Screw feeders are used across a broad range of industries and material applications. This article discusses ways to help mitigate some of the application issues that can occur when using a screw feeder.
Screw conveyors of all types are some of the most versatile bulk material handling equipment available. One specific type, the screw feeder, is used in a wide variety of applications for metering bulk materials. Screw feeders come in many sizes, lengths, configurations, and are constructed of a variety of materials.
Screw feeders are comprised of a screw mounted in an enclosed U- or tube-shaped trough or housing and typically are mounted to a hopper, bin, or silo at the start of a process. The screw is connected to a rotating drive shaft on one end and an end shaft on the other, with the screw supported by bearings at both ends.
Because the inlet of a screw feeder is flood-fed, as opposed to being control-fed like a standard screw conveyor, the units rotational speed and special flight spacing are crucial design factors in determining how much material will be delivered to the discharge with every revolution of the screw. Controlling the feedrate to the next process phase is critical in most processing environments, and screw feeders can be adapted accordingly. The following Q & A helps explain when a screw feeder can meet your specific needs.
A: This producer of nutritional supplements for animal feed needed a solution for an existing outdated and worn screw feeder. Design parameters of the application were for feed supplement densities ranging from 50 to 80 lb/ft3 and a feedrate capacity of 60 ft3/h. The unit had to move corrosive mixtures from a batch mixer and elevate them, at a 22-degree incline, for further processing.
Screw feeders are very capable of handling these types of abrasive and corrosive applications. However, using a screw feeder constructed of standard carbon steel or stainless steel components to move an abrasive material could result in rapid wear and lead to frequent maintenance and downtime, as well as high overall operating costs and premature equipment failure.
To combat the corrosive characteristics of these bulk materials, the new screw feeder was constructed of Type 304 stainless steel with hardsurfacing on the leading edge and periphery of the screw flights, as shown in Figure 1. Hardsurfacing involves applying a layer (or facing) of abrasion-resistant material, such as various combinations of chromium, tungsten, molybdenum, cobalt, or other sometimes exotic materials, onto a softer standard construction material such as carbon steel or stainless steel or other metal alloy base material. This can help combat the corrosive characteristics of the material being fed, improving screw longevity and reducing maintenance and downtime. The type of facing materials you use depends on component materials and your conveyed materials application requirements and operating environment.
A: A food product required a screw feeder system for railcar unloading that could handle bulk materials including grains, corn, soybean meal, and phosphate. Design parameters for the application included bulk densities ranging from 40 to 85 lb/ft3, and a feedrate capacity of 9,778 ft3/h.
To solve the problem, a variable-pitch screw feeder was located in a pit under the railway tracks and extended 46 feet, the full length of a railcar. Each screw section measured approximately 23 feet long with a center bearing support. The screws had a large-diameter center pipe, designed according to torsional and bending load calculations.
To accommodate the varying materials and provide maximum horsepower and torque for metering the heaviest bulk materials, two independent drive units, as shown in Figure 2, were mounted on opposite ends of the screw feeder with a center discharge point. Variable-frequency drives controlled the feedrate.
A: This wood products company needed to control the flow of wood shavings from a hopper to a bagging system. Wood shavings were interlocking and matting together, causing flow problems. The applications design parameters included material densities of 10 to 30 lb/ft3 and a feedrate capacity of 2,200 ft3/h. A twin-screw feeder with a custom pitch design was installed. Breaker bars, as shown in Figure 3, were added on each screw at the discharge to break up the interlocked wood shavings prior to discharge. In addition, each screw was powered by individual drive units and controlled by variable frequency drives. This way, the output speed of each screw could be varied independently to meet flowrate requirements and provide consistent material flow to the bagging system.
A: A mining services company needed four inclined screw feeders to meter crushed limestone from weigh hoppers to batch mixers. Special drive and trough designs can allow screw feeders to be operated in confined spaces. The screw feeders were designed with the smallest footprint possible. Special screw pitches with a close-tolerance fit to the tubular housings were used to increase conveying efficiency, as shown in Figure 4. Material density of 86 lb/ft3 and a feedrate capacity of 453 ft3/h were part of the design parameters. The drive units were mounted on the inlet (lower) end of the inclined feeders to save space. Custom-designed trough ends with adjustable shaft seals minimized material leakage and possible gearbox contamination in the confined-space arrangement.
A: The application required a solution for metering cocoa powder and coffee from storage bins into a blending process. Screw feeders were the solution. Constructing the units from Type 304 stainless steel, with all internal welds polished to a smooth 180-grit surface finish free of pits, cracks, and crevices, allowed the units to meet stringent food-grade FSMA specifications. The screw design promoted a controlled, metered feed to the blenders. Hinged covers with quick-opening clamps, as shown in Figure 5, provided access for easy maintenance and frequent cleanout. Installing food-grade shaft seals helped contain the food products within the feeders, further assuring standards were met.
