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Industrial Mechanic 2nd Block, Harmonized > Alb Mod Bearing Maint A > Flashcards

Alb Mod Bearing Maint A Flashcards

1
Q

When using temperature as a clue to the condition of a bearing, you must be aware that temperature is the result of: (3)

A
  • Friction
  • Heat dissipation
  • Heat transferred from outside the housing
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2
Q

Rapid oxidization of the lubricant occurs above this temperature:

A

55°C 131°F

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3
Q

After the bearings have been running satisfactorily, and temperature then jumps, assuming there is adequate lubrication and no change in operating conditions, what could cause the change in temperature?

A

Rollers and raceways are deteriorating and causing more friction

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4
Q

After bearings are freshly installed and lubricated, a temperature rise of ___° above normal is expected for a few hours.

A

15°C or 27°F

Note: if it continues to rise, this indicates faulty installation or the wrong bearing

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5
Q

Unsealed bearing temperature is too high when it exceeds:

A

125°C (257°F)

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6
Q

A sealed bearing temperature is too high when it exceeds:

A

80°C (176°F)

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7
Q

The surface temperature of a housing is lower than the bearing temperature. To determine the bearing temperature, add:

A

20°C (36°F)

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8
Q

The temperature of the inner ring is usually ___° higher than the rest of the bearing

A

10°C (18°F)

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9
Q

____ is a periodic back and forth movement.

A

Vibration

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10
Q

A deteriorating bearing can generate its own:

A

Vibration

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11
Q

Amperage readings that are above normal indicate:

A

abnormal loads on the machine

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12
Q

When you have an increased amperage reading on a machine, you should investigate further by checking: (3)

A
  • Vibration
  • Temperature
  • Lubrication
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13
Q

If the bearings are the cause of an increase in amperage, it must indicate:

A

Bearings are in very bad condition

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14
Q

A bearing should produce ___ noise to the unaided ear

A

very litte

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15
Q

When listening to a bearing in good condition with a stethoscope, it should sound like:

A

Should have a soft purring sound

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16
Q

When listening to a bearing in a bad condition with a stethoscope, it could sound like: (3)

A
  • Loud hollow noise,
  • High pitched scream
  • growling noise
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17
Q

The causes of bearing failure may be grouped as: (4)

A
  • improper installation and handling
  • Improper maintenance
  • improper selection
  • fatigue
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18
Q

When working near moving equipment, be cautious of parts that may not be covered by the guard and may not be obvious while rotating, such as: (3)

A
  • Keys
  • Setscrews
  • flingers
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19
Q

Built in contamination is when:

A

Dirt is introduced to the machine either when it was built or when it was rebuilt

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20
Q

It has been established that ____ is the biggest cause of premature bearing failure

A

contamination

Most abrasive compounds are smaller than 40 microns, invisible to the naked eye

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21
Q

Always cover exposed bearings when:

A

you are not working on them

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22
Q

Bearing rings have a very small cross section and depend on the:

A

Housing bore for support

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23
Q

If the seating surfaces on the shaft and the housing bore are not true, the bearing:

A

distorts

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24
Q

If the shaft and bore diameters are not to specification, the bearing won’t have the proper:

A

internal clearance

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25
Q

Both distortion and incorrect diameters cause:

A

Early bearing failure

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26
Q

When checking a shaft for straightness, if it has more than ____” runout at the shaft center, seal seats or ends, it must be straightened or replaced

A

0.001”

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27
Q

If a housing bores seats have grooves or hollows from corrosion, the must be:

A

sleeved

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28
Q

If, when measuring for out of round or a taper, your seats are off by more than ___”, it must be fixed or replaced.

A

0.0005”

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29
Q

When a bearing is heated above its stabilization temperature and cooled, it:

A

distorts

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30
Q

It is safest to assume a maximum of ____° when heating a bearing

A

120°C (248°F)

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31
Q

A bearing material that is dimensionally stabilized means:

A

The material has gone through a heating and cooling process

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32
Q

Although bearings can be stabilized to temperatures above 150°C, they cannot be run at that temperature because:

A

The bearing material is weakened at those temperatures

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33
Q

Brinelling is ____ and makes a bearing useless

A

impact denting

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34
Q

Brinelling can be caused by: (3)

A
  • Hammer blows
  • dropping the bearing
  • shock loading on machine
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35
Q

False brinelling is caused by:

A

vibrations on a bearing that is not turning.

