ISO 1940/1 standards calculate the total acceptable unbalance of a rotor (static unbalance) referred to the plane (rotor section) containing the centre of mass.
The acceptable residual unbalance on the two balancing planes (dynamic unbalance) is calculated taking care of the position of the centre of mass with regard to the position of the correction planes.
If the calculated value for U1 , U2 is lower than 0.3 Ut the value 0.3 Ut is used ; if the calculated value is bigger than 0.7 Ut the value to be used is 0.7 Ut,
A frequent application of the above mentioned rules happens with pump and fun impellers (over hang mounted.)
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