A: This crop sciences company needed to meter a fungicide powder from a mixer to a dryer. The equipment needed to be easily cleaned with strong solvents for formulation changes. Failure to properly and completely clean the internal and external surfaces of the equipment could result in product contamination. Manufacturing from Type 316 stainless steel helped prevent corrosion from the cleaning solvents, and continuous welding of all internal screw feeder surfaces, as shown in Figure 6, helped eliminate all cracks and crevices.
Locating the screw feeder on an incline and using special close-tolerance, variable-pitch flights will help to increase conveying efficiency and improve the ability to clean the unit between batches. The drive was configured on the inlet end to conserve space. Air-purged shaft seals were used to prevent leakage of the fine powder.
A: For this mining operation, a heavy-duty screw feeder was needed to remove rock slag that continually spilled from a belt conveyor. Screw feeders constructed out of the appropriate-strength, sometimes exotic materials, or a combination thereof, can stand up to the most difficult environments. The applications design parameters included densities of 60 lb/ft3 and a feedrate capacity of 3,180 lb/h. Some of the rock slag measured as large as 6 inches. Installing a shaftless screw feeder, as shown in Figure 7, which allows open space between flights, works to help eliminate binding. Lining the screw feeder housing with a material like -inch-thick xylethon, an engineered plastic thats tough, dense, and self-lubricating, helped to maintain the feeders abrasion resistance and allowed the unit to hold up well even when metering abrasive rock slag.
A properly designed screw feeder can play a vital role in solving difficult screw feeder processing problems. Ask the important questions of manufacturers to ensure that they understand your specific plant process and have the engineering expertise to specify the right screw feeder for your application.
Bill Mecke, PE (800-543-6558), is president of KWS Manufacturing Company, Burleson, TX. He has more than 25 years of industry experience working directly with customers to solve their material handling problems and meet their needs. He earned his BS in mechanical engineering from Texas A&M University. For more information, visit www.kwsmfg.com.
Featuring a heavy-duty rotating drum that prevents surgesand provides a consistent material feed rate, the CP DrumFeeder cost-effectively layers light and heavy materials at theoutset. This drum is configured with bolt-on cast-chromiumalloy paddles, which helps break and fluff up the materialwithout shredding or tearing. The robust CP Drum Feederis very effective for commercial material, bagged material,and broken bales. This horizontal drum feeder dischargesonto a separate incline conveyor which feeds onto the presortline.
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Screw feeders are used in thousands of material handling applications and designed to meter bulk materials at a controlled feed rate. A standard screw conveyor is normally fed by another conveyor and the amount of material being discharged is directly proportional to the amount being introduced at the inlet. In contrast, the inlet of a screw feeder is always 100 percent or flood loaded and typically mounted directly to a storage device such as a hopper, bin, or silo. The amount of material discharged by a screw feeder is completely controlled by design parameters.
A hopper is typically square or rectangular in shape with sloped bottom and limited storage capacity. A bin is very similar to a hopper but with larger storage capacity. A silo is cylindrical in shape with cone or mass-flow bottom and large storage capacity.
Since the screw feeder inlet is flood loaded, the desired feed or discharge rate directly influences the design of the screw. A screw feeders discharge rate can be accurately determined by speed control and screw pitch design. Utilizing variable speed drives improves metering accuracy and can provide a wide range of feed rates. Pitch control is also a significant consideration in screw feeder design.
Basic Screw Feeder Design A screw is designed to move bulk materials from one flight to the next during every revolution. Therefore, if the screw is 100 percent loaded and the capacity is the same for each flight, new material can only be introduced to the first flight under the storage device, opposite the discharge. Consequently, it is not recommended to design screw feeders with uniform outside diameter and constant pitch because bulk materials will fill the screw from the rear of the inlet opening first, creating ratholing, stagnant material, and possible bridging of bulk materials above the screw feeder. Figure 1 shows the improper design of a screw feeder with uniform outside diameter and constant pitch. To draw bulk materials evenly across the full length of the inlet, each flight must increase in available volume as the screw progresses towards the discharge of the screw feeder. An effective and efficient system requires variable pitch, tapered outside diameter (OD) or mass flow screw design. Figure 2 shows a properly designed screw feeder.
Variable or Stepped Pitch The pitch of the screw varies from shorter to longer as the screw progresses toward the discharge of the screw feeder. With variable pitch, every pitch increases in length in the inlet section creating more available volume for the addition of bulk materials from the hopper. With stepped pitch, the flight pitch changes in increments. See Figure 3. For example, a stepped-pitch screw feeder may have 2 ft of 1/3 pitch, then 2 ft of 2/3 pitch in the inlet section.
Tapered Outside Diameter The outside diameter of the screw is tapered from the rear of the inlet opening to the shroud creating more available volume for the addition of bulk materials from the hopper. See Figure 4.
