For a 2-m tall tank with a 4.5-m diameter and with four baffles (tank baffles are required to effectively mix water without excessive vortexing) filled with water, the volume is about 30 cubic m. One impeller, 2-m in diameter with two flat blades 0.4-m wide, mounted at a 45-degree angle and operating at 25 rpm, will require a minimum power of 2.4 kW.

The appropriate motor specification would be a 3.7 kW motor running at 1500 rpm. The gear drive should have a minimum power rating of 4.7 kW for a 1.25 service factor and a 23.5 Nm input torque, a 60:1 gear reduction for a 25 rpm output speed and a 1420 Nm output torque. The bearing rating and bending load on the output shaft will depend on the mounting height for the mixer and the weight of the impeller.