Gd2 value of a Centrifugal Impeller

the moment of inertia (in the US, it is typically expressed as WR², where W is weight in pounds, and R is radius in feet). This parameter is used in water hammer analysis, pump runaway speed (reverse rotation during check valve failure), and similar transient (non-steady-state) hydraulic problems.

Normally, a complete pump rotor is analyzed, and often even a complete train, consisting of all rotors coupled together: pump, coupling, motor, etc. Impeller is one of the main components with rather significant value of WR², but other components need to be considered also (coupling, for example, may have a very significant effect on rotordynamics).

For the impeller, a pump manufacturer can usually supply the value of WR², but, for a quick approximation, you can assume the impeller as a disk with same weight, and same outside diameter, but the width adjusted to correlate with the known impeller weight. The radius is then the same as for a disk, and you can get it from any text book on dynamics.