Evaluating Commercial Coffee Roasters

We at BURNS Roasters wanted to provide a resource to the Commercial Coffee Roaster Community featuring functional and consequential information about not only roaster maintenance and repair, but also the latest production software, plant automation, and processing best practices. If you are one of those Commercial Coffee Roasters with questions, you have come to the right place.

Types of Coffee Roasting Machines

One of the most important decisions you will make while in the process of choosing a commercial coffee roaster is, without a doubt, size. Determining what type of system to purchase can be just as difficult of a decision as there are many different types of Coffee Roasting Machines from which to choose.

The coffee roasting process involves heating the coffee beans to induce The Maillard Reaction. This is usually achieved with a mixture of convective and conductive heat transfer. But how does this help you decide what type of roaster is your best fit? Here at BURNS, we would like to provide some information about different roasting machine configurations; how each one transfer heat to the coffee beans, and the pros and cons of each design.

Solid Drum Roasters

Types of Coffee Roasting Machines that feature Drum Roasters are the most widespread roasters in the business. These machines roast coffee by heating a rotating drum. The beans receive both conductive heat transfer from the surface of the drum as well as convection from the ambient air. The simple design of a Drum Roaster lends itself well to a variety of heat source choices, flexible manual/automatic processes, longevity of its moving parts, and a variety of sizes. If you are looking for a dark roast profile, a drum roaster is the way to go; they produce more consistent dark roasts than any other type of roaster. One of the big drawbacks to watch with a drum roaster is that some beans will get burnt that are in contact with the drum. This makes it a little bit harder to duplicate roast profiles if you are not used to the specific roaster; however, there are some work arounds in the design of the drum to lessen this.

Single Wall Drum

The single wall drum roaster is your typical drum roaster. It contains a burner that heats the drum from underneath as it rotates, and the drum in turn heats the coffee beans through conduction. This lends itself to inconsistent roasts batch to batch because of the energy retained in the drum.

Double Wall Drum

The double wall drum roaster is a more refined drum roaster that uses the air between the two walls as insulation. Consequently, the beans have time to receive more convection heating. This technology allows the inner wall to stay a bit cooler during roasting, leading in turn to more consistent roasting and fewer scorched beans from batch to batch. The roaster seen below is a great example of this double wall roasting technique.

commercial-coffee-roasting-machine

Perforated Drum Roasters

BURNS employs a unique take on the drum roaster. Instead of relying on the conductive heating from the inner wall of the drum, all BURNS Industrial Coffee Roasting Systems operate with a perforated drum. The perforated drum allows for more convective heat transfer during the roasting process. Through this increased airflow, the roaster can create a more even roast and a wider range of batch size flexibility. Additionally, the roasting process uses less heat than a traditional drum roaster.

commercial-coffee-roaster

Fluid Bed Roasters

If the drum roaster is considered the superior dark roast machine, the fluid-bed is the exact opposite. In general, fluid-bed roasters will roast the coffee faster and with less energy than drum roasters. This lends itself well to lighter roasts as it tends to retain more complexity and acidity than the drum roasters. Fluid-beds can do this because they rely solely on convection to roast the beans: air is pre-heated and subsequently pushed through a column of coffee beans. This airflow makes the beans float on a “bed” of hot air. Fluid-beds are known for more consistency, retention of flavor, and small footprint. However, they are a lot more complex than their drum counterparts, leading to more expensive machines, difficult maintenance, and limited capacity. Also, most fluid-bed roasters do not have the option to inspect the beans during the roast.

Commercial Coffee Roaster Cost

Anyone that’s been searching online for a Commercial Coffee Roaster for sale knows that finding a price listing can be a difficult task. This is because a Commercial Coffee Roaster’s Price can depend on many factors. Commercial coffee roasters, (roasters larger than 2 bags per batch, nominally 500 kgs green per hour), come with various features such as recirculation or non-recirculating design, different options for control systems, as well as pollution control features as to keep compliant with air pollution control regulations.

