Vibration Analysis
& Balancing
What is Vibration Analysis



The study of Collected data taken
with the analyzer, of a machine while
it is running.
Data is collected at each location or
point in the horizontal, vertical and
the axial plans.
Numerous bearing, motor and
condition fault frequencies are
checked and compared.
Vibration Analysis

What is vibration?
• Forces that vary in amplitude or
direction over time cause
repetitive motions called
vibration

When is vibration bad?
• All rotating machinery generates
some vibration
• Only vibration that exceeds
certain amplitude levels is bad.
Vibration Terminology

Amplitude
• The measure of energy or movement in
a vibrating object
• Three common ways of expressing:



Displacement in mils peak to peak
Velocity in inches/second peak
Acceleration in g’s rms
Vibration Terminology

Frequency
• The number of times that a vibrating
object repeats its motion per unit of
time
• The rotational frequency is often
called 1X
• Other frequencies are often identified as
multiples of 1X, such as 2X, 3X, 4X, etc.
Vibration Measurement


We analyze vibration profiles from,
motors, fans and pumps, chillers,
bearings and overall machine health.
Were looking for bearing condition,
mechanical looseness, motor
electrical problems, resonance issues
Overall vs. Running speed-1X



Overall amplitude is a measure of
the vibration energy over a wide
frequency range
1 times amplitude usually refers to
the vibration at operating/running
speed
Overall amplitude includes the
effects of all sources—even those
external to the fan
Vibration Terminology
Vibration Spectrum:
(a display of frequency vs. amplitude)
Profile Plot
PROFILE PLOT
(More Than One Equipment)
FAN MOTOR POINTS
24-Sep-10
09:48:08
4XTS
To
01-Oct-10
13:15:31
3xTS
Full Scale
280. %
2xTS
of Fault
1xTS
MMMMMF MMMM MF MMMMMF MMMMMM MM MM MMMMMMMMMMMMMMMM
1 1 1 2 2 N 1 1 1 2 2 N 1 1 1 2 2 N 1 1 1 2 2 1 1 1 2 2 1 1 1 2 2 1 1 2 1 1 2 1 1 1 2 2
H V A H V V H V A H V V H V A H V V H V A H V H V A H V H V A H V H A H H A H H V A H V
EQUIPMENT A A A A A A B B B B B B C C C C C C D D D D D E E E E E F F F F F G G G H H H I I I I I
AREA
A A A A A A A A A A A A A A A A A A A A A A A B B B B B B B B B B B B B B B B B B B B B
Dynamic Unbalance


Dynamic (couple) unbalance
requires correction in two or
more planes
Heavy
spot
will not
“bottom out”
when rotor
is placed in
bearings
Achieving Lower Vibration Levels

Involves better precision of
many components
• Better balance of all rotating
components




Fan wheel (balance with fan shaft)
Sheaves
Couplings
Motors
• Straighter shafts with precision
diameter tolerance and roundness
• Less hop and wobble in fan wheel
• Better fits in attached
Achieving Lower Vibration Levels

Involves better precision of many
components (continued)
• Reduced internal clearance in bearings
• Bearing mounting surfaces machined
flat
• Premium quality v-belt drives
• Precision alignment of v-belt drives or
couplings
• Precise tensioning of belts
Achieving Lower Vibration Levels

Involves other special design
considerations
• Heavier and more rigid components:
Use Class III instead of Class II
• Aluminum fan wheel (reduced rotor
weight)
• Use inertia base for flexibly mounted fan
• Select lower speed fans if possible
• Avoid operation at any critical
resonance speeds- vibration can
increase up to 10X amplitude
Balance

Balancing
• The process of adding or removing
weight on a rotor in order to move the
center of gravity towards the axis of
rotation
• The purpose of balancing is to reduce
the unbalance forces that damage
machines, there surroundings and
reduce noise transmitted to tenants
Balance Tolerances




Defines the maximum amount of
residual unbalance remaining after
balancing
Originally defined in international
standard ISO 1940/1
Many new standards exist today.
We use the manufactures
specifications along with years of
experience to achieve best balance
possible
Balance and Vibration tolerances
• Proper balance
• Provides for long
life,
• Higher efficiency
and
• Reliable operation
without excessive
cost
Static Unbalance


Static unbalance can be
corrected by adding a single
weight
Heavy spot
will “bottom
out” when
the rotor is
placed in
bearings
Dynamic Unbalance


Dynamic (couple) unbalance
requires correction in two or
more planes
Heavy spot
will not
“bottom out”
when rotor
is placed in
bearings
503 657-4467
END