Section IV Feeding Technology and Product Overview Lucas Frei Regional Sales Manager Ukraine
Why are Feeders Necessary? To set the precise throughput to a downstream process Continuous processes such as mixing or extrusion become slaves to the feeders Provide an accurate blend of bulk solids and liquids for a formulation Eliminate pre-mixing of solids/segregation Using individual feeders for each component of the blend Feeders are used to set the flow rates of both liquids and bulk solids.
Volumetric Feeding
Volumetric Feeding I Speed Regulated Volumetric Feeding: Motor Drive Speed Setpoint
Gravimetric Feeding
Gravimetric Control Principle Controller Weight signal Speed Setpoint
Gravimetric Feeding Loss-in in-weight Feeding
Loss-in-Weight Principle G t G2 G1 G t1 t2 t G = G2 - G1 t = t2 - t1
Refill Levels Refill starts Refill stops
Important Refill Considerations Choosing the Proper Refill Device Reaction Time of the Device Device must be LEAK FREE Material characteristics Choosing the Proper Hopper Size for Refill Choosing the Refill Times Defining importance of accuracy during refill, particularly when low rate feeding
Bellows
Venting Venting with filter bag Central venting
Feeding Modes There are two basic feeding modes: Batch Gain-in-weight batch Loss-in-weight batch Continuous
GIW Batching via Volumetric Feeders Volumetric feeders dose bulk material into a weigh hopper Increase in collection hopper weight is measured Scale s weight info is used to control each feeder based upon setpoint or recipe hopper on load cells volumetric feeders
Gain-in-Weight Batch Gain-in-weight batch operation in slow motion
Gain-in-Weight Batch Systems Advantages Only one scale device for load hopper Cost effective since feeders are volumetric Well suited to large batches Disadvantages Total batch time is dependent upon the number of individual batch times necessary Combination of large single batches and very small batches not as versatile (due to large taring values of the collection hopper)
Loss-in-Weight Batch Principle Loss-in-weight feeders dose bulk material into a collection hopper Click for LIW Batch video
Loss-in-Weight Batch Systems Advantages Each ingredient is batched out in its own LIW feeder Feeders can then operate simultaneously, making overall batching process shorter Can also batch out variety of ingredients at different bulk densities and high variation in mix percentages with high accuracy Used for minor and micro ingredient weighing where individual percentages and accuracies required are outside the realm of GIW or scaling applications (0.5% of full load ) Disadvantages Higher initial investment for loss-in-weight feeders
Continuous Feeding Benefits: Online recipe control No premix station required No product segregation Shorter residence time No waste of premix
Feeding Types
Typical Feeders Used in Processing Weigh belt feeders Rotary Valves Vibratory tray Volumetric Gravimetric/Loss i In Weight Screw Types twin and single screw Volumetric Gravimetric/Loss-in- Weight Microfeeding
Weigh Belt Feeding Belt Speed Drive Command Belt Tare Weight Mt Material il & Blt Belt Wiht Weight Operation: Material is conveyed along a belt Belt is suspended d on weigh bridges Belt load is measured, belt speed then calculated by control unit
Weigh Belt Feeder Benefits Low cost for high volumes of flow Function easy to understand d Compact for high flow rates Can be extended to use as a conveyor Handle large particle size bulk material Low power requirements Works well in difficult environments
Rotary Valves Operation: Series of pockets delivers material volumetrically to process Advantages: Simple design good for free flowing materials Can be designed for explosion containment Disadvantages: Not ideal for packing/cohesive materials No good control on product delivery, i.e. pocket fill may vary Difficult to manage and clean Pulsating Discharge Limited turndown capabilities
Vibratory Feeders Operation: Material is conveyed by vibration Can be volumetric or gravimetric Advantages: Simple design good for free flowing materials Can also be good for difficult flow materials - high aspect ratio Gentle on products where attrition may be an issue Disadvantages: Not ideal for packing/cohesive materials No good control on product delivery, ie LUMPS IN TRAY Limited turndown capabilities
Unique Drive Technology Quick and precise control due to displacement feedback Resonance tracking allows different configurations without adjustment Strong vibration motor with four air gaps Enhanced LWF Algorithm improves accuracy Magnet Tray Feedback Sensor N (S) N S (N) S N (S) Spring Shock mounts Coil
Screw Feeders Operation: Material conveyed by either single or double screw Can be volumetric or gravimetric Advantages: Twin screws can be good for cohesive materials Accurate delivery of product Disadvantages: Design options are critical with regards to overall cleanability
Single Screw vs Twin Screw Single Screw ideal for free flowing materials, high volumes Twin Screw ideal for more cohesive materials Twin screws have a self wiping effect Twin screws can Twin screws can also provide more even flow to the process
Microfeeding as defined by K-Tron Microfeeding is defined as the ability to feed powders consistently and in a dynamic method to a process, at rates as low as 20 gram/hour* Can be provided in either volumetric or gravimetric design, with gravimetric resulting in highest accuracies at low rates Can also be provided d for batch or continuous feeding It has been used in limited cases as a doser, but it is not recommended for constant on/off operation * Reminder: 20 g/h = 0.33 g/min feedrate 1% 2sigma dev. (60s) = 3.3 milligram/min
Gravimetric Feeding Weigh Belt Feeding
WBF Control Loop Controller Setpoint Speed Weight signal
WBF Control Principle I Single scale version Belt load (q) speed pick-up Speed feedback (v) Weigh bridge q Mass flow Q = q * v Setpoint Controller Drive command Controller Motor drive
WBF Control Priniciple II Twin scale version Belt load (q) speed pick-up Speed feedback (v) Weigh bridges Shift register Tare Brutto Netto q Mass flow Q = q * v Setpoint Controller Drive com mmand Motor drive Controller
Gravimetric Feeding Flow Metering
Smart Flow Meter Unique design features: continually free path gentle handling of bulk material easy to clean no energy needed d to transportt bulk material practically maintenance free independent of bulk material integrated t autotare t system no moving parts simple, robust design
Measuring Force F R The resulting force F R is measured by the upper sensor station. F R
Measuring Principle I The flow meter F R measures the force F R exerted by the material on the slide. As with the belt feeder: Massflow = F v g l cos a v=?
