Daniel Ausling and Steve Ash of BG&E Resources explain how a novel innovation involving 200 tonnes of Australian-made steel solved crusher vibration at Rio Tinto’s Hope Downs 4 Site.
Run-of-Mine (ROM) crushing operations are often faced with oversized material impacting the primary sizer or ‘balling’ of rock within the primary sizer, causing severe vibration.
Balling is the bouncing of large boulders in between the sizer heads and against the walls – it leads to high impact-related damage, fatigue, and maintenance issues.
This was certainly the case at Rio Tinto’s Marandoo Hope Downs 4 (HD4) primary crushing facilities, where excessive levels of vibration were identified at the facility over an extended time. Structural fatigue/failure, equipment failure, building components rattling loose, and risk to personnel safety were all witnessed as a result.
BG&E Resources (BGER) and Engineering Dynamics Consultants (EDC) were engaged by Rio Tinto to deliver an innovative design solution to solve the excessive vibrations. By leveraging proven technologies from other industries, BGER and EDC delivered a fit-for purpose solution in what is believed to be a world-first application without any unknown risks for the asset owner.
Understanding the problem
Rio Tinto identified the primary crusher building as a significant health and safety risk to workers due to guarding, handrailing, grid mesh clips and stairs coming loose due to the excessive vibration.
Under further investigation, it was discovered that the severity of the crusher vibrations was so extreme that the reliability and structural integrity of the entire facility was compromised, presenting an unacceptable risk level to personnel and operations.
Unravelling the challenges
Rio Tinto required a solution that not only kept the original level of functionality but would ideally increase functionality and throughput to new levels. It was concerned with the possibility of significant lost production and the requirement to re-train site personnel on the use of new, or substantially different, equipment.
Strengthening the existing structure to reduce the vibration to acceptable limits would have proven almost impossible to achieve within reasonable cost. This is due to the level of vibration experienced and the complexity of the system, coupled with the inability to effectively position additional structural supports. Fundamentally, a complex problem lay ahead, and a different structural form was required.
Delivering a novel solution
BGERs multidisciplinary structural, mechanical and electrical engineering capabilities, combined with EDC’s expertise in detailed dynamics modelling and on-site dynamic testing, resulted in the creation of a world-first application.
Proven technologies from high-rise earthquake isolation, haul trucks and rail chassis were borrowed and combined to minimise the risk of design uncertainty.