A few years ago a large quarrying site in South Australia needed a major crushing and screening plant equipment upgrade and its management decided to invest in the latest technology to meet a growing demand for its product.
LOCATED IN THE ADELAIDE suburb of Seacliff Park, Boral’s Quarries’ hard rock Linwood quarry started operating over 130 years ago supplying limestone to a nearby cement works.
Boral, Australia’s largest building and construction materials supplier, acquired the quarry in 1994, which is currently the largest capacity quarry servicing the Adelaide metropolitan area.
In recent years, the region has seen a flurry of large construction projects such as Adelaide’s Desalination Plant, the city’s Northern and Southern Expressways and the Royal Adelaide Hospital. As a consequence the demand for aggregate products progressively increased, challenging the quarry’s production capabilities.
In 2013, site management decided to upgrade its crushing and screening plant with the latest technology to meet the growing demand.
A new primary crusher
The plant’s 30-year-old primary jaw crusher was struggling to keep up with production demands and the machine’s reliability and downtime were affecting overall plant performance.
Maintenance costs had risen sharply and the availability of spares was an ongoing problem. After considering the cost of refurbishing the existing crusher, Linwood’s management decided that investing in a new machine was its best option and, after a detailed analysis, selected Metso’s C140 jaw crusher.
“Minimising the need to modify our existing civils was a key prerequisite for the new machine,” says quarry manager, Andy Baker.
”Essentially we needed a modern like-for-like crusher that would fit into the existing footprint, increase throughput and be easy to maintain.”
Once the C140 was installed, the crusher’s performance and reliability significantly improved. The new machine’s ability to deliver more consistent output also immediately reduced the load and wear rates in other key areas of the plant.
Where personnel previously needed to constantly monitor the crusher to ensure a consistent product output size, this was now an automated process.
“Now we can simply programme the gap setting and be confident about what product we are going to get,” says Andy.
”The C140’s hydraulic adjustment provides a massive advantage for us in terms of overall efficiency and safety. It eliminates manual adjustments and associated hazards. This saves us time and keeps our production rates up.”
A win in tertiary crushing
Shortly after the new primary crusher was installed in 2014, its increased production capacity shifted the site’s bottleneck to the tertiary crushing circuit, where aggregate is further reduced in size and shaped into final end products. Linwood had two cone crushers responsible for this task that were nearing the end of their effective service life.
By weight and volume, cubically shaped aggregate is characteristically much stronger than flatter, elongated material. The existing crushers did not reliably produce aggregate that met the required index of elongation and flakiness. And to get the right shape, operators had to recirculate the output product through the crushers, and/or channel it for additional screening and polishing. Recirculation required additional processing time that could have been utilised producing new feed material.
Eventually, the team decided that two brand new machines was the best solution and, after an exhaustive selection process, bought two HP3 cone crushers from Metso in 2015.
The latest crusher technology
When Linwood first compared Metso HP3’s specifications with its existing crushers, it was a challenge to reconcile their performance and operating requirements.
There was quite a difference in the crusher’s size, power and capacity. The HP3’s design was physically smaller than the old crushers, yet had a 20 percent higher throughput capacity and can produce a higher precision product with one-pass production.
Sailing into uncharted waters
When Linwood needed to select its new crushers, the HP3 had just been released. There weren’t any of these machines operating in Australia, which meant Linwood’s managment couldn’t call upon the experiences of its usual references within Boral or the broader quarrying community. The availability of spares for the first and only units in Australia was also a concern.
However, Linwood recognised that the next generation HP3 offered many benefits and the new technology would future proof the site’s tertiary circuit and enable the wider integration of automation across the entire plant.
“The benefits were clear to us, but choosing the HP3s was still a leap of faith,” admits Santanu Ghosal, Linwood’s project manager.
”Ultimately I think it was the confidence in Metso’s people and expertise that gave us the assurance we needed. We had access to a very responsive team of local and international experts; and had enjoyed great post-sales support with our C140 primary crusher.”
Overcoming installation challenges
Replacing the old crushers with the new HP3s was always going to be a challenge while maintaining aggregate production rates at the quarry.
From an electrical point of view, the HP3’s larger motor required new mounting and cabling from the crusher through to the switch room. The mechanical work included installing new cooling units and a bigger standalone lubrication system.
A redesign of the feeder to a new location was also required. Alongside this work were the site’s safety improvements, which included extended platforms and improved working areas. The team estimated that the electrical and mechanical upgrades would take the tertiary crushing station offline for at least 17 days.
This made the timing of the installation a critical consideration. Linwood’s management originally considered performing the installation over Christmas, but were concerned about the availability of personnel, parts, and materials during this period.
While they planned to stockpile product in preparation for the installation, at the same time they also had major projects to supply and knew their reserves wouldn’t last 17 days.
To mitigate the loss of production, a trailer mounted cone crusher and screen was refurbished to supplement supply while the main plant was offline. Performance and efficiency were not optimal, but the mobile station closed the gap in production while installation and commissioning was in progress.
A leap forward in productivity and safety
A high degree of automation was involved with the new machines and the HP3’s touch-screen interface allows operators to have quick and easy access to troubleshooting, throughput and motor current information.
Mechanical settings, which previously had to be manually adjusted, are now performed in a matter of seconds via the machine’s touch screen. The productivity benefits and the elimination of safety risks involved in manual adjustments have made these features very popular with site operational staff.
Stray metallic objects, called tramp iron, that enter a crusher can stall and damage it, but the HP3’s innovative tramp release system, with dual-acting hydraulic cylinders and fixed return point, lets the crusher easily eject tramp iron.
If the crusher stops under load, the dual-acting hydraulic cylinders provide a powerful stroke that clears the crushing cavity. In both instances the crusher’s settings are restored without the need for operator intervention.
Also, the HP3’s liner fastening system doesn’t require the backing material that is common with other crushers. When liners are changed or reconfigured, hydraulic motors rotate the bowl completely out of the adjustment ring threads.
These two innovations save a lot of time and labour, iterates Andy.