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Millwright Level 2 > Bearings > Flashcards

Bearings Flashcards

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1
Q

What are the two basic types of bearings?

A

Friction

Anti friction bearings

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2
Q

What is the Main difference between friction and anti friction bearings?

A

Friction bearings have sliding contact between the shaft and the bearing.

Anti friction bearings have rolling contact between the shaft and bearing.

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3
Q

What are the principle parts of the bearing housing?

A

Base
Base bolts
Cap
Cap bolts

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4
Q

What materials are used for housings?

A

Cast iron - light to medium loads

Cast steel - light to heavy loads

Fabricated - for special jobs

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5
Q

What are the factors when choosing bearing housing?

A

Load
Rotational speed
Direction of pull
Support design

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6
Q

What are the different types of friction bearings?

A

Solid - when speed and load are low

Split bearing - two bolt (light medium load) four bolt (medium to heavy loads)

Angle bearings - when bearing is mounted vertical or when the load is parallel or slight angle.

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7
Q

What considerations are taken when deciding a material for journal bearings?

A

Should be softer then the shaft material

Low coefficient of friction

Wear resistant

Good heat conductor and stable

Readily available

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8
Q

What are the different liner materials?

A

Babbitt - general use

Brass or bronze - higher speeds and heavier loads than Babbitt

Aluminum - common in hydraulic pumps

Sintered bronze - this is a porous bronze with built in oil supply

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9
Q

What are the non metallic liners?

A

Nylon

Polyurethane

Phenol laminate

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10
Q

What is an advantage of plastic bearing?

A

Inert to most mild acids and alkalis

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11
Q

What is the difference between expansion rates between plastic and metal liners?

A

Nylons thermal expansion is roughly 10 times that of steel

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12
Q

What is the melting temperature of Babbitt?

A

288 degrees C (550F)

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13
Q

What is the hardest babbitts?

A

Tin based (90% tin)

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14
Q

What are the three temperatures to consider when melting Babbitt?

A

Complete melting point - 275 to 285 Celsius

Pour point - 345 to 371 C

Complete solidification - 25 to 28 C below the melting point. (250)

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15
Q

What happens to Babbitt when it is over heated?

A

Material life is greatly reduced

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16
Q

When pouring Babbitt when must be removed first and why?

A

Water - if the melted babbitt hits the water it causes a very dangerous blow back.

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17
Q

What supplies are needed when pouring emergency Babbitt?

A 
Fire extinguisher 
Oxyacetylene torch 
Putty 
Pliers 
Cake of Babbitt
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18
Q

Where do you cut the oil grooves?

A

Always in the unloaded section

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19
Q

What are shims made of?

A

Material that will not compress or not affected by oil.

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20
Q

What are some general rules for clearances?

A

Medium - loose: constant one direction load and rotation

Medium - tight: reversing rotation and fluctuating load

Tight: reciprocating action

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21
Q

Typically how is a shell held in place?

A

Pins, dowels, or screws

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22
Q

What is crush?

A

When the sleeve sits slightly above the housing it gets crushed to the right tolerance after cap is installed and torqued

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23
Q

What is an advantage to shell liners?

A

Worn liners may be changed by taking the weight of the shaft and rotating the shell out.

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24
Q

What is a bushing?

A

One piece liner made of any of the common bearing materials

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25
Q

What is the purpose of a kingsbury thrust bearing?

A

Designed to take heavy loads and high speeds

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26
Q

What is a guide bearing used for?

A

Positioning a device or guide for linear motion

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27
Q

When is a pivoted shoe bearing used?

A

Used for high peripheral loads and shaft stabilization

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28
Q

What are the three functions of the cage?

A

Prevent rolling elements from rubbing against each other

Push the rolling elements through the unloaded area

Guide the rolling elements with a minimum amount of friction

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29
Q

What are the parts of an anti-friction bearing

A 
Inner ring
Raceway
Rolling elements 
Cage 
Outer ring 
Seal
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30
Q

What are some different types of round ball bearings?

A

Four point contact ball bearing

Self aligning

Thrust

Angular contact

Deep groove, single row

Deep groove, double row

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31
Q

What are some factors that affect bearing load?

A

Area of contact

Direction of load

Loaded zone

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32
Q

What is radial load?

