Monarch Instrument EXAMINER 1000 - Manual (Page 8)

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Why Measure Vibration?
Vibration is considered the best operating parameter to judge dynamic conditions
such as balance (overall vibration), bearing defects (enveloping) and stress applied
to components. Many machinery problems show themselves as excessive vibration.
Rotor imbalance, misalignment, mechanical looseness, structural resonance, soft
foundation, and gearmesh defects are some of the defects that can be measured by
vibration. Measuring the “overall” vibration of a machine, a rotor in relation to a
machine or the structure of a machine, and comparing the measurement to its normal
value (norm) indicates the current health of the machine.
The EXAMINER 1000 measures the vibration of a machine while it is operating.
Trending these measurements shows how a machine’s condition changes over a
period of time. Analyzing these, along with other measurements, provide insight into
the condition of the machine and which components may be wearing or failing. How
to best monitor a machine’s condition requires one to know which measurements to
take and where and how to take them. Sensors are placed at strategic Points on
the machinery to monitor the machine’s condition.
The EXAMINER 1000 processes the accelerometer’s mechanical vibration energy
into an electrical signal and displays the measurement value in numerical form for
evaluation. Commonly measured physical characteristics in Predictive
Maintenance are:
• Vibration (as explained above)
• Temperature
• Oil Analysis
Temperature
As a bearing fails, friction causes its temperature (or its lubricant’s temperature) to
rise. While trending a bearing if the temperature rises followed by a vibration increase,
then it is safe to conclude their was a loss of lubrication which induced the mechanical
failure. If vibration increased first, followed by increased temperature readings then
a mechanical defect caused the lubrication failure.
Lube Oil Analysis (Ferrography)
Monitoring oil condition warns of an increase in foreign substances, such as water,
which can degrade the lubricating properties of the oil and cause bearing failures. It
also detects the presence of metallic particles carried into the oil stream. These
metallic particles are analyzed to determine which part of the machine is wearing
and how fast. Lubrication analysis is the earliest warning of a developing problem.
Lube oil testing results can be trended with On-Time software.
What are you Measuring?
Vibration is the behavior of a machine’s mechanical components as they react to
internal or external forces. Since most rotating machinery problems show themselves
as excessive vibration, we use vibration signals as an indication of a machine’s
mechanical condition. Also, each mechanical problem or defect generates vibration
in its own unique way. We therefore analyze the “type” of vibration to identify its
cause and take appropriate repair action. With overall vibration monitoring (VIB
ISO) using the Examiner 1000, analysis of the cause of excess vibration relates to
the monitoring equipment’s probe position; either horizontal, vertical, or axial.
Horizontal - Typically, unbalanced shafts tend to cause excess radial (horizontal
and vertical) vibrations, depending on the machine support design.
Vertical - Excessive vertical vibration can indicate mechanical looseness as well as
imbalance.
Axial - Excessive axial vibration is a strong indicator of misalignment.
It’s important to note that these are general guidelines and that knowledge of your
machinery and proper hand-held probe techniques are necessary to accurately analyze
the cause of excessive vibration.
Multi-Parameter Monitoring
Using different measurement types to monitor your machinery for changes. This
allows for early detection of specific machinery problems that may not show under
normal overall vibration monitoring. For example, if a rolling element bearing has a
defect on its outer race, each roller will strike the defect as it goes by and cause a
small, repetitive vibration signal. However, this vibration signal is of such low
amplitude that under normal overall vibration monitoring, it is lost in the machine’s
rotational and structural vibration signals. Acceleration Enveloping can measure
these signals better than overall readings. Use both measurement types for
bearings and gearboxes. As ENV values begin to decrease, rely on VEL
readings.
Overall Vibration Monitoring -Monitors normal, low frequency machine vibration.
Detects rotational and structural problems like imbalance, misalignment, and
mechanical looseness.
Enveloping - Amplifies high-frequency, repetitive bearing and gear mesh vibration
signals for early detection of bearing problems, but does not detect non-repetitive
rotational or structural events like imbalance, misalignment, and looseness. Provides
earliest detection of high frequency metal-to-metal contact or poor lubrication in
problem bearings.
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