Practical Solutions to Machinery and Maintenance Vibration Problems
Chapter 3, Detuning and Proving Resonance
Section 7, Bump Test While the Machine is Running
Normally, bump tests are performed with the machine shut down. However, in certain cases a bump test can be performed while the machine is running. A running machine spectrum is obtained. Another is taken while bumping the part. The two spectra can then be compared to determine if there is a resonance.
If peak-hold averaging with running display capability is available, then its use is preferred. With the instrument set up accordingly, take data with the machine running. Then with the machine still running, bump the structure repeatedly. If the bumps generate natural frequency peaks that correspond to a peak produced by the running machine (before bumping), then the amplitude on the analyzer screen should increase. The peak's width will also increase if the peak is affected by resonance.
This textbook contains only part of the information in our Practical Vibration Analysis seminar.