Theory of Rotor balancing Principle of Balancing Rotor Assembly( Pre Balancing) 7.1 Cold Pressing 7.2 Straightening 7.3 Turning Procedure Precautionary Equipments

1. ROTOR BALANCING

2. Table of Contents
• Theory of Rotor balancing
• Principle of Balancing
• Rotor Assembly( Pre Balancing)
7.1 Cold Pressing
7.2 Straightening
7.3 Turning
• Procedure
• Precautionary Equipments

3. Balancing is the process of attempting to
improve the mass distribution of a rotor, so that
it rotates in its bearings without uncompensated
centrifugal forces.
Unbalance in a rotor is the result of an
uneven distribution of mass, which causes the
rotor to vibrate. The vibration is produced by the
interaction
Of an unbalanced mass component with the
radial acceleration due to rotation, which
together generate a centrifugal force. Since the
mass component rotates, the force also rotates
and tries to move the rotor along the line of
action of the force. The vibration will be
transmitted to the rotor's bearings, and any
point on the bearing will experience this force
once per revolution.

4. Principle of Balancing
A rotor is balanced by placing a correction
mass of a certain size in a position where it
counteracts the unbalance in the rotor. The
size and position of the correction mass must
be determined. The principle of performing
field balancing is to make (usually temporary)
alterations to the mass distribution of the
rotor, by adding trial masses, and to measure
the resulting phase and magnitude of bearing
vibration.

5. Rotor Assembly
Cold pressing Operations.
The most basic and economical attachment process is
pressing the rotor onto the shaft. This is usually done in
a vertical hydraulic press. The rotor is placed in a
holding fixture, and the shaft is placed into the rotor ID.
Tolerance control of the rotor ID and the shaft OD must
be maintained. Generally, the press fit should be in the
range of 0.001 in per inch of shaft diameter minimum
If the press fit is too tight, the shaft may bend. If the
press fit is too loose, the shaft may turn on the rotor in
application. Monitoring of the press hydraulic pressure
during the press fit will provide a quality assurance
check (preventing too tight or too loose a fit).

6. FIG. COLD PRESSING MACHINE

7. Straightening of Shaft
A bent shaft can be caused by one or more of the following
factors...
• Mechanical overload:
• Damage during rigging or improper handling
• Impact during operation
• Machine misalignment
• Internal stress relief:
• Unequal machining operations
• Vibration during shipment
• Improper material handling during heat-treating, rolling,
forging, thermal stress relieving

8. FIG. STRAIGHTENING OF SHAFT

9. Turning of Rotors
Turning is the removal of metal from
the outer diameter of a rotating
cylindrical workpiece. Turning is used
to reduce the diameter of the
workpiece, usually to a specified
dimension, and to produce a smooth
finish on the metal. Often the
workpiece will be turned so that
adjacent sections have different
diameters.

10. FIG. TURNING OF ROTOR

11. Procedure (Working)
• The rotor to be balanced is returned from the lathe shop,
the wheels of the machine are oiled to ensure smooth rotation of
the rotor as well as no friction that would come in between.
• The rotor is taken to the equipment and the keys are fit in
and fastened
• There exists a cloth flap that runs through the rotor that
keeps the rotor in place as well as helps gauge the rotations-per-
minute (rpm) of the rotor.
The rpm can be set manually, but in case of rigid motors it
dosent make a difference the imbalance remains the same at any
speed.
• The machine is started and the readings are showed on the
screen, it tells the amount of imbalance and the positions. In, this
case there can be 6,8 or 12 pins in either side.

12. • The required weights are added and then the rotated is rotated
again to see if the deviation falls under the tolerance. The display
will read INTOL.

13. Fig. Balancing machine

14. PRECAUTIONARY EQUIPMENTS:
• FIRE ESCAPE MASK
• DUST MASK
• EAR PLUG
• HAND GLOVES
• HALL FACE MASK
• SAFETY GOOGLE
• EAR MUFF
• HARNESS

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