Companhia Vale do Rio Doce, Projecto Bauxita de Paragominas, Para’, Brasil.
In 2008 a large deep paste tailings thickener in Paragominas, Brazil (Amazon Basin) suffered a catastrophic compressive buckling failure due to hydrostatic pressure on an 8 foot diameter central torsion reaction shaft.
GES Tech Group was retained by the owners to conduct an on-site investigation and determine the root cause of the failure. A second identical sister unit was potentially at risk due to the nature of this failure.
The source of the failure mode was determined and the results presented to the owners in a series of meetings at CVRD headquarters in Belo Horizonte, Minas Gerais, Brazil. The live presentation included a demonstration of the Mode 3 buckling failure suffered by the thickener torque reaction shaft. Pulling a slight vacuum on a plastic water bottle induced the same Mode 3 buckling failure that was observed in the 8 foot diameter torsion reaction shaft of the thickener.
The second unit was ultimately determined not to be subject to the same mode of failure since shipping ‘spiders’, intended to preserve cylindrical geometry while in a horizontal orientation, had been inadvertently left in place after installation. The first unit was modified in accordance with GES Tech Group recommendations, rebuilt and put back into service.
