Some questions catch you by surprise. I certainly was caught off guard when someone at a plant asked: “Are centrifugal pump inlet velocity limits calculated based on the inlet piping or the inlet nozzle?” Quite honestly, I couldn’t ever remember paying any special attention to a pump inlet velocity when sizing lines or selecting pumps.
In many cases, inlet velocity to a pumping system is important. However, that’s because the velocity affects inlet head losses, nozzle sizes or strainer requirements — not because it’s a specific requirement for pump selection.
The concept of a velocity limit on centrifugal pump suction lines has some merit, though. High velocities can lead to pronounced flow patterns at the impeller inlet. This may reduce pump performance and reliability.