Condition monitoring
The following list includes the main condition monitoring techniques applied in the industrial and transportation sectors: Most CM technologies are being standardized by ISO and ASTM.
The level of vibration can be compared with historical baseline values such as former start ups and shutdowns, and in some cases established standards such as load changes, to assess the severity.
These frequencies correspond to certain mechanical components (for example, the various pieces that make up a rolling-element bearing) or certain malfunctions (such as shaft unbalance or misalignment).
For example, high vibration at the frequency corresponding to the speed of rotation is most often due to residual imbalance and is corrected by balancing the machine.
A degrading rolling-element bearing, on the other hand, will usually exhibit vibration signals at specific frequencies increasing in intensity as it wears.
Beside all sensors and data analysis it is important to keep in mind that more than 80% of all complex mechanical equipment fail accidentally and without any relation to their life-cycle period.
Depending on the type of machine, its typical malfunctions, the bearing types employed, rotational speeds, and other factors, the CM specialist may use additional diagnostic tools, such as examination of the time domain signal, the phase relationship between vibration components and a timing mark on the machine shaft (often known as a keyphasor), historical trends of vibration levels, the shape of vibration, and numerous other aspects of the signal along with other information from the process such as load, bearing temperatures, flow rates, valve positions and pressures to provide an accurate diagnosis.
Handheld data collectors and analyzers are now commonplace on non-critical or balance of plant machines on which permanent on-line vibration instrumentation cannot be economically justified.
Recently also on-line condition monitoring systems have been applied to heavy process industries such as water, steel, oil & gas, pulp & paper, mining, petrochemical and wind power generation.
Performance analysis is often closely related to energy efficiency, and therefore has long been applied in steam power generation plants.
The concept of this type of device is that it can be used by normal plant operators and maintainers without the need for specialist interpretation of spectra, although the underlying spectral plots are available if required.
