What is Feeding? For the cake 6 large eggs 1 cup granulated sugar 1 cup all-purpose flour 6 tablespoons melted butter
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Tres leches cake with raspberries
For filling and frosting 1¾ cups raspberries 1½ tablespoons granulated sugar 2 cups whipping cream 2 teaspoons vanilla 1/2 cup powdered sugar
Feeder Definition Any device designed to control the mass flow of bulk solids or powders at a fixed or variable rate
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It controls how much material is going into the process It does not (in any way) changes the material
Why are Feeders Needed?
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To control the flow rate of a bulk ingredient, composite mixture or end product to a downstream process operation To proportion bulk ingredients in batch or continuous recipe formulation Eliminate pre-mixing or reduce pre-mixing time of solids
Basis of Feeding Volume
Weight
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Volumetric feeders control discharge on the basis of volume per unit time Gravimetric feeders control discharge on the basis of weight per unit time
The difference is DENSITY!
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Volumetric Feeding
Volumetric Feeding There are three approaches to control metering device rate:
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Open-loop (no feedback)
Closed-loop (speed feedback)
Volumetric Feeding
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Open-loop (no feedback)
Motor Drive
Speed
Drive Command
Volumetric Feeding
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Closed-loop (speed feedback) Motor Drive
Speed
Setpoint
Volumetric Feeding Advantages Wide range of metering devices
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Simple, inexpensive
Disadvantages
Ignores variations in material density No mass flow measurement/control Rate inferred from speed Requires calibration
Sensitive to material buildup
Does not detect 'no-flow' conditions
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Gravimetric Feeding
Gravimetric Feeding
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It refers to mass metering Feeding based on the principle that a certain weight of material is uniformly discharged in a given period of time by controlling metering speed
Gravimetric Feeding Real mass measurement of the product can be accomplished while feeding product
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Weight Belt
Loss-in-Weight
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Weigh Belt Feeding
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Weight Belt Feeding
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Loss-In-Weight Feeding
+
Volumetric Screw Feeder
=
Scale
LWF
Gravimetric Control Principle
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Controller Weight signal
Speed
Setpoint
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Loss-in-Weight Control Principle
Drive Command
Speed Pickup Drive
Motor Control
Massflow
Controller
Setpoint
Q=
G t
Loss-in-Weight Principle Change in weight over time
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Weight Δt
w2
Δw
w1
t1
t2
Time
Δw = w2 – w1 Δt = t2 – t1
Complications Refill Issue
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In the real process, the hopper has a limited capacity and must be refilled while the feeder is continuously running
Weight Disturbance
The weighing device is also subject to inaccurate reading due to vibrations, material motion in the hopper, and outside influences on the scale
Variation of Product Flow Scale Isolation
Loss-in-Weight Principle Weight change on feeder Weight on LWF max.
1 2 3 4 5 6 7 8 9 10 11
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Refill Stop
Hopper Weight
Refill Start
Hopper contents
min.