A

When contact angle is 0• and the load Carries at 90•

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33
Q

What is axial load?

A

If the nominal contact is at 90• and the load is in line with the shaft axis

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34
Q

What is combination load?

A

If the nominal contact angle is between 0• and 90•

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35
Q

What are some features of a single row deep groove ball bearing (Conrad)?

A

General purpose

Mainly supports radial loads

Can support combination loads and moderate axial loads in both directions

Classes as radial load bearing

Tolerates very little angular misalignment

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36
Q

What is a feature of the double row ball bearing?

A

Higher radial load capacity with increasing the radial dimensions

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37
Q

1 bearing code

A

1 internal self aligning double row ball bearing

Used when alignment is impractical or impossible

Can support only small thrust loads

Speed rating is same as single row deep groove ball bearing

Available in tapered bore to be used with taper sleeve

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38
Q

External self aligning ball bearing?
What is the difference between internal and external self aligning bearings?

A

Intended to accommodate angular misalignment

External self aligning has a spherically ground outer ring that mounts in a spherical housing

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39
Q

Number 7 bearing code

A

Single Row angular contact bearing

Accommodates both radial and thrust loads

Higher load ratings then deep groove

Can move inner and outer rings to adjust internal clearance

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40
Q

Number 0 bearing code

A

Double row angular contact bearing

Takes heavy radial and axial loads in both directions

Speed rating is lower then deep groove or single row angular back bearings

Cannot tolerate and misalignment

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41
Q

Bearing code QJ

A

Four point angular contact bearing

Used for only combination of axial loads

Can handle reversing thrust loads in either direction

Can be manufactured with larger number of balls increasing its load capacity

Often used as a thrust bearing with a radial clearance in housing

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42
Q

Ball thrust bearings?
Bearing code number ?

A

Pure thrust load only

Cannot tolerate angular misalignment

Speed limit is only half the limit for radial load bearings

Slow speed

Bearing code number 5

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43
Q

4 types of roller bearings?

A

Cylindrical

Needle

Tapered

Spherical

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44
Q

Bearing code number N

A

Cylindrical roller bearing

Can only support pure radial load

Great radial load capacity

Can handle small misalignment

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45
Q

3 types of needle bearing?

A

No cage or inner cage

Drawn steel cup and no inner ring

Machined inner and outer rings

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46
Q

Parts of a single row taper roller bearings?

A

Inner ring (cone)

Outer ring (cup)

Tapered rollers

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47
Q

Features of single row tapered bearing?
Bearing code number 3

A

Can carry very heavy combined radial and thrust loads in one direction

Can be used in pairs to accommodate reversing loads

Tolerate little misalignment

Most commonly used tapered roller bearing

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48
Q

Features of double row tapered roller bearing?

A

Designed for heavy applications

Can be used as floating assembly in a housing

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49
Q

Bearing code # 2

A

Spherical tapered roller bearing

Barrel shaped rollers provide wide load carrying contact area

This shape provides combined thrust and radial load capacity in both directions

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50
Q

Compact aligning roller bearings(carb)?

A

Compact aligning roller bearing (CARB)

Can accommodate some misalignment

Same dynamic load rating as spherical roller bearings

Can allow more axial displacement than any other bearings (up to 20 percent of its width

Not recommended for thrust loads

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51
Q

What does the c represent?

A

Amount of internal clearance.

C1 smallest amount of clearance

C5 largest amount of clearance

C2or c3 standard amount of clearance

52
Q

What does the K mean

A

Taper bore

K12 means taper ratio of 1:12

K30 means taper ratio 1:30

53
Q

When using heat to mount a bearing what is recommended temperature? What is the dangerous temperature?

A

80 degrees C

Over 120 degrees C will cause permanent deformity

54
Q

What are methods for heating the bearing for installation?

A

Induction heater

Heating cabinet

Oil bath

Heat ring

55
Q

Max temp for heating sealed bearings?

A

80 degrees C

56
Q

What size feeler gauge is used to determine there is no gap between bearing and shoulder?

A

.001”

57
Q

What is internal clearance?

A

The total amount of clearance between the rolling elements and the raceway when one ring is pushed far away from the other ring as possible.

58
Q

What is axial internal clearance?

A

The clearance between the rolling elements and the raceway when one ring is moved away from the other in a axial direction.

