HomeCentral AfricaKwatani breaks down the science behind screening

Kwatani breaks down the science behind screening

Vibrating screen and feeder OEM Kwatani is challenging the conventional norm in specifying large vibrating screens and feeders.

Technologies should not be the primary factor when choosing a screen, but rather its operating parameters, COO KENNY MAYHEW-RIDGERS tells LAURA CORNISH.

Lowest total cost of ownership is no longer a ‘nice to have’ in the mining industry but has today become a priority and key objective for any operator or developer.

This article first appeared in Mining Review Africa Issue 11, 2019
Read the full digimag here or subscribe to receive a print copy here

In achieving this, the sector has started evaluating and implementing digital technologies that enable real-time machine monitoring which in turn offers preventative maintenance benefit and consequently, reduced downtime and production uptime.

This approach will deliver on the industry’s objectives but is by no means the only option to achieving best processing performance.

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“For screening applications in particular, Kwatani encourages the industry – both engineers and mining companies to change their approach when specifying large vibrating screens and feeders,” says Mayhew-Ridgers.

“Generally speaking, the mining industry is conservative and is comfortable making decisions based on years of standard practice. But following the ‘norm’ doesn’t work in an industry where the guidelines for success have changed.

“What worked in the past won’t necessarily work today and in many instances will definitely not produce the desired outcome,” he continues.

When specifying a screen, most mining companies and engineering houses opt for the best suited screen technology, perhaps a brute force screen for instance instead of a twin-mass screen.

But the parameters between screens supplied by different OEMs can vary quite substantially for the same technology.

It should therefore be non-negotiable that the industry considers these parameters against their own feed material in determining not only what screen to choose but how it should be manufactured and what size it should be as well.

“Now, more than ever, there is a need to establish robust screen sizing protocols that will produce accurate data on both vibrating screen and screen panel performance. And we need to start by marrying the process and mechanics of screening together.”

Addressing the problem

The starting point should be premised on the question – what does the plant need?

It should not be about pushing particular technologies. This does, however, require that decision makers need to be well-informed, which means decisions should not be made without access to the correct information.

In any screening application, Mayhew-Ridgers outlines the three parameter categories that need to be considered before purchasing a screen – the physical screen, the screen panels and the ore itself need to be evaluated according to their specific characteristics.

  • Priority screen parameters include drive angle, operating frequency, stroke, acceleration and deck angles
  • Panel parameters includes aperture size, open area, panel flexibility/stiffness and panel frame design, most of which is not taken into account; and
  • Ore parameters include ore shape, size, density and moisture or stickiness.

Kwatani has started a test work regime that is designed to not only educate clients on the necessity for evaluating screening parameters but to conduct preliminary tests that can, using a pilot wet screen easily change the parameters to fill in the gaps where data for screening performance has largely been guesswork or based on historic practice. In so doing Kwatani can best determine the ideal screen for individual applications.

Knowledge is power and this test work regime will include data that looks at both the mechanical parameters as well as the process parameter influences and how these integrate and affect the operation of large vibrating equipment.

It is time for mining houses to consider every option to improve their processes and production performance and relook its approach to selecting the correct machine for the application – which should be based on updated knowledge and decision-making processes, and not rely on outdated information that was determined more than 40 years ago in a time when the design technology available to do so was not nearly as advanced or able to consider varying options, Mayhew-Ridgers reiterates.

He does add that the various different screening technologies available should also be part of the consideration – “their value should be measured as part of a bigger picture.”

“Through this message and the initiatives we have taken on board as an OEM I am hoping to instigate a paradigm shift that will see enormous benefits for the industry and will change the way OEMs and screen panel manufacturers better provide for the industry,” he concludes.