Condition monitoring is a process of using a technology to detect changes in machine health over time. The frequency with which one takes measurements will depend on the machine, its current condition, and how quickly it degrades. Typically, one will test a machine more frequently (perhaps monthly) in the early stages of the monitoring program in order to develop a baseline and verify that the machine's health condition is stable. If the machine seems to be stable and healthy, then the test frequency might be reduced to one test per quarter for a typical piece of rotating machinery.
At some point the machine will begin to experience wear. Perhaps one will see bearing tones beginning to appear in the vibration spectrum. At this point one will want to increase the test frequency in order to better monitor changes in the machine's condition. If the machine was being tested once per quarter, perhaps one will begin testing it every two months. As the condition of the machine continues to worsen, the test frequency should be increased in order to detect any additional changes and avoid catastrophic failure. If one really wants to push the machine to its limits one might even test it daily up until the point of overhaul. After overhaul, the machine should be tested immediately for quality assurance purposes. It may be wise to test the machine a few times just after installation or overhaul to make sure the machine has been installed correctly. The important point here is that the test frequency should vary depending on the machine's condition. This variability needs to be written into your PM tasks appropriately.
Tip submitted by, Alan Friedman, Senior Instructor, Mobius Institute