Gauteng Business News

Send  Share  RSS  Twitter  23 Nov 2012

MINING: Improved Flotation Cell Control with Festo


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Leading automation solutions provider, Festo, has helped improved the platinum recovery rate from flotation cells at a mine in North West


The mine uses flotation cells to extract the platinum from crude ore: By agitating a mixture of ore, water, frothing reagents and

collecting reagents, the mineral particles rise to form a froth on the surface. The waste material (gangue) settles to the bottom. The

froth is skimmed off, and the water and chemicals are distilled or otherwise removed, leaving a clean concentrate.

When the fluid levels within the flotation cell are not accurately controlled, the mineral-rich foam doesn’t form or the concentrations are

not optimal. The original design had all actuators controlled via an external positioner with feedback fed through a series of linkages.

This type of system is inherently weak and needs regular maintenance and recalibration – a time-consuming process that was happening too

often for the mine. In addition to this, the system needed to operate in a potentially corrosive environment with exposure to sulphuric


Based on experience gained with Festo installations at mines across the world, Festo Sales Engineer, Koot Viljoen, offered the Festo DFPI

cylinder: “The design of the DFPI is compact so the positioner and valves are situated inside the actuator barrel and are therefore

protected from the environment.”

The specific model DFPI that Festo supplied also has an integrated position controller and a self-initialisation feature. The DFPI’s

integrated position controller checks the position of the piston rod within the available stroke range in a self-regulating closed loop

system. The actuator therefore requires no calibration and is effectively maintenance free. Control of the DFPI actuator is through the

positioner via a 4 - 20 mA analogue signal, either from a master PLC/IPC, or manually on-site via an external setpoint generator. The

integrated positioner of the DFPI and the removal of the linkages ensure accurate control of the flotation cell levels, allowing for

improved platinum recovery.

The Festo DFPI further has a factory-defined safety position that is assumed if the operating voltage or the analogue setpoint value fails.

In this case, a Fail to Extend action, which closes the Dart control valve in the flotation cell to minimize loss of valuable material.

As part of the solution supplied to the mine, Festo included an air service unit and signal generator for localised control.

The resulting improvement in control accuracy from the Festo solution has meant better platinum recovery and improved reliability. The

self-calibrating, easy installation provided a speedy commissioning phase for the customer, minimising impact on productivity. “This is

what Festo is all about, improving our customer’s productivity,” concludes Viljoen.


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