Developed to meet both gravimetric and volumetric weighing needs, the PosiPortion feeder brings increased precision to processes in the food industry. Engineered with advanced technology, it streamlines operations with pinpoint accuracy, delivering consistent, controlled performance that enhances throughput and quality across every application.

The PosiPortion is tailored to address the challenges of feeding bulk materials prone to bridging or degradation. Its flexible-wall hopper ensures dependability in flow performance, greatly reducing the risk of production interruptions. External paddle agitators maintain material quality by preventing segregation, degradation, and agglomeration, securing recipe integrity and supporting consistent product quality. These features make the PosiPortion ideal for precise dosing applications requiring consistent quality.

Built within a structural tubing frame, the PosiPortion delivers robust strength and stability, making it easy to integrate into larger process systems. Quick-coupled components enable fast disassembly and cleaning, minimizing downtime and simplifying maintenance routines for operators. Featuring high accuracy feeding capabilities, the PosiPortion ensures consistent and precise material delivery, helping maintain strict standards and process control. It handles various materials efficiently, processing fine powders to large granules with ease.

To help customers achieve peak performance, Hapman offers material testing services that identify the ideal feeder configuration for each application. With this support, operators can optimize system performance and maintain consistent, reliable throughput. The PosiPortion feeding system represents a new benchmark in precision, safety, and operational efficiency, reducing downtime, improving process control, and delivering long-term production value.

About Hapman:

Hapman is a global leading designer and manufacturer of custom bulk material handling equipment for a variety of industries. With 80 years of experience, Hapman provides innovative solutions that improve efficiency and productivity in material handling processes. For more information about the PosiProtion® and to explore how Hapman can enhance your bulk material handling processes contact sales@hapman.com

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TubePro Tubular Drag Conveyor: Safe Material Transport for Wastewater Applications

Hapman featured the TubePro Tubular Drag Conveyor, purpose-built to manage the unique challenges of wastewater treatment. This enclosed system is engineered to prevent hazardous material emissions, helping facilities meet workplace safety and regulatory standards while transporting a broad range of materials with minimal dust and contamination risk.

Solidquid Liquid/Solid System: Streamlined Flocculant Addition

The Solidquid system was highlighted for its ability to automate liquid/solid ingredient mixing and flocculant dosing in wastewater treatment operations. By ensuring consistent blending with reduced manual oversight, the Solidquid system allows treatment plants to maintain dependable water quality while optimizing energy usage and process efficiency.

PosiPro® Feeder: Robust Performance for Demanding Environments

At WEFTEC, Hapman’s PosiPro® Feeder demonstrated its ability to handle challenging materials commonly found in wastewater applications. With a heavy-duty construction and customizable design, the PosiPro® ensures accurate product delivery and smooth operation, even in the most demanding processing conditions.

Customized Material Handling Solutions for Wastewater Facilities

Throughout the show, Hapman’s team discussed how these products combine to address the specific needs of modern treatment plants. Attendees visiting Booth 7232 left with practical insights into equipment that minimizes downtime, increases process reliability, and helps maintain compliance, all supported by over 80 years of Hapman’s industry expertise.

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At this year’s show, Hapman will exhibit its versatile TubePro Tubular Drag Conveyor, Solidquid® Liquid/Solid System, and advanced PosiPro® feeder. These products exemplify Hapman’s commitment to delivering efficient, customizable solutions tailored to meet the unique needs of each customer.

The TubePro Tubular Drag Conveyor is engineered for the unique challenges of the wastewater industry. Designed to efficiently transport a wide range of materials, the TubePro is ideal for conveying materials commonly encountered in wastewater treatment processes. Its fully enclosed, dust-tight design enables zero-emission operation and robust containment of unpleasant or potentially hazardous materials, supporting both regulatory compliance and a safer work environment for facility operators.

The use of the Solidquid® system in wastewater treatment for flocculant addition offers a range of benefits, including improved mixing, energy efficiency, low maintenance, and precise dosing. By automating and streamlining the chemical dosing process, Soidquid contributes to more efficient wastewater treatment operations, reducing the need for manual intervention and ensuring consistent water quality outcomes.

