Millwright Certification Bearing Installation, Maintenance, and Failure Analysis 1

Question 1

When repacking a bearing housing with grease, what is the generally recommended fill level to prevent overheating from churning?

Accepted Answer

One-third to one-half of the free space in the housing

Answer

Fill the housing cavity completely to ensure full lubrication

Answer

Just enough grease to coat the rolling elements and cage

Answer

Two-thirds to three-quarters of the housing cavity

Question 2

A technician finds a reddish-brown powdery debris between a bearing outer ring and its housing bore after disassembly. This condition is most accurately identified as:

Accepted Answer

Fretting corrosion from micro-movement between mating surfaces

Answer

Spalling caused by subsurface fatigue

Answer

False brinelling from vibration during standstill

Answer

Galvanic corrosion from dissimilar metals

Question 3

When pressing a bearing onto a shaft using a mechanical press, to which surface should the pressing force be applied?

Accepted Answer

Only the inner ring, which is the ring receiving the interference fit

Answer

The outer ring, so force is transmitted through the rolling elements to seat the inner ring

Answer

The cage, to distribute the load evenly across all rolling elements

Answer

Alternately to both rings in small increments to equalize stress

Question 4

During inspection, a millwright observes a regular corrugated or washboard pattern of shallow grooves running around the circumference of a bearing raceway. What is the most likely cause?

Accepted Answer

Electrical current passing through the bearing from a VFD or stray ground

Answer

Misalignment between the shaft and housing during installation

Answer

Excessive axial thrust load in a radial-only bearing

Answer

Contamination by abrasive particles in the lubricant

Question 5

New bearings that will not be installed for several weeks should be stored by:

Accepted Answer

Keeping them in original manufacturer packaging, stored horizontally in a clean, dry area

Answer

Removing original packaging and applying a fresh coat of light machine oil for inspection

Answer

Standing them vertically on their outer rings to prevent brinelling from static loads

Answer

Removing factory grease and repacking with fresh lubricant graded for the anticipated service

Question 6

In the context of angular contact or tapered roller bearings, what does 'preload' mean?

Accepted Answer

A deliberate elimination of internal clearance that places the rolling elements under a compressive load

Answer

The maximum dynamic load rating stamped on the bearing by the manufacturer

Answer

The initial radial force applied with a press to seat the bearing fully on the shaft

Answer

The amount of grease pre-filled into a sealed bearing at the factory