Moment of inertia definitions

[stanier]

Hi All,

I have a curious matter where a pump agent has quoted two inertias for a DIN 150 40 pump. The values are exclusive of motor MoI. Both descriptions could not be clarified by them or other pump manufacturers. In 40 odd years in the business I have not come across them so have turned to the experts.

1) Mass MoI (PD2) 1.931 kg-m2
2) Mass Dynamic MoI 0.0452 kg-m2

The value in 1) appears to be too high for the pump. What is PD2? How does this relate to wr^2?

In 2) what is the Dynamic MoI?

In the past I have used pump inertia calculations based on estimates using relationships in Wylie, et al., pp. 148-149.Wylie, E.B., V.L. Streeter & L. Suo, Fluid Transients in Systems Prentice Hall, Englewood Hills, New Jersey, 1993.

For this size of pump a value of wr^2 is about 0.8kg-m^2.

 

[BigInch]

It may be some confusion between MOI and DMOI??

http://books.google.es/books?id=oLw...v=onepage&q=dynamic moment of inertia&f=false

If not that, it might be referring to an equivalent DMOI when running constantly vs when accelerating???

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"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

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[ione]

PD2 could stand for M*D^2 .

M is the mass of the body, in Italian not unusual to see it as P, peso = weight, and D is the distance between an axis the MoI is computed and a parallel axis trough the centre of mass of the body (check Huygens –Steiner theorem)

 

[Drexl]

I've seen some manufacturer give the MMOI calculated using the "diameter" instead of the "radius", which gives 4 times higher value.