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Department of Materials Science and Metallurgical Engineering

SASSDA Stainless Steel Awards 2008 Tuks academic part of the team designated overall winner

Posted on 17 October 2008

David Shklaz, Joseph Roux and Madeleine du Toit inspecting the partially fabricated autoclave
David Shklaz, Joseph Roux and Madeleine du Toit inspecting the partially fabricated autoclave

Prof Madeleine du Toit of the Department of Materials Science and Metallurgical Engineering formed part of the winning Impala Platinum Holdings team, awarded the prestigious overall 2008 Stainless Steel Award presented by the South African Stainless Steel Development Association (SASSDA).

The team was also awarded top prize in the Product Category for its novel stainless steel Second Stage Leach Autoclave.


The Stainless Steel Awards have been held every second year since 1998, and serve to recognise exceptional achievements within the local and international stainless steel industry.  This year’s winning team consisted of Mr Joseph Roux of Impala Platinum Holdings (representing the client), Prof Madeleine du Toit (metallurgical consultant and welding engineer), Mr David Shklaz (design verification engineer) and Metso ND Engineering (manufacturer).


The newly designed second stage leach autoclave was manufactured by Metso ND Engineering and installed at the Impala Platinum Base Metal Refinery in Springs as a replacement for the conventional brick and lead lined autoclaves that have been used in the mining and refining industry for a number of years.  The original design consisted of a heavy wall carbon steel shell with a lead lining and two layers of acid bricks.  The acid bricks act as a wear resistant material and ensure a low surface temperature at the skin of the lead lining.  The lead lining acts as a corrosion barrier to protect the carbon steel shell.  This design is characterised by high maintenance costs and lengthy maintenance downtimes, compounded by the heavy installation.

A solution was needed to reduce the high costs of manufacturing, installation and operation. The team investigated various high alloy materials for the application, but finally decided to replace the carbon steel shell with duplex SAF 2205 stainless steel in the new design.  Use of this steel eliminates the need for lead or brick lining and reduces the wall thickness requirements substantially.  The vessel is welded in circular sections to form an elongated impermeable cylindrical body, with several agitator nozzles and compartments.


“This project exemplifies true innovation – a daring redesign, combined with the novel use of duplex stainless steel in an environment where lined carbon steel has been the industry norm for decades, leading to a technologically advanced product with significantly lower maintenance costs and reduced downtime,” says Prof Madeleine du Toit.


The new duplex stainless steel (SAF 2205) unit has been in continuous operation for the past 18 months and its performance has exceeded the highest expectations.  The design was so successful that a world patent has been registered.  The major benefits of the new stainless steel design include increased throughput, improved performance, less downtime and a safer working environment.  Lead has been eliminated and replaced with a more environmentally safe material, and the total lifespan of the vessel has been exptended.  In addition, the autoclave project has made significant developments in advancing the field of welding and optimising the integrity of welding quality standards in

South Africa.










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