The Pulheim purification plant was put into operation in 1982 and was expanded in 1994. In 2007, the Th. Scholten GmbH & Co. KG rehabilitated the first two spiral troughs with cast basalt with the result that it has not shown any signs of wear in five years of operation.
The situation in the purification plant: In light of the rough operating conditions resulting in a high susceptibility to wear, the concrete linings of the spiral troughs in particular suffer from pitting corrosion due to sulphuric acid. After contracting an expert report, the management decided in mid-2012 to replace the concrete trenches with cast basalt trenches from the Th. Scholten GmbH & Co. KG.
This economical material consisting primarily of silicon dioxide and aluminium oxide is not only resistant to corrosion caused by alkalis and acids (except for hydrofluoric acid), but has also proven itself over decades of use for applications in damp and chemically aggressive operating conditions and materials.
Scholten was contracted to partially rehabilitate the spiral troughs and both pump pits in addition to completely lining the entire screw pump with cast basalt and the associated comprehensive rehabilitation of the concrete according to the applicable concrete rehabilitation guidelines.
The Pulheim purification plant is equipped with four screw pumps with a diameter of 900 millimetres each as well as four more with a diameter of 1.200 millimetres each, over a length of 10.500 millimetres per screw pump. The experts from Th. Scholten GmbH & Co. KG installed prefabricated troughs made exactly to size in the Wülfrath factory in the concrete troughs already moulded to size during the concrete rehabilitation process. During installation, the 30 millimetre thick cast basalt tiles were joined in a mould and preassembled to form elements with a length of 500 millimetres each. At the site in Pulheim, a crane inserted the elements, each of which weighed about 90 kilos, in the six precisely pre-fabricated troughs so that they, when placed next to each other, completely covered the bed of the screws and precisely reflected the profile of the screw pumps.