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Millwright Level 2 > Bearings > Flashcards

Bearings Flashcards

1
Q

On these bearings the area of contact is relatively large and the pressure on the bearing is relatively low

A

Friction bearings

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2
Q

Friction bearings are also referred to as these 3 things

A

Plain, sleeve, and journal

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3
Q

On these bearings the area of contact is very small and the pressure on the rings and balls or rollers is high

A

Anti-friction bearings

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4
Q

The bearing housing is sometimes called this

A

Pillow block

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5
Q

What are bearing housings made from?

A

Cast iron for general use (light to medium)

Cast steel for general use (light to heavy loads)

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6
Q

How are the nominal size of friction bearings classified?

A

As fractions for the ID

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7
Q

What does the choice of bearing depend on for friction bearings

A

Load, rotational (rubbing) speed, direction of pull, support design

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8
Q

These friction bearings are used when speed and load are low in locations where the load is applied to the top part of the bearing

A

Solid bearings

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9
Q

These friction bearings are used when the load is applied parallel to, or at a slight angle to the horizontal.

A

Angle bearings (Also mounted on a vertical support)

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10
Q

Bearing joints come in three general styles

A

Flat joints, gib in joint, angle joint

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11
Q

Types of metallic liner materials are

A 
Babbitt (general use)
Brass (Higher speeds, heavier loading)
Bronze (Higher speeds, heavier loading)
Aluminum (Hydraulic pumps)
Sintered bronze
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12
Q

Non metallic liner materials are

A

Nylon
Polyurethanes
Phenol Laminates

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13
Q

Basic nylon has a thermal expansion rate roughly __ times that of steel

A

10 times

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14
Q

The three babbitt temperatures to consider are

A 
Melting point (275C to 285C)
Pour point (343C to 371C)
Solidification point (25C to 28C below melting point)
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15
Q

The hardest and toughest babbitt, sometimes called nickel babbitt

A

Tin based (up to 90%) for heavy service and extreme pressures

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16
Q

Where should you cut the oil grooves in a babbitt bearing?

A

In the unloaded section

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17
Q

Ways to check for clearance in a friction bearing

A

Feeler gauge, jack and dial indicator, Plastigage, lead wire

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18
Q

These are two piece liners installed in a housing

A

Shells

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19
Q

How is thrust controlled in a friction bearing?

A

Shaft collar, thrust washer backed by a sprocket or hub

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20
Q

The amount the shaft moves axially in a bearing is called

A

end float

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21
Q

This friction bearing is a thrust bearing designed to take high speeds and heavy loads

A

Kingsbury thrust bearing

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22
Q

Two types of Kingsbury bearings

A

Fixed pad and floating or tilting pad

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23
Q

Split journal bearing used mostly for high peripheral speeds and shaft stabilization

A

Pivoted shoe bearing

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24
Q

The different types of radial load

A

Stationary, oscillating, reciprocating

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25
Q

This seat allows the bearing to align it’s bore with the sag in the shaft of a heavy rotor during installation

A

Spherical seat

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26
Q

This must be done to solid bushings after install

A

Reamed to their final diameter

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27
Q

Advantage of wrapped bushings

A

High fatigue strength

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28
Q

These bushings support lightly loaded high-speed shafts such as in turbo-chargers

A

Floating bushings

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29
Q

Porous bronze can hold up to __% of it’s volume in oil

A

30%

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30
Q

Bushings made of slippery material such as graphite or PTFE

A

Dry lubricated bushings

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31
Q

One of the most widely used types of plain bearings, develop full film lubricant

A

Hydrodynamic bearing

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32
Q

An unsteady load at high speeds can cause this

A

Oil whirl

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33
Q

These bearings are found on equipment that operate too slowly to form a hydrodynamic film

A

Hydrostatic bearings

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34
Q

This is a special type of hydrostatic bearing with pressurized oil entering under the loaded area only

A

Oil lift journal bearing

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35
Q

Depend on both hydrodynamic and hydrostatic lubrication, used in situations of imbalance

A

Hybrid bearings

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36
Q

Three types of thrust bearings

A

Flat plate, tapered land, tilting pad

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37
Q

This is required on thrust bearings supporting heavy loads on vertical shafts

A

Oil lifts

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38
Q

This allow the material to yield to misalignment or imperfections in the shaft

A

Deformability (conformability)

39
Q

What is the limitation of babbitt

A

Low fatigue resistance

40
Q

What are the three basic rolling elements in anti-friction bearings

A

Ball
Roller (cylindrical, tapered, spherical)
Needle

41
Q

What types of load do anti-friction bearings endure

A

Radial, thrust, and combination of both

42
Q

What speeds can ball bearings handle

A

Up to 40,000 RPM

43
Q

What is the normal speed range of roller bearings?

A

2000-20,000 RPM

44
Q

What indicates the bore size of an anti-friction bearing?

