7.11: Bearings Flashcards
What should be done if there is damage to the shield/seal?
Damage shield/seal. Reject Bearing
How are sealed bearings inspected?
Sealed bearings are inspected by rotating slowly by hand
How might False Brinelling occur and what might cause it?
False Brinelling
Inspection can be caused by incorrect transport
Occurs through vibration, not necessarily excessive load
How is an axial clearance check performed?
Axial clearance check. Outer race is clamped in a jig
On what surface does spalling occur?
Spalling appears on the load carrying surface
Remember: Spalling is the break away of the race due to foreign debris/objects getting in
Spalling - ALLING - ALL - Chips broke away ALL over floor
What does true brinelling indicate?
True brinelling indicates skidding under high load
What colour does selica gel turn when it absorbs moisture?
When selica gel absorbs moisture, it turns pink
How is a radial clearance checked?
Radial clearance check. Inner race is clamped in a jig
Radial clearnace check = Inner race clamped (i is easy to make into an r)
axial clearance check = outer race clamped (a similar to o in writing)
What can cause Brinelling of a wheel bearing?
Brinelling of a wheel bearing can be caused by a heavy landing
Brinelling - B for Brinelling - B for Ball indented on race
What do small indentations in a race of a ball bearing indicate?
Small indentations in a race of a ball bearing indicate Brinelling
What does chipping of a ball bearing indicate?
Chipping of a ball bearing indicates spalling
What is used to lubricate bearings subject to high temp applications?
Graphite greases are used for high temp applications
How much should you fill a bearing with grease? (%)
Packing bearings. Fill to 70-80%
heavy landing
brinelling
indentations on the race-way due to load transferred through the bearing when static
False Brinelling - caused by AMBIENT VIBRATION & NO LUBRICATION - no hyrdo-dynamic film-Metal to Metal contact. The combination of metal to metal contact & vibration creates a wear pattern that mimics BRINELLING
(When a bearing is not operating it is subject to FALSE BRINELLING in its box or in the machine)
lightly packed with grease
Bearings should be packed 70% to 80% full
Advantages of Grease - Bearings can be pre-lubricated - no need for LUBRICATION SYSTEM./ Requires Less Maintenance./ Not as difficult to seal as oil lubrication system./ Remains in contact to bearing components better than oil.
Disadvantages of Grease: LESS EFFICIENT AT CONDUCTING HEAT away from the bearing as effective as OIL. Increases initial TORQUE means RUNNING TORQUE IS SLIGHTLY HIGHER. SPEED LIMITS FOR GREASE ARE LOWER THAN OIL LUBE (Grease tends to cause overheating at high speed)
oscillate and remove slowly to listen for roughness
Feel Test - Rotated slowly by hand and listen for roughness
Run Test - Run on shaft at 500 to 1000 rpm and applying AXIAL & Radial LOADS IN EITHER DIRECTION
clean, warm, dry compressed air
Spalling
Spalling - Flaking of the surface layer of the raceway caused by Thermal & Shear streeses or ingress of FOD, material flaking away (evidenced by vibration & noise) after a time these stresses cause cracks which extend up to the surface as the roller’s elements pass over the cracks fragments of material break away
high temperature applications
reject bearing
Overheating & Lubrication Failure - Discolouration of the rings, rollers & cages (Temp in excess of 400^C) restricted flow & excessive temperatures degrade the chemical composition of the grease
Option A: are susceptible to brinelling
Option C: A cracked ring
Option B: heavy landing
Option B: shallow smooth depressions caused by the rollers being forced against the cup, due to overtorquing
Option B: both radial and axial loads
Option C: brinelling
Option C: a soft steel or brass tube drift
Option B: sodium based greases
'’Graphite is added to sodium based greases’’
Option B: indentations on the race-way due to load transferred through the bearing when static
Option C: lightly packed with grease
Option C: oscillate and rotate slowly to listen for roughness
Option A: Radial
Option C: white spirit
Option B: clean, warm, dry compressed air
Option A: thrust loads, thus limiting axial movement
Option C: Spalling
Option B: Needle bearings
Option B: high temperature applications
'’Graphite greases are used in high temperature applications’’
Option B: must be degaussed before use
Option B: Nickel
'’Outer rings are made from high carbon chromium alloy steel. Inner rings are made from low carbon nickel alloy steel and deep case carborized’’
Option A: Reject bearing
Option A: Reject bearing
Option C: the outer ring can be removed from its housing for inspection
1/ Lying flat
A. a cracked ring
C. rotating slowly by hand
C. rejection of the bearing
- A watermark on a bearing indicates
A. bearing running dry
B. intergranular corrosion
C. lack of lubrication
B. intergranular corrosion
A. pink
1/ rejection of the bearing
3/ the inner race
1/ the outer race
2/ on the load carrying surface
1/ metallic particles in suspension
3/ skidding under high load
1/ the engine oil system
2/ higher vibration readings
1/ incorrect transport
- Which bearing type would normally carry the heaviest loads?