The PosiPro® is engineered to handle the most challenging dry bulk materials. Its heavy-duty design ensures dependable operation in harsh conditions, reliably delivering materials. With customizable screw and nozzle options, the PosiPro® can be adapted to various wastewater material handling requirements. Featuring bolt-on safety enhancements and configurable components, the PosiPro® enables tailored solutions to fit specific operational needs, reducing downtime and advancing efficiency in wastewater treatment environments.

Hapman will showcase advanced material handling solutions at WEFTEC 2025 with the goal to help customers optimize their processes with equipment that delivers efficiency, reliability, and quality.

About Hapman:

Hapman is a global leading designer and manufacturer of custom bulk material handling equipment for a variety of industries. With 80 years of experience, Hapman provides innovative solutions that improve efficiency and productivity in material handling processes.

For more information about how Hapman can enhance your bulk material handling processes, contact sales@hapman.com.

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Dosing feeders are designed to tackle these challenges head-on. This article explores the common issues encountered when moving difficult dry bulk materials and explains how selecting the right feeder features can mitigate these problems, improve process efficiency, and enhance operational safety.

Common Challenges When Handling Difficult Materials

Clumping and Material Bridging
Materials like flour, cocoa powder, and sugar often clump and bridge within hoppers, particularly when exposed to moisture or pressure. This behavior disrupts feeding consistency, leading to uneven distribution and process interruptions. For industries such as food production or chemical manufacturing, these inconsistencies can significantly affect product quality and throughput.

Inconsistent Material Flow
Achieving a uniform flow rate is essential for production environments. However, materials with varying densities or adhesive properties, such as powders with high fat content, can create blockages that disrupt feeding. These interruptions lead to operational inefficiencies and complications in downstream processes.

Abrasive and Corrosive Wear
Handling abrasive or corrosive materials poses a significant challenge to feeders, often leading to rapid equipment wear and contamination risks. This issue is particularly critical in industries such as pharmaceuticals or food production, where hygiene and material purity are paramount.

Maintenance and Safety Concerns
Balancing ease of maintenance with operational safety is another challenge. Traditional feeders may require frequent disassembly for cleaning or repairs, increasing the risk of accidents and downtime. Ensuring compliance with safety standards while maintaining efficiency can be a difficult equilibrium to achieve.

Key Features to Address Challenges

Selecting a dosing feeder with specific design features can help overcome these obstacles. Here are some key considerations:
An internal agitation system is essential for breaking up clumps and preventing bridging. Agitators, driven by independent motors, ensure a consistent flow of material into the screw, even for sticky or cohesive powders. Adjustable agitation speeds allow operators to adapt to varying material properties, enhancing feeder versatility.

Dosing feeders with independent motor controls for the screw and agitator provide greater flexibility and precision. By adjusting these components separately, operators can fine-tune feeding rates to match material characteristics, reducing over-agitation and optimizing performance.

Stainless steel construction, particularly grades 304 and 316, offers excellent resistance to corrosion and is easy to clean. This durability ensures that feeders can handle abrasive materials and meet strict hygiene standards required in sensitive industries like food processing.

Volumetric and gravimetric feeding systems provide tailored solutions for maintaining consistent feed rates. Gravimetric feeders use weight-based measurements for high precision control, making them ideal for applications where ingredient consistency is critical, such as pharmaceuticals or specialty chemicals.

Modern dosing feeders incorporate enhanced bolt-on safety features, such as nozzles and bar grates, that reduce maintenance complexity while protecting operators. These features prevent accidental exposure to moving parts and ensure compliance with safety standards without compromising operational efficiency.

Customizable components, such as different screw types or extension hoppers, allow dosing feeders to handle a wide range of material properties. Whether it’s a progressive pitch screw for low-density powders or an extension hopper for increased storage, customization ensures optimal performance.

