7 Most Common Foodborne Illness Risks in Your Food Processing Plant

foodborne illness in food processing

A variety of bacteria and viruses, including Norovirus, Salmonella, Clostridium perfringens, E. coli, and Campylobacter, among others, can infect food, causing thousands of illnesses and deaths every year. These pathogens can hide in many different materials, usually originating from infected water or soil. The sheer volume of ingredients and finished products that food processors and manufacturers produce increases the risk of spreading these pathogens, making facility-wide hygiene and sanitation critical. Foodborne illness outbreaks can occur when these viruses and bacteria are allowed to proliferate, eventually infecting ingredients and finished products. In this blog post, we’ll discuss common foodborne illness risks in your food processing plant, and how to prevent them.

7 Most Common Foodborne Illness Risks in Your Food Processing Plant and How to Avoid Them

1. Lack of Hygienic Design and Hermetic Sealing

Hygienic design is one of the most effective ways to mitigate common foodborne illness risks in food processing facilities. Hygienic design standards are outlined by several worldwide regulatory bodies, many which follow similar frameworks. The European Hygienic Design Group (EHEDG), 3A Sanitary Standards Inc., National Sanitation Foundation (NSF) International and, most recently, the Food Safety and Modernization Act (FSMA) all outline hygienic design principles to prevent the spread of foodborne pathogens. These guidelines focus on decreasing the proliferation and spread of pathogens, as well as containing and stopping the spread of allergens or other contaminants, such as metal fragments.

Hygienic design guidelines from every source require that hollow spaces, as well as cracks or crevices, be either filled by proper welding practices, or, if the hollow spaces are necessary by their function, they must be hermetically sealed. If these spaces are not sealed, or if cracks and crevices are present, they provide safe havens for bacteria, viruses and mold to multiply. Utilizing hermetic sealing and inspecting equipment for cracks can eliminate this risk.

Learn more about hygienic equipment design in food processing »  

2. Lack of Hand Washing and Hygiene

The CDC reports that over 50% of healthy people carry Staphylococcus aureus bacteria—the cause of staph infections—in or near their noses, mouths, hair or skin. Though staph infections, which are particularly problematic in hospitals and can be deadly to those with compromised immune systems, are well-known, it is less known that staph bacteria are also causes of food poisoning. Staph bacteria produce toxins that cause foodborne illness symptoms, such as vomiting, stomach cramps and diarrhea. Though staph food poisoning is seldom severe, it is unpleasant. It is also avoidable with proper food safety hygienic practices. Since staph bacteria are so widely prevalent, this is one of the most common foodborne illness risks in your food processing plant.

Since staph bacteria can live on the skin and hair of healthy people, gloves, hair coverings and beard coverings are especially important for stopping the spread of staph. Any workers that are handling ingredients or finished products, whether during the cooking, packaging, inspection, or cleaning process, should take proper precaution. Hand-washing stations should be readily available, as hand-washing is one of the best ways to prevent the spread of staph and other bacteria.

3. Unsanitary Drains

Listeria is not the most common foodborne illness risk for food processors, but it is among the most deadly. Of the estimated 1,600 people who contract Listeriosis, the infection caused by Listeria, about 260 die. Listeria, like many other bacteria responsible for foodborne illnesses, can live in many different environments. A notable feature of Listeria compared to other bacteria is its resistance to freezing temperatures. This makes it a particularly problematic bacterium for producers of ready-to-eat frozen foods.

Listeria bacteria can be eliminated by most sanitary cleaning practices. However, it often propagates in hard-to-reach places and areas of standing water, like drains, or cracks in the floor. Proper facility maintenance, preventing drain back-ups, and cleaning drains regularly can stop Listeria from spreading in these areas. Food processors should take care to prevent Listeria from becoming airborne, which can occur during cleaning with high-pressure hoses or scrubbing.

4. Tracking In Dirt

Bacteria thrives in soil. In many cases, these bacteria are helpful, and vital to the processing of nutrients. However, foodborne illness pathogens also thrive in soil, especially soil that is fertilized with manure or compost. Soil tracked in from trucks, shipping boxes, shoes and many other sources can spread bacteria from the shipping area into the food processing area. Food processors working with raw ingredients or raw foods must take special care to prevent this common foodborne illness risk.

Thorough cleaning can eliminate pathogens hiding in dirt. Separating shipping and processing areas can also help to prevent the spread of pathogens to other areas of the facility. As might be expected, areas with lots of foot traffic or receiving shipping vehicles should be cleaned more thoroughly.

5. Pests

It is well known that flies, mice, rats, birds, cockroaches and other pests carry and spread disease. Since they can be difficult to completely get rid of and they are naturally drawn to food, pests are one of the most common foodborne illness risks in food processing plants. If windows or doors are open during food or ingredient processing in order to keep temperatures down, this can present obvious entry points for pests. Older, larger buildings may also present more entry points. Any messes or spills, food or ingredients that are unsealed and sitting out, or even garbage can attract pests, and eventually lead them to food products.

Regular inspections and a high level of sanitation are the best way to reduce risks of pests. If pests do not have access to food or cannot detect it, they have little motivation to enter the facility. Keeping the facility sealed and using indoor heating or cooling also reduces entry points.

6. Lack of Maintenance

Machines that are not working properly can expose ingredients or finished products to pathogens. This can include a wide range of equipment, from faulty can reformers resulting in botulism to faulty refrigeration or heating equipment failing to kill bacteria, even faulty conveyor equipment allowing ingredients or food to collect and sit in unmoved pockets. Many other types of equipment failures can create foodborne illness risks in food processing plants.

A thorough maintenance program will keep equipment in full working order and it will help to detect problems before they create foodborne illness risks. A detailed maintenance list and timeline, including all procedures and documentation for each, will keep essential maintenance activities organized and verifiable.

7. Lack of Traceability

Though lot tracing does not prevent the spread of pathogens, it can stop the spread of infection if foodborne illness breaks out. A lack of traceability was, in part, what caused the recent E.Coli outbreak on romaine lettuce to become so widespread. Changes to labelling, including harvest time and location, has helped to mitigate this problem.

Lot tracing and tracking is best conducted through automation. RFID scanning and tracking software can help to automatically number and document ingredients or raw foods as they move through the supply chain. Proper labeling then ensures that any contaminated products can be easily identified and removed, wherever they go.

Preventative measures are generally better than reactive measures when it comes to food safety. Proper food processing equipment design, maintenance procedures, traceability, and sanitation from the start will prevent the growth of bacteria, viruses and mold and stop them from becoming a problem. For more information on sanitary equipment design for your food processing plant, contact us online or call (616) 374-1000.

