5.3 Machine speed finder
Vibration-based condition diagnostics on speed-variable machines requires speed ac-
quisition during the vibration measurement. In addition to the vibration sensor, an ad-
ditional RPM sensor is always required to obtain a complete measurement data record
for a comprehensive analysis and reliable diagnostics.
VIBSCANNER 2 follows a different approach and omits a RPM measurement sensor. The
measuring device uses the vibration signal instead to determine the current speed value
at the measurement location. This method is based on complex algorithms, numerous
field tests and a lot of experience in the acquisition, processing, and analysis of vibration
signals. The result of this development is implemented as the so-called “machine speed
finder” in VIBSCANNER 2.
5.3.1 Function
Within the scope of the measurement configuration in OMNITREND Center, a speed is spe-
cified at the machine train level, which is to be expected during measurements on site.
Machine speed finder evaluates the vibration signal with respect to rotational speeds,
which may deviate by 15 % from the expected rotational speed value.
Machine speed finder is activated by default at the reference measurement location. The
measuring device calculates the speed values for all other measurement locations on a
machine train based on the configured kinematic model for the machine train.
5.3.2 Level of confidence
Machine speed finder determines three speed values based on the measured vibration
signal. These are within the specified interval (±15 %). A probability (in %) is assigned to
every value. It indicates the trustworthiness of the value. The current rotational speed
usually corresponds to the value with the highest percentage value – the so-called level of
confidence.
The level of confidence can be verified and readjusted as needed using a stroboscopic
measurement.
5.3.3 Limits
Machine speed finder reaches its limits in the following scenarios:
o
The probability for the level of confidence is below 70 %.
Remedy: Verify the respective speed using the stroboscope.
o
The rotational speed deviates at the measurement location by more than 15 %
from the expected speed.
Remedy: Determine the speed using the stroboscope.
o
Vibration entries from adjacent machines influence the vibration signal.
Remedy: Determine the speed using the stroboscope.
VIBSCANNER 2 87
5 - Appendix
To Next Page
Loading...
Need help?
General
