SUMMER INTERNSHIP PRESENTATION

ROTOR BALANCING

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

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 interactionOf 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.

 

Principle of BalancingA 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.

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 minimumIf 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).

FIG. COLD PRESSING MACHINE

Straightening of ShaftA 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

FIG. STRAIGHTENING OF SHAFT

Turning of RotorsTurning 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.

FIG. TURNING OF ROTOR

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.

• 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.

Fig. Balancing machine

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

THANK YOU……..