You can also add on additional features like shrinkage scales, dark roast features, and/or instruments like online moisture measurement. With all of these possibilities, commercial roasters can have vastly different arrangements. Luckily, most commercial roasting companies are also able to produce an arrangement that will fit the constraints of your building. Designing the roaster around the constraints of the customer’s facility with the options required by the customer results in custom platforms and custom ductwork designs. Because of all of the options listed above, the roaster salesperson will almost always answer the customer price question with a statement like, “The price of the roaster depends upon the options you need.” At BURNS, we’ve designed a standard Commercial Coffee Roaster with the options that customers request. Our engineering teams intentionally designed the BURNS roasters with a compact design. This allows us to produce a roaster with recirculation, thermal afterburner, shrinkage scale cooling, destoning, and profile roasting, all while maintaining a small footprint. This small footprint has become a key feature of the BURNS roaster and it allows us to keep our final price down, making the BURNS Roasters the best value in the market. At the time of this publication, our B270R is priced at $355,000, which includes recirculation, thermal afterburner, shrinkage scale cooling, destoning, and profile roasting. Our B540R is currently listed at $565,000, which also includes the aformentioned features. The chart below summarizes the ranges of both 2 Bag, as well as 4 Bag Coffee Roasters and where the BURNS machines fit into the distribution.

commercial-coffee-roaster-price-points

Commercial Coffee Roaster Energy Requirements

Looking to start or expand a coffee roastery?  One important aspect to consider is energy requirements.  Does your facility meet basic requirements for electrical, fuel, water, and compressed air?  Determining these values early in the planning process will eliminate costly corrections during equipment installation and allow the machinery to operate efficiently.  These values can also be used to forecast facility energy costs.  BURNS will provide a General Arrangement Drawing with equipment utility requirements early in the planning process so facility owners can determine their own Industrial Coffee Roaster Energy Requirements and prepare the site accordingly.

commercial-coffee-roaster-energy-requirements-infographic

Electrical Requirements

BURNS will provide specific manufacturer electrical requirements for purchased equipment.  This will allow facility owners to determine power requirements, circuit sizes, and distribution panels for entire system.  Standard power requirement for BURNS roasters is 480 VAC / 60 Hz / 3 Phase.  *If alternate voltage or frequency is required, this must be known early in the planning stage so BURNS Engineers can accommodate into the design package.  An electrical schematic is provided with equipment.  Electrical connections must be installed in accordance with local codes or in the absence, the latest edition of the National Electrical Code.

Fuel Requirements

What type of fuel will be used for roasting?  Natural gas is standard for BURNS Roasters but can also operate with other fuels such as LPG (Liquified Petroleum Gas).  If LPG is to be used, the heating value (calorific value) must be specified so the burner components can be properly sized.  The gas supply line must be of the appropriate size adequate for the gas volume required by equipment. It cannot be emphasized enough that the sizing of the gas supply line must be properly sized to provide enough volume of fuel gas at the minimum pressure required. Insufficient volume of fuel will result in poor burner performance.  Be sure to account for all building appliances supplied by the same incoming gas line.
BURNS Roasters require 1-psig minimum and 5-psig maximum natural gas pressure at the gas train inlet connection.  Incoming gas pressure must be verified prior to operation.  A pressure regulator may need to be supplied on the incoming line.  Gas piping installation must conform to the applicable city, county, and/or federal codes or in the absence, NFPA 54 latest edition must be followed.

commercial-coffee-roaster-technical-drawing

Water Requirements

The BURNS Roaster has the ability to stop the bean roasting process by spraying water onto the coffee beans.  This requires that the water pressure, flow, and quality must be adequate for the specified roaster.  Consult with a Burns representative for specific roaster details.

Compressed Air Requirements

The last item on our list of Industrial Coffee Roaster Energy Requirements is Compressed Air. Compressed air is used for pneumatically operated components.   A standard BURNS Roasting, Cooling, and Destoning System requires 60 psig and 4 cfm compressed air.  Customers must take into account if their compressor and line sizes are adequate to operate all building pneumatic components.

