hear a grinding noise, you already have a problem. In this case, the bearings may be welded to the shaft, and you will most likely need to buy both new bearings and a new shaft.

Chaff Collectors

Another important cleaning issue is the chaff collector itself. Chaff is like burning paper, which can quickly exceed the 520-degree barrier and start a chain effect.
     You need to keep the chaff cleaned out of the bottom of the chaff collector after every few roasts. The safest way to do this is to cool the roaster completely down and empty the chaff collector. You should always follow the manufacturers’ recommendations for this procedure, as it may vary from roaster to roaster.
     What a lot of people don’t realize when it comes to the chaff collector is that the side walls of the chaff collector also get an oil build-up that needs to be chipped off and kept clean. A lot of the fires that start in a chaff collector are caused by a burning ember getting in there and starting the creosote on fire. Cleaning this out takes a putty knife or something similar that you can scrape the sides of the chaff collector with.

Burners

Burners also need some attention occasionally to make sure the burner orifices don’t become clogged. Burners collect ash and particulate that block the jets and air holes that consequently reduce efficiency. An indication that this is an issue would be longer roast times and varied cupping results.
     If the burner has ceramic on the burner cups, it’s a good idea to check them occasionally to make sure the ceramic is not cracked or broken. The problem that occurs with radiant heat systems is the ceramic plates can become cracked or clogged with ash just like the regular burners. An indication would be backfiring.
     When cleaning and inspecting the ceramics, it is imperative that you are careful, as they are very delicate, and any mishandling can cause you more problems than what you started with. If in doubt, call the roaster manufacturer for specific help.
     The bottom line is that you should never discount the importance of keeping your roaster in the best shape possible. This will keep your costs down by preventing fires and decreasing unexpected maintenance problems and it will keep your coffee quality high because you won’t have any airflow or burner issues.
     When it comes to your roaster, try to think of it as a classic car: a little knowledge, elbow grease and TLC is all it takes to keep you on the road toward the best possible roast.

Boyd Guildner has been in the equipment maintenance field since 1972. In 1989 he chose a new career path, entering the world of coffee. He started as a maintenance mechanic with Allegro Coffee in Colorado and later started his own coffee maintenance company, Ponderosa Roasting Maintenance & Manufacturing in 1990. He has a passion for coffee, is an Executive Council member of the Roasters Guild and is on the SCAA Tech Standards Committee.

SIDEBAR: Playing with Fire

by Boyd Guildner

Roaster and cyclone fires can be a roaster’s worse nightmare. The good news is that most fires can be prevented with a diligent maintenance schedule and the correct equipment. If a fire does occur, these two things, combined with proper staff training, can also decrease the severity of the damage.

Foiling the Fire

When it comes to proper ducting, people sometimes don’t realize the importance of having a roaster maintenance person or roaster manufacturer help them buy the tubing and ducting for their roasters. While it’s temping to take the cheaper way out, say by going to the hardware store or having an HVAC person spec the venting, you may not end up with the correct ducting for roasting.
     There is something called “B” pipe which is used in furnace systems and which is rated at 450 degrees plus ambient. Inspectors or installers will ask you what your operating temperature is, and while it’s true that your roaster operates in a normal environment in that temperature range, that doesn’t mean B Pipe is the answer. First off, B Pipe is not designed for a dirty roasting environment, and, thus, has an aluminum lining that is not easy to clean. In addition, if you were to have a fire in that pipe, it could exceed temperatures of 3,000 degrees F, which is much higher than the pipe’s rating system.
     Stove venting might seem good enough for roasting applications—after all, you are just venting smoke out of it—but stove venting is not rated for positive pressure (positive pressure is created by a blower fan that pushes the air out of the ducting). Often, people don’t understand this difference until they have had a severe fire that melts, ruptures or collapses the ducting and damages the building. The problem is that it is too late by then to do anything about it.
     Many people think that just because an inspector signs off on their B pipe that they are okay and that people who are always spouting off about positive pressure pipe and insulated ducting just want to spend more of their hard-earned money. But in the long run, there is a right way and a way that will possibly get you by. You can either hope that it won’t happen to you or you can pray to the roasting gods daily. Pay the extra money up front, and chances are you’ll be glad in the long run.

Dousing the Flame

If you do have a fire somewhere in the roaster, it’s important that you—and your staff—know the proper way to put it out.
     As mentioned, fires often start in the ducting. If the fire is in the ducting, use water on it externally to keep the temperature from exceeding the pipe’s rated capacity.
     Fires can also start in the roasting drum. Roasting beans can flash and start a fire when they reach approximately 505 degrees. If you do experience a fire in the drum, you want to keep the fire contained in the drum. Do not think that by dropping the roast in the cooling tray to quench that you will have less of a problem. This will actually add oxygen to the fire and make it worse. Instead, remove the trier from the roaster and put a water hose to the hole of the trier and allow the water to put out the fire in the drum. This will create less damage to your roaster and to your roasting environment since the fire will be contained in one place. That’s not to say that you won’t make a mess and that you won’t have roaster damage that will need to be inspected. But it is safer than having the fire in the cooling tray.
     If you have a fire in your cyclone, it is probably caused by lack of cleaning the walls of the cyclone. If you leave the chaff cleaning until the end of each day, you may be waiting too long in between cleanings and run more of a risk of starting a chaff fire. Once the fire is started, it then generates enough heat to soften the creosote build-up on the sides of the cyclone and you will have a very hot fire, sometimes in excess of 3,000 degrees. These fires can be put out by quenching with water, which will drop the temperature below the flash point.
     In addition, make sure you know what your roaster manufacturer recommends to put out a possible fire. Some manufacturers recommend nitrogen or carbon dioxide. The idea is to remove the oxygen from the environment, thereby suffocating the fire.
     As part of a maintenance routine, it is a good idea to train staff on both potential fire hazards and the appropriate response should a fire occur. Proper training and guidelines for everyone working in the roasting environment will ensure that these steps can be implemented quickly in the event of a fire in any area of the roaster.