Mass Flow The mass flow design was developed by Jenike & Johanson and is a combination of variable pitch and tapered inside diameter. A tapered cone is located on the center pipe of the screw from the rear of the inlet opening to approximately the center of the inlet opening. Short pitch flights are mounted on the cone creating available volume for the addition of bulk materials from the hopper. Variable pitch is then added to the screw starting where the cone ends and continuing to the discharge. See Figure 5.
Screw feeders are available in a variety of sizes, lengths, configurations, and materials of construction. Most screw feeders are less than 20 ft in length because the use of internal hanger bearings is not recommended. Screw feeders can be composed of one, two, or virtually any number of screws. A screw feeder with multiple screws is considered a live bottom screw feeder. Figure 6 shows a twin-screw live bottom feeder.
a. Screw b. Trough c. Discharge d. Shroud e. Trough ends f. Drive unit g. Inlet h. CoverFeeder Shroud Screw feeders must be equipped with a shroud for at least two pitches beyond the inlet opening to prevent flooding of the bulk material past the inlet. The shroud is a curved cover that converts a standard U-trough into a tubular housing to prevent bulk materials from flooding past the screw. Extended shrouds, tubular housings, or short pitch flights can be utilized for accurate feed rate control when metering very free flowing bulk materials.
Screw Feeder Capacity and Speed The pitch of the last screw flight going into the shroud determines the feed rate of the screw feeder and is called the control pitch. The control pitch is typically less than full pitch. The capacity of the control pitch is calculated in cu ft/hr per RPM. The speed of the screw feeder can be determined by dividing the maximum screw feeder capacity in cu ft/hr by the capacity of the control pitch in cu ft/hr per RPM. Most screw feeder speeds are lower than standard screw conveyor speeds. For example, in heavy industrial applications, screw feeders typically operate at speeds less than 20 RPM. More torque is generated at lower operating speeds ensuring the screw feeder does not stall at start-up.
Screw Feeder Horsepower Requirements The horsepower and torque requirements for a screw feeder are much higher than a comparable screw conveyor. A screw feeder must start up with a flood loaded inlet and the head load weight of the bulk material in the inlet section. Bulk materials also tend to pack when under pressure in a hopper, bin or silo. As the bulk material density increases, so do the horsepower and torque requirements. The start-up horsepower and torque can easily be 2 times the normal operating conditions. It is recommended to consult with a manufacturer that is a member of the Conveyor Equipment Manufacturers Association (CEMA) for proper screw feeder design.
1. Flow characteristics of bulk material being stored and metered 2. Density of bulk material in both stored and metered condition 3. Maximum and minimum feed rate of process 4. Bulk material size with screen analysis 5. Width and length of screw feeder inlet opening 6. Overall length of screw feeder 7. Height of bulk material in hopper, bin, or silo
Multiple Diameter Screw Feeder/Conveyor Multiple diameter screw feeder/conveyors consist of a screw feeder with an extension conveyor. A smaller diameter screw feeder is located under a hopper, bin, or silo and is flood loaded. The screw feeder meters the bulk material to the larger diameter extension conveyor. When the bulk material reaches the extension conveyor the trough loading decreases and the bulk material is conveyed to the discharge. Hanger bearings are allowed in the extension conveyor as long as the trough loading is below 45 percent. Figure 8 shows a typical feeder/conveyor.
Live Bottom Screw Feeder Live bottom screw feeders are designed for use on large silos, bins, and hoppers with large discharge openings. The live bottom screw feeder utilizes multiple feeder screws in tandem to create a "live bottom" to prevent bridging. Bulk materials are metered and drawn out equally from the full width and length of the inlet opening. Live bottom screw feeders are used on bulk materials which tend to pack or bridge easily. Figure 9 shows a four-screw live bottom feeder.
Inclined Screw Feeders Inclined screw feeders meter and elevate bulk materials from hoppers, bins, or silos, and perform the same function as horizontal screw feeders. However, special care is required when designing inclined screw feeders. Figure 10 shows typical inclined screw feeders. Knowledge of the flow characteristics of bulk materials is extremely important for successful inclined screw feeder design. The angle of repose and flowability of a bulk material will determine the design of the screw feeder and the maximum angle of incline. Testing of bulk materials is required for all inclined screw feeders before a proper design can be established. Most CEMA-certified screw conveyor manufacturers have testing facilities for bulk materials and can test your bulk material before determining proper inclined screw feeder design.
Bill Mecke, P.E., is president and owner of KWS Manufacturing Company, Ltd, one of the largest screw conveyor manufacturers in the U.S. He has over 25 years of experience in bulk material handling. For more information, visit www.kwsmfg.com.
Rotary Feeders are used to control the flow of bulk material in powder, granular form, while the material flows through the vanes of the rotor, good air locking condition is maintained between the inlet and outlet of the Feeder.
