A better way to loosen the nut: Liner changes made simple

A cone crusher liner changeout is a frustrating and time consuming task that can take more than a day to complete. The liner changeout is made up of a number of hazardous manual sub-tasks that have the potential to cause a musculoskeletal disorder injury, which is what caught the attention of Hy-Tec and NSW Trade & Investment, Mine Safety.

{{image2-a:r-w:250}}Hy-Tec’s Yarrabee Road Quarry had the opportunity to participate in NSW Mine Safety’s participatory ergonomics program – with a number of other North Coast quarries – from August to November 2014. The program aims to develop controls for the characteristics of hazardous manual tasks, including sustained force, exertion, awkward postures, repetitive movements, exposure to vibration and task duration.


During the program, Roger Nairne and Tom Sherd from Hy-Tec identified that changing the liners on a Cedarapids MVP380X roller cone crusher was a hazardous manual task. To loosen the nut to the cone crusher, workers would attach a hitting spanner and hit it with a 13kg sledgehammer. It can take up to two hours of hitting to loosen the nut. In addition, the worker is required to stand on the 15cm-wide rim of the crusher, about 4.5m above the ground, while using the sledgehammer.

“When Roger and Tom explained the task to the group and revealed a picture of Roger standing on the rim hitting that nut with a sledgehammer, I think my jaw dropped open!” said Kylie Newton, the health and human factors practice leader for NSW Mine Safety and a facilitator of the participatory ergonomics training.

“Full credit needs to go to Paul O’Connor and his team at Yarrabee Road Quarry – it takes a lot of courage to tackle such a big issue, especially with design implications, as well as share this information with other quarries from competing companies.”

{{image3-a:r-w:250}}On further investigation, Newton identified that Hy-Tec’s Yarrabee Road Quarry was not the only quarry using the cone crusher and dealing with the same issues. “During the program it became apparent that other companies had the same issues. However, some of the quarries managed the situation differently, often using contractors for the task. I had to remind them of their duties under work health and safety legislation and how this duty of care cannot be offloaded by just engaging a contractor.”


During the participatory ergonomics program participants completed a PErforM risk assessment, which paints a picture of the risk involved when completing the task (see Figure 1). Workers are encouraged to consider the hierarchy of controls when looking at options to eliminate the risk.

A focus is given to the higher order controls of elimination, substitution and engineering. Nairne and Sherd identified the liner changeout as high risk in exertion, posture and repetition, and moderate risk for vibration and duration. After consultation with their workmates, they decided to install a platform and re-engineer the cone nut.


Platform: Due to the complexity of the controls, Hy-Tec used a step change approach to implement its ideas.

The first hazards it tackled were posture and working at heights. It engaged a local engineering company, Midcoast Mobile Maintenance, and trialled a number of platform prototypes before the final decision was made to install a modular circular platform that fits on top of the cone crusher.

{{image4-a:r-w:250}}The platform is lifted in two stages by a crane and lowered on to pins on top of the cone crusher. The platform provides a safe workspace for the team to do the hot work needed to break the seal at the top of the cone crusher and to give access to the nut.

Since the team have started using the platform, not only is there more space to work, but they have also noticed a decrease in the time it takes to do the initial preparation work.

New cone nut configuration: Nairne and Sherd identified that even though they now have a safe and level work surface, they still had not reduced the hazardous manual task of swinging a sledgehammer to loosen the nut. The Yarrabee Road Quarry team discussed a number of possible solutions, and decided to change the nut so a power tool could be used.

The team engaged Blackbutt Engineering, Port Macquarie, to explore different nut configurations. The main challenge was the possibility a design change could affect the integrity of the cone crusher.

After much consultation, deliberation and testing, the cone nut was divided into two halves held together by a 12-bolt configuration. The new nut configuration was completed in mid-February and was to be trialled at the next liner changeout in mid-March. The team was hopeful the design change would be fully operational shortly after the trial.

{{image5-a:r-w:250}}This second phase of the project has taken about seven months to implement. It has been a time-consuming process that has cost Yarrabee Road Quarry more than $5000. Yet the benefits of the new nut configuration will far exceed the initial costs. It will reduce exposure to injury and the subsequent cost of a workers’ compensation claim, and will increase production by reducing maintenance time.

Mantle bolts: The next phase of the project for the Yarrabee Road Quarry team is the purchase of a hydraulic torque multiplier to undo the mantle bolts. Currently the team is trying to use different power tools and a long handled wrench. On some occasions the mantle bolts will not budge and a contractor with specialised equipment is called in to remove the bolts. This is a costly and time consuming process during the liner changeout .


An awards dinner was held in collaboration with the Institute of Quarrying Australia on 20 November, 2014, to celebrate the success of the North Coast participatory ergonomics program. Hy-Tec’s Yarrabee Road Quarry was the overall winner, taking home the best ergonomic initiative and the people’s choice awards.

Its win was based on the work it has done and will continue to do with the cone crusher. The main reason the judges awarded Hy-Tec the overall prize was the impact its initiatives will have not only on its Yarrabee Road Quarry and Hy-Tec nationally but all quarries around Australia.

Source: NSW Trade & Investment, Mine Safety



Burgess-Limerick R, Straker L, Pollock C, Dennis G, Leveritt S. Implementation of the participative ergonomics for manual tasks (PErforM) program at four Australian underground coal mines. In: International Journal of Industrial Ergonomics, 2007.

NSW Trade & Investment Participative Ergonomics Train the Work Team Facilitator Guide. Maitland NSW, 2014.

Newton K. Participatory Ergonomics Program prompts safety rethink. In: Quarry 22(9), September 2014.

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