Inertia (Pump and Motor)

Hi

I am modeling a pump shut down after time delay event in Bentley Hammer and I need to insert the Inertia (Pump and Motor) in the dialog box of Pump Definitions.

The pump station already exists and I have the catalog value for the pump GD² value, which is 270 kg.m² (I do not have the inertia value, per say). I do not have the inertia value of the motor, only the rating (1100kW) and the speed (747 rpm). In motor’s catalogs, the GD² value for medium voltage motor as this one, is about 340 kg.m².

For the Inertia (Pump and Motor), which values can I use?

In some technical bibliography refers to the inertia (I) as a quarter of GD². Then the inertia (I) of the pump is equal to 67,5kg.m² and the inertia of the motor is equal to 85 kg.m². The total inertia (pump and motor) is equal to the sum of the inertia of the pump and the inertia of the motor? So is the inertia (pump and motor) equal to 152, 5 kg.m² (85+67,5 kg.m²)?

Can I use the “Pump and Motor Inertia Calculator”? If so, introducing the rating and speed, the Inertia (Pump and Motor) is 279,5 kg.m², very different from the value 147, 5 kg.m².

On the other hand, if the Inertia (Pump and Motor) is equal to the sum of the GD2 values (610 kg.m²), the result is also very different from the value calculated with the “Pump and Motor Inertia Calculator”.

Best regards
Mónica Piedade

AQUALOGUS
License serial number
6085bc6a-6281-4953-8693-5912e2334dd6\1225\08.11.04.50\1000178398