Engineering solutions and steel fabrication company Lani Service Centre, based in Sebenza, Johannesburg, has supplied a tailor-made spillminator equipped with vesconite bushings to a local gold mine for its underground conveyor and hopper system.

“The bushings are self-lubricating, can withstand the high pressures involved in the application, and are able to cope with a dirty and wet mining environment,” Lani Service Centre workshop manager Jonny van Biljon tells Mining Weekly.

The bushings are located at the pivot points of the spillminator, which cost about R300 000 to build, excluding the cost of the hydraulic cylinders and the power pack. The Spillminator took three months to design and build, with the fabrication of the unit taking two months.

It took a further three months to install the unit, which has a basic shell made from S355 mild steel and VRN 500 steel wear plates.

The spillminator is placed at the end of a transfer chute and uses two custom-built hydraulic-powered doors to control the flow of mined rocks and minerals fed into hoppers or transferred onto conveyors installed in underground mines, Van Biljon explains.

The 2-m-high spillminator, measuring 2 m × 2 m, is slanted at a 45º angle to help control the flow of materials by slowing the speed at which the material is transferred to reduce its impact on conveyors and hoppers. The spillminator is galvanised to prevent corrosion, owing to contact with acidic water and other dangerous chemicals, while the hydraulic doors are manually controlled by an operator.

He states that the spillminator includes safety features, such as the electronic safety system built into the operator’s seat, to ensure that both hydraulic doors remain closed, thereby preventing material overflow should the operator move away from or fall off the seat.

The machine will be serviced every three years to ensure that it continues to function according to specification, notes Van Biljon.

Unique Bushings
Van Biljon highlights that the self-lubricating vesconite bushings are greased only when they are installed and have been used by the company for the past four years in various applications.

The company procures the vesconite to machine the bushings from South African low-friction, low-wear polymer bearing materials manufacturer VescoPlastics, in Denver, Johannesburg.

VescoPlastics earthmoving representative Juan van Wyk says vesconite’s chemical composition, developed in 1968 by VescoPlastics founder and chemical engineer Alain Leger, enables it to self-lubricate.

Leger began researching the potential for polymer-bearing materials in the gold mines of the then Orange Free State – a harsh environment characterised by dirty and wet conditions.

Van Wyk highlights that VescoPlastics can supply bushings with any diameter from 8 mm to 900 mm, as well as raw vesconite material for companies that want to machine custom vesconite bushings. The size is virtually limitless, owing to the introduction of bushings made from staves.

“Generally, we can supply our bushings to customers within one or two days, depending on where the customer is and the quantity required,” he concludes.