If an application-specific adjustment is necessary, the limit values can also be adjusted
manually.
9.3.1.4
Variance
(Index 4489-4491)
As with the
v-RMS
, the variance describes the strength of the vibration. It enables the
detection of:
•
Unbalance
•
Relaxation
•
Misalignment
9.3.1.5
Skewness
(Index 4492-4494)
Skewness
indicates abrupt and fundamental vibration changes and can be an indicator
of bearing damage.
9.3.1.6
Kurtosis
(Index 4495-4497)
Kurtosis
can be used to detect changes due to occurring pulses in addition to the RMS
values.
9.3.1.7
Peak to peak
(Index 4498-4500)
The
Peak to peak value
can be used to detect a pulse-like fault in the vibration signal. One
example of possible causes of an increased
Peak to peak value
is bearing damage.
9.3.1.8
Shape factor
(Index 4501-4503)
An increase in the
Shape factor
indicates an increase in the amplitudes of harmonics in
the signal. Reasons for this may be:
•
Loosening of screws
•
Unbalance
•
Misalignment
9.3.1.9
Crest factor
(Index 4504-4506) and
Impulse factor
(Index 4507-4509)
The
Crest
and
Impulse factors
are very similar and essentially differ in their normalization,
which means that depending on the application, one of the indication values may be
more sensitive. High values for these indication values indicate that pulse-like faults
are present in the vibration signal, caused for example by bearing damage such as
cracks in the bearing shells or defective balls. A major advantage of the
Crest
and
Impulse factors
is that these values are, to a first approximation, independent of the
speed of a machine and these indication values thus provide meaningful information
even for machines with variable speeds.
9.3.1.10
Teach-in process (Index 4538-4539)
The simplest way of condition monitoring in the time range is via teach-in. The limit
values are set automatically based on the current measured values. For the
RMS values
,
all three limit values (maximum, pre-maximum, minimum) are set, for the other values
two limit values (maximum, minimum) are set. The following teach-in operations can be
performed:
9
OPERATION
34
O P E R A T I N G I N S T R U C T I O N S | MPB10
8028041/2022-08-16 | SICK
Subject to change without notice