For Precision Batching of Bulk Materials under repeatable accuracy and time control is offered with Main and Metering Screw combination having Quick Shut Off Valve with Coarse and Fine Dosing capability. Metering Screws are optionally provided with Variable Speed Drive Motors with Servo Ventilation Cooling Fans for operation under Super Fine Mode to achieve Critical Accuracy.
Special construction of Screw Flights Short, Tapered, Expanded Pitch are used for materials of High Compressibility Factors or Hygroscopic nature. Wear Resistant HARDOX or Hard Faced Flights are used for Abrasive materials. Several different types of Shaft Seals are used for Fine Powders.
The Main Screw are available from 150mm to 600mm diameter having capacity ranges from 500 kg / hour to 50,000 kg / hour. The Metering Screws having diameters 80mm to 150 mm diameter delivers precisely over 50 gm / minute to 5000 gm / minute under optional Variable Speed Drives. Both the Main & Metering Screws operate up to a preset Target of 90 95% of the Batch Weight in COARSE mode. The Main Screw then turns off with an optional cut-off Valve, shutting any accidental overflow of materials. The Metering Screw continues to discharge material in the FINE mode. For very high accuracy, the speed of the Metering Screw is further reduced by a Variable Speed Drive precision dosing in SUPERFINE mode for a small percentage of the Batch Weight.
Material Characteristics Testsare available for correct selection of Screws construction of various grades, optional Accessories in Stainless Steel, Carbon Steel like Flexible Connectors, Load Cells, Weighing Controllers, Dust Filters are available for complete Batching Operation.Conveyability Testswith Materials provided by the customer are available at our R&D Facilities.
Vibratory Feeders are driven by patented Electro Permanent Magnetic Drives for handling Fine Powders, Granules and Flakes from Storage Hoppers to process. Construction in Stainless Steel, Carbon Steel, special wear and heat resistant materials are available. The capacity can be controlled and interlocked by Digital or Analog Controls signals like NO/NC contacts, 0-10 VDC, 4-20 mA signals or Potentiometer. Integration with existing or future installations with PLC can be easily done for multiple Storage Hoppers or Packing Machines. Sanitary construction for Food Applications with Discharge Gates and Flow Diverters are available. Engineering and Performance of the Equipment are backed up by Eriez Magnetics, USA.
Various standard constructions of Tray Types Flat, Tubular, 90 V, Half Round are available. More than 12 different Models of High Speed Electro Magnetic Drives are available for Feeding of light, Bulky materials. Greater efficiency in Feeding, Filling etc. are provided which are ideal for use in conjunction with several types for Weigh Scales and Packaging machines.
Simple tuning mechanisms by replacement of easily accessible Glass Fibre tuning springs. Rubber Isolators reduce the vibration transfer to support structures. High deflection models provide up to (5mm) / (Low Frequency) 30 CPS for trouble free service. Various types of Solid State Controls are available with suitable enclosures. Special Sanitary Constructions are available for applications with Food Production & Packaging. Capacities ranging from a few grams / minute up to several hundreds meter / hour are available. The advantages are low power consumption, no moving parts or maintenance, easy access for cleaning, capacity or speed change by simple controls.Conveyability Testswith Materials provided by the customer are available at our R&D Facilities.
Feeder machine is a kind of feeding equipment which can feed bulk and granular materials from the stock bin to the receiving devices evenly, regularly and continuously. Which has been widely used in cement, mining, metallurgy, coal, chemical industry, ceramics, grain, electric power and other industrial and mining enterprises.
Feeder machine is the most ideal equipment to realize production automation. The feeder machines can not only be used with electronic scales or microcomputers, but also can work alone for feeding. The common types of feeder machine are as follows:
When vibrating feeder is working, the vibrating motor drives the eccentric shaft or eccentric block to drive, and the centrifugal force produced by the rotation of the eccentric block is used to make the screen box and vibrator move in a continuous circle or approximate circle, and the bulk and granular materials from stock bin are fed into the receiving device uniformly, regularly and continuously .
Vibrating feeder is widely used in crushing and screening equipment of coal mine, mineral processing, chemical industry and mills etc. Usually suspended under the stock bin by a spring, the feeder trough can be arranged horizontally or with an angle of no more than 10.
Belt feeder is the same as that of belt conveyor in structure, but the roller space of belt feeder is smaller to bear the pressure of materials in the silo. Guide baffles are arranged on both sides of the conveyor belt to prevent spreading. The belt speed < 0.5 m/min. The feed rate can be adjusted by changing the belt speed or the height of the outlet baffle.
Belt feeder has the advantages of large bearing capacity and short length, so it is also a kind of economical feeding equipment. The feed ore size suitable for belt feeder is less than 350mm and the belt speed is below 0.3m/s generally. Belt feeder is mainly used in ore buffer bin discharge after coarse crushing, ore feeding of medium/fine crushers or screening equipment, discharge of powder bin.
