Weigh Belt Feeders Handle Fragile Bulk Materials at Higher Feed Rates
The Weigh Belt Feeder is a relatively simple, extremely reliable gravimetric feeder providing high feeding precision and efficient process monitoring
Weigh belt feeders can be used as a feeder, batcher, or meter. The most typical application is for feeding / weighing into a continuous process. By utilizing different control software, K-Tron's Smart Weigh Belt can also be used to feed material into a batch system.
Weigh Belt Feeder Principle of Operation
In a weigh belt feeder, product is fed as a continuous band onto a conveyor belt, through an inlet slide gate or automatic pre-feeder. A load sensor under the belt continuously measures the weight of the product over a defined length of belt.
The controller continuously compares the actual weight with the setpoint weight, and automatically adjusts the motor speed to either increase or decrease belt speed, in order to maintain a constant feedrate. Any variation in the density of the material is reflected as a change in belt loading, which is compensated for by adjusting the belt speed.
Weigh-belt feeders can be positioned directly beneath a silo, making them suitable extraction devices for foodstuffs, animal feed, detergents and plastic pellets. The ideal inlet gate has an adjustable width, so that the profile (and thus the volume) of the material being discharged can be varied to meet the needs of the application.
For inventory control or metering, the Smart Weigh Belt can be placed into a constant speed configuration to measure or totalize the amount fed into a process.
When to choose a weigh belt feeder rather then a loss-in-weight screw feeder:
- Relatively lower price for high mass flow feed rates
- No refill device required
- Compact height allows easy fit in low headroom situations
The weigh belt feeder offers gentle material handling, an important benefit compared to other feed devices, such as a screw feeder, when handling certain materials:
- Flakes (e.g. corn flakes, bran flakes, and wheat flakes)
- Lumpy bulk solids (e.g. vegetables and fruits)
- Shear sensitive materials (e.g. corn flakes, frozen vegetables and frozen fruits)
- High abrasive bulk solids - due to a low friction coefficient applied to the materials
- Low melting bulk solids (e.g. fat flakes)
K-Tron Weigh Belt Feeder Models for Mid-Rate and Hi-Rate Applications
Two sizes of mid-rate Smart Weigh Belt are available in belt widths of 300 mm and 600 mm, with and without housing, for medium gravimetric feeding or metering. A continuous auto-tare option reduces downtime for calibration and maintenance.
SWB-300 / 600 feed rates: 10 - 80,000 dm3 / hr (0.4 - 2,800 ft3 / hr)
An Open Frame (OF) version can be provided to allow direct discharge onto the belt surface. This feature can also be an important benefit for fragile materials like potato chips, when easy access is needed or when feeding very warm or very cold materials.
Online Auto Tare with Optional Second Weigh Bridge
Weigh-belt feeders must be regularly inspected and serviced. They must also be cleaned frequently, since materials sticking to the weighing surface or belt may prevent the scale from adequately zeroing, or cause belt-tracking problems. K-Tron's mid-rate Smart Weigh Belt is the first weigh belt feeder to offer a solution with its optional continuous online auto tare compensation.
The auto tare option uses two Smart Force Transducer (SFT) weighing units. The first SFT measures the actual belt weight before receiving the material, but includes the weight of material sticking to the belt. The second SFT determines the gross weight after receiving material onto the belt. The feeder compensates for the difference and belt speed regulation guarantees highly accurate and longterm feeding stability.
Even when feeding sticky materials, you get increased accuracy and reduced downtime for cleaning, maintenance, and calibration. The new tare technology also provides an automatic cleaning indicator and increases the feeding range of the weigh belt feeder, allowing it to accurately feed lower than 50 lb/hr.
Three sizes of hi-rate Smart Weigh Belt feeders are available, with closed or open housing, for high rate gravimetric feeding or metering.
SWB-650 / 800 / 1000 feed rates: 2,000 - 120,000 dm3 / hr (70 - 4,200 ft3 / hr)
All K-Tron Smart Weigh Belt feeders use digital load cells instead of analog load cells with the following benefits:
- High resolution (1:4,000,000)
- Insensitivity to electrical noise during data transfer
- On-board microprocessor to linearize the weight output and compensate for temperature fluctuations
- Calibration done at the factory
- Elimination of low frequency vibrations without reducing the resolution