59
Q

What is residual clearance?

A

The internal clearance (radial or axial) After the bearing has been mounted.

60
Q

What is the running clearance?

A

The internal clearance in a bearing when it is running at its operating temperature

61
Q

What are the 3 classes of preload?

A

1: lighter then normal preload
2: normal preload
3: heavier than normal preload

62
Q

How is preload set?

A

By using spacers of shims to push one ring axially against the rolling elements

63
Q

1 self aligning ball bearing

A

Great for misalignment

Often used on the coupling end of overhung fan shafts

Can support small axial load

64
Q

2 spherical ball bearing

A

Intended to accommodate angular Mis alignment

65
Q

3 taper roller bearings single row

A

Carry heavy combined radial and thrust loads in one direction

Can use in pairs to accommodate reverse loads

66
Q

4 double row taper bearings

A

Heavy applications

Can be used as floating assembly in housing

67
Q

5 thrust ball bearing

A

Pure thrust only

Speed limit only half the limit for radial load bearing

Intended for slow speeds

68
Q

6 single row deep groove ball bearing

A

General use

Mainly supports radial loads

Can support combination loads and moderate axial loads in both directions

Tolerates very little angular misalignment

69
Q

7 single row angular contact bearing?

A

Accommodate radial and thrust loads

Can order different contact angles to change axial loads

Can be used as one or in pairs

70
Q

N single row cylindrical roller bearing

A

Support only radial load only

Can prevent axial movement in one direction

71
Q

NA needle roller bearings

A
72
Q

Series code 0

A

Extra light

73
Q

Series code 1

A

Extra light thrust

74
Q

Series code 2

A

Light

75
Q

Series code 3

A

Medium

76
Q

Series code 4

A

Heavy

77
Q

Series code 8

A

Extra thin section

78
Q

Series code 9?

A

Very thin section.

79
Q

What are the bearing clearance codes?

A

C 1-5
C 1 smallest amount of clearance
C-5 most amount of clearance

Normal clearance lies between c2 and c3 it is the clearance in standard bearings and has no designation.

80
Q

What are the shield codes for bearings?

A 
Z single side metal shield 
ZZ both side metal shield 
RS single rubber seal 
2RS both side rubber seal 
V single non contact seal 
VV double non contact seal 
NR snap ring and groove 
M brass cage
81
Q

What are the last digit codes in bearing number?

A 
00 = 10mm
01 = 12mm
02 = 15mm 
03 = 17mm 
O4= (x5) = 20mm
05= (x5) = 25mm 
06 = (x5) = 30mm 
And so on
82
Q

Bearing sounds through a stethoscope should have a soft purring sound.
- loud hollow noise means?
- high pitched scream or whine?
- growling noise?

A

-To much internal clearance

  • clearance to small
  • surfaces of the rollers and raceways are deteriorating
83
Q

Brinelling is impact denting and cause by:

When installing bearings

A
  • hammer blows
  • dropping the bearing on hard surfaces
  • Shock loading on the machine from any source
84
Q

False brinelling is round depressions worn into the raceways by a rolling member. What causes false brinelling?

A
  • bearing is not turning and vibration is present
  • the vibration causes the film lubricant between the rolling elements and the raceway to break, allowing metal to metal contact.
  • rolling elements vibrate against raceways
85
Q

How can false brinelling be eliminated?

A

Do not store bearings in areas subject to prolonged vibration.

86
Q

Lubricant can generate its own contaminants as it breaks down (acids, sludges, and varnish. What are some measure to reduce this contamination?

A
  • keep temperature of the bearing housing below 55 degrees C(130F)
  • establish an oil change interval
  • circulate oil through filter
  • use oil mist system
  • use oil that resist oxidation
87
Q

Grease level inside a housing should be ________ full

A

1/3

88
Q

Even total fill grease should only be filled to _______%

A

80

89
Q

Two main causes of vibration are:

A

Imbalance - accounts for half the causes of vibration.

Misalignment -

90
Q

Arc tracks in bearings look like?

A

Pencil lines on the raceways at each rolling element

91
Q

If you have to remove your hand immediately from a bearing the temperature is about ______ degrees C

A

60

92
Q

What are the things to check within the bearing housing when the temperature is running hotter than normal ?

