Maintaining a steady hopper discharge

Flow Measurement & Control

January 2004 Flow Measurement & Control Design Automation

Pelchem, division of NECSA in Pelindaba, have been able to resolve difficulties maintaining uptime with the purchase of a Promoflow from Mucon for its moist sodium bi-fluoride (NaF HF) hopper.

The Mucon Promoflow consists of a screen that is mounted on the inside of the hopper; parallel to the wall in the lower half of the discharge cone where flow problems generally occur. An external air piston vibrates or actuates the screen to ensure continuous material flow without bridging, segregation or 'rat-holing'. There are two screen types available to suit various materials - mesh screens for powders and granules up to 20 mm diameter and rib cage screens for large particles or fibrous material.

Replacing an auger/agitator system - which did not function satisfactorily and created a restriction in the silo outlet - the Promoflow was specified by Pelchem because it shakes the contents of the silo rather than the silo itself. As the silo is manufactured from plastic (polypropylene) it could not cope with externally driven vibration, which could result in the silo cracking. Due to the corrosive nature of the product, all of the contact parts had to be coated with plastic.

The Promoflow unit comes as a complete package, which includes the discharge unit, the filter/lube set, which supplies clean lubricated air, and the solenoid and timer for the intermittent operation of the unit and full instructional book for the installation of the system. The units are linked to the bag-filling process through the solenoid and timer, so it only operates when product is required. This serves both to control the amount of vibration and the amount of air used, reducing operating costs. Once the bridge or 'rat-hole' has been broken and product flow has been restored, the Promoflow unit no longer needs to be active. (Continuous vibration can result in secondary compaction of the product - this is not always desirable.)

The client has expressed satisfaction with the end result, especially the reduction in downtime and increased safety around the bagging system. The Mucon Promoflow system is available in three sizes, based on the size of the silo and the product being handled. Each system is custom made to suit the customer's requirements. A test hopper is available for a demonstration using the customer's own product, either on their site or at Mucon's offices in Lanseria.

For more information contact Stephen Moul, Mucon, 011 701 3455, [email protected]

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Flow Measurement & Control

Maintaining a steady hopper discharge

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