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Posts Tagged ‘metering screw feeders’

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Metering Screw Feeder

Metering screw feeders are used to accurately meter powdered, granular or flaky products in a process system.

Fresco offer both Volumetric (product flow rate by volume and set over a given time) and Gravimetric (product flow rate by weight and controlled using loadcells) types of metering screw feeders, with throughputs ranging from 1.76 l/ hr up to 13650 l/hr. Where very fluid powders are handled Fresco installs a pneumatically actuated flow control valve on the discharge of the screw tube to prevent flushing.

The crucial factor in achieving accuracy is consistent product bulk density by proper design and selection of an agitator in the conditioning zone above the screw auger. The agitator de-aerates and densifies the product to a uniform density and breaks any bridges, preventing hold-up in the hopper. This combination with a vast selection of screw sizes and types allows a wide cross-section of products to be fed very accurately.

Volumetric accuracy of ± 1% to ±2% and gravimetric accuracy of ±0.25% to ±1%, depending on the product, can be easily achieved. Weigh platforms fitted under the standard feeder linked to a batch controller provide accurate loss-in-weight feeding. Two-way RS 232 serial ports can be used to send and receive signals from other plant control systems. An easily removable front section provides access for cleaning and screw changes.

Fresco provides multiple weigh batching solutions, gain-in-weight and loss-in-weight systems that can be easily integrated with your equipment. Working with our electrical control and automation engineers we can provide high accuracy batching solutions that will ensure reliability and precision whatever your requirements.

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Oats Handling System

As part of their expansion plant, a muesli manufacturer contacted Fresco Systems to assist in handling various types of oats to and from bulk bags.

Their processes require batching from bulk bags as raw materials and then filling bulk bags as finished products.

Being a new user to bulk bags, they were concerned with handling oats in bulk bags, in particular breakages and flowability. Fresco Systems recommended the electric hoist type bulk bag unloaders fitted with vibratory trays and metering screw feeders. The electric hoist enables the operator to handle bulk bags from pallet trucks in the process room rather than forklift. Once lifted, the bulk bags then rest securely on the vibratory tray.

The vibratory tray provides acts as a gentle flow aid compared to the paddles of the bag massagers which might damage the products. The spout clamp then seals the bulk bag spouts creating dust tight, secure attachment, totally enclosing the interface between the bulk bags and the feeder hopper below.

To eliminate the risk of breakage, a larger feeder screw was selected with minimal clearance between the screw edge and the outer tube. This eliminates the risk of the product pinching and breaking during feeding. The bulk bag unloaders are on loadcells which enable the operators to key in desired amounts of product to be batched out.

The end result is an effective way of handling and batching fragile products from bulk bags.

At the end of the process, two bulk bag fillers are positioned side by side to allow continuous feeling of bulk bags. The bi directional belt conveyor feeds into a bulk bag while the other filled bulk bag is being replaced. Once the operator connected an empty bulk bag to the fill head and press the ready button, the bag inflators remove creases and folds in the bags which can cause irregular filling of the bag, making it unstable. The bulk bag fillers are also on loadcells and the belt conveyor feeds each station until the desired weight is reached.

Stand alone control systems were supplied with all systems with the capabilities of communicating to the plant PLC.

As Fresco Systems consulted with the client from concept stage, delivery and commissioning of the systems have been seamless and the customer is now discussing further system upgrades increase their capacity.

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