IMPACT ROLLERS DOING WHAT THEY DO BEST
An increase in haul truck rolling resistance has been found to have a significant triple effect on costs, according to a recent study. Research by Western Australian School of Mines professor Dr Rodger Thompson showed that fuel burn, plant damage and cycling times all suffer at the hands of a poor haul road surface.
As high as 50pc of operating costs in open cut mines sit with loading and hauling, Dr Thompson said.
He found three factors of a failing or uneven haul road sent operational costs up. Firstly, the energy required to ‘climb’ the weight out of each depression in the road was adding up to 5pc in fuel costs; secondly, the increased cycling of suspension and friction on tyres was accelerating truck maintenance; and lastly, the cycle times were suffering badly.
The study found that the addition of only 3pc in rolling resistance was recording up to a 20pc increase in segment cycling times, pretty damning evidence that not enough attention is being paid to this high cost area of mining operations.
SQUARE IMPACT, HIGH IMPACT
The findings have not surprised Adelaide-based roller manufacturer Broons, which says they were recognised by the company long ago and indeed have been addressed by the release of its Square Impact Rollers. For more than three decades, Broons has been supplying these rollers to eradicate these exact problems; so much so that they have acquired legendary status.
The revolutionary patented BH-1300 Roller was released into the world market in the mid-1980s, quickly bestowing Broons an international reputation as a specialist in the application and operation of rolling dynamic compaction equipment.
The impact module imparts a massive 50kJ to 100kJ kinetic energy (or more, subject to module mass and width, ground conditions, etc) with every blow.
With its high energy output, the Broons Square Impact Roller compacts deep beneath the surface in the subgrade layers to secure the haul road structure, preventing the formation of ‘waves’ so detrimental to haul truck costs.
Even today, no alternative compaction equipment comes close to the Impact Roller on performance, productivity and price.
Broons’ experience in dynamic compaction is unequalled anywhere around the globe, and has been used by civil engineering contractors, property developers, mining companies, state, local and Federal Government road agencies, forestry sectors, and cotton and rice growers.
In the mining industry, Broons’ enormous BH-1950MS has revolutionised the way to reduce tyre damage and ultimately consumption of these expensive tyres.
NEVER TOO TYRED
Of course, the more compact a road surface, the less the wear on tyres. Many companies are using Broons Square Impact Rollers to flatten surfaces and help reduce tyre damage, and ultimately save money on wear and tear.
An investment in a Roller is quickly recouped by the savings made from improved tyre wear and reduced damage to both the tyres and the haul truck suspension.
A number of mines throughout Australia and overseas are using the Broons Impact Rollers to rubbilise rock on their tip heads and waste dumps as a way of improving their tyre management regime.
According to Broons director Stuart Bowes, mining companies are always looking for a solution to minimise premature wear and damage to haul truck tyres.
“When times are good, high prices and low availability forces them to look for options to extend the life of tyres,” he said. “When resource prices are low, operating cost savings are the driver for improving tyre life….. there’s always a need for our equipment.”
Large or sharp rock will slice through and critically damage even a brand new tyre, while smaller rocks can lodge between the lugs and eventually penetrate and puncture the tyre.
The Broons “MS” (mine specification) Impact Rollers are world leaders in minimising haul truck tyre wear by improving the running surface on haul roads, tip heads, and pit floors. Supplied as a package with a suitably matched tow tractor, the Impact Rollers quickly reduce sharp edges and allow haul trucks to travel easily without the fear of tyre damage.
An improved running surface on haul roads and waste dumps has also shown it’s possible to reduce mechanical wear and tear on haul truck suspension and associated components, delivering lower overall maintenance costs.
COMPACTION AND CAPPING
The Impact Rollers have also been employed in many other applications, including the compaction of capping layers on waste dumps, where the equipment has proven to be both productive and cost-effective.
