7.11 Bearings Flashcards
Bearings are used to support what?
Shafts and axles
Bearings that accept forces at right angles to the drilling axis are known as what?
Journal or roller bearings
What are bearings that accept forces in the longitudinal direction called?
Pivot or axial bearings
The journal of a slider bearing operates in what?
Bearing box
Bearing bushing
Or directly in bearing body
To decrease friction between the journal and bearing what must you do?
Have sufficient lubrication
What does the amount of bearing play depend on?
The demands the bearing is subjected to
Characteristics of sliding bearings?
Resist radial loads
Make little to no noise
Suitable for both slow and fast rotational journal speeds
Disadvantages of sliding bearings
High starting resistance
Continuous maintenance
Five basic types of anti friction bearings?
Tapered roller bearing
Needle bearing
Spherical roller bearing
Ball bearing
Cylindrical roller bearing
What does lubricants prevent for bearing?
Prevents heating
Prevents corrosion on bearing surface
As a bearing rotates, the mating surfaces create what?
Lubricant film that separates components
What happens if you over grease a bearing?
Excess churning will occur
Could generate extremely high temperatures that is a fire hazard
Bearings are protected with what in shipping?
A preservative coating but is NOT a lubricant
Is the preservative coating on bearings compatible with lubrication?
Yes
It doesn’t need washing off prior to installation
What does excessive loads cause?
Premature fatigue
What else can cause early fatigue failure in bearings?
Tight fits
Brinelling
Improper preloading
What is the solution for bearings with excessive loads?
Reduce the load
Make a bearing with higher weight capacity
What are symptoms of overheating in bearings?
Discolouration of the rings
-balls and cages go from gold to blue
What can overheating cause for bearings?
Deformation of the balls and rings
Degrades and destroys the lubricant
What are common reasons for overheating in bearings?
Heavy electrical loads
Inadequate heat paths
Insufficient cooling or lubrication
What does false brinelling of bearings indicate?
Excessive external vibration
How do you correct false brinelling?
Isolate bearings from external vibration and using greases containing antiwear additives
What is fatigue failure?
Fracture of the running surfaces and subsequent removal of small, discrete particles of material.
Where can fatigue failure occur?
Can occur on inner ring
Outer ring
Balls
How else can fatigue failure be recognised?
Vibrations that indicates abnormality
Angular contact bearings are designed to take what load in how many directions?
Axial loads in one direction
Angular contact bearings must be installed in what way?
With resultant thrust on the wide face
(It is marked thrust)
Symptoms of contamination of bearings?
Denting if the bearings raceways and balls which results in high vibration and wear
Some examples of contaminants?
Dust
Dirt
Abrasive substances
What are some sources of contamination?
Dirty tools
Contaminated work areas
Dirty hands
How to reduce chance of contamination?
Clean work areas
Tools
Hands
Keep bearings in correct packaging until ready for application
Symptoms of lubricant failure?
Discoloured blue or brown tracks and balls
How are lubricant failures usually caused by?
Restricted lubricant flow
Symptoms of bearing corrosion
Red/brown colour on balls, cages or bands
How to reduce corrosion for bearings?
Divert corrosive fluids away from bearing areas and use integrally sealed bearings where possible
What are the most prevalent causes of misalignment?
Bent shafts
Burrs or dirt on shaft
Shaft threads that aren’t square to shaft seats
What indicates a tight fight?
Temperature rise
4 general instructions for bearings?
Always use correct tooling
Apply correct greases
Check bearing block and bearing surfaces for damage
Carry out test loading
When handling a bearing what should you remember?
Your hands must be clean and dry
Surrounding area should be clean
How should you store a bearing?
Coat with a preservative
Store bearing flat
Tightly wrap the bearing in vapour corrosion inhibitor wrapping paper
Follow all bearing storage requirements
What should the storage area be like for bearings?
Clean
Dry
Have consistent temperature
Free from air flow that would change temperature
Humidity less than 75%
Free from vibration
What is the leading failure of bearings
Contamination
What is a symptom of lubricant failure
Discoloured blue/brown ball tracks
What is a symptom of corrosion within bearings
Red/brown areas or balls
How can misalignment be detected
By a ball wear bath nit being parallel to the raceway edges
How can you tell if there is a loose fit
As fretting will cause a generation of fine metal particles which oxidises, leaving a brown colour
Why are tight fits accompanied by
High temperatures
What is a symptom of overheating
Balls and cages go from gold to blue
