CVA Bearing Analysis & Fault Detection 3

Question 1

What is the primary advantage of using acceleration for high-frequency bearing analysis compared to velocity?

Accepted Answer

Acceleration is more sensitive to high-frequency impulsive events that characterize early-stage bearing faults

Answer

Accelerometers have frequency response extending to tens of kHz, making them well-suited for detecting the high-frequency stress waves generated by early-stage bearing impacts, whereas velocity is preferred for lower-frequency general machinery monitoring.

Question 2

Which bearing defect frequency is most affected by shaft speed variation?

Accepted Answer

All bearing defect frequencies scale linearly with shaft speed

Answer

All four bearing defect frequencies (BPFO, BPFI, BSF, FTF) are directly proportional to shaft rotational speed, so any change in operating speed shifts all defect frequencies proportionally.

Question 3

What does 'bearing clearance' affect in terms of vibration characteristics?

Accepted Answer

Load distribution, contact stress, and vibration amplitude; excessive clearance increases vibration and reduces bearing life

Answer

Excessive bearing clearance increases load zone width, raises contact stress, produces higher vibration amplitudes, and reduces bearing life; insufficient clearance causes preloading, heat generation, and premature fatigue.

Question 4

In rolling element bearing failure analysis, what does 'spalling' refer to?

Accepted Answer

Fatigue cracking and flaking of material from bearing raceways or rolling element surfaces

Answer

Spalling is subsurface fatigue cracking that propagates to the surface, causing flakes or chips to break away from raceways or rolling elements; it produces the impulsive vibration signatures detected by bearing analysis techniques.

Question 5

What is the typical shape of a shaft orbit for a machine running with pure rotor unbalance?

Accepted Answer

A circular or slightly elliptical loop rotating at 1× shaft speed

Answer

Pure unbalance generates a nearly circular or elliptical orbit because the centrifugal force is constant in magnitude and rotates at shaft speed with a consistent phase relationship in both measurement directions.

CVA - Certified Vibration Analyst Practice Test

CVA - Certified Vibration Analyst Practice Test

CVA Bearing Analysis & Fault Detection 3