8 FSMA Food Safety Risks Processors and Manufacturers Must Know

FSMA food safety risks

The Food Safety and Modernization Act (FSMA) created stricter food safety rules for farmers, growers, and food processors of all kinds. Compliance means preventing or dramatically reducing the chance of contamination, while non-compliance can result in FDA fines, consumer illnesses, and legal battles. Process design, planning, and controls play a key part in FSMA food safety compliance, as well as the everyday activities for food processors. The following are common FDA food safety risks that food processors and manufacturers face, many which can be prevented or minimized through proper process and system design.

8 FSMA Food Safety Risks Processors and Manufacturers Must Know

1. FIFO System Not in Place

When it comes to mixing and coating, perishable ingredients should be used on a first-in-first-out (FIFO) basis. This seems easy and logical at first glance, but a system that is not designed to ensure FIFO can easily pose FSMA food safety risks. A common and easy way to use bulk materials on a FIFO basis is through a silo or hopper which is refilled at the top and opened at the bottom. Gravity pulls the oldest materials towards the bottom, so they can be used first. However, there are some risks to this concept that must also be taken into account (see the next section).

Another common method to add ingredients is through bulk bags or super sacks. When bulk bags are shipped, they may be stored on the plant floor or loading dock until they are ready for use. If bulk bag shipments accumulate, the most recently delivered may be the most accessible, leaving older bags sitting for long periods. This can allow bacteria, mold, or pests to proliferate. The system for storing and using bulk bags and similar items must be clearly marked and employees should be aware of the importance of the FIFO system.

2. Dead Spots in Storage Tanks

Silos and hoppers appear to be the ideal FIFO system; filling from the top and taking from the bottom creates an automatic FIFO process. However, the tank must be designed to ensure that all the material is moving simultaneously, or dead spots can create FSMA food safety risks. Material segregation problems and flow problems can slow or stop movement in certain regions of the tank. This allows newer material to move through the tank too quickly, and causes older material to sit, inviting mold and bacteria over time. This will also create product consistency problems, as the ingredient may segregate based on particle size, viscosity, density, or other factors.

An angle of 70 degrees can help to ensure material flows evenly through a silo or hopper. Teflon coatings and stainless steel coatings can also help to promote flow. Highly disparate mixes that segregate within the storage unit may need additional mixing, smaller storage tanks, or separation prior to processing.

3. Equipment is Not Suitable for Clean in Place

Clean in place (CIP) equipment can be easily sanitized and decontaminated on-site. FSMA food safety regulations require that food processing machines be regularly cleaned. This prevents bacteria and mold from accumulating on wet, powdery, or greasy surfaces. It also prevents cross-contamination between batches.

CIP can be a challenge for equipment that also utilizes sensitive electronics, like load cells, or equipment with hard-to-reach places, like conveyance. Instead of avoiding the electronics in a machine while washing it—and thus creating potential for bacteria build-up—use hermetically sealed devices that prevent washing water from entering the enclosed device. Proper system planning and design can ensure that the system is equipped with sanitary, CIP conveyance, usually made from stainless steel.

4. High Oil Content Resists Microbial Heat Treatments

If you rely on heat to eliminate microbes, it is important to know the oil content of the product or ingredient mix. Oil creates a protective effect around some types of bacteria, making them harder to eliminate through heat alone. Soybean oil, olive oil, other vegetable oils and liquid paraffin, among others, are known to create this effect. This is an especially important consideration for animal feeds with high fat content. The build-up of oil on equipment or in the product itself due to inconsistent mixing can create harbors for bacteria.

Sterilizing washes designed to use on oil can eliminate heat-resistant microbes. Consistent mixing and regular testing can help to prevent pockets of oil from developing in the product which can shield bacteria.

5. Electronic Lot Tracking and Process Controls Don’t Integrate

Lot tracking is a critical FSMA food safety protocol. It helps to track the ingredients used in food processing, and it allows manufacturers, distributors and retailers to remove any contaminated products quickly. While electronic lot tracking systems have automated this process and helped to increase food safety enormously, they can be difficult to program or reprogram when the process or ingredients change.

Batch process controls that can be easily reprogrammed and integrate with your lot tracking system allow you to accurately track your products while giving you the flexibility to change your recipe as needed.

6. Food Safety Plan is Not Adaptive

Once you have a plan required by FSMA food safety rules, it’s tempting to consider the boxed checked and move on. However, just as your businesses and processes change to become more efficient, you food safety plan should also be able to recognize new threats and challenges. This might include new machinery and cleaning processes, new ingredients and potential cross-contamination or allergen risks, adding manual processes and increasing staff training, adding automated equipment, expanding processing operations or storage, and a number of other things.

If you have changed your operation in any way that affects how your product or ingredients are mixed, stored, handled or processed, it is important to also assess your food safety plan.

7. Insufficient Staff Training

FSMA food safety regulations require a safety plan and hazard analysis from a Process Control Qualified Individual. Some businesses contract with outside companies for this, others have a staff member dedicated to this role. However you choose to do it, this person should be trained to identify hazards, prevent them from happening, and change processes where appropriate.

Staff who handle food and ingredients or clean equipment should also receive training on the importance of FSMA food safety regulations. While it is important to explain what FSMA is, it is perhaps more important to explain why staff participation matters. This might be a common precaution such as using hair nets and clean gloves, or a job-specific duty such as adherence to FIFO, as mentioned in the first point.

8. Increased Mycotoxins Threats for Feed Producers

Mycotoxins produced by fungi in grain are particularly critical risks for animal feed producers, including livestock as well as pets. Recent increases in rainfall have increased the risks of mycotoxins in grains, making testing, sanitation and prevention even more important. All of the above FSMA food safety precautions, especially lot tracking and proper storage tank construction, can help to prevent the spread of harmful mycotoxins.

FSMA food safety regulations were designed to keep consumers safe and prevent the spread of illness. Food processors of nearly all sizes are now responsible for FSMA adherence, though there are many ways to accomplish this. Food processors and manufacturers should take note of these FSMA food safety risks, and pay close attention to system design when upgrading, expanding, or designing new facilities.

Improving Accuracy in Automated Processing Systems: Finding the Right Load Cell

improving automated process accuracy

Automated systems have made food, pharmaceutical and chemical processing systems faster and more efficient. An important part of this process is the accurate weighing of ingredients. As ingredients have become more concentrated, the importance for highly accurate scales has increased. The challenge for many engineers is designing an automated system that is both efficient and accurate. To improve weighing accuracy in automated processing systems, you have to start with the load cell. Finding the right load cell can help to improve the accuracy of the automated process in general, without sacrificing efficiency.