Note: Allows film of lubricant to break and metal to metal contact. Wears bearing, causes depression under each rolling element

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36
Q

To prevent false brinelling:

A

Machine must be isolated from isolation and the shaft blocked to support it

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37
Q

Bearings should never be stored on a surface that is subject to:

A

prolonged vibration

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38
Q

The durability of an anti friction bearing depends on its:

A

accuracy

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39
Q

What are two practices relating to maintenance procedures that can lead to bearing failures? (2)

A
  • Allowing contamination into housing

- incorrect lubrication

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40
Q

Contamination can be built in, or it can be: (2)

A
  • Ingested during operation

- come from breakdown of lubricant

41
Q

What are three of the contaminant entry points? (2)

A
  • breather

- Faulty seals

42
Q

Why should you filter new oil before putting it in a machine?

A

New oil does not meet cleanliness recommendations

43
Q

Lubricants may be clean when they are installed, but they can generate their own contaminants as they break down. The breakdown is accelerated by: (3)

A
  • Heat
  • Moisture
  • metal particles
44
Q

Some of the contaminants produced by lubrication breakdown are: (3)

A
  • acids
  • Sludge
  • Varnis
45
Q

The oxidization rate of lubricants doubles ever ___° above ____°

A

Doubles every 10°C (18°F) above 55°C (130°F)

46
Q

Inadequate lubrication means the lubrication is not doing it’s job of:

A

Minimizing friction

47
Q

Why could you have inadequate lubrication? (3)

A
  • Wrong type of lubricant
  • Wrong amount of lubricant
  • Wrong type of lubrication system
48
Q

What level should your oil be at in your bearing housing?

A

Only enough to wet contact surfaces, 1/3 to 1/2 up lowest roller

49
Q

The normal recommended grease level for inside a housing is:

A

1/3 full

50
Q

Most of the grease in a housing is used to:

A

prevent entry of water

51
Q

When filling a housing with grease, there should always be room left to allow:

A

excess grease to escape

52
Q

Vibrations can cause damage to machine parts, and can be caused by: (2)

A
  • Imbalance

- Misaligned bearings or couplings

53
Q

Imbalances account for __% of the causes of vibration

A

50

54
Q

An added payback on the cost of balancing is a large savings in energy consumption, from 20% to ___%

A

50

55
Q

Misalignment accounts for ___% of vibration problems

A

40

56
Q

The two areas of misalignment in a machine are:

A
  • Bearings

- Coupling

57
Q

Besides causing vibration, misalignment causes a bearing to run at an angle to its normal running surface. This results in:

A

improper loading of the bearing surfaces and early failure

58
Q

Coupling misalignment is caused by: (3)

A
  • Faulty installation
  • poorly supported/anchored machine
  • thermal growth
59
Q

Electric arcing in bearings refers to:

A

An electric arc jumping across the clearance inside the bearing and leaving a track on the surface.

60
Q

What are the 3 common causes of electric arcing in bearings? (3)

A
  • Welding
  • Residual magnetism in shaft
  • Static charges developed by dry gas
61
Q

Static charges can be short circuited away from a bearing by installing:

A

a ground brush

Note: in an axial direction as close as possible to the center of the roller

62
Q

When checking a rotor for magnetism with a magnetometer, the rotor needs to be de-magnetized if the readings exceed:

A

3 gauss

63
Q

Ceramic coatings are provided on the outside of plain bearings on large electric motors, these isolate the bearing from the:

A

induced current

64
Q

Heat degrades a bearing in the following ways: (4)

A
  • Bearing may be distorted if above its stabilization temperature
  • high temperatures lower a bearings load capacity
  • high temperatures reduce clearance
  • high temperatures change lubricant properties
65
Q