Best Practices for Feeder Operation

Beyond selecting the right feeder, following best practices is crucial to ensure long-term reliability and efficiency:

• Avoid Material Buildup: Regularly clearing hoppers of residual materials prevents clogging and contamination.
• Conduct Material Testing: Testing materials for bulk density, moisture content, and flow characteristics helps optimize feeder configurations.
• Schedule Routine Maintenance: Periodic inspections and cleaning ensure components remain in peak condition, minimizing downtime.

The Hapman PosiPro®: A Comprehensive Solution

Hapman’s PosiPro® dosing feeder is engineered to address the challenges of handling difficult dry bulk materials. Its advanced design features, including independent motor controls and robust agitation systems, ensure consistent material flow and adaptability for a wide range of applications. Constructed with durable stainless steel, the PosiPro® offers resistance to corrosion and ease of cleaning, making it ideal for industries requiring strict hygiene standards.

By incorporating bolt-on safety features and offering customizable components, the PosiPro® minimizes maintenance requirements while enhancing operational safety. Additionally, Hapman provides material testing services to help customers identify the optimal feeder configurations for their specific needs.

For industries seeking a reliable solution to the challenges of moving difficult materials, the Hapman PosiPro® dosing feeder delivers consistent performance, durability, and precision. By addressing these challenges head-on, operators can improve production efficiency, reduce downtime, and ensure long-term operational success.

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In our latest discussion, we delve into the critical role of feeders in managing challenging dry bulk materials. Ryan Coburn, Technical Sales Specialist at Hapman, shares his insights into the operational hurdles companies face when dealing with materials prone to clumping, bridging, or inconsistent flow—and how selecting the right feeder can make all the difference.

Key Challenges Identified:

• Material Inconsistencies: Sticky or high-density materials often cause irregular flow, leading to batch inconsistencies and increased scrap.
• Environmental Impact: Hygroscopic materials absorb moisture, further exacerbating flow problems and production reliability.
• System Design Mismatches: Using the wrong feeding method—volumetric vs. gravimetric—can result in inaccurate dosing and inefficient processing.

Volumetric vs. Gravimetric Feeding:

• Volumetric systems provide material over time based on volume—ideal where precision is less critical.
• Gravimetric systems measure exact material weight, offering tighter accuracy for batching and continuous processes.

Customizing for Performance:

• Tailored screw types and hopper configurations (e.g., conical vs. square) are essential for optimizing flow and minimizing material hang-ups.
• Customization supports the unique flow properties of each material, reducing downtime and increasing operational reliability.

Spotlight on the PosiPro® Dosing Feeder:
Designed specifically to address the nuances of tough materials, the Hapman PosiPro® offers:

• Integrated agitators to prevent bridging and clumping.
• Interchangeable screw designs tested in Hapman’s in-house lab to match each application.
• Tool-free disassembly for quick cleaning and reduced maintenance-related downtime.
• A conical hopper design to ensure consistent, obstruction-free feeding.

Ryan summarizes it best: “We built the PosiPro to eliminate the headaches our customers face with difficult materials—easy to clean, easy to service, and highly adaptable.”

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Industry: Food Processing, Snack Foods

Customer Profile: An industry-leading supplier specializing in nuts, seeds, and specialty snack products, providing premium ingredients to renowned names within the restaurant and snack food industries.

Challenge: The customer required a precise and consistent method to evenly distribute seasoning along the entire length of a horizontal tumbler. Their previous approach resulted in uneven coverage, impacting product quality and consistency.

Hapman Solution: Hapman implemented a customized model 281SV PosiPortion feeder, featuring an 8 ft³ extension hopper and an extended-length, slotted discharge nozzle designed specifically to span the full length of the horizontal tumbler.

Goal: The primary objective was to achieve uniform and controlled seasoning dispersion within the customer’s existing horizontal tumbler, ensuring consistent product quality and enhancing efficiency.

Integration Process: The integration involved mounting the Hapman PosiPortion feeder on a tailored stand, positioning the feeder nozzle precisely at the required height for optimal insertion into the horizontal tumbler. The feeder’s screw and slotted nozzle were meticulously sized to guarantee even distribution of seasoning across the entire length of the tumbler, effectively addressing the customer’s production challenge.