Commercial Coffee Roasting Process

Ever wonder what happens after you press the charge button on your roaster? Yes, the beans get roasted, but what steps does the roaster go through to get them to your desired color, flavor profile, and moisture content? While the specific process varies depending on the roaster type and options this is a general overview of the entire Industrial Coffee Roasting Process.

Pressing the charge button

The Roaster has been preheated, and there is a batch in the Charge (Feed) hopper. When you press the charge button the roaster checks a few things before allowing the beans to be dropped (Charged) into the drum. These processes all happen simultaneously.

The Roaster first checks it has a place to discharge the batch when complete. The roaster then begins to bring the temperature up to Charge Temperature. If you have an exhaust abatement system, the roaster may also check to ensure it is running and at temperature before charging.  Once all the parameters are met, the gate opens, and the beans begin their journey.

Roasting: Curve Tracking and Recipe Control

Curve Tracking– This process allows for a much tighter control of the roasting process and can help ensure consistent quality of your roasts. Before using Curve Tracking you must have developed a recipe that meets the quality requirements for that “Recipe”. Curve Tracking uses a record (Master Batch) of the actual temperatures and settings of the roaster throughout an initial (Master Batch) roast to control the roast process. This allows for consistent roasts even during different ambient conditions.

commercial-coffee-roaster-curve-tracking

During the roasting process it is important to keep a negative pressure inside the drum, this helps to ensure a good flow of air is continually moving through the beans in the roaster (as seen below), and any smoke and CO is exhausted out of the building. This is achieved by the speed of the roast fan, and control of various flaps.  If you have ever noticed a roaster that seems to release a lot of smoke into the building, that is a sign that something could be causing the pressure inside the drum to be positive. This is what allows the smoke to escape from the roaster into the building.

Recipe Control – This process simply follows the recipe you have selected. The Roaster monitors the current product (Bean) temperature and adjusts various settings per the recipe. This is changed per “stage” as each stage is triggered by the temperature set in the recipe.  These settings include various settings such as burner percentage, fan speed, etc.  The roaster continues through the stages until it reaches to the final bean temperature.

Finishing the roast: Quenching, Drying, Discharging, and Cooling.

Quenching When the bean temperature has reached the final temperature set in the recipe or the curve profile, the roaster prepares to discharge the beans.  The beans are very hot and will continue to roast even if they are removed from the heat. The roasting process also removes quite a bit of moisture from the beans, quenching helps to not only cool the beans, but add some moisture back to them. You may have an option to set a “Quench Delay”, this is a delay after the beans reach their final temperature until the quenching process starts. Once this time has elapsed, the roaster will quench the beans with a specified amount of water. This value is controlled via the recipe.  Depending on roaster type, you may have the ability to do a “First Quench”, or “Pre-Quench” This limits the amount of water introduced to the beans at first to reduce the amount of steam that is created. Once the time or quantity of First Quench has been reached, it will then continue to quench until the desired total quench amount has been released. If you experience water pressure issues at your facility, you may get a quench fault (Roaster Quench Overtime Fault). The roaster monitors the total time the quench process takes, if it exceeds a calculated time, this fault will occur.  When the quenching occurs, steam is created when the cold water hits the hot beans and drum, this causes the drum pressure to increase so it needs to be able to pull that extra volume out and release it.  Depending on the roaster, it may open the exhaust flap or increase the roast fan speed to help remove the excess pressure.

DryingOnce the quench process is complete, the roaster is in its Drying stage. This process is as simple as it sounds. The roaster does not release the beans until the Drying Time has elapsed. This allows the beans to dry enough so they are not wet when released into the cooler.

