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 2: Ingredient System Planning Pitfalls For Micro-Ingredient Scales, Conveyance and Controls

In the previous post, we discussed common problems that can occur with the start of a micro-ingredient system, including ingredient bins and feeders. The latter half of the system is generally more complex, and more issues usually arise here. In this blog post we’ll cover micro-ingredient scales, conveyance and controls, and what you can do to design the most effective system.

7 Ingredient System Planning Pitfalls for Micro-Ingredient Scales, Conveyance and Controls

1. Miscalculated Scale Error

To find the right scale for your formula, you’ll need to to add all of the possible ingredients and the quantity of each. This will tell you the size of the scale that you need, but you also need to consider the margin of error. If the scale can accurately measure within +/-5 grams and the required accuracy of the formula is 1%, you won’t be able to measure 10 grams of a micro-ingredient, because the possible error will be 50%.

Reduce error and improve efficiency. Download the Engineer’s Guide to Weighing and Batching >

2. Miscalculated Resolution and Accuracy

The scale resolution is also important to consider. The minimum increment a scale will display is generally one 10,000th (1/10,000) of the total scale capacity. So, a 100 kg scale would display in increments of .01 kg. If this isn’t suitable for your accuracy measurements or your feeder output, you may have to reconsider your scale capacity. Using the 100 kg scale example, if your feeder puts out more than .01 kg of material a second, and the control system can only time shut-off to within a second, the system will be inaccurate by this amount.

3. Incorrect Scale Hopper Design

The type of materials, the available height in the facility, and the downstream conveyance must all be considered to design the right scale hopper. Limited vertical space in some facilities can prevent the use of some types of scale hoppers, like a conical scale. Use of a roll-over tub with a slide gate may be a better choice then for facilities with lower ceilings. However, since a roll-over tub discharges material all at once, this will only work if the downstream conveyance or next process can accommodate all materials. If your materials are better suited to pneumatic conveying, like fine powders, then a conical scale hopper will transition into the pneumatic system easier. If you prefer to skip conveyance and discharge into the mixer, a conic scale hopper or roll-over tub will work.  

4. Cycle Time Doesn’t Match Mixer Time

For the micro ingredient system to reach maximum efficiency, the cycle time of each ingredient—including the time it takes for the materials to fill, settle, and discharge—must align with the batch mixing time of all ingredients. If, for example, it takes 30 seconds to fill, measure and discharge each ingredient in a 10 ingredient mix, it will take 300 seconds total to weigh the material in the scale so the mixer could be waiting for the weighing process to complete. If the mixing time only takes 150 seconds, it will be idle half the time. To solve this problem and reach maximum efficiency, you might use two scales, each with 5 ingredients.

This will require some careful calculations, as the fastest cycle time time, average time, and slowest time will vary. The times for each ingredient will also vary by density and amount. Be sure to allow some room for timing variation.

5. Vibration Interference

Vibration can be used  i in a micro ingredient system to prevent bridging, ratholing, and other no-flow conditions in bins and hoppers. It’s also desirable to keep the different parts of your system close together to prevent the need for extraneous conveyance. However, if scales are placed too close to vibrating equipment, it can cause fluctuation of the scale reading. If the scale readings are dampened to eliminate the fluctuating readout, the scales may appear to be working normally and showing normal readouts, but the process duct may be weighing  incorrectly. In this case, interference through vibration may be to blame.

6. Conveyance Contamination

The most efficient type of conveyance is through gravity, however this is not always an option, especially for facilities with low vertical clearance. In these cases, you might use pneumatic, belt or drag conveyors. When using belt or drag conveyors, it’s important to prevent contamination from one batch to the next. Materials, powder or coatings that become stuck on the belt can not only damage the belt and cause it to stick or slide, but can also contaminate new material. Use scrapers or brushes to prevent material build-up on the conveyor. It may also be advisable to run a flush material through the conveyor to clean off the residual material.

7. Slow or Damaged Controls

The micro ingredient system cannot function properly without direction from the right controls. The control system, whether you are using a PLC or PC, should be able to sample each scale quickly and stop feeders without a long delay, otherwise overfilling will ruin the batch. The system should also be powerful enough to control all scales, feeders, mixers, metered liquids, and other functions with accuracy. Finally, the control system should be enclosed if dust, moisture, heat, vibration or other hazards are a concern. Often, a PC will be used outside the factory floor for extra processing and data storage power, and communicate with a more durable PLC directly controlling equipment.  

