Scorpion EW Joint Movement
This project was brought to A&T by Anglo American plc in 2003 after the plant suffered a catastrophic failure in the acid lining system within 7 months of live commissioning. These are some of the pictures taken at the time, which show how reactive the Namibian soil is when contaminated with acidic fluids. Some of these slabs heaved over 300mm threatening all of the tanks and in particular, the cell house which was calibrated to very tight tolerances of movement.
The areas re-lined by A&T using TCRL were the PLS, Copper Nickel Extraction, Carbon Columns, Manganese Addition, Effluent bunds, Belt Filters, Re-acidification bund, thickeners and the EW Tank farm (which was the most severely damaged area). The area shown in this case study is the Electrowinning tank farm which is parallel to the cell house.
The tank farm area is about 4000m² and at the time contained eight concrete tanks approximately 10m diameter by 15m tall. These tanks where built on independent foundations prior to the floor slabs being cast.. The lining system that failed was a bonded system with joints at approx. 10m intervals.
A&T’s brief was to design a retrofit solution that would substantially reduce the need to excavate and rebuild large areas of the plant, get the plant back on line quickly and would remove the vulnerability of joints in the slabs thereby removing further threat to the plant . After exhaustive investigations and tests the solution used for the EW was the following
.As TRCL is non bonded, joint-less system and can cover all expansion and movement joints, TCRL was specified to cover all of the slabs and joints in the bund floors and walls.
Only one half of the bund needed excavated to a depth of 4m to remove contaminated soil that was threatening the tanks adjacent to the SX Plant. This was backfilled with non contaminated soil and new slabs thrown on which TCRL was applied within 3 – 5 days from casting.
The other half next to the cell house was not excavated – only the worst of the heaved slabs were removed, and the contaminated soil was removed to a shallow depth. TCRL was installed over the old damaged lining and joints very quickly..
After TCRL was installed and the EW was put back online there has been no movement since.