The vibration waveform of a bearing with a fault in the initial stage is shown in the example below.
Compared to the waveform of a normal bearing, the crest factor is higher.

A: Newly installed machinery will normally be within this range.
B: Long-term continuous operation allowed.
C: Long-term continuous operation not allowed,
but limited-term operation allowed.
D: High risk of injury. Operation not allowed.

Using the normal condition as a reference, threshold values for caution and hazard conditions are set.
When the caution level is exceeded, monitoring is reinforced, and detailed diagnosis is performed when the hazard level is exceeded. A commonly used factor for setting the levels is as follows: caution level = 2 to 3 times the normal value, hazard level = 2 to 3 times the caution value.
After deciding on the vibration measurement location, measurement direction, and measurement frequency, a time series graph is commonly used for trend management, comprising measurement values and other data.

Trend management diagram

Machinery usually comprises a variety of vibration
sources such as motors, gears, bearings, fans, etc. When devising measures to minimize vibrations and when trying to locate the causes of problematic vibrations, measuring only the magnitude of vibrations often will not provide enough information. It is also necessary to perform frequency analysis, in order to determine
which types of vibrations exist and what their levels are.

As shown in the illustration, the locations where vibrations occur will affect the vibration frequency.
Frequency analysis makes it possible to pinpoint
vibration sources with greater accuracy

This shows the variations over time at the location of the
accelerometer.

It provides information that is not available from the spectrum display, such as whether the vibration is normal or impact related, whether it has shifted upwards or downwards, etc.

Comparison to reference spectrum（Overlapping of stored data）

Bearing problems will cause a significant increase in acceleration values.
As seen in the example, envelope analysis shows the peaks at equal intervals.
When the size, number of rolling elements, axis rotation speed and other parameters are known, the primary frequency of the lined-up peaks will provide information about the problem location.

When there is a misalignment, large vibration components that are an
integral multiple of the rotation speed will appear in the axis direction.
The type of bearing joint affects the multiplication factor. In the example shown here, there are large vibration components with a factor of 3.

When there is an imbalance, large vibration components at a frequency equal to the rotation speed will appear in
the circumferential direction.
Vibrations of other frequencies will be largely absent. The vibration amplitude is proportional to the imbalance magnitude. At higher rotation speeds, the vibration amplitude is proportional to the square of the rotation frequency.