Capping layers are typically used to reduce the likelihood of spontaneous combustion coal waste and overburden, or the infiltration of surface water through mine waste that can lead to environmental problems with drainage and runoff.
Water infiltration and/or the convective transport of oxygen into a dump
can be reduced to very low levels by constructing a low permeability compacted cover over the dump.
Trials and ongoing use have shown that by placing around one metre of inert material over the waste and then compacting with the Square Impact Rollers will pay dividends.
Studies undertaken by Dr Mark Jaksa and Brendan Scott of the School of Civil, Environmental and Mining Engineering at the University of Adelaide have also shown that by using a single thicker capping layer, greater recycling of mine spoil materials can be used without the need to screen out large quantities of oversized materials.
Deep fills have traditionally been undertaken by compacting soil in thin layers using relatively small sized material placed in a highly controlled manner.
While conventional rollers can satisfactorily compact fill in layers up to 400mm thickness, studies at mine sites have shown that the Impact Roller can typically achieve thick-lift compaction in layers of 500-1500mm, depending on the material composition and the number of passes by the roller.
With just six to 10 passes applied on the surface, improvement in density can occur to at least one metre, while 30-40 passes can result in significant improvement down to 2m and beyond in some materials.
The Square Impact Roller was also used in trials in Emerald, Queensland, aimed at creating a capping layer over mine waste. Ensham Resources used a BH1300 (8t module) and a BH-1300HD (12t module) over a 40,000m2 trial area, planning to achieve a low permeability capping layer.
Ensham hopes to reinstate close to 150ha of the open-cut coal mine to flood plain conditions. Results from the trials were obtained to determine the most efficient method to meet strict environmental and engineering requirements for the ongoing placement and compaction of capping layers.
HEADS UP ON TAILINGS
Broons Impact Rollers were used by Cooks Construction to carry out layering work for the Century Zinc mine in Lawn Hill, Queensland, one of the largest zinc mines in the world.
With several tailings dams at the site ranging from 50m to 1000m in length, and varying in height from 5m to 30m, storage capacity will total 56m m3 of tailings deposits when complete.
Concerns about the in-situ densities of the earthfill resulted in the need for completed layers to be proof-rolled prior to the placement of subsequent layers.
Broons BH-1300 (8t module) machines successfully proof-rolled completed layers previously compacted with vibrating rollers, ensuring absolute confidence in the integrity of the dam, while identifying soft spots for treatment.
GOING THE DISTANCE
With the continued globalisation of mining and construction companies, there can be operations across many time zones.
Broons employs sophisticated transport infrastructure to support the demands of its truly international customers. Since the 1980s, the manufacturer has been sending the Square Impact rollers via road, rail, sea and even air, to meet the demand from companies the world over.
Often matched with suitable tractors, the machines can be stripped down for the most effective packaging.
“Given most of our clients work in remote regions, the transport costs can be significant so our operations team spend a lot of hours finding the best transport solution,” Mr Bowes said.
“Often this can be dictated by the urgency of the need for the equipment. “In the Middle East we flew 25 units with tractors, which was unprecedented; but our clients were working just three days after the equipment left our shores.” Domestically, long haul road freight into WA from the east can be expensive but Broons recently partnered with SCT Logistics to provide a cost-effective solution using the rail service across the Nullarbor.
The rollers have been revered worldwide for transforming haul roads, with their deep compaction, low maintenance and speed to sites.
Costing a fraction of the savings to be made, a Square Impact Roller with matched tow tractor is ready for hire or purchase now, from Broons’ extensive Australia-wide fleet. Broons is renowned for its commitment to customer service, and provides full in-field operator training and service to the industry, backed up with a comprehensive and prompt parts operation.
Resistance is futile.
A Broons Impact Roller doing what it does best: breaking rocks.
A tyre damaged by driving on rocks.
An example of tyre wear caused by driving on poor condition roads.
Rock and roll: A before-and-after comparison of rocks after they’ve been rolled.