Measuring Force F P The resulting force F P is measured by the lower sensor station F P
Taring at the touch of a button The K-SFM can easily be tared at any time by diverting the flow of material through the bypass. SFM VIDEO
Bulk Solids Pump:a New Approach To Solids Feeding
Feeding Concepts Definition of a Bulk Solids Feeder A method of bulk solid flow control based on the correlation between machine speed and discharge rate. Typical conveying systems are: Screw feeder Belt feeder M Rotary feeder M Vibratory feeder
BSP Technology Ideal Feeder Characteristics: Gentle Product Handling True Positive Displacement Action Absolutely Linear Over Full Operating Range Excellent Uniformity of Discharge 100% Active Discharge (minimal residual material) Able to Handle Differential Pressures Low Maintenance Design High Wear Resistance Low Power Consumption Quick and Easy to Clean
Comparison of Feeding Concepts Feature Screw Feeder Belt Feeder True positive displacement action Linear over full operating range No Poor (dep. on screw fill) Dependent on material Dependent on material Rotary Vibratory Feeder Feeder BSP No No Yes Poor No yes Uniformity of discharge Poor Dependent on Poor Good Good (pulses) material (pulses) Active discharge (no residual material) Unaffected by differential pressures limited (product build-up in screw flight) limited (product build-up on belt) Bad (product build-up on the rotary wall) Bad Good Limited No Yes No Yes Mechanical & maintenance Yes No Yes Yes Yes simplicity Wear Resistance Poor Poor Poor Good Very good Power Consumption High Medium High Low Low Product Degradation High Medium High Low Very low
Lock-Up Principle The BSP principle p provides continuous, positive displacement volumetric control by exploiting the phenomenon known as lock-up. LOCK-UP
BSP Video Clip click on the graphic to start the video
Liquid Feeders
Feeding Liquids Depending on the application and accuracy required, two feeding modes are possible: Volumetric Loss-in-weight
PID Control Principle setpoint pump flow meter controller drive command current motor drive thoughput feedback M DC motor
Design The liquid tank is mounted on either 3 SFT s or a scale Flexible connections to the pump which is independent of the weigh system The controls are standard K-Tron loss-in-weight controls
K-TRON Weighing Technology
The Principle Forc e vibrating wire temperature sensor The K-SFT supplies a fully compensated true weigh signal. electronic exciter temperature converter power supply weight processor microprocessor calibration EEPROM RS 485 serial interfac e * ASIC: Application Specific Integrated Circuit
SFT Features One-time only calibration by manufacturer Integrated linearization and temperature compensation High accuracy and reliability in any environment Fast sampling time - 112 samples per second 1: 4`000`000 resolution in 80ms Improved filtering techniques - real time calculation - not just sample averaging Simultaneous sampling/processing
Improved Performance Weight (g g) 50 40 30 20 10 0-10 -20-30 -40-50 0 Conventional Weighing Technology 10 20 30 40 50 60 70 80 90 100 Frequency (Hz) (g) Weight 30 20 10 0-10 -20-30 0 K-Tron SFT II Output With Digital Filtering 10 20 30 40 50 60 70 80 90 100 Frequency (Hz)
Accuracy
ActiFlow Prevention of bridge building with Prevention of bridge building with difficult flowing materials
Hoppers & Agitation AC Agitator Drive Vertical Agitator Horizontal Agitator
Vertical Agitation Requires additional headroom above the feeder Heavy motor on lid can make servicing difficult Needs a separate motor starter (DOL) Causes clean-ability issues. Expensive
Poor Flow in Hoppers = Poor consistent feeding Difficult powders: May get compacted Form ratholes & bridges Result in operation: Production interruption Quality problems Screw feeder accuracy is a function of consistent screw fill Ratholes or bridges
Alternative Solutions for Improved Hopper Flow Design Options Vertical Agitation Flexible Elastomer Liners (eg FlexWall, Shear Hoppers) Bin Vibrators Air Injectors (eg Magic Mushrooms) Elastomer Coatings
Hopper Flow Aids Pros and Cons OPTION PROS CONS Vertical Agitators Flexible Liners May be better suited for Large Hoppers Keeps material fluid in hopper Require additional headroom for operation and maintenance Can cause weight disturbances in gravimetric feeders Cleanability and accessability are concerns Can cause additional packing and densification of cohesive materials Liners can stain ti =cleanabilityconcern Can cause weight disturbances Bin Vibrators External to process Can cause additional packing of material Can cause weight disturbances depending onfrequencies
CAUTION - Disconnect po wer before opening. 115/230VAC 50/60 HZ,2000Watts (Max) CAUTION - Disconnect po wer before opening. 115/230VAC 50/60 HZ, 2000Watts (Max) Flow Aid for LIW feeders - ActiFlow Serial Weight Channel KCM Weighing System ActiFlow Control Unit KCM ActiFlow CONTROL Extension Hopper ActiFlow Device Coil Power / Position Feedback Feeder Motor Power / Speed Pickup Click for Actiflow video
ActiFlow Design The ActiFlow Device is bolted to the outside of the hopper wall, with no product contact. It is ideal for applications which require a stainless steel hopper. The special design ensures material activation has a minimal effect on the weighing system.
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