Dynamic Balancing

Dynamic Balancing? Difference b/w Balanced and Unbalanced Rotary Machines?

“A geometrically perfect Rotary Machine is incomplete without Dynamic Balancing”

Dynamic Balancing:

ROTARY MACHINES

Machines in which one or more than one rotors are fitted in a typical sequence and they run together to perform some useful job. Such machines are Motors, Pumps, Fans, Turbines, Generators, Engines, Wheat Thrashers, Harvesters, Wheat Grinding Machines, Chaff Cutters, Silage Makers and many others. Two Types of Rotary Machines now-a-days we are dealing with:

  1. BALANCED ROTARY MACHINES: All rotors of Balanced Rotary Machines are balanced on high speed before or after the assembling. High Reliability, High Durability and long lasting.
  2. NON BALANCED ROTARY MACHINES: Rotors of Non Balance Rotary Machines are not balanced on high speed. Apparently these both types of Rotary Machines look identical but due to unbalance the are of low quality, low durability, low reliability and low performance.

WHY YOU NEED DYNAMIC BALANCING FOR ROTORS?

It has come in the experience that in 80% cases of vibrations of Rotary Machines, major cause of vibration found is Unbalance. Unbalance Force is actually a Centrifugal force and a man can experience this Unbalance Force by rotating a stone tide with string, around his body.

In rotary machines this outward flying Centrifugal Force of Unbalance increases at the rate of “Square of Rotor Speed”. This force put a tremendous Crushing Pressure on the balls of bearings.

This force becomes a HAMMER OF UNBALANCE and keeps on hitting the balls of bearings continuously, during each rotation, against sliding race of Roller Bearings or hydraulic oil film supporting the shaft in Journal / Sleeve Bearings.

Unbalance of only 100g-m become a HAMMER OF UNBALANCE of weight equal to 1000kg=1Ton at 3000 rpm and 4000kg/4 Ton at 6000 rpm

What will happen when you will ignore Vibration in your Rotary Machines?

Due to “Unbalance Centrifugal Forces” it becomes “Hammer Of Unbalance” and first indication you will observe in your rotary machine will be rise in “Vibration Levels”. What will happen when you will ignore Vibration in your Rotary Machines?

  • When this vibration is ignored for a long time balls of bearing start to slip and scratches/spalls are formed on the shining races of bearings and friction rises.
  • Due to high friction in bearings their temperatures rise and lubrication wipes out from bearings.
  • Due to abnormal rise in temperature bearings deform & loose and start to rotate on the rotor shaft or in the pedestal and undersize the rotor shaft or oversize the bearing housing.
  • Due to further ignorance a day comes when bearing collapses during operation at high speed and
    Rotor of Motor, Generator or Turbine strikes or rubs with its stator and machine damages.

This type of failure mechanism of high speed machines is found very common in our local industry.

These types of losses can be saved and 100% avoided by adopting the practice of periodic Vibration Analysis of rotating machines and Dynamic Balancing of Unbalance Rotors.

If all rotors of a machine are fitted after balancing the life of Rotary Machines increases many times. This is because, Vibration due to Dynamic Unbalance has direct relation with the life of bearings. It is a scientific truth that if the vibration due to Unbalance Force is reduced to half (1/2) Bearing life will increase by 8 times. It means if a bearing under one vibration has one year useful life, same bearing with half vibration will have Eight (8) years useful operational life. This is a very big advantage of Dynamic Balancing of Rotors which makes Rotary Machines Maintenance Free.

DYNAMIC BALANCING INCREASES OPERATIONAL LIFE OF THE ROTARY MACHINES