SKF CMSS500 Series, Руководство пользователя, Страница: 70 / 76

General Severity Level Guidelines
Vibration Enveloped Acceleration Measurements
B- 4 SKF Machine Condition Transmitter
User Manual
Vibration Enveloped Acceleration Measurements
Severity levels for machine vibration and bearing defect
detection by means of the enveloping technique are
needed to classify the machine condition according to
standards and practical guidelines.
For enveloped acceleration in all forms, severity levels are
related to speed and bearing size. The bearing size is
generally related to the load capabilities of the machine.
The higher the speed, the higher the energy generated by
impacts as elements roll over bearing damage.
The relation: Maximum shaft speed times shaft diameter
has a maximum, depending on the bearing technology.
Notice that for bigger bearings the speed is limited, and
therefore, the severity levels are also limited. Carefully
select the severity levels for enveloped acceleration using
machine knowledge. Sensor location and sensor
installation is important for successful machine
monitoring. The boundaries between different states of
severity conditions are less defined. Comparative and
relative judgement methods are preferred above absolute
judgement and the application of standards.
For creating a comparative measurement, the process
control system is able to create a trend of the vibration
signal. This signal can be compared against a 'baseline'
overall measurement of that measurement point, with
the knowledge that the machine is running under normal
conditions.
In many cases, periodic measurements have been
performed on equipment before a permanent monitor
(such as the MCT system) is installed. The knowledge of
those measurements and the machine behavior provides
a good indication of effective alarm level settings.