Test Conditions
The vibration signature of a machine is strongly dependent on the operating parameters as well as its physical condition. These operating parameters include such things as running speed, load, pump discharge pressure, and compressor delivery pressure.
The machine must be in its normal operating condition when vibration data is collected. If this is not the case, the vibration signature will not match the vibration signatures previously recorded, and trending vibration levels over time becomes impossible. Running speeds of induction motors depend on the load, and should not vary from one collection time to the next by more than a few percent. This means that load conditions must be as nearly as possible the same.
The vibration level contributed by extraneous sources, such as nearby machines, must also be the same for each data collection time. Do not collect data with adjacent machines turned off if the previous spectra were recorded with them running. This is especially true with strong background vibration levels, as in the engine room of a ship. Propulsion diesels must be operating at the same speed for each data collection session!
Azima DLI provides products and services for Predictive Maintenance including vibration analysis instruments, monitoring and diagnostic software, and consulting for CBM programs.
© 2009 - Azima DLI