Page 213 - Rollingbearings

Inspection and monitoring
Inspection and 5 Severe damage occurs: fatigue fracture of Vibration monitoring is based on three
the bearing inner ring fundamental facts:
monitoring 6 Catastrophic failure occurs with secondary
damage to other components • All machines vibrate
• The onset of a mechanical problem is gen-
This section describes various aspects of erally accompanied by an increase in
inspecting and monitoring bearings in oper- Monitoring noise and vibration vibration levels
ation for the purpose of preventing prob- • The nature of the fault can be determined
lems It also gives an introduction to trouble- A common method used to try to identify by analyzing the vibration characteristics
shooting and links to more detailed deterioration or damage in a bearing is to
troubleshooting procedures listen Bearings in good condition produce a
soft purring noise Grinding, squeaking and
other irregular sounds usually indicate that
the bearings are in poor condition, or that
Inspection during something is wrong However, sound moni-
operation toring is of limited use SKF recommends
vibration monitoring It is more thorough
and allows better monitoring of bearings
Spotting early indications of bearing damage and rotating equipment
makes it possible to replace bearings during
regularly scheduled maintenance This Fig. 58
avoids otherwise costly unscheduled Progress of damage
machine downtime if a bearing fails Import-
ant parameters for monitoring machine con-
dition include noise, temperature and
vibration
Bearings that are worn or damaged usu- 1 2 3
ally exhibit identiiable symptoms (Trouble-
shooting, page 213) There can be a number Sealing, mounting and dismounting
of possible causes and this section helps
identify some of these
For practical reasons, not all machines or
machine functions can be monitored using 4 5 6
advanced systems In these cases, trouble
can be detected by looking at or listening to
the machine However, if deterioration can Diagram 1
be detected by human senses, damage may The advantage of advanced condition monitoring
already be extensive Using objective tech- B.8
nologies, such as advanced vibration analy-
sis, means damage can be detected before it
becomes problematic (diagram 1) By using
Vibration level
condition-monitoring instruments and the
SKF enveloped acceleration technology, the
pre-warning time can be maximized Pre-warning time 6 Catastrophic
failure
An example of how damage can progress
is shown in ig. 58 and shown conceptually Depending on 5 Severe failure
in diagram 1 A damage scenario may fol- the background
2 Detection using SKF
low this sequence: enveloped acceleration noise, the
technology pre-warning
time can vary
1 Bearing starts to show abrasive wear
2 First spall, detected by SKF enveloped 1 Damage initiated 4 Detection by
acceleration technology “Listen and feel”
3 Spalling has developed to an extent that
the damage can be detected by standard 3 Detection by standard
vibration monitoring vibration monitoring
4 Advanced spalling causes high vibration
and noise levels and an increase in oper- Operating time
ating temperature

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