● Position 1 and 2: Condition monitoring of the vacuum pump and the pump bearings
● Position 3: Condition monitoring of the motor
1. Screw the sensors in at the designated positions.
2. Use suitable adapters for sensors with a different thread.
3. As an alternative, fix the sensors to the intended positions using magnets (recessed areas).
Evaluating the measurements
Regular measurements are necessary in order to ensure the safe evaluation of the pump, motor and
bearing condition.
1. Perform vibration measurements every two weeks and evaluate the results.
2. Shorten the interval to weekly and daily measurements if there are anomalies in the trend.
Carrying out a bearing replacement
1. Carry out a bearing replacement (in accordance with Maintenance Level 3) if significant changes
occur in the trend (significant rise or drop) in accordance with the guidelines VDI 3836 or
VDI 3832 during condition monitoring of the vacuum pump or the pump bearing.
2. In accordance with your own experience of condition monitoring, define limit values that result in
Maintenance Level 3 for the vacuum pump in the event of a change in trend.
Carrying out an motor replacement
1. Carry out a motor replacement if significant changes occur in the trend for vibrations (significant
rise or drop) in accordance with standards DIN ISO 10816-1 or DIN ISO 10816-3 during condition
monitoring of the motor.
2. In accordance with your own experience of condition monitoring, define limit values that result in a
motor replacement in the event of a change in trend.
6.6.1 Condition monitoring of the vacuum pump
Condition monitoring takes place in accordance with guideline VDI 3836. You must evaluate the vibra-
tions in two relevant frequency ranges in accordance with the broadband method:
● Frequency range A incorporates the significant mechanical and aerodynamic vibration stimula-
tions of the roots pump.
● Frequency range B takes into account the vibration stimulations through imbalance of the rotating
components.
When evaluating the respective frequency ranges, you must calculate and evaluate a broadband root-
mean-square-value for the vibration speed (v
eff
).
Frequency
Frequency limits (ro-
tation speed)
Description
Frequency
range A
10 Hz – 1000 Hz
Due to the permissible rotation speeds, only the range
between 10 and 1000 Hz is relevant
Frequency
range B
10 Hz – (2 × n) Hz
Deviating from VDI 3836, the upper limit is derived
from twice the rotation frequency.
Tbl. 11:
Evaluated frequency ranges
6.6.2 Monitoring the bearing condition
Carry out the vibration diagnosis or condition monitoring of the pump bearings in accordance with
guideline VDI 3832. Evaluation of the pump bearing oscillations is based on the frequency-selective
method (narrow band method).
● A performance spectrum or envelope curve spectrum extracts the anti-friction bearing-specific
(ball pass frequencies, bearing damage frequencies) or characteristic frequencies.
● Evaluation of the amplitudes as characteristic values.
● Concentrating multiple lines of a characteristic frequency to a narrow band.
● Assessment of the root-mean-square-value of the vibration acceleration and / or the maximum
value amount of the vibration acceleration in a band.
Evaluating the vibration spectrum
Due to the early and clearer diagnosis for bearing damage, Pfeiffer Vacuum recommends
using the envelope curve spectrum.
Operation
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