Discharging and CoolingJust before the drying process ends, the cooler/destoning fan along with the stirrer will start. This closes a flap in the duct work causing air to be pulled up, or down through the cooling tray. At this time, the roaster will open the discharge door to release the beans into the cooling tray. The stirrer motor helps move the beans from the roaster door.  The cooling air is often sent through an abatement system for a period after cooling begins, then switches to exhaust into the atmosphere when the beans have stopped smoking.  This begins the cooling process; the stirrer moves the coffee away from the discharge door and distributes the coffee evenly over the cooling tray. In addition, the stirrer continually moves the beans around, so they all get cooled evenly. Some roasters can adjust the amount of time the stirrer stays on during the cooling process (also set through a parameter). This helps to reduce breakage for darker roast profiles. How long the total cooling process takes is adjustable to ensure the coffee is cooled enough for destoning or other transport.

Destoning – This process is relatively simple but can cause increased bean breakage if not setup correctly.  This step switches an air flap causing the cooling/destoning fan to draw a vacuum into the destoner bin. Dual Fan systems are also which uses separate fans for the cooling and destoning process.  Once the destoning system has started, the cooling tray discharge opens allowing the beans to drop into the destoner boot, the stirrer is designed to push the beans to the chute to clean it out completely. The bottom of the destoner boot is what allows the air to be pulled up into the destoner creating a vacuum.  The beans, which are now much lighter than they were when they are green get sucked up into the destoner hopper. Because the beans are lighter any stones that were in the mix will fall to the bottom of the boot into a removable tray so they can be discarded.  The speed at which the beans are pulled into the destoner hopper depends on how much vacuum is created.  It is important that this be checked as too high of speed will cause the beans to break when entering the destoner.  Some roasters use VFD (variable frequency drive), and the fan speed is adjustable, other systems have manual gates and flaps on the destoner to allow more fresh air in thereby reducing the vacuum. Finally, once the destoning time has completed, the cooling tray flap is closed and the destoning fan has stopped, the last step in the industrial coffee roasting process is to get an accurate weight of the roasted beans.  This weight is added to the batch report along with all the other data from the roast and stored into the historical batch files, and or transferred along with the batch to a Handling system.

While this is a simple overview of the industrial coffee roasting process, it helps to understand what is going on after you press the Charge Button. The roaster has several more tasks it handles while roasting which were not discussed, the most important of which is ensuring both a good roast, but also a safe roast. Monitoring temperatures along with gas and water pressure, along with the monitoring of CO levels, chaff removal systems, bean handling interaction, inline bean moisture analyzers, and automatic samplers are all essential for both roast quality and safety.

Commercial Coffee Coffee Handling Systems

There are several types of commercial coffee handling systems, each with their advantages and disadvantages. In this section, we hope to define a few different modes of bean transportation so you can plan your facility’s product highway in the most efficient way possible.

commercial-coffee-handling-system

Pneumatic: (Dilute Phase Transfer)

One of the most common types of green bean coffee transfer utilizes either a regenerative or positive-displacement blower to push product through one or a series of pipes to your roaster. These are primarily used on green bean systems because of the raw product’s durability; you would not want to send a roasted bean through this and expect it to show up whole on the other side. If the integrity of the roasted bean is not of concern, i.e., it’s on its way directly to the grinder, then the pneumatic system becomes a viable option. These systems are relatively simple to install and maintain, but one common drawback is the higher noise level during operation.

Tubular Conveyors (“Puck” style)

If operational noise reduction is a concern, then the tubular “puck” conveyors may be the preferred product transfer method. When installed and maintained properly, these can provide a quieter method of green or roasted bean transport. More commonly used on roasted bean products, this type of industrial coffee handling system helps ensure that the beans arrive at their destination unscathed. Though they are relatively a more expensive option, they cover a wide range of product transfer rates to make process timing and multi-roaster staggering a breeze.

Bucket Elevators

This type of coffee transfer system utilizes a series of, you guessed it, buckets to carry the product vertically. This handling system also takes up considerably less floor space when compared to the previous methods. Due to the larger bend radii of the pneumatic and tubular “puck”-style conveyors, they are usually placed farther away from the roaster whereas the bucket elevator can be alongside it. A common consideration for the bucket elevator is the addition of a recessed floor in which the equipment sits so that green coffee bags may be opened at ground level.

