Special rotor balance process
LARGE FAN ROTER END DRIVE
spectrum analysis with vibration analyzer
Vibration is an important characteristic of the
return mechanism. Using data collector, such as
vibration analyzer to collect vibration information
of mechanical equipment running state, and then
through vibration spectrum analysis, we can quickly
and accurately diagnose the causes of faults, such
as rotor imbalance, shaft bending, bearing damage
and looseness, shafting misalignment, so as to
achieve early fault detection, diagnosis quickly and
timely, conclusion fixed-point quantitative,
mechanism Clearly understand the purpose. Mechanical
vibration analyzer is the basic instrument for
condition monitoring and predictive maintenance in
the factory, and it is also a powerful tool for
equipment reliability management and TPM. It is easy
to operate, suitable for equipment maintenance and
spot check personnel, and also suitable for
production operators. It is used to measure, record
and track the machine status, find abnormalities,
and diagnose and trend monitor common machine
Most common faults of rotating equipment:
It mainly includes the following faults:
Resonance ● unbalance ● misalignment ● shaft bending
● mechanical looseness ● motor problem ● sliding
● rolling bearing problem ● gear problem ● belt
● fan problem ● pump problem ● compressor problem ●
Resonance is a common problem in rotating machinery.
The resonance of rotating parts such as shafts is
usually called critical speed. Resonance exists in
all parts of a structure, even in pipes, cement
floors, etc. it is important to avoid the machine
running at the frequency that causes resonance. A
simple way to identify resonance is to compare the
vibration values of the same bearing in three
directions: horizontal, vertical and axial. If the
vibration in one direction is more than three times
of that in other directions, the machine may have
resonance in that direction.
The way to solve the resonance problem is to change
the rotating speed of the machine under possible
conditions, and the common solution is to change the
mass or rigidity of the machine structure.
When the center of gravity of the rotating parts is
inconsistent with the center of rotation, that is,
when the mass is eccentric, imbalance occurs. The
unbalanced rotor produces centrifugal force, which
damages the bearing and reduces its service life. A
displacement of the center of gravity of just a few
millimeters can cause very large forces. The
unbalance causes obvious frequency rotation
Misalignment refers to the misalignment of two
coupled axes. If the state centerline is parallel,
it is called parallel misalignment. If the axis
centerline intersects at one point, it is called
angular misalignment. In reality, the misalignment
is a combination of two types.
The vibration caused by shaft bending is similar to
misalignment. Shaft bending may be caused by uneven
heating of rotor caused by motor rotor cage bar
fault. If the bending occurs in the center of the
shaft, the dominant vibration is 1 x rpm, and if the
bending occurs in the proximity, coupling, the
dominant vibration frequency will be 2 x rpm.
There are two kinds of mechanical looseness,
rotating and non rotating. Rotating looseness means
that there is too much space between the rotating
and fixed parts of the machine; non rotating
looseness means that the gap between the two fixed
parts is too large. Both of them produce excessive
1x RPM harmonic vibration in three measuring
The motor has the same faults as other rotating
machines, but some faults are unique to the motor.
Such as rotor thermal bending, air gap eccentricity,
rotor looseness, eccentric rotor, coil looseness,
rotor cage bar failure, etc.
The problem with plain bearings is that they often
produce vibration peaks at frequencies less than 1 x
rpm, known as subsynchronous peaks. Sometimes there
are even harmonics of these peaks, indicating very
Oil film whirl: oil film whirl is the oil film that
excites the frequency vibration between 0.38 x rpm
and 0.48 x rpm. The vibration is caused by the
abnormally large margin and small radial load. It
exerts a pressure on the oil film and drives the
shaft to move along the bearing. Whirling of the oil
film can cause the oil to not lubricate the shaft.
Changing the viscosity and pressure of the oil and
the related load will also affect the oil whirl.
The vibration caused by bearings is called bearing
tone. All rolling bearings produce a certain degree
of tone. The more serious the bearing is worn, the
higher the degree of bearing tone.
The vibration produced by each fault bearing is not
an accurate 1 x RPM harmonic frequency, that is, the
asynchronous vibration components. In addition to
these components, the fault of the bearing produces
? in a flawless gearbox, the relative dominant tone
appears at the meshing frequency, which is the
number of teeth multiplied by the speed (RPM
frequency). When the gearbox is used for a period of
time, the meshing composition of the gear decreases
because the edge of the tooth is slightly rounded.
However, the continuous wear will increase the
meshing vibration level again. This vibration level
is also affected by the alignment of the gear shaft.
Worn or loose belts produce the vibration of belt
frequency and its harmonic frequency. In a system
with two pulleys, the second harmonic frequency
usually dominates. The basic belt passing frequency
FBF is calculated as follows:
FBF = π (D/L) RPM
FBF = basic belt passing frequency
D = pulley diameter
L = belt length RPM = speed of pulley D (Hz)
The basic belt frequency is always less than 1x rpm.
Eccentric pulley produces high radial 1x component
vibration, especially in the direction parallel to
the belt (radial refers to the direction from the
sensor to the pulley Center).
The axial 1xrpm vibration and the axial harmonic
frequency FBF of the basic fluctuation frequency of
the belt are produced by the poor belt wheel pair.
If the tension of the belt is not correct, the belt
will produce vibration of natural frequency, which
is taken in a large range.
Fans are usually produced on blades
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