Recycling gets a concrete solution

As an essential construction element of modern buildings, roads and bridges, concrete underpins urban development across the globe. But as concrete-based infrastructure is replaced with new structures, an enormous amount of building waste is produced - much of it steel-reinforced concrete. There was a time when this building rubble would end up as landfill, but more recently new waste minimisation strategies have emerged. Here, concrete recycling processes are proving extremely valuable, both economically and environmentally.

One company leading the way in this field is Australian construction and demolition materials recycler, Alex Fraser Group. With demand for its recycled products increasing steadily in recent years, Alex Fraser Group decided to establish a new concrete recycling facility at its Laverton North site in western Melbourne, Victoria. The new facility features a sophisticated materials handling system, founded on the latest geared motor technology from drives solutions group, SEW-Eurodrive.

The new Alex Fraser Group concrete recycling facility has been designed with reliability, efficiency and safety at its core. Underpinned by the latest crushing and conveying technologies, the new facility is capable of product throughput rates of 550 tonnes per hour.

The new facility comprises over 600 m of heavy-duty belt conveyors. With all conveyors requiring geared motors, Alex Fraser Group chose to implement SEW-Eurodrive’s drive solutions plant-wide. Over 30 SEW-Eurodrive IP66-rated geared motor combinations, up to 55 kW in size, provide the driving force for the facility’s conveyer applications.

“It was crucial that we implemented a dependable geared motor solution and this is what SEW-Eurodrive provided,” says Dean Walsh, Alex Fraser Group Plant Projects Manager. “The SEW-Eurodrive geared motors boast an impressive duty cycle, enabling us to turn them on and off frequently and still have them come up to speed and torque extremely quickly.”

The entire process is controlled and monitored from a centrally-located management centre. Operators are able to interrogate the process via a plant-wide SCADA system, which is fed by a central ethernet network.

Safety is a primary consideration across all of Alex Fraser Group’s sites and operations. As a result, all of the geared motors used on the conveyors at the new facility feature direct-coupled, geared motor/shaft arrangements. Previously, v-belt-to-gear box arrangements had been used, which required extra guarding and maintenance. “By direct coupling, we are able to avoid this,” says Walsh. “However, in the past, we’ve avoided direct-coupling gearboxes - in a corrosive environment, it is often difficult to remove the gearbox from the shaft, and it’s not uncommon to have to cut them off with a gas axe.”

SEW-Eurodrive’s TorqLOC keyless, hollow shaft mounting system presented the ideal solution for direct-coupling the geared motors onto the conveyor shafts. It provides a keyless connection with a shrink disc, with the interfacing surfaces relying on two conical tapered bushings, made from bronze and nickel-plated steel. “Traditional hollow shaft securing solutions suffer from corrosion problems, creating disassembly difficulties,” says Andrew Kurzem, SEW-Eurodrive Technical Sales Representative. “TorqLOC components are designed so you only have to loosen the steel bushing taper a little and it will fall away.”

Inherently environmentally friendly, Alex Fraser Group’s concrete recycling operation is setting the benchmark for the provision of sustainable building materials. Recently, an Alex Fraser Group-funded Royal Melbourne Institute of Technology (RMIT) research program highlighted the environmental benefits of recycled concrete. It was found that the carbon impact of recycled concrete produced by Alex Fraser Group is 65% less when compared with traditional manufacturing.

Environmental performance is further enhanced by improved operational efficiencies. According to Kurzem, this was a key parameter when specifying the SEW-Eurodrive geared motor combinations. “Each gear motor has been selected to deliver optimal operational efficiency,” he says. “All motors are MEPS-compliant, high-efficiency varieties. In combination with Alex Fraser Group’s recycling process, real environmental savings can be made.”

Another key issue was reliability. Alex Fraser Group’s concrete recycling process is a 24-hour-a-day, seven-days-a-week operation. “We need our conveyors and our process to operate uninterrupted,” says Walsh. “This, of course, is dependent on the ongoing performance and maintenance of the geared motors.”

With the new concrete recycling facility online and on schedule, Alex Fraser Group is looking to the future. The new concrete recycling plant has performed well above expectations during commissioning trials and is on target to achieve a production rate of 600 tonnes per hour. Here, the conveyors and geared motors have been sized to accommodate this increase. “Alex Fraser Group is looking forward to bringing the plant up to full production capacity,” says Walsh. “By working alongside like-minded, environmentally aware industry partners like SEW-Eurodrive, we’re confident of reaching our 2014 production target of 40 million tonnes of recycled concrete.”