KOHTECT BT-77
can be easily filtered out all other vibrations, i.e. vibration frequencies. The shock pulse
method involves monitoring and analyzing the decaying transient process.
3.2 How Shock Pulse Measured and Evaluated for Rolling Bearing
The outer raceways of the bearing always feature roughness. Therefore a bearing under
normal operating undergoes the mechanical impacts and creates shock pulses. Shock
pulse value is dependent on the bearing surface condition and the peripheral condition
of the bearing. Shock pulse value of the regular bearing features 1000 times increase
since the time a bearing is new up to the moment when a bearing needs replacement.
Because of the very large dynamic range shock pulses are measured on a decibel
scale.
Empirical tests showed that even the new and lubricated bearing generates shock
pulses. The value of this initial impact is set as dB
i
(dB, initial value). As the bearing
wears, the value dB
a
(average shock pulse value) increases. �ormalized value dB
n
for
the bearing can be shown as follows dB
n
= dB
a
- dB
i
(Bearing Life)
Fig-3.1. depicts dBn and bearing life ratio.
In order for the shock pulses reading to be quickly and easy to evalutated on the bearing
condition, in simple understanding scale dB
n
has been derived. It categories the bearing
condition into three different zones by indicating the extent of bearing damage from
good to poor condition, Fig-3.1:
100%
0
50
20
40
60
dB
n
100%
0
50
20
40
60
dB
n
15
Summary of Contents for BT-77
Page 1: ...BT 77 Bearing Tester with Non Contact Tacho Operating Instruction Manual...
Page 2: ......
Page 4: ...KOHTECT BT 77...
