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CASE STUDY: PROMINENT HILL Organisation

Oz Minerals

SiteProminent Hill, South Australia

Year2010

ApplicationCopper-Gold concentrate

Challenge � Prominent Hill’s first simultaneous reline

� Shutdown and relining concurrent with other major works on site

� Working within high foot traffic footprint

� Site had only one reline machine

Solution � Highly specialised Outotec team perform mill relining and maintenance works

Result � Reline completed on time and on budget

� Incident free (zero harm)

The Prominent Hill operation comprises both an open pit mine and a newly developed underground operation with a 10Mtpa milling capacity. Prominent Hill produces some of the world’s highest grade copper concentrates. The site is a fly-in/fly-out operation employing approximately 1,200 employees and contractors.

Pneumatic torque unit being used to tighten bolts.

PROJECT OVERVIEW

Prominent Hill’s high grade ore production guidance for 2013 is between 90,000-95,000 tonnes copper and 130,000-150,000 ounces gold. The newer Ankata underground mine produces ore with similar metallurgical characteristics as the original Malu open cut mine, allowing the two run-of-mine ores to be blended together.

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Prominent Hill engaged the specialised mill relining capabilities of the former TME Group, now part of Outotec’s Services division, to perform the mill’s first dual shutdown since installed in August 2008. Both the SAG and Ball mill were scheduled for simultaneous relining to take place early in 2010, to replace the worn liners.

MILL RELINE SCOPE

As the mill liners had originally been installed by the Outotec team (then TME), they were aware of the technical specifications. A subsequent site audit facilitated assessment of the worn linings, additional works required and any

constraints in the working area. Originally the client anticipated the replacement of only the shell lifters, feed end lifters and plates and discharge grates on the Ø34’ SAG mill. However, following inspection, the scope of works was extended to include replacement of all the shell plates, along with the discharge end outer grates. The Ø24’ ball mill also required feed end outer and inner plates, as well as shell and discharge plates, to be replaced.

PROCESS

A team of 56 specialised personnel took part in the reline works which involved the replacement

and removal of over 1200 parts, with each mill taking less than 73 hours to complete. Skilled personnel and purpose designed equipment are critical in reducing reline time and ensuring safety.

Many of the mill reline personnel have worked together for almost a decade and are all qualified specialists in their field with a reputation for expediency, innovation and safety. The reline team have worked on the complete range of mill types and lining configurations for gold, copper, lead, zinc, uranium, nickel, diamond and cement mills.

The project managers worked closely with the client to manage the critical

Installing a new shell lifter on the SAG mill using the reline machine.

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path. This continual focus on reducing reline incurred downtime ensured completion within the planned shutdown schedule. This was accomplished by expertise in planning, monitoring and evaluating the shutdown timetable as well as utilising Short Interval Control, a bespoke programme used to track the progress of reline tasks. The programme provided up-to-the minute information including parts moved, time lost, estimated time of completion and took all delays into account.

CHALLENGES

To make optimal use of the shutdown period, Prominent Hill scheduled two major maintenance works by other teams to be carried out in addition to the relining project. During the works, the mill deck was therefore subject to high foot traffic and equipment congestion. As such, it was critical to ensure that strict safety standards were adhered to and a strong working relationship forged with mill staff and the other work forces on site. This had proven results in that the job was completed without incident or injury to the teams or equipment.

As site had only one mill reline machine available, completion time would essentially have been doubled if works had to be performed consecutively. To combat this, the Outotec team worked around the clock to complete the SAG mill and used a boom crane to remove all of the dismantled lining from the ball mill until the reline machine became available. Utilising available resources in this way saved

additional downtime and ensured the project was completed to deadline.

Additional minor works were identified and completed as the job proceeded, including assisting with the isolations, set up on the mill and installation of the Davit crane. Also, the discharge end and trunnions gaps were filled with ceramic.

SAFETY FIRST

Health and safety on-site is a primary objective for any project and during the mill reline the Outotec team ensured strict standards were adhered to. At the beginning of each shift a pre-start and toolbox meeting was held, with site safety inspections conducted per shift. Prior to shutdown, safety performance was discussed in detail and the actual shutdown closely monitored, resulting in a safe procedure without incident.

One area that existed within the former TME Group was a Safety and Training operation. Transfer of the licenses are due for completion in 2013, allowing the Registered Training Organisation (RTO) capability to be incorporated into Outotec’s remit. This fast-track, industry-specific training ensures highly qualified personnel are always available and readily expedited to site.

RESULTS

Through efficient planning and a strong working partnership with Oz Minerals and site, Prominent Hill’s first simultaneous shutdown of the SAG and Ball mill was executed on site with ‘zero harm’ to personnel, equipment or the environment. Outotec was also on-site for the mill restart, completing the retorque of the bolts for both mills after the first day of operation.

Feedback from site was very positive, with Graham Dearing, Process Superintendent saying, “Despite the downtime incurred due to only one available relining machine, works were completed on schedule. The reline machine and liner removal tools on-site performed well with no issues, however, the Outotec team also identified site equipment improvements that would benefit future, long-term performance”.

SCHEDULED MAINTENANCE SERVICES

Proactive maintenance ensures optimum grinding mill operation and Prominent Hill ensure this by scheduling maintenance shutdowns to be performed regularly at 14 week intervals. Outotec has been contracted to inspect and perform these future maintenance and repair works.

If you would like more information, click here to contact

andre.cuthbertson@outotec.com