When it comes to dynamic balancing there is a choice:-
- dis-assemble the machine and have the rotor balanced in a universal balancing machine.
- Field balancing - where the rotor is balanced in service without dissasembly.
The next question is which one is best ?
There is a place for both, - it depends on the circumstances.
The balancing process is very fast in a balancing machine; so where the rotor is disassembled for maintenance this is the obvious choice. Very large unbalances can be accurately measured at low speed and removed without endangering the safety of the equipment, personel or other machinery.
Unbalance can be introduced during the process of assembly and re-commissioning so it is a good idea to check the unbalance before machines are put back into service, with a field balancer / vibration analyser.
Other rotating equipment eg dust extraction fans, pulverizers,experience change in unbalance during service and field balancing at intervals while in service can dramatically reduce maintenance costs and help avoid breakdown.