Vibration Analysis/Monitoring is used to monitor the health of rotational equipment. It involves the trending and analysis of certain machinery performance parameters to detect and identify developing problems before failure occurs (which can often cause extensive damage). The detection and diagnosis of faults before they become a problem is obviously the most desirable way to maintain machinery. An effective condition-monitoring programme will help to detect faults at an early stage such as when rolling element bearing defects are still minor and do not affect the performance of the machine. This allows time to analyse the problem while the machine stays online and production continues normally. This advance warning allows planning of the repair at a convenient time.
Once machinery problems have been detected i.e. (a change or upward trend in vibration levels are detected) by the Condition Monitoring programme, the next stage is to identify the specific problems or single root cause of the change in vibration level. This is the role of vibration analysis, to pinpoint specific machinery problems by revealing their unique vibration characteristics. These vibration characteristics are then broken down into individual vibration frequencies, which are then matched to known defect frequencies that a range of different problems normally appear at. These frequencies will largely depend on the type of machine, speed of the machine and the type of bearings installed etc. There are literally hundreds of specific mechanical and operational problems that can cause a machine to exhibit excessive vibration; this is where knowing the frequency of vibration is most important. Since the forces that cause vibration are usually generated through the rotating motion of the machine’s parts and because these forces change in direction or amplitude according to the rotational speed of the machine components, it follows that most vibration problems will have frequencies that are directly related to the rotational speeds. Some of these problems have there own individual, unique characteristics in the vibration spectrum, while some of these problems have similar characteristics. It is only through training, skill and experience, and a thorough knowledge and understanding of how the machine internals work, that the vibration technologist learns how to decipher and interpret the vibration signatures of individual machines and machinery problems.