With different ingredients and recipes there are different challenges for each part of the micro ingredient system. If you have questions about the needs and capabilities of your micro ingredient system or ingredient automation system, take a look at the Engineer’s Guide to Weighing and Batching. This guide addresses the issues from this and the previous blog post in more detail, as well as many others not discussed here.

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.

7 Ways Feed Mill Automation Drives ROI

feed mill automation ROI

In any industry, automation is based on goals: solving problems, minimizing risks, and reducing costs. The same is true for feed mill automation. There are a number of ways that feed mill automation can improve the end product and solve or reduce problems throughout the operation. Though some facilities may automate all processes at once, step-by-step automation is also a viable option. Feed mill automation can drive ROI in the following ways, and many of these benefits may occur simultaneously, depending on which process or processes you choose to automate.

7 Ways Feed Mill Automation Drives ROI

1. Reducing Labor Costs

Automation not only ensures that tasks are completed consistently, but also eliminates the need for manual operation. Repetitive tasks no longer require physical labor, and free up manpower for more sophisticated and important jobs. Automation can also protect workers from safety risks, either by removing them from dirty or dangerous environments, or by putting reliable safety controls in place.

Reduce error and improve efficiency. Download the Engineer’s Guide to Weighing and Batching >

2. Enhanced Production

Enhanced production is one of the most common factors driving ROI in feed mill automation. With the right design and maintenance, automation can streamline processes and remove the need for breaks and pauses. The right machines can also work at a faster rate.

3. Measureable Regulatory Compliance

Feed mill automation can simplify regulatory compliance for rules like the Food Safety Modernization Act (FSMA), among others. Track and trace is an important part of FSMA compliance, but can be difficult to accurately implement without systematic controls. Tracking lot numbers manually not only introduces error, but takes up workers’ time and energy. Lot tracing can easily be automated, and it will greatly improve accuracy. With a reliable, automatic system in place tracking where your ingredients came from, what they went into, and where the product ultimately went, you can reduce liability and meet compliance requirements with minimal costs.

4. Consistent Testing

To prevent moisture, toxins and other substances from ruining ingredients and the finished product, proper sampling and testing is essential. With automated sampling and testing, you can gather uniform, accurate information about ingredients and products. Detecting excessive moisture in ingredients from the start will prevent product from being contaminated, and allow you to hold suppliers accountable for defects. Detecting aflatoxins and other harmful substances in ingredients also reduces liability, as well as product loss. With feed mill automation for testing and sampling combined with automated track and tracing, any problems with ingredients or products can be accurately recorded.

5. Reducing Batching Errors

Batching is one of the most common areas for feed mill automation, and often offers the highest initial ROI. By automating your batching and mixing processes, you can substantially reduce error and variation. When your recipe is programmatically controlled, corn, soy, vitamins, minerals, enzymes and other additives are each exactly measured. With an easily re-programmable controller, you can even change the recipe without significant downtime.

6. Automatic Routing

Automation of the batching process is usually the first section of the feed mill to be automated, but the addition of downstream routing of material can enhance the payback of the system. If the system has to wait for the operator to setup the routing of material to the downstream packaging or load-out, then valuable production time can elapse while waiting for a route to be selected.

7. HACCP

Through most zones, feed mill automation makes hazard analysis and critical control points easier to regulate and monitor. By gathering more data, more often, with less manpower required, you can get holistic, up-to-date information about your production line. You can also eliminate risks altogether by automating repetitive tasks with a high risk of human error. Automated regulation ensures that critical control points are monitored at the same time, in the same way, with no exceptions.

Before starting or continuing feed mill automation, plan and design your system carefully. Conduct ingredient testing to ensure that the system is suitable for your recipe, and be sure to factor any maintenance costs into your ROI calculations. With the right system automating the right process, you can realize a return quickly and eliminate risks at the same time.

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.

4 New Food and Workplace Safety Regulations For Grain and Pet Food Manufacturers in 2018

workplace safety regulations for grain and pet food 2018Recent changes in food, environmental, and worker safety have caused many grain and pet food engineers to take another look at their manufacturing facilities. Some of these rules are newly changing, others are just recently subject to penalties for noncompliance and all deserve adequate attention. For greenfield sites or renovations, appropriate attention to food and workplace safety regulations from the outset will save thousands in fines down the road. No matter the situation for your grain or pet food facility, we’ve put together four key safety regulations for manufacturers to know in 2018.