Outcome: The precise control and consistency provided by the Hapman feeder significantly improved seasoning distribution, ensuring product uniformity and enhancing overall operational efficiency for the customer. This tailored solution has strengthened their position in supplying high-quality snack ingredients to their notable clientele.

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Improving efficiency in batching and blending is simple in concept. All you need to do is produce the most possible product using the least possible resources. That’s easier said than done, but by identifying challenges and applying engineering know-how you’ll find that small steps can lead to great strides in your batching and blending operations.

Efficiency improvements can start small with a single improvement in your process or a design upgrade to a single piece of equipment. A single “win” can get you in the race, be it a way to speed a machine’s changeover, block a material flow obstruction, improve metering accuracy, or remove a bottleneck. Each success leads to another. No matter the scope of your efforts or applications involved, you’ll likely confront some or all these challenges in engineering a solution for you, your process, and your customers:

1.           Inefficient batching process

2.           Poor recipe control

3.           Loss of material

4.           Labor/experience shortage

These challenges are interrelated, and we will discuss them — and solutions to overcome them — below.

1. Inefficient batch processing

Batch processes in any industry share many common efficiency challenges. Inefficient batching can be both the cause and result of production bottlenecks, delays between process steps or machine hand-offs, and overall waste in all its forms.

On the other hand, equipment and process design that addresses the right problems can unlock new levels of process performance. For example, adding a lump breaker can eliminate agglomerations in small-volume metering, or a feeder upgrade can improve dosing accuracy by improving the flow of sluggish granules or powders. (Related reading: Turn Batching Challenges Into a Competitive Advantage.)

In other cases, efficiency can be optimized by rethinking how materials can be moved from Point A to Point B within the constraints of the physical realities of your facility. For example, not all buildings can accommodate mezzanine levels for filling or conveyors to transport materials long distances. In such cases, alternative approaches can provide an efficient solution, as Lawrence Foods, a manufacturer of premium bakery ingredients, learned.

The company needed to pre-weigh bulk bags of powdered sugar from incoming 2,200-pound bags and create two 1,000-pound bags for downstream processing. However, the facility lacked sufficient ceiling height to unload the bulk bag directly into a filler in a single, vertical common frame.

The solution took the form of an integrated system using side-by-side frames incorporating a bulk bag unloader, a 15-foot screw conveyor, and a bag filler to create the 1,000-pound bags of powdered sugar. Weight and process controls ensured accuracy and filling directly onto a pallet enabled easy fork truck removal and transport to production. As a result, the company gained an engineered solution to overcome challenges due to space constraints, bypassing the need to modify its facility. Additional features aid efficiency, safety, dust control, ergonomics, and flexibility for future changes. (Learn the details of Lawrence Foods’ installation by reading  Unload, Convey, Fill, Repeat.)

2. Poor recipe control

Recipe control picks up where batch management leaves off. A lack of comprehensive controls, from accurate measurement to connected digital controls, can lead to many sources of process inefficiency. These include errors caused by manual keying-in recipe parameters, lost time, production bottlenecks, reduced productivity, and increased costs. The solution to these and other weaknesses is digitalization, which enables the additional benefit of recipe management software tools for analyzing accuracy, quality, and other efficiency-related factors.

Many companies rely on manual data entry, which leads to quality deficiencies, product scrap and rework, inefficient labor, and downtime. This can result in losses of $1,000 or more for a 2,000-pound batch. We have seen companies with more than 50 recipes whose operators manually key-in parameters based on information from disparate sources such as clipboards and spreadsheets. In some cases, a vital piece of missing information caused delays, and the lack of efficient tracking documentation during and after processing compromised proper quality control and slowed efforts to improve processing.

Today, process control technology addresses such problems with long-established machine and process control technology. An operator panel connected to the programmable logic controller (PLC) running the equipment stores all recipes. These can be loaded for processing with little more effort than pressing a touchscreen of a menu selection (or even scanning a QR code for a recipe). Improvements can enhance process consistency, product quality, productivity, waste reduction, and more.

