When Rio Tinto needed one of their thickeners rebuilt in a remote part of Western Australia, it turned out to be more than just a routine modification. As FLSmidth customer service, site and project personnel started the draining and cleaning process, they discovered additional required repairs and maintenance that greatly increased the scale of the project and provided opportunities for FLSmidth to showcase its professionalism and quality service repair work.
Designed and supplied by FLSmidth over 20 years ago and installed in 1995, the 75-meter iron ore fine tailings thickener is located at the Rio Tinto Pilbara Iron site at Paraburdoo in Western Australia, just over 1,500 kilometres north of Perth. For several years now, Rio Tinto had good intentions to overhaul the thickener and in 2009 had purchased a new slew bearing to start the rebuild process. Unfortunately, plans were put on hold and the bearing sat in storage for the next four years until 2013, when FLSmidth received a request to perform the design of a bridge support for this same thickener to allow installation of the previously purchased slew bearing.
As the project progressed, Rio Tinto requested quotes in early 2014 for the installation of the slew bearing together with the supply and installation of a new launder drop box, new wear blades and the aforementioned bridge support to enable installation of all the new equipment.
After FLSmidth was awarded the job, our team started work on site in September 2014, with the 75-meter thickener being drained and cleaned of 21.6 mega liters of liquid using submersible pumps and high-pressure hoses. The cleaning of the thickener took four full days.
The installation of a temporary bridge support commenced so the original bridge structure could be removed – along with all piping and electrical components of the bridge. The team was now able to remove the original slew bearing and its supports and install the new bearing, launder drop box and wear blades.
During the installation, the site service team conducted a visual inspection on the rake arms, cage and caisson, and discovered major failures on the thickener cage and rake arms. The following problems were detected:
- The trench scrapers were damaged and unserviceable
- The rake arm blades were bent and worn out
- The SHS braces were bent and buckled
- Areas on the rake arms (which were previously repaired) had excessive corrosion and weld cracks
- The product had varying levels of density, hardness and size with the highest concentration around the caisson area
- The rake arms had weld cracks in the original welds. They were bleeding water (which indicates the chords were full of water)
- The rake arm top bracings were corroded and delaminated
- There was misalignment between the long rake arms of around 210 mm
- Misalignment between short rake arms of approximately 50 mm
- Caisson support cone segment and holding bolts were corroded and delaminated extensively
- The hydraulic lift arms were identified as lifting independently during operation, causing unequal lift distances
- Tramp material/contaminants were found in the thickener
- Flocculant 6-inch pipe completely blocked at feed well dosing point
These findings were presented to Rio Tinto management, and consequently, FLSmidth received a request to quote for the supply and installation of a new cage with rake arms and to provide an inventory of spares for future maintenance.
The job was long and challenging for all the personnel, especially as they were working in a hot and remote area of Western Australia. The temperature in the Paraburdoo area averages around 28°C/83°F in winter and a hot 39°C/102°F in summer. The highest maximum temperature has been recorded at a sweltering 48.9°C/120°F.
With FLSmidth’s recent addition of our site services group, we were able to not only supply the parts and manage each of the projects, but we were also capable of successfully completing the installation in the required time. One major highlight of this entire project is that all personnel involved in the project worked over a combined 16,000 hours incident free! This is definitely a major achievement for our customer services efforts globally and shows our focus on making safety and quality part of our culture.
With close collaboration between FLSmidth’s Customer Service Spares, Projects, Site Services and the assistance provided by locally contracted providers for items such as electrical and scaffolding works, this project was a great success and a perfect example of FLSmidth’s vision to be a One Source preferred full-service provider. The Pilbara Access group was also a great support to all of our sub-contractors at different stages of the job, including draining, cleaning, structural, mechanical, piping, and electrical.
The combined projects were all safely, efficiently and successfully completed to the satisfaction of the customer, opening up a great potential for FLSmidth to perform similar repairs and modifications at other sites throughout Australia. A further request from Rio Tinto has already been received for the complete removal and rebuild of the CV10 screen house discharge conveyor, as well as discussions to supply additional specialized equipment next year.
CONTACT: David Williams