Vibration testing in the field
Editor's Note: This is the second of two articles on vibration testing. The first, titled "Vibration Analysis of Motors in the Service Center," appeared in the March 2007 issue of CURRENTS. The article below describes the external conditions that may exist once the motor is back in service. In the previous article referenced above, I covered methods and criteria for testing motors in the service center. Service centers make every effort to ship a quality rebuild. On occasion, the test-run data may have suspicious characteristics. Even though the motor meets the vibration standards, further investigation is warranted. The motor may exhibit a noise, rumble, or excessive bearing temperatures. Spectral data might contain harmonic families, or wave-form data contains impacting. In this circumstance, I will make the statement: "It will never be as close to a motor repair service center as it is now." Accurate test-run documentation can prove invaluable as a comparison tool when judging the performance of a motor once it is installed. After all, you did ship a quality product, didn't you?