Bucket Elevator For Commercial Coffee Handling System

Process Timing Study

In order to plan your green bean transfer and roasted bean takeaway, we recommend consulting with one of our specialists to choose the most efficient methods and capacities. During this process we will consider the following inputs from you:

  • Your combined roaster throughput, usually in pounds per hour.
  • How many roasters are in operation and pairing certain roasters based on individual throughput.
  • The typical roasts per hour “schedule”; how long do you normally roast & cool the beans?

With your operational inputs, we will determine the transfer “window”, usually the amount of time between the completion of the destoning processes. With this information we can size the transfer systems to ensure that the process of getting beans to and from the roaster is seamless, even in the case of multiple roasters being fed from or dispensing to a single transfer line.

Green Bean Processing Equipment

Just how dirty is that burlap bag of green coffee beans you’re feeding through your roaster? Removing foreign contaminants early in the Roasting Process through proper green bean processing not only protects your Roaster, but also provides you with a quantifiable representation of the defects in your coffee.

Before feeding the system, you’ll want to weigh your coffee for a “starting weight”. You can use this value later to compare to the clean coffee weight you are expecting from your supplier.

Now you’re ready to start feeding your beans into the system. If you’re only feeding one mid-size roaster, you’ll probably be utilizing a single dump station. This dump station would then pneumatically or mechanically feed the cleaning process that leads to your green coffee storage solution. As you grow and begin to add a few new Probat or BURNS Roasters to the line-up, you may want to consider a dual or even triple dump station to process as many green coffee beans as possible.

With either a single or multi-dump station set up, as the burlap bags are slit open, the potential arises for strings or other contaminants to enter your system. If left in the product flow, these items pose the threat of a thermal event in the roaster or surrounding ductwork. Different pieces of Green Bean Processing Equipment can be introduced within the process flow to prevent such occurrences.

A “wind cleaner” (as seen below) is a great addition to remove burlap strings or light foreign particles from the product flow. These particles could cause fires during the roasting process if left in the system.

commercial-coffee-roasting-machine-wind-cleaner

A “sieve cleaner” can also be used to remove sticks or other foreign parts. Through different screen sizes, it can remove foreign elements that are both larger and smaller than a coffee bean.

commercial-coffee-roasting-machine-sieve-cleaner

You’ll also want to be protected against more significant contaminants such as metallic items, i.e hardware. In the event that any of these items fall into the green bean flow, a downstream metal separator will save your equipment by removing these potentially harmful objects.

commercial-coffee-roaster-machine-metal-separator

Once you have thoroughly cleaned your green coffee, you’ll want to take a weight measurement to see how much acceptable product you are left with. You may find it more cost productive to pay extra for cleaner beans from a different supplier. Upon being weighed, the coffee beans are sent to storage and await their shining moment in the coffee roaster.

The strong correlation between successful scalability of production and the ability to measure and remove any defects during your green coffee bean processing can make or break whatever growth aspirations you may have as a Commercial Coffee Roaster. No matter the size or set up of your Roastery, our engineers can customize a Green Bean Processing System to your exact specifications.

Commercial Coffee Roaster Maintenance: Burner Issues

Ever find yourself troubleshooting a faulty coffee roaster burner? If so, you’ve come to the right place. We’ve put together a guide to diagnosing your burner issue and resolving its root cause. Let’s get started.

If you start your roaster and it won’t light, you’ll need to follow one of two diagnostic paths in order to remedy the situation…

  1. The burner does not even attempt to light.
  2. The burner tries to light but fails.

The Burner does not try to light

In general, the burners on all industrial coffee roasters are going to need air, fuel, and spark to light.

The air is provided by the combustion fan. Check to make sure that the fan is running. There is a pressure switch associated with keeping the fan running. Ensure that input is on. (Inputs vary by roaster)

There are also pressure switches on the exhaust air side. Those need to be checked too. (Again, inputs will vary by roaster)

Next we can take a look at the gas. Check to ensure that the gas is turned on and that there is sufficient pressure. There are high and low pressure switches associated with the gas pressure. Ensure they are in the appropriate state. Low should be on and High should be off. (Inputs will vary by roaster, so be sure to check the manual)

There is a gas valve positioner that controls how much gas is allowed into the burner during any given phase of roasting. This could be out of adjustment or inoperable. If you suspect this to be the problem item, the gas valve positioner will need to be assessed by a Probat service technician.

