Identifying and correcting the mass distribution and thus minimizing the force and resultant vibration is the technique known as dynamic balancing. Research shows that a wheel and its shaft have to be in a state of balance. The mass needs to be evenly distributed about the rotating centerline so that the resultant vibration is at a minimum. This balance needs to be achieved fist during the manufacturing process and as wear occurs so that the maximum service life can be archived from the system.
Causes of Unbalance
Material problems such as density, porosity, voids and blowholes can contribute to the unbalance condition. Fabrication problems such as misshapen castings, eccentric machining and poor assembly.
Distortional problems such as rotational stresses, aerodynamics and temperature changes
Deposit build up dirt and deposits can break off unevenly, which can lead to severe unbalance, this especially applies to fans, blowers, compressors and other rotating equipment process variable.
Rotors that operate within 70%-75% of a critical speed are considered flexible rotors. Rotors that operate below that speed are considered rigid. Many times rotors are balanced at the factory for a rigid condition using a low speed balancing machine, but when the get put into service they become flexible rotors. These flexible rotors require a multi plane balancing procedure.
When unbalance has been identified, the correction is straightforward weight has to be added or removed from the rotating element. The goal is to reduce the uneven mass distribution so that centrifugal forces and vibrations induced in the supporting structures are at an acceptable level.
Why we balance in the field
Balancing is performed on the complete assembled machine and compensates for assembly tolerances. It is often costly and time consuming to disassemble and move the rotor to a balancing machine.
The effects of temperature, pressure, distortion and other environmental influences can be incorporated.
The vibration can be adjusted for resonance or natural frequencies vs. published balance tolerances used in a balancing machine. The unbalance may have to be adjusted to abnormally fine levels to minimize the resultant resonant structural vibration.
Our state of the art instrumentation and field experience provides us with accurate information to identify the causes of unbalance. Our vibration analyzer identifies the amount of vibration at the rotating speed frequency. We then measure phase (the relative motion of one part of a machine to another) to determine the location of the unbalance. Through detailed thorough analysis we determine if the vibration is a result of unbalance.
Benefits of well balanced machines
Minimize noise vibration
Unbalance is the major source of machine vibration and noise
Reduce structural stress
The forces produced by unbalance have to be absorbed the surrounding structure.
Minimize operator fatigue and annoyance.
Exposure to vibration affects operator efficiency
Increase machine life
The time between outages can be extended if the machine is running smoothly
Increase bearing life
Bearings bear the brunt of unbalance forces
Increase product quality
Minimizing vibration, especially on machine tools, produces better parts.
Increase personnel safety
Dangers with machine failure are minimized
Lower operating costs
Energy consumption is reduced and increase machine availability.
L.P. Larson has the equipment and experience needed to solve your vibration problems. Our engineers are called upon to balance everything from power plant turbines to exhaust fans. L.P. Larson is available 24 hours a day to meet your dynamic balancing needs.
We have balanced:
Fans and Blowers
L.P. Larson Corporation 64R Hancock Street
Braintree, Ma. 02184 24x7 Service