Crushing big time

A Metso Lokotrack LT160 is the largest mobile crusher being used in the Southern Hemisphere.

Boral in Australia has implemented an innovative in-pit crushing project at its new Peppertree Quarry in the NSW Southern Tablelands, around 180 kilometres southwest of Sydney.

The new quarry, which became operational this year, will supply the Sydney metropolitan area and greater NSW building and construction industries with up to 3.5 million tons of aggregate products per year.

Construction of these new facilities at Peppertree started in July 2011 after a decade of planning. A risk assessment of the crushing process led to the selection of in-pit crushing as the safest and most efficient option for the new plant. Boral site manager Steve Parsons says that the use of in-pit crushing for quarry applications has been a trend in Europe for some time, but is relatively new in Australia.

“Boral is now looking to optimise its quarrying process and get away from the traditional load and haul operations, where you have a large number of trucks and people moving between the blast site and the fixed crushing plant.”

Research into finding a crusher that could handle the planned production volume led Boral to select Metso’s Lokotrack LT160 together with the company’s patented Lokolink mobile conveyor system.

Weighing in at a whopping 285 tons and measuring 12 metres high by 25 metres in length, this is the largest mobile crusher in the Southern Hemisphere, and extensive design consultation between Boral’s technical staff and Metso’s design team prior to manufacture has, arguably, produced the most sophisticated machine of its kind, with a number of innovations never before seen on a mobile machine.

A major challenge, says Boral, was to customise the LT160 to meet its strict safety requirements, which, it claims, are even more stringent than Australian and European standards. To achieve this, Boral put together a team of designers, engineers, operators and OHS personnel to review the LT160 design and to identify any potential hazards and improvements before accepting the final design.

As a result the LT160 at Peppertree has a number of features that make the machine unique with regard to current safety practices.

Some of the solutions, such as guarding and using stairs

rather than ladders for maintenance access, are requirements of Australian standards whereas others are unique.  These include shrouds around the crusher to reduce dust and noise, rubber wear liners on the hopper to reduce noise, a service crane installed for jaw liner changes to eliminate the need for a mobile crane, as well as walkways that extend the full length of the Lokolink conveyors on both sides.

Anatomy of a truckless system

In a conventional crushing plant, a drill and blast team blasts the shot and develops a muck pile. A front-end loader at the muck pile loads haul trucks that transport the rock to a fixed primary crusher.

With the in-put crushing solution at Peppertree, an excavator located on the muck pile loads material directly into the Lokotrack crusher’s hopper. The rock moves along a grizzly feeder that passes undersized rock directly onto the machine’s outbound conveyor. Only the large rock that needs to be crushed passes through the jaw crusher, which is capable of processing rocks up to one metre in size. In this way, energy isn’t wasted on passing small material through the crusher.

Crushed rock is then transported to the fixed, in-pit belt conveyor via two mobile Lokolink conveyors. The fixed conveyor carries crushed rock from the Lokotrack to the fixed plant for further processing. A patented swivel mechanism on the Lokolink conveyors ensures crushed material flows freely at all conveyor angles.

The Lokotrack crusher can crush 1150 tons of rock per hour and needs to be relocated every few hours – a process that can be done in minutes by an operator via a remote console worn around the operator’s waist.

When blasting is performed, the crusher and conveyors are moved to a safe distance around 70 metres away. After the blast, a wheel loader cleans the quarry floor and the crusher moves to the new muck pile. Operation resumes with minimal production downtime.

When it’s time to move to a different pit location, the Lokolink conveyors are disconnected from the field hopper using hydraulic actuators.

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