Improving Accuracy in Automated Processing Systems: Load Cell Capacity and Weighing Instrument

The load cell capacity, weighing instrument and the ingredients themselves all play an important role in the weighing accuracy of automated processing systems, regardless of the industry they’re used in. In today’s blog post, we’ll start with these important factors. Other considerations, like the size of the feeder, the scale vessel mounting position, the controls, and environment, also play an important role, and we’ll cover these in our next post.

Load Cell Capacity vs Scale Instrument Capacity

Finding the right load cell means looking at both the weighing sensor and the weighing instrument. How a scale displays weight and the most accurate measurement it can use are determined by the weighing sensor, commonly called the load cell, and the weighing instrument, commonly called the scale head. A typical load cell is accurate with 5,000 divisions. So, in a 100 lb cell, it could display incremental changes by .02 lbs.

More finely-tuned scale instruments make it possible to improve this accuracy further. Most scale instruments can exceed load cell capability, with the ability to divide by 10,000 or even 20,000. So the 100 lb load cell could show increments of .01 lbs or .005 lbs, respectively.

Scales legal for trade must adhere to scale standardization rules published in the National Type Evaluation Program’s Handbook 44, and scale instruments with this level of specificity are considered outside the standard. However, process scales may not be required to meet these standards, and the additional accuracy offered by the improved scale instruments can improve accuracy in the automated process.

Full-Scale Capacity vs. Individual Ingredient Accuracy

The scale’s division accuracy is a percentage of the full-scale capacity, sometimes expressed as the full scale capacity multiplied by the division. For example a 100lb scale may be shown as 100lb x .02 if the scale divisions is 5,000. This is often misconstrued with an individual ingredient’s accuracy requirement. If, for example, the scale is accurate to within .02lb and an ingredient requires 2% accuracy, it’s easy to assume that the scale will be sufficient. However, this is not the case. It depends on how much you are trying to weigh.

For example, 1% accuracy in a 100 lb scale is 1lbs. If you are trying to weigh 25 lbs of an ingredient on the 100 lb scale with a scale division of .02lb to within 1% then you will be OK since the .02 lb division is 8 hundredths of a percent of 25lbs. However, if you want to weigh .25 lbs of an ingredient in the same scale and you are off by one division of the scale then the potential error is 8% of the target weight. In order to find out what the minimum division should be for .25 lb target weight with a desired accuracy of 1% we need to divide .25 by 100 to get the desired percentage of the target weight. This means that the scale divisions would have to be .0025 instead of .02 so the scale should be much smaller.

Efficiency vs. Accuracy in Automated Process Weighing

The use of small amounts of highly concentrated ingredients alongside larger amounts of base ingredients presents a measurement challenge. A scale that is large enough to measure out the larger ingredients may not be accurate enough for the smallest ones, but a scale that’s accurate enough for the smallest ones will be too small for the large ones.

There are a few solutions to find a balance between efficiency and accuracy in automated process weighing:

  • Use two or more scales. Divide the recipe based on the desired accuracy for each ingredient. Two 50 lb scales capable of 5,000 divisions will each provide .01lb divisions, which will be twice as accurate as one 100 lb scale capable of 5,000 divisions, and the two scales working simultaneously will maintain speed and efficiency.
  • Fill a smaller scale more then once. If there is an ingredient that exceeds the scale capacity then it is possible to weigh the ingredient up to the scale’s capacity, discharge the scale and continue to weigh the same ingredient in the scale until the target weight is achieved.
  • Use a microingredient system. A specialized microingredient system can increase efficiency when there is a significant difference between the amounts and accuracy between highly concentrated ingredients and base ingredients.
  • Dilute the ingredient. A highly concentrated ingredient may require accuracy within +/- .01 lbs. However, if the ingredient is diluted—say, by ten times—the accuracy will drop to +/- .1 lbs.

Finding the right load cell and scale to accommodate every ingredient in the mix is the first step towards creating an automated processing system that is both accurate and efficient. In our next post, we’ll cover the next elements to consider, including the feeder, controls, surrounding environment, and more.

Liquid Coating Processes for Uniform Snack Coating

Whether for flavor, vitamin content, shelf life, or texture, liquid coating is the preferred application method for many cereals, snacks, pet food mixes, and more. Though this provides a number of efficient, time-saving advantages for snack coating, it can introduce some challenges if the process isn’t correct. Consistency and uniformity in liquid coating are two of the most common challenges in pet food and snack coating. With careful process design considerations, you can find the right process for your coating and substrate.

Liquid Coating Processes for Uniform Snack Coating

Before Application: Measurement

A standard mass flow system.

Before applying the liquid coating to the substrate, it’s essential to accurately measure the flow of each material. There are several way to do this, and which you choose will depend on the accuracy you require, moisture or temperature conditions, the composition of the carrier ingredient, and the layout of your facility. The carrier ingredient will be the “master flow” and the liquid coating process will depend on it, making accuracy even more important. You may need to consider potential flow problems at this stage.

You might choose the following flow measurement systems for continuous snack coating:

  • Volumetric: A screw conveyor, rotary feeder, or belt conveyor measures solid flow through RPMs (or Hz). A nutating disk, positive displacement pump, piston pump or turbine measures liquid flow through RPMs (or Hz) or pulses. Volumetric measurement is sensitive to changes in density, and not recommended for applications with high accuracy. Calibrate often to adjust for elevated temperature or moisture content,
  • Mass flow: Mass flow measurements have more versatility, with a variety of measurement systems. Weigh belts, weigh screws, impact scales, and nuclear gauges more accurately measure flow through RPMs and weight simultaneously.
  • Loss in weight: This measurement system works similarly to mass flow systems, however it measures weight as the material flows out. A garner hopper and scale hopper work in unison to take accurate measurements in a continuous flow system. This system is also quite accurate, however a facility’s height restrictions may be problematic. The scale hopper operates in weight exception mode during re-filling to accommodate continuous operation, and this should not exceed acceptable tolerances.

Liquid Coating Applications

With the measurement system determined, you have the right amount of liquid coating and substrate, but you still need to decide how to apply an even, consistent coating in the continuous process. You might use a screw conveyor, rotating drum, or mist coater.

Screw Conveyor and Spray

liquid application screw conveyor
Two spray nozzles and a screw conveyor.

As the screw conveyor moves the substrate, spray nozzles apply the liquid coating. In a simple screw conveyor very little agitation of the product takes place. To get a uniform coating, the substrate will require agitation. Some of the screw conveyor flights can be cut away to form more of a ribbon to agitate the product while moving it forward. Lifting flights and paddles on the screw conveyor will provide more movement, and there should be enough space for the material to tumble through.

