Capital Equipment News November 2017

MINING NEWS

Rock intrusions a problem when specifying sizers and breakers

With coal miners moving into more difficult geological conditions, a detailed characterisation of the ore body is increasingly vital when specifying feeder breakers or mineral sizers, according to PC Kruger, capital sales manager at FLSmith Buffalo. “Most of the ‘easy’ coal seams in the Witbank coalfields have been mined, and what remains tends to include a high level of hard rock intrusion as well as tramp material such as steel, wood and concrete,” he says. In particular, a strip mining of old under- ground bord-and-pillar mine often encoun- ters a substantial portion of rock, which has a much higher ultimate compressive strength (UCS) than the coal. While the UCS of coal ranges from about 40 MPa to about 60 MPa, tests in the Witbank region, over a number of decades, have found that some rock in- trusions easily measure up to 210 MPa in strength. He says that feeder breakers are well suit- ed for most underground mining conditions where the coal is relatively soft and homoge- nous. “However, they are not designed to deal with high strength material,” he says. “Where there are regular hard rock intrusions, you will generally opt for mineral sizers.” Another critical consideration in specifying equipment for coal processing is the princi- ple of reduction ratios in each stage of siz- ing. Kruger says the “the rules of the game” require that, in the primary sizing stage, the

A critical consideration in specifying equipment for coal processing is the principle of reduction ratios in each stage of sizing.

ratio between the input size of coal and the output size should be about 4:1 or 5:1. “In other words, a large chunk of materi- al with dimensions of 1 200 mm in two or three dimension can realistically only be re- duced to about 300 mm in size in the primary phase,” he says. Similarly, in the secondary sizing stage, the ratio should be 3:1, which can reduce the 300  mm coal down to 100 mm. In the tertiary sizing stage, a ratio of 2:1 is the norm, break- ing the material down further to the minus 50 mm size that the end-user usually requires. “Trying to operate outside the boundaries of these reduction ratios invariably leads to increased wear and running costs,” he says.

“Putting over-sized material – say, larger than 150 mm material – into a tertiary sizer designed for 100 mm material, prevents the positive ‘bite’ that breaks the product down. Instead, the size and geometry of the pieces means that they do not pass cleanly through the rotors, and cause undue wear on the ro- tor teeth and other components.” He emphasises that trying to reduce capital expenditure by having fewer sizing stages – and therefore less equipment – is usually false economy. With the capital cost of the equipment making up only 8% to 10% of its total cost of ownership over its lifespan, the operating cost normally outweighs any upfront saving by orders of magnitude. b

Global Powerscreen award for ELB Equipment ELB Equipment has been awarded the highly prestigious Regional Dealer of the Year award by its principal crusher and screen supplier, Powerscreen. Measured among distributors in the Middle East and Africa region, ELB Equipment emerged as the overall best performer in terms of sales, training, technical support, servicing and dealing with warranties, among others. According to ELB Equipment divisional director, Pierre Nel, this is the second major award the company has received from Powerscreen, with the previous one being the World Dealer of the Year Award. The business score card criteria used to rank dealers included the dealer’s stockholding of equipment and parts, training of staff and coverage of skilled staff throughout the region and upholding the manufacturers overall brand image. “The criteria shows that ELB Equipment is able to compete with the best in the world and it also underscores our proposition to distribute the world’s leading mining and construction equipment, which we support to the satisfaction of the original equipment manufacturer and the expectations of our customers,” says Pierre. He adds that ELB Equipment, with its 100-year history in support of equipment in South Africa, has a long-established relationship with Powerscreen and has grown to become one of its largest dealers worldwide. Powerscreen is the world leader in terms of mobile crushing and screening technology and upholds the strict- est manufacturing and support standards for its products. “To win an award like this means that we have been acknowl-

ELB Equipment’s Pierre Nel (left) receives the Regional Dealer of the Year award from Powerscreen dealer manager, Tony Duggan.

edged globally for the high standards which we uphold in support of our customers here in southern Africa. It also serves as confir- mation of our hard work and our efforts to improve and grow with our customers,” concludes Pierre. b

CAPITAL EQUIPMENT NEWS NOVEMBER 2017 39