Operator interface software also provides alerts and tracks process data for additional uses. These include tracking and trending data for one or more pieces of equipment locally; or using a central workstation to track key performance indicators (KPIs) across a fuller set of operations. Process data can also be presented to multiple users in different roles for different reasons: plant initiatives, vendor remote maintenance services, corporate data analytics, compliance reporting, or any number of good, approved uses. (Click to read an overview of related Controls & Automation solutions.)

3. Loss of material

Material losses can occur anywhere in conveying, handling, and processing — from spills in manual or mechanical handling operations to dust from improperly sealed conveyors. In terms of equipment, bag filling is perhaps the most common source of costly material losses due to excessive overfilling, or product giveaway, to ensure compliance with weight requirements.

In one case, a company was experiencing losses with small, 320-ounce batches of a valuable material costing $1,200 per ounce. To ensure it met weight requirements, the company was overfilling and giving away profits, sometimes by more than two ounces per batch. Once the company identified the problem, the company upgraded to new, more accurate loss-in-weight feeders, precisely controlled overfilling to within 25 grams, and saved approximately $2,000 on each batch.

Loss-in-weight, or gravimetric, feeders are generally preferred for such quality-critical applications, however, volumetric feeders can be used for accurate filling at higher speeds. However, this choice is unlikely if your material’s bulk density varies such as when a hygroscopic material reacts to humidity and/or forms agglomerations. (Related reading: Volumetric vs. Gravimetric Feeder Operation).

Competitive realities typically lead plants to integrate multiple equipment assets with custom engineering and, increasingly, digital automation. One company used both techniques to more efficiently meter controlled amounts of four powdered ingredients. The project included several components including bulk bag unloaders, a dust collector to prevent a separate waste stream and lost product; pneumatic bag agitators to fluidize the material; and a lump breaker to tackle any agglomerations. From there, the powders were ready for loss-in-weight screw feeding

to a slurry tank for processing. The result was that the conditioned materials contributed to the optimal downstream mixing process performance. Process controls and user-friendly monitoring tools further eased the job and reduced labor requirements. (Click for related reading on Bulk Bag Unloading, Pneumatic Conveying, and Material Metering.)

4.Labor/experience shortages

Properly engineered mechanical and automation solutions provide additional benefits for productivity to reduce labor costs and overcome the difficulty of finding and training skilled labor.

Automation brings positive impacts in many ways to overcome labor and productivity challenges. It’s most visible to operators in the form of user-friendly interfaces that ease

tasks and save time. The benefits are also critical for operational continuity as experienced workers exit the workforce, taking their experience and knowledge with them. It also reduces companies’ requirements for up-front training and everyday labor requirements.

When discussing the company that used automation to improve recipe control (Challenge No.2 above), that operation used to require two operators: one to load the batch, and another to manage the recipe. After the automation upgrade, only one operator is needed for that processing station.

Digital automation together with mechanical design features both contribute to labor savings. Material handling equipment that is easy to operate alleviates environmental concerns and promotes health and safety in a processing facility in addition to solving labor challenges. Likewise, today’s equipment designs feature time-saving features that offer easy access for maintenance operations, quick clean-in-place with easy disassembly for cleaning, quick-release features, and more. In turn, digital automation makes it easier for one person to manage more parts of a process, which is essential for companies relying on fewer workers.

In the chemical industry, processors face the ongoing challenge of effectively mixing solids and liquids to blend slurries while minimizing labor (among other factors such as floor space, dusting, and energy usage). This traditionally entailed multiple workers and labor-intensive operations. Examples include workers climbing ladders and opening equipment doors with ingredients/materials in hand; controlling mixer agitators; and incurring risk in potentially caustic or hazardous environments. Today, solutions are available such as sealed conveyors

(e.g., pneumatic, tubular, helix) and automated bag-handling and processing equipment; valves on bag-handling equipment, and self-contained batching/blending equipment offer enhanced worker safety, labor savings, and high throughput. (Learn more by reading Pre-Mix Solutions and Slurries – Effectively, Economically, and Safely.)

