Machinery and Equipment Troubleshooting Flashcards

For a typical rolling element bearing, the outer race defect frequency (BPFO) is roughly what multiple of running speed?

Answer: About 0.4 times the number of rolling elements

A common rule of thumb is BPFO ≈ 0.4 × N × RPM, and BPFI ≈ 0.6 × N × RPM.

The fundamental train frequency (FTF, cage frequency) of a rolling element bearing typically falls at what fraction of shaft speed?

Answer: About 0.4X

Cage frequency is subsynchronous, usually around 0.35 to 0.45X running speed.

A pinion with 30 teeth turns at 1,800 RPM. What is the gear mesh frequency?

Answer: 900 Hz

GMF = teeth × shaft speed = 30 × 30 Hz = 900 Hz.

Sidebands around gear mesh frequency spaced at the output shaft speed most likely point to a problem with which component?

Answer: The gear on the output shaft

Sideband spacing identifies which shaft's gear is modulating the mesh, such as through eccentricity or wear.

Which technique is most effective for detecting the earliest stage of rolling element bearing wear?

Answer: High-frequency methods such as enveloping, PeakVue, or spike energy

Early bearing defects generate high-frequency stress waves and impacts that demodulation and HF methods detect before the discrete defect frequencies show up.

Why are BPFI peaks commonly accompanied by sidebands spaced at 1X running speed?

Answer: The inner race defect rotates in and out of the load zone once per revolution

On a rotating inner race, the defect passes through the load zone each revolution, amplitude-modulating BPFI at 1X.

Ball spin frequency (BSF) peaks accompanied by sidebands at FTF most likely indicate what?

Answer: A defect on a rolling element

Rolling element defects show at BSF (often 2×BSF) modulated by cage speed, because the elements travel with the cage.