CMRT Predictive Maintenance Technologies 2

Question 1

In vibration analysis, what does a high amplitude peak at exactly 1× running speed (1X) typically indicate?

Accepted Answer

Unbalance

Answer

A dominant 1X peak in the vibration spectrum is the classic signature of mechanical unbalance in rotating equipment.

Question 2

Which FFT window function is best suited for detecting closely spaced frequency components with similar amplitudes?

Accepted Answer

Hanning

Answer

The Hanning window provides good frequency resolution and reduces spectral leakage, making it ideal for detecting closely spaced peaks.

Question 3

A vibration spectrum shows peaks at 0.5X, 1X, and 1.5X running speed. This pattern is most consistent with:

Accepted Answer

Fluid-film bearing instability (oil whirl)

Answer

Sub-synchronous peaks near 0.5X are the hallmark of oil whirl instability in fluid-film bearings.

Question 4

When using an accelerometer for high-frequency vibration measurement, what mounting method provides the widest usable frequency range?

Accepted Answer

Stud mount

Answer

Stud mounting provides the most rigid coupling, extending the usable frequency range up to the sensor's full specification.

Question 5

The kurtosis value of a vibration signal is most useful for:

Accepted Answer

Detecting early-stage bearing defects

Answer

Kurtosis measures impulsiveness in a signal; a rising kurtosis value (above ~4) indicates early-stage bearing defects before they appear in the spectrum.

(CMRT) Certified Maintenance and Reliability Technician Practice Test

(CMRT) Certified Maintenance and Reliability Technician Practice Test

CMRT Predictive Maintenance Technologies 2