The reliability of pitot tube pumps in low flow high head applications makes them a great choice for tough applications in which there is high fluctuation in flow rate. In this White Paper by Weir, tests demonstrated that the size and number of blades in the pitot tube has a large impact on the pressure distribution inside the rotating case. There can be a region of higher than anticipated pressure at the center of the rotor. This pressure adds significantly to axial thrust loads and increases seal pressure (in the between bearings arrangement). This has a large impact on bearing life and seal selection. Adding enclosed channels to the rotating case eliminates this pressure without sacrificing pump performance.
The White Paper can be found by going to the 'Download' section on this website and filling in a brief registration form.