Additional technologies offer greater cost-effectiveness and labor savings than ever, including labor-saving automated storage and retrieval systems (ASRS) and autonomous mobile robots (AMR) that shuttle materials across warehouses and production areas. (Learn more by reading: Using Material Handling Automation to Improve Efficiency.)

Efficiency: It’s not a sprint, it’s a marathon

There’s no single solution for any given material handling, batching, or blending application. Significant efficiency improvements require varying degrees of customization to meet your material, processing, and business goals. Asking the right questions of your internal team and your external partners can take you closer and closer to your project’s finish line — and beyond, because the race toward greater efficiency and competitiveness is an ongoing journey.

When it comes to selecting a partner to provide equipment, systems, and engineering services, it’s most important that they have the breadth of expertise and deep knowledge of your needs, This, in turn, can go beyond solving problems to open new opportunities and benefits spanning design, reliability, serviceability, and much more.

About Hapman

We are a global manufacturer of standard and custom bulk material handling equipment and complete material handling systems, with locations in North America, Europe, and Asia. Our process has been proven across 12,000 applications across all major bulk material processing industries in every US state and 56 countries worldwide.

Whether your equipment needs are standard and straightforward or elaborate and controlled, Hapman’s team of applications experts will assist you with any level of support.

Our company culture is driven by new ideas, fresh thinking, and continuous improvement. That’s why Ideas that Move is more than a slogan. It’s an integral part of who we are. We seek to acquire and share new knowledge, build on our experience, collaborate with you and other industry experts, and push perceived process limitations — all while fully embracing disciplined engineering and quality material handling practices.

At Hapman, we are more than a material handling systems provider. We are your business partner. We are dedicated to achieving your highest level of trust and satisfaction and earning your confidence in our commitment and expertise.

Take the next step towards innovation and excellence. Contact our experts at (800) 427-6260 or sales@hapman.com for a personalized consultation.

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Whether you work in the manufacturing or production industry, you need the right feeder system to regulate the flow of bulk materials into your company’s machinery. Feeder systems are typically used in conjunction with other types of material handling equipment, including conveyors, lump breakers, and mixers, to name a few.

There are two basic variations of feeder operations known as volumetric and gravimetric. Understanding the differences will help processors select and implement the best type of equipment for their application needs.

Volumetric Feeding

The principle of feeding volumetrically starts with keeping the auger full. We know the volume that is displaced by the auger in the nozzle, the pitch of the auger, and the rotational speed. So an auger with a one-inch pitch that is turning at 100 revolutions per minute will move the volume of material forward 100 inches per minute. Varying the rotational speed of the auger provides linear control of the volume of material being dosed.

This method provides precise, consistent, accurate, and repeatable metering with linear control with materials that are considered “good” powders. A good powder has a consistent bulk density and manageable characteristics.

Volumetric feeding falls short of capacity requirements when a material has a varying bulk material density. Material that can vary widely in bulk density within a batch will struggle to meet dosing requirements with a Volumetric feeder.

Gravimetric Feeding

Gravimetric feeders (loss in Weight or gain in weight) provide a means for dosing discreetly by weight or metering continuously. It offers methods for recording and tracking materials used and can provide the means to run recipes for dosing systems.

A typical LIW system can cost double the initial purchase price of a volumetric feeder because it adds a scale, control module, and a microprocessor-based HMI. However, overall control, record keeping, and accuracy gained with the Gravimetric feeder are necessary for some applications regardless of the overall cost.

Choosing the right gravimetric feeder or volumetric feeder for your application is important to the cost and quality of the output of your facility. The basics are outlined here, but speaking with a bulk material handling expert to design the optimum system for your application is important to achieving quantifiable savings in the long-run.

