Question 420General Subjects - 1st Asst/Chief70% to pass
When reviewing results of vibration analysis, vibration at a bearing occurs at the same frequency as the motor rpm, with a displacement in the radial direction that is twice that of the axial direction. Which of the following could this indicate?
AI Explanation
The correct answer is B) Mechanical unbalance.
When vibration occurs at the same frequency as the motor's rotational speed, and the displacement in the radial direction is twice that of the axial direction, this is a classic indicator of mechanical unbalance. Mechanical unbalance occurs when the center of mass of the rotating assembly (e.g., motor, pump, or other equipment) is not aligned with the center of rotation. This creates an imbalance that results in vibration at the rotational frequency, with greater radial displacement compared to axial displacement.
The other options are not the correct explanation for this vibration pattern. Loose foundation bolts would likely result in vibration at lower frequencies, a bent motor shaft would cause vibration at multiples of the rotational speed, and rubbing would generally produce vibration at higher frequencies.
Related Questions
#418 Vibration analysis can provide comparative data of operating condition of rotating machinery. At what positions should such readings be taken at bearing housings and foundations? #419 While examining results of vibration analysis of a rotating piece of machinery, you find find very high amplitude/displacement readings at a very high frequency at one measuring point. What would that indicate? #421 When measuring vibration, an engineer should be concerned with recording the velocity or displacement of the measurement. Which other factor should also be of concern? #422 While examining vibration analysis of a particular piece of rotating machinery, one of the measurement location readings exhibits high amplitude/displacement in vertical and horizontal direction at 2 X RPM frequency. What would this indicate?