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Service factor multiplier (continued)Table 5-1:
Machinery type Service factor
Turbine, Turbine Generator, Centrifugal Compressor 1.6
Miscellaneous Equipment 2.0
Figure 5-3 shows the Overall Velocity thresholds for root-mean-square (RMS) velocity in
units of inches per second. Particularly, in digital acquisition systems, it is customary to
measure and calculate with RMS quantities. While it is accepted practice in the industry to
convert between RMS and peak values using the 1.4142 conversion factor, it is not
technically correct to do so except for a pure sinusoidal waveform. For this reason, the CSI
9420 measures, calculates, and reports Overall Velocity in RMS, and it is necessary to
multiply by 1.4142 to get the corresponding peak levels if this is the preferred format.
Default velocity levels in CSI 9420Table 5-2:
Alert level Velocity (in RMS)
Advise 0.14 in/s
Maintenance 0.35 in/s
Failed 1.0 in/s
5.2 PeakVue
PeakVue
™
is a patented Emerson technology that is very useful for isolating high-
frequency phenomena associated with developing faults, especially in rolling-element
bearings.
The premise for PeakVue is that the high-frequency components are not readily detected
with more conventional measurements such as Overall Velocity, low-frequency energy
(LFE), or digital overall. This is because the low-frequency measurements either average
the energy or provide an energy summation over a relatively large frequency band, and the
relative amount of energy that is typically contributed by the high-frequency components
is quite small. As a result, even large "spikes" are difficult to detect with classic techniques.
The difference in the vibration waveform and the associated measurement for overall
vibration versus PeakVue is shown in Figure 5-5 and Figure 5-6. The overall vibration is well
below the established advisory and maintenance alert levels indicating that the machine is
running well. In contrast, the PeakVue graph shows that the values have increased from
zero, and that they are already crossing the advisory alert level and approaching the
maintenance alert level. This early warning about impending defects is key to maintaining
good machine health.
The PeakVue algorithm isolates the peak energy of interest to provide early indications of
developing bearing faults such as inner and outer race defects, ball defects, and lubrication
problems. Any type of "impacting" fault, where metal is contacting metal, is readily visible
with PeakVue long before there is any significant increase in Overall Vibration. PeakVue is
especially useful for monitoring rolling-element bearings.
Velocity, PeakVue, and temperature
94 MHM-97408, Rev 15