Refurbished Outotec Pressure Filter solves dewatering constraints at Xstrata Nickel Australasia’s Cosmos site in WA

When the life of a corroded-out Outotec filter couldn’t be extended any longer, Outotec (Larox at the time) provided Cosmos Nickel Project (Cosmos) with an innovative and ecological solution for upgrading its dewatering capacity: a large, refurbished and modernised second-hand filter.

Despite low nickel prices during the 2008-2009 global financial crisis and unexpected sea freight delays, Outotec and Cosmos worked closely together during the filter project to overcome these obstacles.The end result was the commissioning of a large, modern pressure filter at Cosmos with 28% more capacity than the old one and within a 9-month timeframe that coincided with Cosmos’s mill optimisation.

With its dewatering constraints solved by a freshly painted, refurbished and modernized Outotec Larox pressure filter, Cosmos is ready to produce new benchmark dewatering rates. These improved rates will meet Xstrata Nickel Australasia’s (XNA’s) production target of 13k nickel tonnes per annum (Ni t pa) for 2010, a significant increase from 7.5k Ni t pa in 2009. 

Cosmos is a remote nickel-sulphide operation situated about 900 km north-west of Perth in Western Australia. The mine produces high-grade nickel concentrate containing 18-22% nickel that is trucked south to Esperance Port and shipped to Xstrata Nickel’s Sudbury smelter in Canada.

Throughout 2009, Cosmos systematically upgraded and optimised its processing plant in preparation for XNA’s doubled 2010 production target. The plant’s debottlenecking process included a review of a 17-year old Larox pressure filter, inherited with the Cosmos site when XNA bought out Jubilee Mines in February 2008.

The Cosmos filter review identified that the Outotec Larox pressure filter model PF 25/32 (25 m2) was working to full capacity for its configuration and that its small size would become a constraining factor in meeting XNA’s higher production production rate. Service technicians from the Outotec Perth office were sought for a filter audit, as well as a quote for upgrading and modernizing the existing equipment to a 32/32 capacity. 


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  • Debottlenecking dewatering process whithin a short timeframe that conincided with Cosmos's mill optimization


  • Refurbished and modernized second-hand pressure filter


  • 28% more capacity 
  • Ecological benefit when compared to manufacturing a new pressure filter

Outotec’s filter assessment found that the structural components were badly corroded after extensive outdoor weathering. Outotec deemed the filter’s life to be very limited and that an upgrade and modernization of its mechanical parts were not in Cosmos’s best interest long term. 

Concurrently planned with debottlenecking the dewatering constraints, Cosmos’s mill optimization was scheduled for completion within nine months. This timing, however, didn’t allow for a longer delivery time that was required for a brand new filter replacement. In response, Outotec searched worldwide for an available, suitable, second-hand pressure filter.

Providentially, a hydraulic Outotec Larox pressure filter model PF 32/38 (32 m 2 ) was sitting unused in England, leftover from a previous starch and chemical operation. It was perfect for Cosmos’s needs. Further expandable to a maximum capacity of 24 plates (38 m 2 ) (i.e. a PF 38/38 size), the available second-hand filter could also be easily converted to an abrasive minerals slurry application.

During the filter’s shipping to Finland, its refurbishment and modernization and then it's further shipping to Perth, Outotec kept Cosmos continually up-to-date with the filter’s progress. As a result, when unexpected logistics delays occurred during the filter’s shipping travels, Cosmos was able to readily accommodate these reports into the filter’s installation schedule.

The refurbishment and modernization of this second-hand filter also produced an ecological benefit by reducing the unnecessary carbon footprint of new filter manufacture through the use of an existing one.

When the filter sailed into Perth, Outotec agents quickly contacted Australian custom agents and within just a few days, the filter was released and ready for delivery to site. The filter was carefully trucked to Cosmos in an upright position with an accompanying traffic escort, arriving at its final destination by the end of July 2009.

An Outotec team arrived at Cosmos a day after the filter and promptly assisted site supervisors Ross Saxby and Glenn Kearns and their teams to undertake the required installation preparations.

The old filter was removed using a mobile 180t crane and over the subsequent 11 days, the teams prepared a reinforced steel platform for bearing the weight of the new filter’s larger structure and attached load cells. The filter platform also needed additional reinforcement for bearing the weight of a fully-loaded pressure filter sized as a PF 38/38.

The second-hand filter was successfully installed and began operating the first week of August 2009. Despite its sea freight delays, the newly commissioned filter met Cosmos’s increased production schedule, on time for Cosmos’s planned mill optimization.

Stewart Keenan, Cosmos’s maintenance superintendent, remembers Outotec’s involvement at the filter changeover: “I was more than happy with the services Outotec provided, particularly in the way they followed up. They were here night and day as soon as we shut the old filter off. They gave back-up support and the servicing technical guys were first-rate.”

Site General Manager, Andrew Millar, also gives credit to his Cosmos teams: “They got everything done in the timeframe and safely as well, considering the team worked in congested environments and with an 180t crane. Cosmos achieved 1 year LTR-free and 1 million man-hours LTR-free during the mill optimization period. If we had to do this project over again, we’d consider buying a second-hand Outotec filter again for sure.”

Cosmos’s refurbished and modernized pressure filter operates automatically and requires minimal attention. A 12-month warranty added to an Outotec service agreement gives Cosmos’s workforce time to learn the filter’s fine-tuning needs. They are assisted by an Outotec technician who is located in the vicinity for optimal customer support.

In the reconfiguring and re-piping of the processing plant, float circuitry and dewatering system, Cosmos also upgraded the SAG mill’s capacity, upsized the compressed air tank, added extra flotation capacity and installed a small ISA mill for regrinding concentrate.

The ten-year-old, second-hand filter’s new life expectancy has been extended by an additional 15 years and already producing high volumes with energy-saving benefits for Cosmos. One example is the filter’s newly affixed load cells, which are enabling optimization of the feed cycles through accurate logging of the production tonnage at regularly set intervals.

Keenan reports: “There weren’t really any hidden costs with our filter project. A couple of optimization changes were made along the way that required a separate costing. In particular, load cells were added for ensuring that cake thickness is consistent 100% of the time, saving unproductive time when using old time-based slurry feed termination parameters. We also added guards around the pinch valves to prevent any safety risk.

Outotec Australia Service’s structure of four regional areas ensures Outotec Service can provide extensive professional installation and maintenance capability and be close to its customer sites.

As a global filter solution provider of equipment, service and spare parts, Outotec’s primary intention is to maintain ongoing cooperation with its customers. As a happy Outotec customer, Keenan sums up the Cosmos filter project by saying: “All went very well. It was a really good project. There was lots of communication between Outotec and Cosmos after the filter decision was made so there were no surprises. So all in all, our second-hand Outotec filter is a success story – it came on budget, on time for production and with no injuries”.


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“The refurbishment and modernisation produced an ecological benefit by reducing the unnecessary carbon footprint of new filter manufacture through the use of an existing one “
“I was more than happy with the services Outotec provided, particularly in the way they followed up. They were here night and day as soon as we shut the old filter off“ - Stewart Keenan, Comos's Maintenance Superintendent
New automation system was provided with the refurbished filter.


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