MATERIALS HANDLING
Marvin Woodie explains how getting the best performance from a vibrating screen starts with the way material is fed to the equipment
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SMARTER SCREENING
et’s start at the beginning. A common problem seen throughout the industry, both in dry and wet screening, is how material is
presented to the vibrating screen. You can’t dump material directly from a chute, pipe or belt onto a vibrating screen and expect optimum effi ciency. A vibrating screen is a separation device and trying to make it do something it’s not designed to do will only cause problems. To increase the wear-life of vibrating screen components and screen media, in addition to maximising screening effi ciency, begins with how material is fed to the machine. T is is accomplished by introducing a customised feed system between the feed point and the vibrating screen. Proper design of a feed box, fl at or curved sieve, or confi gurations of both will take into consideration the surrounding area and the source of feed to get the most out of your vibrating screen. Brad Parker, a process engineer for
Rosebud Mining Company responsible for optimising metallurgical performance at its coal preparation plants, reports great results from the sieve fl umes that have been incorporated for many years in all fi ve of the company’s heavy media coal preparation plants. “Conn-Weld sieve
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fl umes ahead of banana desliming screens makes fi nes removal more effi cient, increases the capacity of the banana screens and increases screen media life on the screens,” he states. “Likewise, the sieve fl umes ahead of our heavy media drain and rinse screens do the same thing with the added benefi t of increased magnetite recovery. Using the sieve fl umes ahead of desliming and heavy media drain and rinse screens also ensures proper introduction of material to the screen it is feeding to insure longer screen media life.” Feed system solutions are as countless as the challenges presented by mining applications. Here, we assess solutions in dry and wet applications incorporating a feed box and fi xed fl at sieve.
DRY SCREENING
A key factor when it comes to dry screening is uniform distribution. A properly designed feed box will successfully use all the screening area, maximising throughput, thus making the screening more effi cient. T e design of a feed box will vary depending upon what is deemed necessary for the application and the available space there is to work with. Additionally, the right liner (AR, ceramic tile, urethane,
rubber, etc.) plays an instrumental role in not only preventing premature wear but designed correctly, will also distribute the fl ow properly as it transfers onto the screen surface. T ere have been cases where the material is not distributing across the width of the machine until a third of the way down the screening area. T is causes uneven wear and loading, resulting in ineffi cient screening. Material fl ow can be managed by customising the liner to the vibrating screen feed box. In one example, a conveyor was
dropping material fed through a chute onto a Conn-Weld 8ft x 20ft TD Circular Motion Incline. Out of 160ft2
of screen area, only 120ft2 was
being used, with screening effi ciency worsening even more on the lower decks. Challenged with a very abrasive aggregate application, a conventional feedbox would wear within a couple of weeks. T e solution? Conn-Weld designed
a feed box with rubber liners to include end-dams moulded onto a steel liner. T e dams created an evenly distributed fl ow across the entire screen. T e fi nal outcome is that the customer uses 100% of the screen area while providing long wear-life.
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