This metric standard defines classes of flexible coupling potential unbalance, one of which the user must select in order to meet the needs of their system. The classes are established using mass and speed and system sensitivity to arrive at a mass displacement value that defines the potential unbalance. The standard defines types of unbalance, provides amethod of selecting balance class, identifies contributors to potential unbalance, and provides a method of determining potential coupling unbalance. The balance classes are derived from consideration of the potential unbalance of the coupling.

The balancing requirements for a flexible coupling depend upon the rotating system into which it is mounted. Each half of the coupling is mounted on a separate rotor with thewhole coupling providing the connection. Each of the connected rotors is balanced independently of the coupling and the coupling is added when the rotors are installed.

This standard is usedwith ISO1940—1:2003 which applies to balance quality requirements of rigid rotors. If ISO 1940—1:2003 is used for balancing coupling components and assemblies in the balancing machine, then potential unbalances are introduced after the coupling is disassembled andreassembled either in the balancing machine or the rotor system. These potential unbalances are primarily the result of:

— balancing mounting fixture inaccuracies;

— displacement of coupling components with respect to the axis of rotation of the rotor system during disassembly and reassembly of the coupling.