The tumbling action through the screw conveyor must be gentle for fragile materials, which can slow down the process. Liquids moving through the spray nozzles can also present problems. If the liquid flow rate changes a great deal, then additional spray nozzles may be needed so the quantity being sprayed does not drop below or go above the rated capacity for flow and pressure, which can affect the quality of the atomization. If the liquid has suspended solids, spray nozzles will easily clog.

Rotating Drum and Spray

This liquid coating process works similarly to the screw conveyor, except the material moves through an open-ended cylinder. Flights lift and tumble the material, and spray nozzles coat the material as it moves through. This method is generally gentler and ideal for fragile snacks or foods.

Since the rotating drum is open on both sides, fugitive liquid and dust can quickly become an issue. Without proper ventilation or cleaning, the liquid or dust can create slip and fall hazards, unpleasant or hazardous working conditions, or it may damage equipment. The required length of the drum may also be a concern for facilities with limited space.

Spinning Disk and Mist Coating

liquid coating spinning disk atomization
Liquid application through spinning disk atomization.

During this process, the material moves across a spinning disk and flows over the edges. As it falls, the liquid coating hits additional disks moving much faster in the opposite direction below. The liquid atomizes into a mist that coats the material as it falls.

Atomization through spinning disks solves many of the liquid coating problems presented by spray nozzles. Since pressure is not required for the liquid coating application, density changes and solid suspensions are no longer a concern. This also allows for multiple liquid coatings simultaneously, regardless of changes in density or viscosity. Finally, the system is completely enclosed, which prevents fugitive dust and liquid from escaping.

Finding the right pet food or snack coating process will help you not only increase product quality and consistency, but it can also reduce costs, product loss, labor, and maintenance needs. Always test the process before installation, and work closely with your equipment manufacturer to get the right system.

 

Part 1: Ingredient System Planning Pitfalls from Micro-Ingredient Bins to Feeders

Proper planning before an ingredient system redesign or new installation is pivotal to ensure the system runs efficiently.  With so many moving parts and considerations, it’s not easy to plan for every eventuality, and a few problems are consistently missed. In this blog post, we’ll cover some of the most common problems that can arise at the start of the system with your micro-ingredient bins and feeders.

6 Ingredient System Planning Pitfalls from Micro-Ingredient Bins to Feeders

1. Incomplete, Inaccurate Information

Proper planning starts with accurate information. When your numbers are exact and you have all the information you need on your ingredient system up front, every step in the process will be easier. Whether you are installing a new system or conducting an ingredient system redesign for automation, you will need key information about all of your ingredients. You will also need information about your new or existing facility. Finally, you’ll need some measurements about your recipe as a whole to bring your system together properly. It’s helpful to have all of the following information available and well-organized in a spreadsheet:

  • Number of ingredients
  • Recipe composition
  • Ingredient types
  • Ingredient bulk density
  • Minimum weight required
  • Maximum weight required
  • Daily usage
  • Weekly Usage
  • Monthly usage

Get the secrets to feed mill and pet food automation systems design. Download the Engineer’s Guide to Weighing and Batching >

2. Insufficient Ingredient Storage

The usage of each ingredient as well as the delivery means and schedule will both play an important role in determining ingredient storage needs. For micro-ingredient systems and ingredients delivered infrequently, this will be particularly important for planning the rest of the surrounding system. If the daily usage of any ingredient exceeds 250 kg, consider using a super sack unloader to improve efficiency. For this, you’ll need adequate vertical space or design solutions to ensure ingredients flow properly.

3. Flow Problems From Bin Design  

You want to make sure that you have space for all ingredient bins of the correct size, and it’s also important to consider the construction of the bins themselves. Micro-ingredient bins without sloped walls, or without an adequate slope, can introduce flow problems. Generally, an angle of 70° is sufficient, but this will also depend on the characteristics of the ingredient. Ingredients that tend to clump, stick, or don’t flow freely may need additional design considerations, like vibration. If ingredients aren’t flowing properly from the bin, it can create costly downtime and other problems further downstream.

4. Contamination From Bin Design

Sometimes, when ingredients do not flow from the bin properly, the material may stick to the sides or stay in dead zones. When new shipments are loaded into the bins, this can introduce contamination. If the material in the bin becomes rancid and then mixes with a new batch, it will upset the quality of the product. Special coatings inside the bin can further enhance flow and reduce sticking and dead zones, and stainless steel will allow the bin to be easily cleaned at regular intervals.

5. Incorrect Feeder Type

Knowing the maximum and minimum weight for each ingredient, as well as ingredient characteristics, will be particularly important for choosing the right feeder type. You might choose an auger-type feeder for powders or other ingredients that won’t easily break or generate heat through friction. If the materials are susceptible to these problems, use a vibratory feeder instead.

6. Inaccurate Feeder Output

Both auger-type feeders and vibratory feeders must feed ingredients through the system with the proper output. The desired feeder output will vary depending on the accuracy needed and the total volume of the system. Here it is important to have accurate density measurements, as the material density will affect output calculations by weight. Output may also be affected by flushing if the ingredient is free-flowing. Use a knife gate or butterfly gate to prevent this problem.

 

Problems with ingredient bins and feeders are often overlooked, as these parts of the system are generally simpler than mixers, scales, and controls. However, problems anywhere in the process can affect the end result. Our next post will cover common issues with the later half of the micro-ingredient system, including scales, conveyance and controls.

How to Optimize Your Ribbon Mixer

Ribbon mixers in many industries are designed similarly from facility to facility with few variations. However, some design considerations can minimize the up front investment and maintenance, and maximize production and quality. The best way to get optimal efficiency from your ribbon mixer is to get the right design from the start. Depending on your materials, environment and overall mixing system, there may be more to consider than you think.

How to Optimize Your Ribbon Mixer

Compile Ingredients List

Your ingredient characteristics will play a role in several ribbon mixer design elements, and starting with this information will help your equipment manufacturer optimize the design. This way, you will have the size and features you need, without expensive extras. What characteristics you include will depend on whether your ingredients are solid, powder, liquid, or paste. For solids, it’s helpful to know any of the following that apply:

  • Number of ingredients
  • Names
  • Bulk density
  • Weight
  • Particle size variation
  • Adhesion
  • Friability
  • Shear sensitivity

Design the ideal system for your ingredients. Download the Engineer’s Guide to Weighing and Batching >

Record Facility Requirements

In some facilities, space may be a concern. This will impact the footprint and profile of your mixer, which in turn affects volume and production. If you require a large 8 or 10 ton ribbon mixer to meet production, be sure that this will not crowd out other equipment or create workplace hazards.

Calculate Total Production

How much you need to mix will help you determine the size and profile of the ribbon mixer design, or how many mixers you may need. This way, you aren’t investing in a larger mixer than you need, or one that doesn’t make sense with your total cycle time.

