Challenge for pumps
The mine operator Hellenic Copper Mines (HMC) in Nicosia/Cyprus is one of the large opencast copper ore mines (Fig. 1). The hydrometallurgical extraction at Skouriotissa in the western part of the island was problematic for years. Due to a pH value of 2-3 and sediment in the water, the sewage pumps from various manufacturers had a service life of in part only two weeks in part.
Although the best one had a service life of three months. Therefore, the appropriate solution should not only offer a clearly longer service life in the extremely acid environment, but also cope with the harsh handling due to the continuous change of locations in the quarry. The last pump specialist consulted, D.I.S. Powerplant Ltd., introduced the series SFQ from the Japanese manufacturer Tsurumi. This pump of special steel had been developed particularly for the conveying of corrosive materials. All parts, which are in contact with liquids, are of austenitic steel and, consequently, extremely resistant. The data of the manufacturer proved to be true. Now, the pumps have been running without complaint for more than two years (Fig. 2).
The medium-sized type 80SFQ23.7 with a rated power of 3.7 kW was used. These three-phase pumps convey a maximum of 1180 l/min and achieve discharge heads of up to 24.6 m. Other types in this series offer up to 2000 l/ min and 44 m. With a dry weight of 52 kg, the purchased SFQ can be handled well by just two men. The pumps are equipped with an open vortex impeller, a double inside face seal of the shaft, maintenance-free, fully enclosed ball bearings as well as a Tsurumi oil distributor that lubricates irrespective of the position. As a result, they are capable of dry running, i.e. they do not blow out if there is no cooling water. Even the electrical parts are optimally protected due to the hermetically tight sealing compound around each electric conductor.
These properties proved in practice convinced the mine operator already in the second quarter so that more pumps were purchased, i.e. various types of the PU series, which are considerably lighter with a maximum weight of 15.8 kg, but also weaker with max. 800 l/min. Pumps of this series have a combined casing of special steel and glass-fibre reinforced plastics that offers a similar acid resistance. With their free inlet passage of up to 46 mm, they can tolerate a lot of sediment in the conveying water. The paradox of this is that the SFQ from Tsurumi have proved almost too robust where various pumps failed. Thus it seemed possible to complete them and partially substitute them by the smaller, one-phase PU pumps (Fig. 3). Finally HMC was not disappointed in this field either. The first pump of this series is still running after it was commissioned one and a half years ago.