Plate feeder is suitable for short distance transportation and can bear heavy working load, including 3 types: heavy, medium and light. The maximum ore size of heavy plate feeder can reach more than 1000mm. The plate feeder is mainly used for coarse crushing ore feeding, ore buffer bin drainage after coarse crushing, and coarse ore heap discharge.
Plate feeder can be installed horizontally or tilted, with a maximum upward inclination of 20. It is suitable for materials with loose density less than 1200kg/m, block weight less than 140kg and temperature below 350.
Chute feeder is suitable for the ore feeding of medium-sized materials, the maximum particle size can reach 450mm, and the ore feed can be adjusted by adjusting the eccentricity of the eccentric wheel of the transmission mechanism. The width of the trough body of the chute feeder is 2-2.5 times of the maximum particle size of the ore feed, which is mainly used for the feeding of jaw crusher and bulk lime in the preparation of lime milk.
Pendulum feeder is suitable for short distance transportation and high specific gravity materials with a particle size of 35 100mm. Pendulum feeder is not suitable for conveying dry powder materials, otherwise dust pollution and outlet blockage will occur.
Pendulum feeder is mainly used as the feeding equipment of the belt conveyor when collecting ore in the ball mill, and the feed particle size is generally less than 25mm, which belongs to intermittent feeding.
Disk feeder is a kind of continuous volume feeding equipment composed of driving device, feeder body, metering belt conveyor and metering device, which makes use of the fluidity of materials. The material is scraped from the container to the receiving equipment through a rotating disc and an adjustable scraper, which is suitable for all kinds of non-viscous and not very good fluidity -20mm fine materials.
Screw feeder can be installed in the lower part of the silo and is suitable for horizontal, vertical or inclined conveying. The material flow is controlled and adjusted uniformly and continuously by changing the spiral speed. The screw feeder is easy to feed non-viscous powdery, granular and small particle materials evenly to the receiving equipment from the silo and other storage equipment.
Screw feeder has the features of conveying, sealing, homogenizing and stirring. It is a common equipment in cement raw meal homogenization and silo sealing feeding. There are many types of screw feeder, such as solid screw, belt screw, variable pitch screw, conical screw and so on.
Impeller feeder is composed of a group of blades installed on the shaft and the outer sealing shell. Driven by the motor, the impeller on the spindle is driven by the reducer to drive the material from the upper silo through the impeller groove to feed out evenly. The feeding capacity is changed by adjusting the speed of the impeller.
Scraper feeder is composed of many scrapers fixed between two chains with a certain distance between them. The scraper moves along the slot bottom, which can be used for horizontal transportation or inclined transportation. When transporting upward along the incline, the inclination of the material layer shall not exceed 25 , and when transporting downward, the inclination shall not exceed 20 .
The working principle and traction parts are the same as the scraper conveyor. Scraper feeder can realize closed and multi-point feeding, which is suitable for materials with less powder or granule, grindability and stickiness.
Electromagnetic vibratory feeder uses the electromagnetic vibratory exciter as the vibration source to drive the hopper, which has the features of small amplitude, high frequency, slow conveying speed. Electromagnetic vibratory feeder is a new type of quantitative feeding equipment, which can meet the requirements of continuous production.
The maximum ore feeding particle size of electromagnetic vibratory feedercan reach 500mm, it is widely used for ore feeding of medium and fine crushing equipment and screening equipment, ore discharge of ore bin, etc.
You may agree with me that the best possible way to attract birds is food. Well, you may have seen several times on TV that people covered themselves with bird feed, and the birds were eating from them even while they were moving around.
On average, an American tosses 4.4 pounds of trash every day. With 323.7 million people in the United States, 728,000 tons of garbage is produced in every 24 hours, including 22 Billion plastic bottles every year.
The USA has a 4% population of the world but produces 12% of wastages alone. This fact contradicts with China and India. They recycle only 34% of solid waste, while Germany recycles around 66% of its total garbage.
Handy Hint: To read more about birds feeder, visit our other article about best platform bird feeders [here], best hummingbird feeders [here..], best pigeon feeders [here] and top window bird feeder [here..]
Among all the conventional methods, plastic bottles for making bird feeders are the most common waste materials. You can use a single bottle or a couple of bottles to make a bird feeder. Im going to share both of them with you guys.
Choose your lucky bottle and remove all sorts of stickers and level if possible. Then wash it with soapy water and remove any residual glue attached to its body (You dont want to stick the birds on the feeder, right!).
Next, create feeding holes above each perch on both sides. It should be around 2 to 5 centimeters long. Just make sure that its enough for the birds to use their beak to take the feed from the bottle.
Use your knife to cut them out. You can have the knife with little heat to cut them easily (No matter what you do, please be cautious, or you may injure yourself while doing so). Then, cut the bottle in the middle to separate the bottom part of the bottle.