If you have air and fuel, then the last item to take a look at is the ignitor.

The ignitor is a sort of specialized spark plug. This is the most complicated item to check but can be done if you’re comfortable around live electrical items and confident in your abilities. Do keep in mind, however, that when you attempt to complete electrical type repairs on your own you put your own health, the health of others, and your property at risk. Please only proceed if you are experienced in this area.*

To check the ignitor, remove it from the threaded hole. There are two types. One looks like a conventional spark plug.

To test the conventional spark plug looking ignitor, grab the body of the ignitor with insulated pliers, and hold the ignitor body against an uninsulated part of the roaster. (an exposed bolt thread for example)

When you try to start the roaster, you should see a spark jump the gap from the center electrode to the metal tab.

To test the other style ignitor, again hold the body of the ignitor with insulated pliers, and place the metal tip close to an uninsulated part of the roaster.

Again in this instance, when you try to start the roaster, you should see a spark jump the gap from the center electrode to the uninsulated part of the roaster.

The burner tries to light but fails.

Path 2 indicates something more subtle, but still on the order of some condition not being met.

If the burner tries to light but then stops or goes out, then the possible culprits are;

  • Marginal air, water or gas pressure, or the flame sensor. The pressure is just enough to get the process started, but then fluctuates causing the process to abort. This could be due to actual pressure fluctuations or faulty sensors giving fluctuating readings. This is especially true when dealing with gas pressure. If the supply volume is insufficient to support the burner needs, which are generally higher at startup, then these demands of startup can cause the pressure to drop.
  • If the burner lights but the flame then goes out within a few seconds, it could be the flame sensor. When working with a flame rod type, the flame sensor can be checked by using a torch to apply heat to it (a lighter isn’t sufficiently hot.) Alternately, if you are working with the UV type, you can check the flame sensor by simply holding a flame (a lighter works well here) a few inches in front of the sensor.
  • If you do this when the burner lights and it then stays lit, then the flame rod/sensor is defective.

commercial-coffee-roaster-burner

 

The UV type sensor has a glass window on the front of it. The flame rod just looks like a ceramic rod. Refer to the image above for a visual on both the placement of the sensor within an open roaster, as well as the component itself where the ceramic rod is exposed. These images come from a shop roaster from our production floor but offer a general illustration of placement of these components.

*The information contained herein is not mean to be comprehensive and is for informational purposes only. You should not undertake to perform anything described herein without adequate training and/or supervision. The Author disclaims any responsibility for any injury, damage, or loss as a result of reliance upon the information found on this site/blog.

Sight Oilers Maintenance

BURNS Roasters Technician Graham Conners walks us through the placement, adjustment, and maintenance schedule of the sight oilers on a B270R Commercial Coffee Roaster, as well as the recommended replacement oil.

Quench Pipe Replacement

BURNS Roasters Technician Graham Conners and Jeremy Baldiga walks us through the replacement of a quench pipe on a B270R Commercial Coffee Roaster. Prior to attempting any of the repairs or preventative maintenance recommendations shown within these videos, please follow appropriate LOTO procedures; assure all energy sources (electric, gas, air, water) are turned off, locked out and appropriately tagged.*

If there are other maintenance procedures you’d like covered or if you have any other questions about Commercial Coffee Roasters or the BURNS Product line, please leave us a message using the form below.

    *Probat Burns Inc. recommends safe practices when performing any repairs including those seen and implied within these videos. Probat Burns Inc. assumes no liability for property damage or injury incurred as a result of the information contained in these videos. Prior to attempting any of the repairs or preventative maintenance recommendations shown within these videos, please follow appropriate LOTO procedures; assure all energy sources (electric, gas, air, water) are turned off, locked out and appropriately tagged.