4 New Food and Workplace Safety Regulations For Grain and Pet Food Manufacturing

1. Amended OSHA Slip and Fall Regulations

Violations exposing workers to fall or slip accidents occupied three of the top ten most common violations of workplace safety regulations in 2016, including non-compliant ladders, scaffolding, and fall protection equipment. Seeking to remedy these preventable accidents, OSHA amended Regulation 29 CFR 1910 Subpart D, which regulates safety requirements for walking and working surfaces, in 2016. Many of these provisions are already in effect, and several others are required as of November, 2018.

Grain and pet food manufacturers who are building up instead of out, as well as grain elevators and feed storage facilities should pay particular attention to these workplace safety regulations, some which are already enforced with fines.

  • Ensuring exposed workers are trained on fall hazards (required May 17, 2017)
  • Ensuring workers who use equipment are trained (required May 17, 2017)
  • Inspecting and certifying permanent anchorages for rope descent systems (required November 20, 2017)
  • Installing personal fall arrest or ladder safety systems on new fixed ladders over 24 feet and on replacement ladders/ladder sections (required November 19, 2018)
  • Ensuring existing fixed ladders over 24 feet … are equipped with a cage, well, personal fall arrest system, or ladder safety system (required November 19, 2018)

2. NFPA 652: New Standards on Combustible Dust

The dangers of combustible dust are no mystery to pet food and grain manufacturers. Between 2007 and 2016, 91 explosions occurred due to grain dust alone. In 2016 the National Fire Protection Association’s (NFPA) Standard 652 outlined best practices for evaluating risk and protecting against dust and powder fires. The new standard’s biggest departure from previous standards is the development of Dust Hazards Analysis on existing or future processes.

Though OSHA recently abandoned expanded regulations on combustible dust due to regulatory reform under the Trump administration, experts remind businesses that workplace safety regulations on dust hazards exist under a number of other OSHA standards. Project managers and engineers can manage their combustible dust risk in a number of ways;

  • Proper machine maintenance to eliminate dust leaks.
  • Separating feed mixing processes into different buildings to manage risk and loss.
  • Conducting thorough risk analysis to understand threats.
  • Utilizing temperature monitoring sensors to prevent sparks.
  • Installing dust monitoring and dust collection systems suitable for your facility and particulates.

3. OSHA New Respirable Dust and Crystalline Silica Standards

Combustible dust laws are not the only dust-related workplace safety regulation grain and pet food manufacturers should be aware of this year. OSHA regulations governing respirable dust particles require workers to use personal protection equipment (PPE) and requires facility managers to measure, manage and keep levels within Permissible Exposure Limits (PELs). In 2017, OSHA amended regulations on exposure to crystalline silica, one of the most common types of harmful respirable dust. When crystalline silica dust is inhaled it sticks to the lungs, causing scarring and irreparable damage.

Though these workplace safety regulations are most important in the construction industry where workers are regularly exposed to hazardous crystalline silica levels, some steps in raw material feed processing, particularly cleaning, can pose respirable dust hazards. To mitigate exposure, take the following precautions;

  • Know who is exposed, where, and what causes exposure.
  • Measure and monitor harmful or nuisance dust levels.
  • Make PPE available and cultivate a culture of safety compliance.
  • Utilize dust collection with the right air intake and appropriate filtering.

4. USDA and FDA: Food Safety and Modernization Act

The USDA and FDA jointly oversee provisions within the Food Safety and Modernization Act (FSMA), including those regulating food and pet food. Signed into law in 2011, many FSMA regulations are only now going into effect and under enforcement.

FSMA covers nearly all food and pet food facilities. The FDA’s current FSMA guidance document developed solely for pet food “covers facilities that manufacture, process, pack, or hold food intended for all animal species including food-producing animals (e.g., livestock, poultry, and aquaculture species), companion animals (e.g., dogs, cats, horses, and guinea pigs), laboratory animals, and animals maintained in zoological parks. “Animal food” means food for animals other than man and includes pet food, animal feed, and raw materials and ingredients (see 21 CFR 507.3).”

Pet food and grain processors undergoing process development should be aware of FSMA regulations which concern the following cases, among others;

  • Animal foods with high oil content which resist microbial heat treatments.
  • Mycotoxins (Aflatoxins, Fumonisins, Deoxynivalenol, Ochratoxin etc.) proliferating in grains.
  • Pesticides on grains.
  • Plant toxicants (lectin, protease inhibitors, cyanogenic glycosides etc.)
  • Animal-specific nutrient deficiencies and toxicity hazards.
  • Process or product cross-contamination.
  • Metal contamination from process equipment.

Evaluating and planning for food and workplace safety regulations during project design and installation will prevent future problems. Working with an experienced and reputable process equipment manufacturer specialized in your industry will help to anticipate safety concerns and hazards specific to your facility.