Any feeder I used, which was made of plastic, didnt last long. The squirrels chewed them up in no time flat. There was absolutely no way a plastic or wood feeder could be mounted to keep squirrels at a distance; if the birds could reach it, the squirrels could too. So, beware of squirrels. At least our plan doesnt involve any cost, and you could as much as you like just spending some time.
You can also use a toilet paper roll to make a bird feeder. To begin with, apply peanut butter on the outside of the roll by using a spoon or knife. Then, roll it with birdseed so that it will stick to the peanut butter.
Besides that, you should choose bird feed according to your desired birds youre trying to attract to your feeder. Before doing so, research it online on which birds are common and what food they like.
Birdsadvice.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. As an Amazon Associate, we earn from qualifying purchases.
Screw feeders are designed to meter bulk materials and are typically located at the beginning of a process. Capacity or feed rate can be accurately controlled with screw feeders. Variable speed drives improve metering accuracy and can provide a wide range of feed rates. Screw feeders are available in a variety of sizes, lengths, configurations and materials of construction.
Most screw feeders are less than 20-feet in length because the use of internal hanger bearings is not recommended. In most applications a short screw feeder will meter a bulk material to a screw conveyor for transfer to the next step of the process.
The pitch of the screw varies from shorter to longer as the screw progresses toward the discharge of the screw feeder. With variable pitch, every pitch increases in length in the inlet section creating more available volume for addition of bulk materials from the hopper. With stepped pitch the flight pitch changes in increments. For example, a stepped pitch screw feeder may have 2-feet of 1/3 pitch, then 2-feet of 2/3 pitch in the inlet section.
The mass flow design was developed by Jenike & Johanson and is a combination of variable pitch and tapered inside diameter. A tapered cone is located on the center pipe of the screw from the rear of the inlet opening to approximately the center of the inlet opening. Short pitch flights are mounted on the cone creating available volume for addition of bulk materials from the hopper. Variable pitch is then added to the screw starting where the cone ends and continuing to the discharge.
It is not recommended to design screw feeders with uniform outside diameter and constant pitch because bulk materials will fill the screw from the rear of the inlet opening first, creating rat-holing, stagnant material and possible bridging of bulk materials above the screw feeder. To draw bulk materials evenly across the full length of the inlet each flight must increase in available volume as the screw progresses towards the discharge of the screw feeder. Variable pitch, tapered outside diameter (OD) or mass flow screw design is required.
Screw feeders must be equipped with a shroud for at least 2 pitches beyond the inlet opening to prevent flooding of the bulk material past the inlet. The shroud is a curved cover that converts a standard U-trough into a tubular housing to prevent bulk materials from flooding past the screw. Extended shrouds, tubular housings or short pitch flights can be utilized for accurate feed rate control when metering very free flowing bulk materials.
The pitch of the last screw flight going into the shroud determines the feed rate of the screw feeder and is called the Control Pitch. The Control Pitch is typically less than full pitch. The capacity of the Control Pitch is calculated in cubic feet per hour per RPM. The speed of the screw feeder can be determined by dividing the maximum screw feeder capacity in cubic feet per hour by the capacity of the Control Pitch in cubic feet per hour per RPM.
Most screw feeder speeds are lower than standard screw conveyor speeds. For example, in heavy industrial applications, screw feeders typically operate at speeds less than 20-RPM. More torque is generated at lower operating speeds ensuring the screw feeder does not stall at start-up.
The horsepower and torque requirements for a screw feeder are much higher than a comparable screw conveyor. A screw feeder must start up with a flood loaded inlet and the head load weight of the bulk material in the inlet section. Bulk materials also tend to pack when under pressure in a hopper, bin or silo. As the bulk material density increases, so do the horsepower and torque requirements.
The Material Factor or HP Factor (MF) can exceed 4.0 for some bulk materials when under pressure and packed. The start-up horsepower and torque can easily be 2.5 times the normal operating conditions. Please consult the KWS Engineering Department for proper screw feeder design.
Multiple Diameter Screw Feeder/Conveyors consist of a screw feeder with an extension conveyor. A smaller diameter screw feeder is located under a hopper, bin or silo and is flood loaded. The screw feeder meters the bulk material to the larger diameter extension conveyor. When the bulk material reaches the extension conveyor the trough loading decreases and the bulk material is conveyed to the discharge. Hanger bearings are allowed in the extension conveyor as long as the trough loading is below 45-percent.
Live bottom screw feeders are designed for use on large silos, bins and hoppers with large discharge openings. The live bottom screw feeder utilizes multiple feeder screws in tandem to create a "live bottom" to prevent bridging. Bulk materials are metered and drawn out equally from the full width and length of the inlet opening. Live bottom screw feeders are used on bulk materials which tend to pack or bridge easily.
