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Case study: Metering screw feeder with grate magnet

Supplier: Fresco Systems Australasia
14 June, 2010

Recently a large cereal manufacturer approached Fresco Systems Australasia seeking a solution to a problem of dispensing 1,000kg bulk bags of soya beans, rice and oats on a continuous basis into their process.

The specification had a number of critical requirements including a system accuracy of <2%, variable discharge rate, 10,000 gauze magnet, discharge height of 1,600mm and a storage capacity of 1,500 litres.

To address these requirements Fresco designed a system where the products were unloaded from the bulk bags and transferred to the 1,500 litre storage hopper via a flexible screw conveyor and then metered in the process using a metering screw feeder. A 10,000 gauze draw type grate magnet was installed at the discharge of the storage hopper allowing easy access for inspection/cleaning and providing product integrality. 

The metering screw feeder selected for the duty is designed to be installed directly to the discharge of large hoppers creating clean lines and reducing base mounted support frames. The metering screw was fitted with an agitator to condition the product providing consistent product bulk density to the feed screw.

The agitator is powered by a separate drive motor so it can be cycled, reducing product degradation caused through over working the product. The agitator also provides a consistent feed discharge rate at when using a constant speed. A variable speed controller linked to the existing process provided speed fluctuations matching the required feed rate for each product.

To prevent product flushing when filling the empty hopper and to provide a positive cutoff a pneumatic flow restrictor was fitted. The plunger closes off the end of the discharge spout sealing it when not in use.

The standard Fresco metering screw feeder is completely demountable by removing the front face plate exposing the internals. This ensures easy cleaning for the operator when changing products. Additional face plates and screw sizes can be supplied increasing the versatility of the metering screw feeder when handling multiple products or large variances in through-put rate. A safety switch provides isolation to the screw and agitator when the face plate is removed.

For further information please contact Fresco Systems Australasia. Phone 1800 141 414 or visit our website