In brief
Vibration analysis is a condition monitoring method that measures machine vibrations in order to detect damage to rotating components early.
Contents
What is Vibration analysis?
Every rotating machine vibrates. If the level or composition of these vibrations changes, this indicates unbalance, misalignment, loose fastenings, bearing damage or gear tooth defects. Vibration analysis is therefore a core tool of condition-based and predictive maintenance of motors, pumps, fans, gearboxes and compressors.
Measurements are usually taken with accelerometers at the bearing points, either with portable equipment on fixed measuring routes or permanently with online systems. The RMS value of vibration velocity in mm/s is used for general assessment; evaluation criteria for different machine classes are set out in the ISO 20816 series of standards, successor to ISO 10816. For diagnosis, the frequency spectrum is evaluated: certain patterns point to unbalance or misalignment, while envelope analysis reveals early rolling bearing damage on the basis of its defect frequencies.
The greatest benefit lies in the time gained: bearing damage is often detected well before failure, so that spare parts can be procured as planned and repairs scheduled during a shutdown. This requires consistent measuring points and operating conditions so that trends remain comparable.
In practice: maintenance and procurement
For reliable bearing diagnosis, the exact bearing designations should be recorded for each measuring point, as the defect frequencies depend on the bearing geometry. If the analysis signals damage, procurement of the replacement bearing can begin immediately.
Synonyms and abbreviations: vibration monitoring · vibration measurement · vibration diagnostics · machine vibration analysis
Frequently asked questions
What can vibration analysis detect?
Typical findings are unbalance, misalignment of shafts and couplings, mechanical looseness, rolling bearing damage, gear tooth defects in gearboxes, resonances and certain electrical faults in motors. Often it is possible not only to detect damage but also to estimate roughly how far it has progressed and how urgently action is needed.
Which standard applies to the evaluation of machine vibration?
For evaluating vibration on machine housings and bearings, the ISO 20816 series of standards is used, which replaces the former ISO 10816. Depending on the type of machine, it contains zones ranging from good to unacceptable. The specific limit values depend on machine class, power and installation and are set out in the relevant part of the standard.
What is the difference between vibration analysis and thermography?
Vibration analysis measures mechanical movements and is particularly suitable for rotating machines such as pumps, motors and gearboxes. Thermography measures surface temperatures without contact and mainly shows heating, for example at electrical connections or overloaded components. The two methods complement each other in condition-based maintenance.
How often should vibration be measured?
The interval depends on the criticality of the machine and on the time a typical fault takes from the first signs to failure. Regular intervals are usual for route-based measurements and are shortened if values are conspicuous. Very critical machines are often monitored permanently online.