1/ air bearings
2/ roller bearings
3/ ball bearings
2/ roller bearings
Note: r for roller - radial
ball bearings -thrust loads
- Needle roller bearings are limited to only one type of load
1/ radial loads
2/ axial loads
3/ linear thrust loads
1/ radial loads
radial loads - r for radial
- The most important factor in determining a bearings ability to carry axial loads is the:
1/ angular contact
2/ the internal clearance
3/ the available space
1/ angular contact
- A hardy spicer coupling is also known as:
1/ self aligning bearing
2/ silent running coupling
3/ a universal/constant velocity bearing
3/ a universal/constant velocity bearing
- Which type of bearing is more rigid:
1/ ball bearing
2/ roller bearing
3/ air bearing
1/ ball bearing
- How do we position bearings for storage:
1/ Lying flat
2/ On their side
3/ Stacked side by side
1/ Lying flat
- A Hardy Spicer coupling has what type of bearing?
a) Plain bearings
b) Ball bearings
c) Needle bearings
c) Needle bearings
- Needle roller bearings
A. can accept a small amount of misalignment
B. are susceptible to brinelling
C. are designed to carry axial loads
B. are susceptible to brinelling
- When rotating a ball bearing by hand, a regular click indicates
A. a cracked ring
B. damage to the balls
C. intergranular corrosion in the outer ring
A. a cracked ring
- A journal load is:
A. Compression
B. radial
C. Axial
B. radial
What kind of bearing is used in a landing wheel?
A. Needle roller bearing
B. Tapered roller bearing
C. Caged ball bearing
B. Tapered roller bearing
A tapered roller bearing handles radial loads and axial loads in one direction only -> used in pairs
Where are needle roller bearings used?
Where there are space restrictions
- Loads on tapered roller bearings are:
A. thrust only
B. radial only
C. radial and thrust
C. radial and thrust
A self aligning bearing is a
A. angular bearing
B. precision bearing
C. radial bearing
A. angular bearing
A crankshaft would be fitted with a
A. cylindrical roller bearing
B. taper roller bearing
C. spherical roller bearing
cylindrical roller bearing
Where heat is likely to be transmitted through a bearing
A. group 2 bearings are used
B. group 4 bearings are used
C. group 3 bearings are used
B. group 4 bearings are used
Shielded ball bearings are inspected by:
A. running at operating speed and listening for signs of wear
B. dismantling and inspecting
C. rotating slowly by hand
C. rotating slowly by hand
Thrust bearings take:
A. radial loads
B. journal loads
C. sideloads
C. sideloads
A single row ball bearing is best suited to accepting
A. radial loads only
B. axial loads only
C. axial and radial Loads
C. axial and radial Loads
Bal bearings take primarily thrust loads, some axial and small radial
Taper roller bearings are used for which of the following purposes?
A. To transmit radial loads whilst resisting axial movement
B. To transmit thrust loads with radial loads
C. To permit axial movement whilst resisting radial load
B. To transmit thrust loads with radial loads
The stationary race of a journal bearing is normally:
A. A clearance fit
B. An interference fit
C. A transition fit
B. An interference fit
Damage to the shield of a bearing should result in
A. no action
B. replacement of the shield
C. rejection of the bearing
C. rejection of the bearing
A thrust bearing is designed so that
A. it transmits radial loads, therefore limiting axial movement
B. it transmits axial loads, therefore limiting radial movement
C. it transmits axial loads, therefore limiting axial movement
C. it transmits axial loads, therefore limiting axial movement
Which type of bearing seal is most appropriate to high temperature applications:
1/ Labyrinth seals
2/ Neoprene rubber type seals
3/ carbon type seals
1/ Labyrinth seals
Plain bearings use:
1/ phosphor bronze
2/ High carbon steel
3/ Inconel steel
1/ phosphor bronze