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Nov 21, 2019

Rapid, seamless installation and commissioning of Outotec bolted thickener for Carosue Dam, Australia

Bolted 26m Outotec thickener is commissioning-ready in 14 days for Saracen’s Carosue Dam, Australia.


Saracen Mineral Holdings Limited owns and operates the Carosue Dam gold mine, which is located near Kalgoorlie, in Western Australia. In 2019, Carosue Dam completed the construction of a new thickener and paste plant as part of an upgrade to its existing processing infrastructure. Outotec was tasked, under contractor GR Engineering Services (GRES), with supplying a thickener as part of this project.

Bolted solution

Following various studies, it was agreed that optimal sizing for the new thickener was 26m diameter. GRES then tasked Outotec with the design and supply of the thickener. Although the bolted design, with its large modular pieces, incurs higher capital fabrication cost due to the significant number of bolts and flanges, it’s almost always a better value proposition overall. Bolted designs require more fabrication time in the workshop but significantly less (costly) time is spent on site installation.

Carosue Dam’s 26 thickener
Carosue Dam’s 26 thickener

Time minimizer

With 30 years of experience and over 150 installations, Outotec bolted designs have shown to be both reliable and economically competitive. Procedures and materials for unpacking, lifting, bolting and sealing have all been perfected over time and lead to very rapid and trouble-free installation. Quality bolted design comes down to good engineering, testing and field experience, so it’s critical to use a competent and experienced supplier. The Carosue Dam thickener also featured Outotec’s Vane Feedwell™ technology, a standard on all Outotec thickeners for over a decade.

Reduced site risk

Site risk is significantly reduced with a fully bolted thickener design. Site activities such as welding, grinding, blasting, painting, rubber lining, confined space, time and working at heights are all completed in the workshop. Often, the higher initial capital cost of bolted design will translate into overall project savings by replacing hundreds of meters of site welds and painting with simple bolt tensioning and joint sealing. The fully bolted tank solution allows for easily transportable sections as well as rapid and safe site erection.

Workshop trial assembly 

For the Carosue Dam thickener, the full tank was trial assembled in our workshop in China and quality inspected to ensure accurate fabrication tolerances and ease of construction at site. Outotec has full-time workshop QC inspectors in our China facilities who monitor all aspects of the fabrication process including document and drawing management, receipt of materials, dimensional and fit-up checks, welding and blasting and painting, to highlight a few.

The workshop trial assembly included full tank, bridge, drive, feed system and mechanism. The power pack and controls are also fully workshop tested. Surface treatments were applied in the workshop under the correct temperature and humidity, rather than outside in the elements. In effect, all of the hard work was completed in the workshop, so site installation was greatly simplified.

Trial assembly at Outotec workshop
Trial assembly at Outotec workshop

Installation logistics and support

The Outotec workshop ensured every component, nut and bolt was organised to facilitate an efficient and seamless install. For example, items which were to be used first in the install were packed last, so they would be unpacked first at site. We also provided clearly visible and documented match marking prior to workshop disassembly, as well as detailed drawings to facilitate a study lift and erection sequencing. Packing of all components was designed to maximise ease of handling and minimize the possibility of transport damage. Comprehensive installation drawings and instructions were also provided to facilitate a speedy and seamless installation.

Quality management is key

Quality management is always key, particularly with large vessels such as thickeners. With the bolted design, quality is better controlled, as most QA is performed in the workshop. Quality management also extends to Outotec’s established systems and procedures, managing the entire process from design through to delivery and beyond.


The GRES construction team, using day shift only, fully installed the thickener in just 14 days. The 26m thickener was commissioning-ready in 14 days. The pre-commissioning site check was completed in 16 hours in total.

GRES Senior Project Engineer, Matt Sala Tenna, commented “All went well. Fabrication quality, packaging and marking of all materials was good so it was easy to assemble and find parts”. The quality of the supply from Outotec and quality of Outotec IOM / install drawings was good too which helps us on site” he added.

Since commissioning, the thickener has been performing to expectations.

“The installation of this piece of equipment has allowed the processing plant to not only produce a product suitable for underground backfill but also reduce the processing plant’s lime consumption significantly” explains Cleo Leunig, Processing Manager at Carosue Dam. “The thickener has allowed a quicker return of process water back into the circuit and has reduced lime consumption by ~3kg/t” she continued.


*Metso Outotec was formed July 1, 2020 when Metso and Outotec merged into one company. This case study has been written prior to the merger under the old company name.

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