Determine Mixing Time

Your ingredients generally must move through the mixer completely three times to be adequately mixed. How long this takes depends on the ribbon mixer dimensions, as well as the ingredient characteristics. To be considered adequately mixed, you’ll need a coefficient of variation of 10 or less. Testing the mixer and the system with your ingredients beforehand will prevent excessive variation, while providing the ideal cycle time.

Record Weighing Time

Minimizing mixing time can yield efficiency gains, but not if the mixer sits idle while ingredients are measured. How long it takes to weigh and discharge ingredients will give you a guideline for the ideal mixing time. If your weighing time and mixing times are close to the same, you can minimize idle time for each process.

Accurate Agitator Profile Design

To get a good mix, you’ll need to fill the ribbon mixer to its swept volume. This means the agitator profile determines, in part, how much the machine can mix in one cycle. The mixer profile should not exceed 2.5 times the diameter of the agitator. The design of the agitator itself, including the ribbon thickness and shaft, may also be a factor, as a heavier agitator will require more energy to move and will have more shear. A simpler agitator design can reduce the initial investment if it’s suitable for the ingredients and facility.

Determine Ribbon Mixer Profile

With the previous information, you can determine the optimal ribbon mixer profile. Longer mixers will be able to mix more volume, but it will take longer, though this won’t be a problem if the cycle times aligns with the weighing time. For lower mixing time and more volume, you’ll need to scale up the ribbon mixer profile proportionately.

Number of Ribbon Mixers

In some cases, it may be more economical to use two ribbon mixers instead of one that is double the size. This way, a problem with one mixer will only reduce production instead of stopping it.

Liquid Coating Considerations

If your ingredients require a liquid coating, you may wish to apply it during the mixing stage. Keep in mind that some liquid coatings may not be evenly applied at this stage, or they liquid may not be suitable for spray nozzles. If the liquid coating can be applied during mixer, be sure to factor in any additional adhesion that may occur. If material stick to each other or to the mixer, extra maintenance may be required, which can eat into ROI.

Determine Shear

Ribbon mixers are generally gentle and impose little shear on ingredients, however it can be an important consideration with some shear sensitive materials. Consider any solid ingredients as well as liquid coatings; are they likely to break apart or separate? Do the ingredients require more shear to break up clumps? Most mixer manufacturers are happy to do testing in order to determine the best configuration for your product.

Accurate Horsepower

Most ribbon mixers operate at around 20 RPMs, though the horsepower it requires will depend on the size of the mixer and the characteristics of the ingredients. Make sure you don’t overestimate your motor and overspend, or underestimate your motor and reduce power to your ribbon mixer.

Install Proper Discharge Gate

The discharge gate on your ribbon mixer(s) will depend on your cycle time, downstream process and your materials. Drop bottom discharge gates will discharge quickly, but they can be harder to seal and allow powders to escape. This can be a challenge for very fine ingredients. Slide gates will discharge more slowly, but will seal more tightly. Multiple slide gates can provide a tight seal with faster discharge.

Reduce Maintenance

The type of gear reducer used in your ribbon mixer motor can impose unnecessary maintenance costs. A shaft reducer in lieu of a jack shaft or foot mount eliminates the need for an oil bath on the sprocket.

Some ribbon mixers are straightforward, and the mixer design varies little over time and throughout the industry. Others are more complex, and considering all the elements can help you improve the design. With the right ribbon mixer design from the start, your mixer will continue to work quietly in the background, with optimal efficiency and no problems.

Solving 5 Common Super Sack Unloader Problems

The right super sack unloader system allows you to measure and process materials quickly and cost-effectively, with very little waste, error or manpower required. Unloading materials may seem like a straightforward process, however the wrong bulk bag discharge system can cause product defects, ingredient loss, and pose workplace safety hazards. The ingredients you’re using as well as the design of your system and the volume processed will all play a role in choosing a safe, effective, durable super sack unloader.

5 Super Sack Unloader Problems and Solutions

1. Design for Space

The first thing to consider with your super sack unloader is the design, which will depend on how you transport the bulk bags, and the design of your facility. Your bulk bag unloader design may be any of the following:

  • Forklift: If you are transporting the bag from the top using a forklift, this will most likely be the easiest and simplest option. This allows a forklift operator to easily load the bag into the frame from the top, with no other steps required.
  • Dedicated Hoist: In some cases a clear path may not be available for a forklift. A dedicated hoist design allows you to secure the bag to support arms and lift, then push it into place. With this design, it is important to motorize the lifting and pushing mechanism to put the bag in place.
  • Bottom Lift: Facilities with low clearance, such as those retrofitting from individual bag unloading, may use a bottom lift mechanism. With this design, a forklift operator can move the super sack and support frame from the bottom and lift it into place with only about half the height needed.

Keep in mind that staff should never be below the bags at any point while loading the bag, as this presents a serious workplace hazard. Though bulk bag failures are uncommon, they do occur.

2. Preventing Bag Deformation

As the ingredients flow out of the bulk bag, it will begin to lose its shape and ingredients will flow slowly, or even stop. There are several ways to stop flow problems, and which you choose will depend on the ingredients you are using and the design of the super sack unloader.

  • Raise the Bag: With vertical clearance available, you can lift the bulk bag support arms as the bag unloads, increasing the flow angle.
  • Retractable Arms: If the arms supporting the super sack are spring-loaded, they will retract as the bag loses tension. This maintains the flow angle.
  • Paddles: Pneumatic paddles at the bottom of the bag can push the ingredients up as the bag discharges. For ingredients with low flow, or for sticky materials prone to clumping, paddles and other flow aid devices are useful.

3. Accounting for Material Characteristics

The characteristics of your materials are also important to consider when choosing your super sack unloader. Some materials are more susceptible to flow problems or segregation, which can cause other problems in the process. How the material flows, its moisture content, whether it is prone to static charge, clumping or flushing, and other characteristics will decide what type of special features your bag unloader may need to be effective.

  • Flushing: Dry, light, free-flowing materials may have a tendency to flush, continuing to flow after shut-off. Pay special attention to the valve or gate below the bag to prevent flushing.
  • Dust: Dry, light materials also tend to produce dust. A ventilation or vacuum system may be required around the bulk bag unloader to prevent dust build-up and workplace safety hazards. When the bag is empty, dust can be trapped inside, so it is also important to tie the empty bag before removing it.
  • Clumping: Adhesive materials may form clumps within the bag, or the bag may become solid if it is compressed. In some cases, a bag liner preventing moisture can stop clumping. Pneumatic rams can break up solid blocks, or paddles can break apart clumps.
  • Static: Very fine materials as well as some plastic resins can become statically charged as they flow, especially in dry conditions. This can cause materials to stick to the sides of the bag or feeder and decrease the feeder capacity. The static charge can also pose a risk to scales, load cells or system controls. Make sure the super sack unloader frame is grounded to prevent static build-up.
  • Moisture: Some materials may need protection against moisture to prevent spoiling or clumping. A bag liner can prevent this, but the bulk bag unloader frame should also secure the bag liner to prevent it from becoming lodged in the feeder.