At 200C a bearings load capacity is reduced by:

A

10%

66
Q

at 250C a bearings load capacity is reduced by:

A

25%

67
Q

at 300C a bearings load capacity is reduced by:

A

40%

68
Q

The result of selecting a bearing with too small a clearance is:

A

Will run hot or seize

69
Q

The result of selecting a bearing with too much clearance is:

A

The bearing is noisy and runs hot because the elements skid

70
Q

What materials can be used to make a bearing cage? (3)

A
  • Steel
  • Brass
  • Fiberglass-reinforced polyamide
71
Q

Selection of the wrong cage material can lead to failure due to: (2)

A
  • Corrosion of the cage

- Overheating at high speeds

72
Q

A specialty stainless steel bearing is made for use in:

A

highly corrosive environments

73
Q

A specialty vacuum remelted high temperature steel bearing is made for use in:

A

Jet aircraft, with temperatures up to 600C

74
Q

A specialty plastic bearing is made for use in:

A

lightweight, low load, no heat appications

75
Q

Selecting the wrong bearing type almost always leads to:

A

Early failure

76
Q

____ is the failure or breaking up of any material that has been repeatedly deformed.

A

Fatigue

77
Q

______ occurs as each rolling element enters the loaded zone and deforms itself and the raceway until it passes into the unloaded zone

A

Elastic deformation

78
Q

Elastic deformation happens thousands of times per minute in a bearing. It eventually leads to developing micro cracks. This is known as:

A

Normal fatigue

79
Q

Basic rating life of a bearing is based on fatigue tests. It is the number of millions of revolutions that 90% of bearings will take before ____ of a certain area is produced

A

spalling

80
Q

____ fatigue results in failure before the rated bearing life

A

Abnormal fatigue

81
Q

Bearing noise is most commonly monitored by ear, or with: (2)

A
  • stethoscope

- screwdriver

82
Q

If you hear an unusual sound from a bearing without the use of a stethoscope, it usually has to be replaced within:

A

Days or hours

83
Q

Changes in ___ and ___ give much earlier warning of trouble than the hearing method

A

Temperature and vibration

84
Q

When the machine is running, feel the machine bearing housings to sense:

A

temperature and vibration changes

85
Q

When a machine is down, what checks can you do to the shaft in regards to bearing fit/condition?

A
  • Turn by hand, look for roughness of movement
  • lift the shaft, look for radial looseness
  • push the shaft back and forth, look for axial looseness
86
Q

During operation, the following areas should be checked for leaks: (3)

A
  • Lubricant leaks at seals
  • Lubricant leaks at joints in housing
  • Discoloration of oil in sight glass. Sign oil is contaminated
87
Q

___ is the most effective way to track the condition of a bearing while it is in operation

A

Vibration monitoring

88
Q

____ measure vibration and are permanently mounted in a bearing housing.

A

Vibration probes

89
Q

____ can collect, record and analyze vibrations in a single unit

A

Vibration analyzer

90
Q

The use of vibration analysis equipment requires an understanding of: (2)

A
  • Vibration theory

- The equipment

91
Q

Oil analysis tells you about the condition of: (2)

A
  • Oil

- Machine

92
Q

By examining oil, you can learn a lot about the root cause of:

A

Bearing faiure

93
Q

Darkened oil indicates:

A

oxidization

94
Q

sludge and acids in oil indicates:

A

advanced oxidization

95
Q

If oxidization of oil occurs early, it could be from:

A

excessive heat

96
Q

On-site oil analysis involves checking for the following: (6)

A
  • Dark oil
  • particles in oil
  • sludge
  • sour smell
  • thicker viscosity
97
Q

An increase in bearing temperature is due to: (3)

A
  • Transfer of heat from another source
  • reduced cooling affect
  • increase in friction
98
Q

Increased friction due to something rubbing against a moving part can be caused by: (5)

A
  • Too much, too little, or the wrong lube
  • Seal rubbing too hard
  • bearing failing
  • increase in load or speed
  • additional heat from outside source

Industrial Mechanic 2nd Block, Harmonized (28 decks)

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