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SpinTech for all your Balancing Needs
Excessive unbalance in rotating machinery can cause
unacceptable levels of vibration and noise and substantially reduce the life of
bearings and other parts of the machine. The ideal solution would be to remove all causes of vibration and run
the unit completely "smooth". Unfortunately
in reality, this ideal solution cannot
be achieved. No matter what is tried some
inherent cause of vibration no matter how low, (usually unbalance) will
remain. The best one can do is to reduce
this unbalance to a level that will not adversely affect the machine life and
will reduce noise levels to an acceptable level.
This being the case, there are industry standards that set limits
for acceptable vibration levels in various types of equipment and situations. These standards are used by balancing
companies to achieve acceptable vibration limits without “over balancing” and
increasing balancing costs unnecessarily.
Reasons for balancing in the field Visit our Field Balancing Page
An in service rotor can have material buildup (dirt or
grease on fans) or material loss (erosion on material moving fans), bearing
wear that affects the center of rotation (severely worn parts need to be
replaced before balancing), shaft distortion due to residual stress relaxation,
structural changes, or speed increases. This causes vibration that will result
in premature failure of bearings and other machine components. It can also
result in cracks and other structural defects that could cause catastrophic
failure. When possible, balancing in place is very cost
effective compared to disassembling the machine and removing the rotor.
Reasons for shop balancing Visit our Shop Balancing Page
If a rotor is damaged to the point where it needs to be
removed and repaired (welded, etc.) then shop balancing is the best option. If the rotor is removed for other reasons, checking
and balancing before reassembly is also a good practice.
Newly manufactured rotors are usually shop balanced prior to
assembly in their respective machines. Cast parts may have voids that are not
apparent from the outside and even machined parts that appear perfectly symmetrical
can have inconsistencies for various reasons. Balancing before assembly assures quality and
Trim balancing in the field
Occasionally a shop balanced rotor, e.g., a fan, may have
residual vibration when installed in the field.
Assuming everything is assembled properly, this is usually a structural
issue such as system resonance. A simple trim balance may help to reduce the
vibration, however in some cases the mounting structure may need altering (changing
mass or stiffness) to reduce the vibration.
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