Inclined screw feeders meter and elevate bulk materials from hoppers, bins or silos and perform the same function as horizontal screw feeders. However, special care is required when designing inclined screw feeders.
Knowledge of the flow characteristics of bulk materials is extremely important for successful inclined screw feeder design. The angle of repose and flowability of a bulk material will determine the design of the screw feeder and the maximum angle of incline. Testing of bulk materials is required for all inclined screw feeders before a proper design can be established. Bulk material samples can be sent to KWS for laboratory and field testing.
Inclined screw feeders must be designed to meter a desired capacity or feed rate and elevate a bulk material to a desired height. Screw feeders become less efficient when inclined over 5-degrees from the horizontal position. The loss of efficiency is determined based on the degree of incline of the screw feeder and the angle of repose and flowability of the bulk material. The diameter of the inclined screw feeder can be selected once the incline efficiency factor is determined.
Inclined screw feeders utilizing U-troughs are typically used on inclines up to 15-degrees and tubular housings are recommended for inclines over 15-degrees. Reducing the pitch of the screw increases the incline efficiency factor because the shorter pitch provides a better conveying surface and bulk materials do not fall back when compared to full pitch flights. Full pitch flights are the least efficient at metering and conveying bulk materials on an incline.
Inclined screw feeders typically operate at higher speeds when compared to horizontal screw feeders because additional speed is required to elevate a bulk material and overcome the forces of gravity and bulk material fall back. The desired capacity is adjusted using the incline efficiency factor calculated from testing of the bulk material. The speed of the inclined screw feeder can then be determined.
Inclined screw feeders require more horsepower and torque when compared to a horizontal screw feeder. Additional horsepower and torque is required to elevate a bulk material and overcome the forces of gravity and bulk material fall back. Bulk materials can become packed inside an inclined screw feeder, causing more demand on the drive unit.
The inlet length on an inclined screw feeder must be kept to a minimum to prevent the bulk material from falling back over the top of the flights in the inlet section. Typically, the length of the inlet should not exceed 2 times the diameter of the screw for an inclined screw feeder.
Inclined screw feeders are typically designed with multiple flight pitch changes. Shorter flight pitches are used in the inlet section to control the capacity or feed rate. Typically, the flight pitch increases beyond the inlet to reduce the trough loading to less than 100-percent. The conveying efficiency must be calculated in the longer flight pitch section to make sure the desired capacity or feed rate is met. Improper design of the flight pitches could result in the inclined screw feeder becoming plugged at the transition from shorter to longer pitch flights.
I wonder if i need to change the feeder tension when switching printing materialas i found there is occasion grinding of material over feeder when switching material with great hardness different such as from PLA to TPU95A.
14 Bird Feeder Projects For Kids These DIY bird feeders are a great lesson for kids to learn about zero waste. It teaches them to take something like trash or food waste and turn it into something new and useful. Photo Credit: confessionsofanover-workedmom.com Simple Bird Feeder This easy birdfeeder can hold your favorite birdseed mix or black oil sunflower seeds. Make it in just a few minutes with no waste. Continue Reading Photo Credit: thriftyjinxy.com Bird Feeder Hearts These Heart-Shaped Bird Feeder Hearts are an easy DIY way to give a treat to your feathered friends! Continue Reading Photo Credit: familyfocusblog.com How to Make a Milk Jug Bird Feeder Here is how to make a quick and easy milk jug bird feeder with your kids. Continue Reading Photo Credit: www.twopinkpeonies.com Homeschool Preschool Bird Activity This fun pinecone bird feeder craft is perfect for toddlers and preschoolers. Its super easy to make and your child will love watching the birds come by to grab a snack. Continue Reading Photo Credit: www.happy-mothering.com How to Make DIY Hanging Bird Feeders These hanging bird feeders are easy to make in any shape using cookie cutters. They're also peanut butter free, making them a great DIY for kids with allergies. Continue Reading Photo Credit: www.glitteronadime.com DIY Sharpie Mug Bird Feeder Kids will love decorating coffee mugs to make this adorable bird feeder! Continue Reading Photo Credit: diaryofafirstchild.com Lollipop Stick Bird Feeder Use up all your extra lollipop sticks with this bird feeder project that will degrade with time, making it environmentally friendly too Continue Reading Photo Credit: www.findingmyselfyoung.com How to make a DIY Recycled Bird Feeder Save an empty milk bottle to recycle into a cute bird feeder. Fill it with bird seed, brown sugar mix or fruit for local birds. Continue Reading Photo Credit: www.darcyandbrian.com How to Make a Shell Bird Feeder Craft for Kids Grab a seashell from your summer collection and let your kids have fun making a DIY bridfeeder. Continue Reading Photo Credit: www.animallama.com DIY Pink Milk Carton Bird Feeder Let your kids make a custom birdfeeder from a recycled milk carton. Continue Reading Photo Credit: www.naturalbeachliving.com Apple Birdseed Feeders These apple feeders are simple to make and a delicious treat for our feathered freinds. Continue Reading Photo Credit: ottawamommyclub.ca Pipe Cleaner Bird Feeders Take a pipe cleaner, shape into a U and make a knot on one end. Then feed Cheerios and grapes through the pipe cleaner until the pipe cleaner is almost full. Once full, tie the ends together in a tight know and hang! Continue Reading Photo Credit: threekidsthreecatsandahusband.com DIY Toilet Paper Roll Bird Feeder (with or without peanut butter) This Toilet Paper Roll Bird Feeder is a simple craft that even toddlers and preschoolers can help make. You can make a couple of them to hang at different heights to attract different animals Continue Reading Photo Credit: reusegrowenjoy.com DIY Bird Feeder Have your child use a recycled water bottle to hold all of bird sseeds in this crafty bridfeeder. Continue Reading Be sure to sign-up for the monthly Mom Hacks 101 newsletter to stay on top of more fun crafts for kids and more ways to to make mom-life a little easier.
