All three of the pump models selected for this project had known hydraulic profiles, but they had never been manufactured for such large flows with the associated power requirements. Bruno Antoniassi, Head of Sales, Brazil Energy Business for Sulzer, explains: “It was essential that we create scaled-down models to validate the suction well geometry, the hydraulic performance and the mechanical structure of the pumps.
“Due to the dimensions and the weight of the proposed pump designs, it would not be possible to test them on a commercially available test stand. Fortunately, our designers were able to overcome this and several other challenges that arose during this project. Using computer modelling as well as scaled-down pumps, we resolved all of the issues.”
One of the main complications concerned the river levels, which can vary considerably, depending on the rainfall in the area. The design of the suction layout and the pump itself had to accommodate this variation and still deliver the required flowrate, especially when water levels were low and demand in the arid areas was at a peak. The solution was to create pump designs that could operate at different suction levels, with the flowrates and power demands matching the changing situation.
Of course, with such large power requirements to drive these pumps, efficiency was one of the major challenges for Sulzer. Since the running costs make up 90% of the overall expenditure of each pump, creating a design that delivers optimum efficiency was a major priority for the project.
Overall pumping efficiency is calculated from mechanical, hydraulic and volumetric efficiencies, all of which are determined by the engineering design of the pump components. Sulzer refined the design of each pump to ensure it precisely matched its role and provided the customer with a guaranteed efficiency at the rated point.
Having finalized the design and tested the models, manufacturing could begin. With such large castings and a considerable amount of machining to be done, the build time for the six pumps was estimated at 12 to 15 months. All of the work was completed in Sulzer’s Brazilian facilities, which enabled the customer to monitor progress easily.