In order to explain what vibration analysis is and why it’s used, it’s important to first understand what vibration is.  One definition of “vibration” is that it is the oscillatory (repetitive) motion of a mechanical system about a central position of equilibrium.  It occurs when a machine or structure experiences periodic or random disturbances (variation of force), resulting in repetitive or irregular motions.  Mechanical vibrations can arise from many different sources, including rotating machinery (unbalance, misalignment, degrading bearings) as well as car engines, moving vehicles, and environmental factors such as wind, temperature changes, and seismic activity.  These vibrations can have significant effects on the machine’s performance, reliability, and lifespan and may need to be analyzed, monitored, and controlled to ensure optimal operation and safety.

Vibrations (the physical movement of a system) are inherent to operating machinery and the vibration occur when these machines perform tasks for us (like an air conditioner unit).  Whether a machine generates electricity, pumps water, or supports construction processes, all operating machines have measurable vibration levels. However, when left unchecked these vibrations can increase over time due to wear, adverse operating conditions and environmental changes, resulting in increased repair expenses, and if not corrected, eventually failure. Vibration serves as a dependable indicator of when these movements point to a degrading issue, alerting us to potentially minor faults before they degrade and cause an equipment failure.

Hence, vibration analysis serves as a crucial tool for detecting a wide array of potentially costly and catastrophic faults in machinery. Through vibration analysis, the trained person can identify issues such as broken welds, loose or missing fasteners, rotor wear in motors, improper installation of bearings, and the overall quality of machine assembly or alignment.  This vibration data can be collected periodically or, more effectively, in real-time. Monitoring a machine 24 hours a day allows fluctuations in vibration to be seen as soon as they begin to happen and with historical data, can determine exactly when faults may begin to occur due to changes in operating conditions.

 Utilizing vibration data obtained through periodic vibration testing can be used to inform machinery owners of improper maintenance activities, abnormal operating conditions, and degrading conditions.  The uses of vibration trend are exceptional, ensuring machinery functions correctly and prolonging equipment life while preventing failures. In addition, machine repairs can be scheduled at opportune times while mitigating the risk of costly failures.

Consider the analogy of assembling complex furniture at home.  When a few components are misplaced or incorrectly installed, the furniture may initially operate. However, over time, failure occurs at the point of improper assembly (loose or missing fastener). This analogy holds true for any type of industrial machinery.

Consider a motor / gearbox / pump at a nuclear power plant. When the pump flow was increased to meet updated IST test conditions, the gearbox experienced a sudden increase in vibration levels.  Since this gearbox was part of an integral safety-related component, NRC regulations required a resolution within 36-hours or the plant would have to shut down the unit.

After reviewing the pump’s work history, it was evident that the previous alignment was out of specification. Due to time constraints, a complete relocation of the pump to rectify the alignment was not feasible. However, by applying good vibration analysis principles, we determined what the optimal positioning for the gearbox should be.  Our analysis (resonance testing) determined that be adding a mass to the top of the gearbox (tuned dynamic absorber) we could effectively mitigate the vibrations and possibly restore the pump to specification. Time was almost up but by following VAI’s suggested maintenance moves, the gearbox vibration levels decreased to an acceptable level, preventing a costly downtime.