Trim Balance - Take a measurement in each plane to confirm that
the rotor is balanced. Any residual imbalance can be removed via
additional trim balance cycles.
Tips for Balancing
• Before performing a balance job, clean the rotor removing
any dirt or loose-hanging material such as rust, flaking paint
etc, which may affect balancing results if they fall off later.
• Ensure that any weight(s) you add will not come loose at the
normal rotor speed and that it will not obstruct machine
motion. If possible, manually rotate the rotor to ensure that
the weight does not clash with any part of the machine,
keeping in mind that the rotor's center line may shift when
operated at its normal speed.
• Ensure the weight of any mechanism used to hold the
correction weights in place is included as part of the
correction weight. If you are welding on the weight, make
sure that the weight of the flux is not included (scrape the
flux off before weighing the electrode).
• Ensure that the shape of the correction weight does not
cause it to become a dirt trap since dirt accumulated on the
weight may cause rotor imbalance.
• It is important to attach the correction weight(s) at the same
radial distance that the trial weight was i.e. if the trial weight
was attached 'n' mm/inches from the center of the rotor, the
correction weight must also be attached 'n' mm/inches from
the center of the rotor.
The Tachometer
The tachometer provides the instrument with information regarding
the rotational speed of a rotor and the angle at which the rotor is
vibrating. The angle is measured from a fixed reference mark on the
rotor and is called the ‘phase angle’. To balance a rotor you must
consider both the amplitude of vibration and also the phase angle.
The amplitude shows the severity of the imbalance and the phase
angle indicates the geometry of the imbalance (i.e. the location of the
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