4. The Right Discharge System

To accurately discharge ingredients, you’ll need to choose the right discharge system using either loss-in-weight or volumetric measurement. Which method you choose will depend on the level of accuracy you require.

  • Loss-in-weight: With load cells mounted underneath the bulk bag base or frame you can measure discharge through the weight of the bag. This is suitable for ingredients in large amounts, but more accurate scales will be required for ingredients discharged at 40 lbs or less with 1% accuracy, based on a one-ton bulk bag.
  • Gain-in-Weight: For more accurate measurements, gain-in-weight measurement may be preferred. In this case, the scale be sized for the actual amount being weighed, so the accuracy can be adjusted to your needs.

5. Meeting Sanitation Requirements

If your materials must meet food grade or other USDA or FDA standards, you’ll need to make sure the super sack unloader and the bag itself are suitable. A bag liner is useful here to protect the materials inside from moisture, damage or contamination. In this case, the frame around the bag should secure both the bag and the liner, or the liner may collapse and enter the feeder. The frame, as well as any surface the materials come into contact with should be made from stainless steel to allow for easy sanitation.

 

With the right bulk bag unloader system, you can process materials quickly, safely, and efficiently. The best way to make sure your system works effectively with your materials, as well as your downstream and upstream processes, is to design and test it properly. Your equipment supplier can help you address these issues and make each part of your system efficient.

Complete Ingredient Mixing Systems Design Checklist

ingredient mixing system design

There is no one-size-fits-all for ingredient mixing systems design, whether you are working in snack foods, animal feed, dry bulk solids or any other industry. Ingredient mixing system designs require careful consideration of all ingredients as well as production schedules, variation, storage and more. In this blog, we’ll provide a basic roadmap for automated ingredient mixing system design that business owners, facility managers, engineers and others can easily follow.

Automated Ingredient Mixing System Design Checklist

Planning System Design Requirements

Your ingredient mixing system design starts with needs and goals, including your ingredients, production volume and product variation. The accuracy of this initial information will determine the design of the rest of your system, so it’s important to be as clear and correct as possible at this stage.

You’ll need all of the following information

  • Ingredients: number, names, bulk density, weight, ingredient delivery schedule, special considerations (friability, viscosity, adhesion, particle size variation etc.)
  • Production: daily, weekly, monthly amounts
  • Environment: temperature, humidity, seasonal changes

This information will not only help you design your ingredient mixing systems for volume and production, but will also help you avoid any complications that could arise from system’s surrounding environment, or challenges with the materials or ingredients themselves, such as material segregation or flow control problems.

Get the secrets to automation systems design. Download the Engineer’s Guide to Weighing and Batching >

Storage Bins

Your production volume, number of ingredients, and ingredient delivery schedule will help you determine the size and number of storage bins you will need. Consider the minimum and maximum production levels of your facility, as well as the minimum and maximum ingredient volume delivery for each ingredient to determine the storage bin size you will need. Also, consider any safety requirements you will need when unloading ingredients, or any special considerations the ingredients may need during storage, such as temperature requirements or bin coatings for acidic or adhesive ingredients.

Consider these factors as you design your ingredient loading and storage area:

  • Storage bin size
  • Storage bin placement
  • Unloading area
  • Unloading safety requirements
  • Bin coating requirements

Feeder Design

Feeders are one of the most important parts of your ingredient mixing system design. Designing your feeder improperly can cause incorrect measurement and mixing, resulting in product defects, or slow-downs and downtime when ingredients don’t move through the feeder at the desired rate.

The maximum and minimum weight of each ingredient you determined in the planning stage can help you determine your feeder volume output. The feeder must be able to feed the smallest micro-ingredients as well as high-volume base ingredients, all within tolerances. This may mean installing multiple feeders or installing additional features on one feeder, such as speed controls. You’ll also need to determine your feeder drive mechanism, either hydraulic or electric, as well as a cut-off valve to prevent flushing.

To get the right feeder, consider the following:

  • Feeder volume output
  • Number of feeders or features
  • Feeder drive
  • Feed cut-off valve
  • Accuracy

Scales

To properly design and install scales for your ingredient mixing system, you’ll need to determine the maximum and minimum number and amount of ingredients you’ll be measuring, as well as how accurate the measurements must be. Remember that scales, like feeders, must be capable of meeting volume and accuracy requirements for micro- and macro-ingredients. This means they should be large enough to handle heavy volumes, but accurate enough to measure micro-ingredients without too much error. If there are large variations between your ingredients, using several scales or diluting ingredients can help you maintain accuracy.

The type of scale you choose will also have a dramatic impact on the system at large. The right type of scale can help you save time and eliminate extra processes, like a conveyor scale, make mixing easier and more uniform, like a conical scale hopper, or integrate with a variety of bins, like a roll-over tub. The best scale type will depend on your facility, ingredients, and product.

You’ll need to know the following:

  • Maximum scale weight
  • Maximum scale error
  • Number of scales
  • Scale inclusion rate
  • Scale display resolution
  • Scale type

Mixer

It’s important to choose a mixer that will properly mix all ingredients together, but will also give you an efficient cycle time. You’ll need to measure the cycle time of your mixer and compare it to the cycle time of your weighing and discharging system for maximum efficiency. This will allow you to run all processes simultaneously, instead of leaving your mixer or feeders idle. You’ll also need to consider any special requirements of your ingredients, such as adhesion, friability or heat and shear. Finally, remember that the mixer must be filled at least to swept volume to work properly, so all ingredient mixes, including the lowest possible volume, must fill the mixer at least to swept volume.

Consider all of the following for your mixer:

  • Mixer cycle time
  • Mixer footprint and profile
  • Mixer swept volume
  • Ingredient considerations

Controls

Without the right control system, even the best ingredient mixing systems designs won’t work. Your control system keeps you automated system running smoothly, and alerts you to any problems. You’ll need to choose a computer or PLC that integrates easily but completely with your system design. This means your controls must be able to work with all of your inputs and settings, including multiple feeder or mixing speeds, scales, sensors, and all upstream or downstream functions.

Keep in mind that your system, ingredients and recipe may change, and your controls may need to be reprogrammed at some point. The best control systems will adapt to your needs without the need for complex programming knowledge.

