ITT i-ALERT2, Application Manual

Page: 18 / 64

i-ALERT2 Application Guide 18 of 64
CONDITION MONITORING MEASURES
Implementing a condition monitoring technology requires the user to first understand the equipment failure modes and
what physical parameters are responsive to changes in the equipment’s state. Since not one single device can hope to cover
all possible machine configurations or physical measures we will instead offer recommendations for utilizing temperature
and casing vibration to detect some of the most common failure modes.
TEMPERATURE
Monitoring and trending the
Temperature
of a bearing housing provides
insight into many common problems with rotating machinery such as:
•
Inadequate lubrication of rolling element bearings
•
Damaged rolling element bearings
• Excessive loading of rolling element bearings
• Inadequate cooling flow from housing fins, jacketed
cooling systems or cooling fans
•
Excessive ambient or process fluid temperatures
VIBRATION – RMS VELOCITY
Monitoring and trending
RMS velocity
of a bearing housing provides an
assessment of how much overall energy is contained in the machines vibration.
This can be used to indicate changes to both process conditions and machinery
health. Numerous failure modes or machine faults can cause the RMS velocity
to increase so an exhaustive discussion of them here is not going to be
attempted. RMS velocity increases can also corroborate a Temperature
increase, which assists the reliability practitioner in narrowing down potential
failure modes. RMS velocity is by far the most common vibration parameter
utilized to gauge overall machine condition.
There are no “absolute” levels of vibration that can be used to indicate if a machine is good or bad. There are too many
factors that influence of the overall vibration from one machine to the next. The chart below is provided to assist the user
to establishing warning and alarm limits and is taken directly from the ISO 10816 standard. These limits can and should be
modified based on the equipment’s actual vibration data and user’s experience. Remember, a doubling of the overall
vibration is almost always related to a change in machine condition.
Figure 9: Example weekly trend data