Airborne dust is a long-standing and common problem in bulk materials handling operations. The inability to control dust results in increased conveyor belt wear, with its associated downtime and loss of productivity.

Not only is productivity at stake, but mineral processing plants are under pressure to comply with international environmental regulations. By incorporating a chute system that is able to reduce both dust and noise pollution, organisations will be able to increase their environmental friendliness.

Without giving careful consideration to the design of a transfer point, larger materials will bounce and roll, thus creating a belt wear problem. In addition, air is entrained in the fines and creates a dust problem.

According to Mark Baller, managing director of Weba Chute Systems, it is important to approach each transfer point in an individualistic manner. “Weba Chute Systems has more than 3 000 transfer chute installations in place in South Africa, in many African countries and in several other parts of the world. This, together with the intellectual property we own on transfer point design and our ISO 9001:2008 accreditation, places us in a good position to provide a chute solution that works for each application.”

Due to the variability in particle size or moisture content of the material, there will be a resultant build-up in the chute, which will alter the flow of material through the chute. If the material drops through the chute and onto the receiving belt in an off-centre manner, this is likely to result in spillage at the loading point. In addition, if the belt is forced to ride up on the idlers eccentrically, spillage will occur along the route.

Historically, conveyor systems design focused more on the structural integrity of the system and the selection of the mechanical components. Unfortunately, the design of the transfer points was considered of secondary importance and has been constrained by a lack of design analysis of the material flow characteristics and needs. This has resulted in innumerable transfers that are inefficient and expensive.

A correctly designed and efficient transfer point will eliminate these problems. Baller cautions that the object of the exercise is not to decrease the momentum of the material entering the chute. “In fact, momentum can be used to keep the speed of the flowing material close to the belt speed all the way through the chute. If you attempt to slow down the flowing stream of material, this will result in an increase in the cross sectional area, which may cause the chute to become blocked. Also, by slowing the material down and then accelerating it again, one is providing an ideal environment for entraining air and creating dust.”

Leveraging a vast and varied number of successful projects, Weba Chute Systems believes that any successful transfer point design begins with a comprehensive site visit. “We consult with the plant’s engineers and maintenance staff to ensure that the final product meets all their requirements, as well as complying with SHEQ (safety, health, environmental and quality) standards,” says Baller.

“We incorporate the operation’s unique product specifications and data, belt width, belt speed, material sizes and shape, and throughput as well as the plant layout, including the position of belt scrapers and dust suppression/extraction systems. We consider a holistic design which does not focus only on the entry and exit points, but also incorporates the control of the flow, volume and velocity of the material being transferred at all times,” Baller continues.

Years of research and experimentation have resulted in the development of the Weba Chute System, which uses a ‘supertube’ effect with a cascade scenario. This means that 95% of the material runs on material at all times.

“There are a number of benefits accruing from this principle including reduced degradation of materials, wear and tear, noise and dust pollution, spillage, excessive impact and subsequent belt damage. In all Weba Chute Systems installations, we have received feedback that there is an immediate decrease in the levels of unwanted dust and noise pollution. This creates a working environment where workers are more productive and healthy,” Baller explains.

“By investing in a transfer point system that considers the necessary elements, mineral processing plants are able to drastically reduce the maintenance costs and man-hours that occur as a result of wear and failure. Similarly, the costs incurred for clean-up of material clogging in transfer chutes, spilling around the transfer area, and dust build-up on equipment and working areas, is reduced,” Baller continues.

Aligned with these bottom line costs are the advantages derived from an environmental perspective. Primarily these include reduced power consumption, lower noise levels, less spillage, and a drastic decrease in the presence of visible/respirable dust.

Not only does excessive respirable dust have a negative impact on the health of workers, but it is also responsible for increased maintenance requirements when it builds up on conveyor mechanical components. It can also result in reduced visibility on site which provides an environment that is conducive to accidents as well as lowered employee morale. In the worst case scenario, dust build-up can result in an explosive situation.

“Controlling the transfer of material onto the conveyor belt eliminates a high proportion of wear and tear and minimises the rebound that traditionally sends clouds of dust into the air. This ensures not only increased cost saving advantages for customers, but also boosts occupational health and safety compliance. The twofold effect that results from using a customised Weba Chute System, impacts positively on the profitability and reputation of an organisation,” Baller concludes.

ENVIRONMENTALLY FRIENDLY CHUTE SYSTEM PIC 01 : Weba Chute Systems control the material flow onto the conveyor belt.

ENVIRONMENTALLY FRIENDLY CHUTE SYSTEM PIC 02 : Weba Chute Systems are associated with a significant decrease in unwanted spillage and dust.

ENVIRONMENTALLY FRIENDLY CHUTE SYSTEM PIC 03 : There are more than 4000 Weba Chute Systems in operation globally.