To get the right controls you’ll need to know:

  • Number of scales
  • Number of feeders
  • Number of mixers
  • Variable speed controls
  • Sensors and alarm conditions
  • Upstream or downstream processes
  • Reprogramming conditions

To complete your system, you’ll also need to consider upstream and downstream processes, which may vary depending on your ingredients, ingredient delivery system, and batching process. At each point in the process, your environmental conditions will also be a concern, as high temperatures or humidity can cause materials to separate, stick, or flow slowly. As you design and build your system, work closely with your equipment manufacturer to make sure your system is build for your ingredients and volume.

18 Batch Mixing System Design Considerations for the Best Dry Solids Mix

batch mixing system ribbon mixer

Producing high-quality finished products from dry solids starts with getting the right mix. Mixers are not one-size-fits-all, and your batch mixing system must be designed with your ingredients, facility, capacity, and other considerations in mind. Without the right mixer, segregation problems, dead zones, an low mixing activity can cause harm to your product. Go through this list of batch mixing system design considerations when working with horizontal ribbon mixers or other dry solids mixers and make sure your mixer works at optimal efficiency.

18 Batch Mixing System Design Considerations for the Best Dry Solids Mix

Individual Batch Mixer Design Considerations

1. Capacity: One of the most important batch mixing system considerations for dry goods is capacity. When working with a ribbon or paddle mixer, the total capacity cannot exceed swept volume (space occupied by the ribbon mixer). Over and under filling can increase the variation in the mix and may also increase the mix time.

2. Time: Many batch mixing systems for dry solids use horizontal ribbon mixers because of their ability to fully mix ingredients in one to two minutes. However, the ideal cycle time for your batch mixing system will depend on the upstream and downstream processes, and the output you wish to achieve. Changing the capacity, profile, or number of mixers in your batch mixing system can help you coordinate timing between processes so all the systems can run simultaneously, maximizing utilization.

3. Mixing Cycles: A rule of thumb for horizontal batch mixers is that the ingredients should move from end to end at least three times. The actual required mix time can vary depending on the ingredients. Not enough circulation will give you an incomplete mix, too much circulation can cause unnecessary breakage or fines generation. Your particular mix should be checked to make sure that you have a complete mix.

4. Mixer Profile: Since ingredients in a horizontal ribbon mixer or paddle mixer move horizontally through the mixer, a longer mixer will lengthen the cycle time. In general, the diameter to length ratio should be between two and two and a half. You’ll need to consider the available footprint and desired production rates to determine the size of the mixer.

5. Motor Horsepower: Ingredient density and capacity will affect the horsepower required for the mixer to run. If the weight is the same, the horsepower requirements will also be the same. However, a low-density mixture might completely fill the mixer but impose only half the weight, while a high-density mixture at full capacity will weigh much more. Choose your motor in your batch mixing system carefully so your mixer has enough power, but isn’t pulling unnecessary energy.

Material Considerations

6. Friability: Horizontal ribbon mixers generally impose a low degree of force on ingredients, but especially friable ingredients can still break apart during mixing. When working with especially friable ingredients in your batch mixing system, paddle mixers may be preferred for a gentler mixing action. The angle of the paddles will also lessen the force of the mixer.

7. Heat and Shear: Ingredients with high shear sensitivity will be subject to heat from the friction of the mixer. If these ingredients have high fat or sugar content, as well as high shear sensitivity, they may melt and stick to the mixer. Sticking ingredients will not only affect the quality of the mix and efficiency of the batch mixing system, but it will also damage the mixer over time. A non-stick coating or stainless steel polish can prevent sticking due to shear sensitivity.

8. Material Bulk Density: To properly calculate capacity, you will need to know the bulk density of all ingredients you’re currently using or expect to use in the future. Keep in mind that low-density ingredients like wheat middlings will take up more space than the same weight of another, denser ingredient like soybean meal.

Maintenance and Safety

9. Ribbon Maintenance: Mixer ribbons can last the lifetime of the mixer, but materials that are abrasive will cause a ribbon to wear down faster. Check the mixer ribbon clearance and thickness at regular intervals. Replace a ribbon before it becomes thin enough to break or the clearances between the ribbon and trough become too large. This will avoid unexpected downtime in your batch mixing system.

10. Motor Maintenance: If you are using a chain and sprocket mechanism to reduce RPMs, you will need to regularly adjust the tension and check the oil bath lubrication system. Using a shaft mount reducer can eliminate the need for this extra maintenance.

11. Safety: If adding ingredients manually to the batch mixing system, the input should be blocked with a bolted grate. Unblocked inputs or removable grates put workers at risk and expose businesses to unnecessary liability. Cultivate a culture of safety and encourage workers to report any maintenance issues or hazards.

Overall Batch Mixing System Considerations

12. Discharge Gate: Several discharge gate options are available depending on your ingredients and downstream processes. A drop bottom gate will release the entire mixture at one time, which is ideal for moving the ingredients fast. However, drop bottom gates must be tightly sealed and seals must be regularly checked to prevent leaks. Slide gates require less stringent seals and hold adjustment better, but they won’t discharge as quickly. Butterfly valves can move product quickly and will require less maintenance, but they can create dead zones over the valve.

batch mixing system drop bottom
A 4 ton ribbon mixer with a drop bottom discharge gate

13. Downstream Processes: Even if your horizontal ribbon mixer or another batch mixer is completely effective, material segregation can occur at any point in the process. Place your mixer as close to extrusion, pelleting, packaging, or another finishing process as possible to limit the opportunities for material segregation to occur. When working with very fine ingredients, make sure powder flow control problems upstream around a hopper or feeder aren’t affecting the batch mixing system.

14. Number of Mixers: Two small mixers may be a better option than one big one. This depends on physical space available and whether a surge hopper is possible in the system. If two mixers are used, then a mixer problem will decrease the output by fifty percent instead of shutting you down
Testing and Verification

15. Testing:  Ask your manufacturer about an on-site ingredient test with your mixer to make sure there are no problems and address any concerns. Test the ingredients at the end to verify the entire process, and immediately after mixing to verify the mixer itself. You may wish to use chemical analysis to test for particular ingredient distribution or micro tracers to test without a lab.

16. Dead Zones: dead zones can form if the mixer is improperly filled (too much or not enough), and can sometimes form in the upper corner of the mixer. Test these areas to ensure dead zones aren’t disrupting the mix.

17. Ribbon Testing: As the ribbon wears down, it will require more time to completely mix all ingredients. If your coefficient of variation has steadily deteriorated, a worn-down ribbon may be the cause. Test your product regularly to avoid this problem.