Take a pipe cleaner, shape into a U and make a knot on one end. Then feed Cheerios and grapes through the pipe cleaner until the pipe cleaner is almost full. Once full, tie the ends together in a tight know and hang!
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Peat, rock, flour no matter which material you process, your hoppers must move it to feeders at an optimal flowrate without damaging the material. To accomplish this, both the hopper and the feeder need to work together. Sub-optimal design of either piece of equipment or of both of them can adversely affect processing.
This article focuses mainly on the hopper and hopper-to-feeder transition. The benefits of an ideal hopper design include uniform flow patterns, maximum capacity, optimized feeder size and performance, and reduced potential for material buildup and spillage.
Generally speaking, a properly designed hopper produces uniform material flow to the feeder trough, with material at the front of the hopper moving slightly slower than at the rear of the hopper. In addition, a properly designed hopper produces a bed depth of discharged material thats slightly lower than the height of the hopper gate. This varies based on material particle size and cohesion. Uniform flow is achieved when the ratio of the hopper throat (T) and the gate height (H) is 0.6. (T = 0.6 x H or T/H = 0.6.)
While 0.6 is ideal, a ratio range of 0.5 to 1.0 also is acceptable. A T/H ratio below 0.5 or above 1.0 means material flow patterns can become distorted, which significantly reduces a hoppers feedrate. Excess throat or improperly angled hopper walls and tapered skirt boards can result in non-uniform flow patterns, reduced capacity/bed depth, reduced material velocity, material buildup at the inlet, spillage at the back and sides, higher amperage draw, and an increased material load, possibly resulting in collapsed suspension springs. Compared to an ideally designed hopper, an improperly designed hopper might mean a larger feeder would be required to meet desired processing capacities.
To maximize your hoppers effectiveness at moving material into a feeder, keep in mind the following recommendations. These pertain to free-flowing material. For non-free-flowing materials, contact your equipment supplier for specific design and specification advice.
Brad Nichols (662-869-5711) is the engineering manager for Syntron Material Handling and is responsible for the development and design of the companys material handling products. Brad holds a BS in electrical engineering from Mississippi State University and has more than 25 years of manufacturing and fabrication experience.
Magaldi has developed a reliable belt feeder for handling hot and abrasive materials. The working concept is similar to the one of conventional belt feeders installed under hoppers, but the use of the Magaldi Superbelt conveying technology ensures a higher resistance to heavy impacts and shock loads. This equipment can be easily transformed into a weighing feeder by means of load cells. The Superbelt conveyor is a steel belt made of partially overlapping steel pans bolted on a steel double-wire mesh, that form a virtually sealed conveyor belt. The driving force is transmitted by friction between the head pulley and the mesh belt, while a pneumatic take-up device on the tail pulley provides a constant tension. This ensures a perfect fitting in the overlapping pans area so that fine residuals cannot leak among the pans. The steel belt is supported by carrying idlers across its entire width in order to withstand heavy mechanical loads. Next to the loading points, the idlers can be closely spaced or mounted on a shock absorber frame. Wear is negligible, since material is slowly conveyed with no relative motion against steel parts. Power demand for conveying and noise are at the minimum levels. The Superbelt can be easily converted into a weighing feeder by means of load cells, that are installed on the supporting structure of the carrying idlers, whose signal is processed by a PLC along with a dedicated software - both included in the scope of supply. The size (length and width) of the weighing feeder depends on the layout specification and the required capacity. The actual feed rate is determined by integrating the belt speed, monitored by an encoder, and the weight signal given by the load cells. The controller compares the actual feed rate with the desired one and it adjusts the belt speed to deliver a constant feed rate. In this configuration the Superbelt conveyor is mainly applied in cement factories, steel mills or wherever it is necessary to extract and dose a material.