A

The last two digits in the bearing number

45
Q

Most bearing codes give these three pieces of information

A

Type of rolling element
Service weight
The bore in millimeters

46
Q

How are ball bearings marked for clearance?

A

C1-C5 (lowest clearance to highest)

47
Q

What gives further subdivisions of the C clearance markings?

A

P numbers (P2 to P6)

48
Q

Anti-friction bearings have these two types of fit

A

Push fit and interference fit

49
Q

This is the very slow rotation of of a push fit bearing race

A

Creep

50
Q

The purpose of this fit is to hold the bearing ring in position and reduce clearance to a specified amount

A

Interference fit

51
Q

What temperature should you not heat a bearing past?

A

120C (250F)

52
Q

A device to hold a bearing in place is called

A

Positive keeping

53
Q

For standard clearance of spherical roller bearings the rule of thumb is to reduce the initial clearance by

A

50 percent

54
Q

Another name for a cup puller

A

Inside puller

55
Q

The loaded section of the raceways is called this

A

Degrees loaded zone

56
Q

The most common type of ball bearing

A

Deep groove ball bearing (Conrad)

57
Q

The two types of self-aligning ball bearings

A

Internally and externally

58
Q

Difference between internal and external self-aligning ball bearings

A

External - accommodates angular misalignment in mounting

Internal - Used when alignment is impossible to maintain (shaft wobbles)

59
Q

Angular contact ball bearings are used to accommodate this

A

Both radial and thrust loads in one direction

60
Q

The shapes of roller bearings

A

Cylindrical, needle, tapered, spherical

61
Q

Needle bearings support these types of loads only

A

Radial

62
Q

Needle rollers are this much longer than cylindrical rollers

A

2.5 to 10 times

63
Q

These bearings are used for carrying heavy combined radial and thrust loads in one direction

A

Tapered roller bearing (mount in pairs for both directions)

64
Q

This letter indicates a tapered bore

A

K (K30 on large bearings 1:30 ratio)

65
Q

What do the letters Z and RS indicate

A

Z - Shield (can exclude only coarse contaminants)

RS - Rubbing seal (factory sealed, restricts running speed)

66
Q

The total permissible variation for it’s size is called

A

Tolerance

67
Q

The range of permissible tightness or looseness of mating parts is called

A

Fit

68
Q

What are the three types of ring loading

A

Rotating load, stationary load, intermediate load

69
Q

How do you determine the difference between shaft fits and housing fits

A

Shaft fits are lower case letters, housing fits are uppercase

70
Q

Never heat a sealed bearing above this temp

A

80 C (175 F)

71
Q

You should cold mount bearings with these size bores only

A

1.5 inches or less (tapered bores under 4 inches)

72
Q

This is the load the rolling elements are under before any external load is applied

A

Preload

73
Q

To ensure the pillow block does not get pulled out of alignment stops should be installed at this many degrees

A

55-120 degrees

74
Q

When there is axial force on a pillow block it’s radial capacity is reduced to this

A

65% of the capacity at 90 degrees

75
Q

Where should you install locating rings

A

Only one one bearing on a shaft (usually the drive end)

76
Q

At what temperature is the lubricant oxidizing and inadequate?

A

55 C (131 F)

77
Q

When a new bearing is installed it will run at this many degrees above normal for the first few hours

A

15 C (27 F)

78
Q

Unsealed bearings temperature is too high when it exceeds

A 
125 C (257 F)
80 C (176 F) for sealed bearings
79
Q

The surface temperature of the bearing housing is this many degrees cooler than the rolling elements

A

20 C (36 F)

80
Q

This is the biggest cause of premature bearing failure

A

Contamination (most abrasive contaminants are smaller than 40 microns)

81
Q

If a shaft shows more than this amount of runout it must be straightened or replaced

A

0.001”

82
Q

This is impact denting and makes the bearing useless

A

Brinelling

83
Q

How high should the oil be for an anti-friction bearing

A

One third to one half way up the lowest rolling element

One third full for grease

84
Q

How much energy consumption can be saved by proper balancing?

A

20-50%

85
Q

Misalignment accounts for how much of vibration problems

A

40%

86
Q

When should a bearing be packed with grease

A

After it has been mounted

87
Q

The most secure and effective puller

A

Bearing splitter

88
Q

What are the service weight in order?

A 
0 - Ultra light
1 - Extra light
2 - Light
3 - Medium
4 - Heavy Duty
89
Q

What does 6208 represent?

A

6 - Single row deep groove ball bearing
2 - Light service weight
08 - 40mm bore

90
Q

What does 22208 represent?

A

22 - Double spherical roller bearing
2 - Service weight light
08 - 40mm bore

91
Q

A loud hollow noise indicates this

A

Too much internal clearance

92
Q

A high pitch scream or whine indicates this

A

The clearance is too small

93
Q

A growling noise indicates this

A

The surfaces of the rollers and raceways are deteriorating

Millwright Level 2 (10 decks)

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