Page 350 - Machinery Component Maintenance

Appendix 6-A

Balancing Terminoloi

NOTE: The definitions followed by a number are taken from IS0 1925
2nd Edition.

Amount of Unbalance (3.3): The quantitative measure of unbalance in a
rotor (referred to a plane), without referring to its angular position. It is
obtained by taking the product of the unbalance mass and the distance of
its center of gravity from the shaft axis.
Angle of Unbalance (3.4): Given a polar coordinate system fixed in a
plane perpendicular to the shaft axis and rotating with the rotor, the polar
angle at which an unbalance mass is located with reference to the given
coordinate system.
Angle Indicator (5.18): The device used to indicate the angle of unbal-
ance.
Angle Reference Generator (5.19): In balancing, a device used to gener-
ate a signal which defines the angular position of the rotor.
Angle Reference Marks (5.20): Marks placed on a rotor to denote an an-
gle reference system fixed in the rotor; they may be optical, magnetic,
mechanical, or radioactive.
Balancing (4. I): A procedure by which the mass distribution of a rotor is
checked and, if necessary, adjusted in order to ensure that the vibration of
the journals and/or forces on the bearings at a frequency corresponding
to service speed are within specified limits.
Balancing Machine (5. I): A machine that provides a measure of the un-
balance in a rotor which can be used for adjusting the mass distribution of
that rotor mounted on it so that once per revolution vibratory motion of
the journals or force on the bearings can be reduced if necessary.
Balancing Machine Accuracy (5.24): The limits within which a given
amount and angle of unbalance can be measured under specified condi-
tions.
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