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6 Large drop in the readings
If the shock pulse level drops after a sequence of normal
readings, you have either a malfunction of the instru-
ment, a failure in a transducer installation, or a serious
bearing fault.
Check the instrument by measuring on some other
bearing. In case of an installed transducer, try to get
a reading by tapping on the bearing housing. If your
reading is correct, it is possible that one of the bearing
races is slipping, either on the shaft or in the housing. In
case of a heavily loaded bearing with previous readings
in the red zone, suspect cage failure.
5 Rhythmical peaks
Single, rhythmical peaks can be caused by load and
pressure shocks which occur during the machine’s
normal operation. Other possible causes are clicking
valves or loose parts knocking regularly against the
machine frame.
If the signal is strongest on the bearing housing, you
can suspect a cracked inner ring.
4 Periodic bursts
Periodic bursts are a typical interference signal, caused
by rubbing between machine parts, e.g. shaft against
bearing housing or seal. The burst occurs at an rpm
related frequency.
dBm
dBc
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