A major city in Mexico has three different propeller pump stations to handle combined wastewater and stormwater pumping. For nine months of the year, the stations transport wastewater and during the three month rainy season a combination of sewage water and stormwater. Backup diesel generators are installed to deliver power during power failures. To dimension the generators, accurate start calculations are essential.
We recommended the installation of 27 Flygt 7121 propeller pumps for a total capacity of approximately 80 m3/s (1,268,000 US gpm) at the three stations. To verify that the pumps would have sufficient starting torque and start currents that are not too high, we conducted and analyzed start calculations to ensure that the values for both torque and current were sufficient.