1 2 3 4 5 6 7 8 9 10 109 8 7 6 5 4 3 2 1
-1
min (Screws)
no ramp-up
Motor Speed
30 Start of change in volume
Time t (min.) 60 61 Refill: time scale expanded
Control Mode Gravimetric mode
Volumetric mode
Loss-in-Weight Principle
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Feeder and material are continually weighed Metering speed is controlled to maintain desired discharge rate Feeder is refilled before it is empty Care must be taken in the design of the refill system
Loss-in-Weight Feeding Advantages High accuracy
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Flexible, can employ any type of metering device Excellent low-rate performance
Auto adjusts for buildup; detects 'no flow' conditions
Disadvantages
Less economical for high feed rates Required headroom
Requires suitable weighing environment
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Volumetric vs. Gravimetric
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Mode of Operation
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Modes of Operation
Feeding
Batch
Continuous
Batch Proportioning
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Dispense a fixed quantity of product into the process defined by a “batch” value
Dispensed Amount = Batch Value
Batch Proportioning Dribble Drive Command
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Batch Weight Delivered
Stop Fast Drive Command
Stop
Batch time (sec)
Drive Command (%)
Fast Drive Command
Dribble Drive Command
Stop
Stop Batch time (sec)
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Techniques
Feeding
Gain-in-Weight (GIW)
Loss-in-Weight (LIW)
Gain-in-Weight Batch Benefits
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Cost-effective system since only volumetric feeders required Well-suited to large batches
Combination with LWB system possible
Loss-in-Weight Batch Benefits
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Online recipe control No premix station required No waste of premix Short mixing time
No product segregation
Coordination of batch times
Short batch time for multiple components
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Continuous Feeding
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The objective is to maintain a gravimetric flow rate (massflow) 40 of an individual 35 material at a target 30 (setpoint) value 25 Mass Flow = Set Point
Mass Flow Kg/h
20 15 10 5
Time (s)
0 5
10
15
20
25
Continuous Feeding
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Loss-in-Weight batch feeding involves the use of gravimetric feeders simultaneously discharging to a central hopper (weighed or not) or directly to a mixer
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Elements and Principles
The Generic Feeder Model
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All process feeders, regardless of principle, operating technique or design configuration have the same five basic subsystems: Material Input
Containment & conditioning Metering
Measuring & sensing Control
The Generic Feeder Model
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UPSTREAM
MATERIAL INPUT
MEASURING & SENSING
CONTAINMENT & CONDITIONING
CONTROL
METERING
DOWNSTREAM
Feeder Components
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Filter Receiver
Gate
Hopper
ActiFlow
Agitation
Motor Drive
Screw Design Load Cell
The Generic Feeder Model
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UPSTREAM
MATERIAL INPUT
MEASURING & SENSING
CONTAINMENT & CONDITIONING
CONTROL
METERING
DOWNSTREAM
Material Input Filter Receiver
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Gates & valves
Pellet Receiver
Powder Receiver
Containment & Conditioning Hoppers & bins
Agitation & flow aids Bin activators
Surface coatings
Air fluidizers
Pressure control
Vibrators
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Venting & dust control
Feeder support
Air hammers ActiFlow
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Hopper Types
The Generic Feeder Model
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UPSTREAM
MATERIAL INPUT
MEASURING & SENSING
CONTAINMENT & CONDITIONING
CONTROL
METERING
DOWNSTREAM
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Vertical Agitation (Symmetrical)
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Vertical Agitator (Asymmetrical)
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Agitation & Flow Aids
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ActiFlow
Horizontal Agitator
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Different type of agitator
The Generic Feeder Model
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UPSTREAM
MATERIAL INPUT
MEASURING & SENSING
CONTAINMENT & CONDITIONING
CONTROL
METERING
DOWNSTREAM
Measuring & Sensing Speed Sensing
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Weight Measurement
Smart Force Transducer (SFT) Suspension
K-SFM
SWB
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Platform
K-SFT-II 18-120, 80-200N
K-SFT-III 60, 200, 500, 1000N
Smart Force Transducer Features
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One-time only calibration by manufacturer Integrated linearization and temperature compensation
High accuracy and reliability in any environment
K-SFT-II - L 200-1000N
Smart Force Transducer Features Fast sampling time
KCM K-Tron Control Module Software matched to the controlled device
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Continuous or batch operation Local or remote mounting Network interface
Patented screw speed modulation algorithm
Integrated refill control
Extensive host communication capabilities
Controls and Communications
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K-Tron’s SmartConnexTM control environment provides comprehensive control capability with maximum flexibility and connectivity for systems that include feeders, flow meters or PID controlled devices.
Multi-Line Control KSC Smart Commander is a PCbased interface able to control a total of 32 devices in up to 8 process lines.
Single-Line Control K-Vision™ offers touchscreen operator interface for single process lines consisting of up to 16 feeders or PID devices. Device-Level Control KCM Control Module combines machine mounted feeder control and motor drive modules into a compact housing, offering maximum flexibility and excellent performance.
KCM Connectivity Communication Protocols
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Modbus RTU (KCM Slave) Allen Bradley DF1 (KCM Slave) Modbus Plus
Modbus/TCP Ethernet/IP Device Net
Profibus DP ProfiNet
SmartConnex Puts the ”Brain“ at the Feeder
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Integrated Package Simplifies Installation and Operation Lowers Cost