Benefits of a Feeder from Hapman

Feeder systems from Hapman are designed for a wide range of materials. A few of the benefits to purchasing Gravimetric feeders or Volumetric Feeders from Hapman include:

• Measuring with precision
• Achieving superior volumetric performance
• Cleaning easily
• Design versatility
• Maintaining material quality
• Ideal for silos and surge hoppers
• Getting the strength and stability of structural tube-frame construction with the ability to support large hoppers on ancillary equipment

If you need a feeder for your applications, don’t hesitate to contact the experts at Hapman for more information. Hapman’s line of Volumetric and Gravimetric Industrial Feeders provide you with the accuracy and efficiency that you need in your dosing application. Whether it be the Flexible Wall feeder or the U-trough Screw Feeder, Hapman’s wide variety of industrial feeders will provide you precisely what you need, when you need it.

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CHALLENGE

A screw feeder is commonly used to meter flow in powder processing applications because of ease of use, low maintenance, and material integrity without degradation. The relatively simplistic equipment design of the screw feeder can be misleading when selecting and specifying motor and auger sizes.

Sizing feeders with the proper motor and auger for optimal processing is not as straight forward as matching the capacity of the auger/ feeder to the material. Horsepower requirements can vary significantly with different materials. As the auger diameters increase, the differences in material can result in a dramatic increase in horsepower requirements. This is because the surface area of auger and material contact increase dramatically.

Please download the full document for equations used to calculate the proper motor and auger size for your specific application, as well as supporting figures.

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Based on the above specifications, the flexibility of an eductor system proved beneficial for several reasons. An eductor type mixing system can be used on a batch or continuous basis. A continuous process can control the concentration based on outside requirements, such as pH, conductivity, flow, pressure, temperature, and rate of reaction.

A batch system can also be adjusted from one batch to another varying the concentration of the solution or slurry (see Figure 2). The bulk bag unloader was included in the system and put on load cells to correctly measure how much material was delivered over time. To help EP Minerals design an optimal system for their application, Hapman first established a materials rate to determine the most efficient size for the feeder and the eductor. The bulk density of the diatomaceous earth was stated as 16 lbs/ ft3. The rate was determined to 22 ft3/hr to successfully achieve a concentration of 7.15%. The following steps were used to determine feeder and eductor size:

1. Determine the feed rate required (22 ft3/ hr) and select the feed rate, (see Table 1).
2. Select the maximum discharge pressure required (5 psig). NOTE: Using the standard educator, the maximum pressure drop allowed is 5 psig.
3. If the feed rate is in excess of 24 ft3/ hr, or the maximum discharge pressure is not acceptable, then find the appropriate multiplier and divide that multiplier by the actual rate, (see Table 2).
4. Use the multiplier to find the required liquid flow rate.

The data from the EP Minerals application is shown in tables 1-3. The selected eductor is 1”, to meet a feed rate of 10 gpm, with a not-to-exceed 5 psig back pressure on the discharge of the eductor. Because of the abrasiveness of diatomaceous earth, stainless steel construction was selected for the system.

Next, the auger size of the feeder was determined, based on feed/dosing rate, (see Table 3.). An appropriate nozzle was then selected to match the screw.

The final step was to determine if the system should be controlled by volume or by weight. Because of the application’s need for accuracy, a weight-based system was selected. Though more expensive and complex than standard volumetric controls, a weight-based system allows for ± 0.5% accuracy. A volumetric control has an accuracy margin of between ± 2% to 5%, and would not have worked with this application’s process specifications.

SUMMARY

This case study demonstrates how an eductor-based mixing system can effectively handle a wide range of materials, and how overall process optimization can be achieved. In addition, the eductor mixing system offers increased efficiencies over a conventional system of mixing by allowing solutions and slurries to be made on demand – as opposed to pre-mixed in large holding tanks. Another important benefit is the system limits exposure to operators, and mitigates issues of delivering solid material in a large vapor space.

The design flexibility of an educator-based mixing system offers a high level of customized configurations. This allows process design engineers the opportunity to efficiently and effectively meet the demands of a facility’s many different raw material handling needs.

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