Transfer points into mill feed or scrubber feed chutes are traditionally high wear and high maintenance installations. However, this need not be the case. By correctly controlling the feed into the scrubber or mill feed, it is possible to reduce wear and tear, and consequently maintenance.

The transfer point into the scrubber or mill feed is critical as this area is subjected to high velocity, and the speed of the product is directly linked to the wear and tear. Problems can arise because of the very nature of the operation. The material is fed into the mill or scrubber chute with a large quantity of water that is required for the milling process. Additionally, if it is a ball mill, then the balls are also fed through the chute into the mill itself. Traditionally, mills are lined with either cast high chrome, manganese or rubber liners, and even though mill chutes may have similar lining materials applied these are not always sufficiently robust to counter the excessive wear caused by the uncontrolled discharge of materials. Another challenge in this application is the interface between the stationary chute and the rotating mill. The uncontrolled discharge of bulk materials and water will escalate the cost of maintenance, and could also result in other related problems, all of which add up to unnecessary expenditure and added aggravations for the engineers concerned.

Appropriate design use of the Weba Cascade Chute configuration in the head section of the chute will reduce the wear and gain full control over the material. “With this exacting design clients will be able to limit the impact into the lined feed spout section where the water is introduced through a separate flood box. By gaining full control of the product flow in the Weba chute, customers can greatly reduce wear rates traditionally experienced in the mill feed spout and reduce the associated costs related to transfer points,” Mark Baller, managing director of Weba Chute Systems, says. Traditionally the mill feed spouts are provided by the mill OEM supplier. Through successes being achieved with reduced maintenance costs and reduced mill loading, end users are now replacing the OEM supplied spouts with customised Weba Chute Systems.

Designing for dynamics of material
Weba Chute Systems’ pragmatic approach to the dynamics of bulk materials handling not only eliminates the problems so often associated with conventional transfer chutes, but also results in significant savings. “Each Weba Chute System is tailor made for its specific application and factors such as belt width, belt speed, material particle size and shape as well as throughput are taken into account during the design phase,” Baller says. Achieving the optimum design for each application remains the objective at all times, and it is this philosophy that ensures the appropriate configuration with the best belt cleaning arrangement and optimum selection of belt type and size. The locally manufactured Weba Chute System is completely different in its approach to handling and controlling the material.  “The Weba Chute System uses a ‘supertube’ with a cascade effect, where 95% of the material runs on material at the same time,” Baller says.

“When viewed in slow motion, what becomes apparent is that the bottom layer of particles in the product stream moves in a tumbling motion and does not glide down the chute, product runs on product. It is this design concept that significantly reduces wear. This concept is taken further by designing the internal angle of the transfer chute to match the product with the belt speed, and in this way spillage is either completely eliminated or greatly reduced,” he explains.