18. Multiple Formulas: If your batch mixing system is dedicated to a single formula, you’re less likely to run into surprises or problems. However, if multiple different mixtures move through the system, you’ll need to separately calculate bulk density, shear sensitivity, friability and other aspects. A horizontal ribbon mixer or batch mixing system that works optimally for one recipe might not work for another. The solution may be as simple as increasing the mix time for some formulas or decreasing or increasing the batch weight to optimally fill the mixer.

The right batch mixing system design and the right dry solids mixer can reduce downtime, increase efficiency, and eliminate costly maintenance expenses. When designing a batch mixing system, work with your manufacturer to find the right size, volume, power, and design for your materials, facility and process.

Solving Material Segregation in Batch Mixing Processes

material segregation in batch mixing processes

When solid materials mix, a degree of material segregation is inevitable. A variety of processes are used to achieve a predetermined level of uniformity in batch mixing processes, however other processes downstream can cause the materials to separate again. With proper design considerations and awareness of the material segregation physics at work, processes and products can be tested for separation, and product defects can be avoided.

Material Segregation Problems In Batch Mixing Processes

Sifting

How It Works

Scientifically known as granular convection and known in practice as the Brazil nut problem, sifting is one of the most common material segregation problems in batch mixing processes. Sifting occurs mainly through the relationship between the particles’ size and mass; particles significantly larger and more massive (like Brazil nuts) rise to the top of the mixture, and smaller, less massive particles (like cashews) fall between the spaces towards the bottom. It can occur without movement, but movement worsens the problem, since vibration or shaking causes smaller particles to relocate faster into empty spaces. The degree with which this material segregation problem occurs depends on the variation between the particles’ size and mass, and the amount of each.

What You’ll See

Sifting is a material segregation problem impacting many processes. A vibrating conveyor belt can cause sifting, as well as some stirring processes. Even shaking a completed package (like a jar of mixed nuts) can cause this separation.

Angle of Repose

How It Works

The angle of repose material segregation problem in batch mixing processes works similarly to sifting, but operates on a different principle. Instead of sinking to the bottom, smaller, finer particles form a hill when they are poured or dispensed. When thicker, coarser particles reach the hill, they tumble down towards the edges. The materials’ differing angle of repose—the angle at which it will be stable and not tumble down—causes this separation.

What You’ll See

This material segregation problem in batch mixing can be especially difficult. In silos and hoppers it’s often the cause of flow problems like ratholing and bridging. If the coarser particles stick to the sides of the hopper they can get rancid and contaminate the next batch. Since air flows through the coarse and fine materials at different levels when they are dispensed, it can create a pressure differential that can damage a holding unit, such as a silo. Most commonly in batch mixing, the material segregation causes different concentrations of ingredients when the mixture is dispensed from an improperly designed hopper.

Fluidization

How It Works

Fluidization occurs when a mixture is suspended in a gas or liquid. In batch mixing processes, this material segregation problem most commonly occurs in plain old air. When a mixture is aerated (which may occur simply through free falling), the finer, less dense particles retain air and move towards the top of the mixture, while the larger, denser particles which didn’t absorb air sink.

What You’ll See

This material segregation problem in batch mixing commonly occurs in powder ingredients. If the powder does not bind sufficiently to another material, it will separate through fluidization if aerated or allowed to free-fall. With all the powder at the top, the uniformity and product quality can be compromised. Fluidization, combined with the previous two material segregation problems, also poses workplace safety risks from powder explosions and respiratory hazards as large amounts of powders separate into the air.

Trajectory Segregation

How It Works

Unlike the previous three material segregation problems, trajectory segregation occurs through horizontal movement. This occurs by two different principles. In a fluid mixture, trajectory segregation occurs through a relationship between particle size, density, viscosity, and velocity. Particles with the same viscosity and velocity, but different size or density will travel at different rates. This causes the mixture to seperate.

In a solid mixture, trajectory segregation occurs through friction. Finer materials with more surface area and therefore more friction move slower and will deposit closer to the end of the horizontal path. Larger materials with less surface area and less friction move faster and deposit further.

What You’ll See

This material segregation problem in batch mixing processes commonly occurs in ribbon blenders and conveyors or chutes. In ribbon blenders, the particles in a fluid suspension separate in the blender due to their differing size or density. In chutes and conveyors, friction causes the materials to move at different rates, creating a pile of fine materials near the end of the chute and coarse materials further away.

Material Segregation Solutions In Batch Mixing Processes

Ingredient Testing

In order to solve material segregation problems in batch mixing processes, the materials and processes must be well understood. Knowing the particles’ density, size, mass and other properties can help you predict how the materials will segregate. While designing process automation equipment, ask your manufacturer if they will conduct ingredient testing for angle of repose, sifting capacity, and other issues. With this information, your manufacturer can design equipment to prevent material segregation problems in batch mixing processes.

Material Segregation Testing

When testing material segregation in existing batch mixing processes, make sure to test accurately. Remember that material segregation in the end product will also affect any tests on the end product. Use a sample thief or a riffler to get samples that accurately represent the whole, and see where and to what extent problems exist in the process chain. Remember to check the coefficient of variation at different points of the process, not just at the mixer, to see if your downstream process is causing segregation.

Feed Bin Design

Angle of repose problems are most commonly caused by an improperly designed feed bin and hopper. Using a mass flow hopper designed according to the materials’ angle of repose will prevent the mix from dispensing unevenly. In general, an angle of at least 70 degrees is recommended. Hopper inserts or low-traction coatings can also be used.

Mixing And Blending

Mixing and blending processes should be carefully selected and placed. The wrong mixer or blender can actually cause materials to separate through trajectory segregation. If the mixer is placed too early in the process, the materials may simply resegregate downstream. Placing a mixer immediately before dispensing can mitigate segregation effects.

Coating

Many material segregation problems only occur in free-flowing mixtures. Adding a binder can stop problems like sifting, though other problems like sticking and clogging should also be considered.

Agitation

Aeration or vibration can remix some materials, particularly if they are separated in a silo or hopper. With both of these methods, be careful not to introduce sifting or fluidization.

New Materials

More drastic differences between materials cause more drastic material segregation problems in batch mixing processes. If your materials are especially coarse, or a large variation between particle size and density exists, talk with your supplier about material quality. Or, consider additional processing to a diverse material; would adding another process for more material uniformity prevent material segregation problems? Would it be cost-effective?


Material segregation may occur in areas that operators never see. This means you might only see the results in low product quality or contamination. You might also experience repeated processing problems and machine errors due to clogging, flooding, low flow and other issues. If you’ve noticed these issues, assess your batch mixing processes and see where material segregation problems may occur. Once you identify the problem, a simple fix may increase product quality significantly.