A
  • to much or to little lubricant
  • a seal could be rubbing to hard
  • bearing is failing
  • there is an increase load
  • there is additional heat from an outside source
93
Q

Darkens oil indicates?

A

Oxidation and means oil should be changed

94
Q

Sludge and acids in oils indicate?

A

Advanced oxidation and oil change intervals should be shorter

95
Q

Sand in the oil indicates?

Paint chips in the oil indicate

A

Sand is coming out of the casting

Paint on the inside of housing is incompatible with oil.

96
Q

Hydrostatic lubrication uses pressure instead of velocity to force fluid into the loaded area. What are some advantages?

Plain bearings

A
  • no wear at start up
  • low friction and therefore low power consumption at start up
  • can dampen out vibrations
  • cool operation
  • best solution for slow speed, heavily loaded bearings, where low friction and accurate shaft positions are important.
97
Q

Hybrid lubrication is?

A

A combination hydrodynamic (velocity) and hydrostatic (pressure) to lubricate bearings.

98
Q

Advantages of hybrid lubrication?

A
  • can support large, unbalanced loads at high speeds.
  • it had the highest load rating of any bearing
  • provides accurate shaft positioning when the load is unsteady.
  • it provides full film lubrication at any speed or when journal is at rest
99
Q

Oil mist systems use compressed air at ______ to _______ psi to atomize the oil and spray it on the bearing?

A

10 to 50

100
Q

What does a sour smell from the bearing lubricant indicate?

A

Acid build up from oxidation in the lubricant or from external contamination

101
Q

Why is it important to inspect bearing while it is running?

A

Noise, vibration and leaks are more easily detected

102
Q

When is it best to re-lubricate bearings?

A

When machine is not running

103
Q

Bearing is running to hot you would check and correct?

A

Oil level - to low add, to high drain

Check for external heat source

Check for soft foot

Check for rubbing seals

Check for coupling alignment

Check vibration levels

104
Q

If a floating bearing is heating up you should check it has sufficient axial space in the housing to move. This is obtained by?

A

Removing the fixing ring

Or

Adding shims to the end cover

105
Q

Unsealed bearings can be heated to a max temp of 120 Degrees C (248 F) but a sealed bearing can heated to _______ degrees C?

A

80 (175)

106
Q

Cold mounting bearing should only be done with bearing bores up to ______ inches ?

A

1 1/2

107
Q

When is preload applied to a bearing and why?

A

When the operating load is to light to make the rolling element roll properly. It ensures that the rolling elements have enough traction to roll and track properly.

Preload is also applied to reduce radial deflection of the shaft and make a stiffer assembly

108
Q

When using coolant to remove a bearing is it important to not apply to the part you are apply force to. How come?

A

Parts become extremely brittle when chilled with dry ice or nitrogen

109
Q

Why should you never pull on the outer ring of a self aligning ball bearing?

A

It can explode under tension

110
Q

When using a punch to remove a bearing it is important NOT use brass, how come?

A

It work hardens when struck and a piece will break off

111
Q

Rubbing seals are capable of?

Downfalls of a rubbing seal are?

A

Retaining oil and not just grease

Provide a positive seal against moisture and fine contaminants

Limited operating speed due to heat caused by friction

112
Q

Non rubbing seals have no contact with with sealing surface, what are the advantages and disadvantages of non rubbing seals?

A
  • There is no rubbing friction
  • there is no wear as long as no contact is made
  • they are not easily damaged by solid contaminants
  • there are no speed limits
  • they can operate at high temperatures
  • pressing grease into gaps can increase sealing efficiency

Cannot retain oil

113
Q

Radial labyrinth seal

A

Can only handle limited axial and radial movement

114
Q

Axial labyrinth seal allows for what type of movement?

A

Axial movement will not affect sealing gaps

115
Q

Combination labyrinth seal

A

Provides better sealing

116
Q

Sealing washer set

A

Cheapest labyrinth seal and Efficiency can be increased by added more sets

117
Q

What can extend the use of the labyrinth to oil lubricated bearings?

A

Flinger ring

118
Q

If pillow blocks are mounted at 55 to 120 degrees ________ should be installed to stop pillow block from
Getting pulled out of alignment.

A

Blocks

119
Q

When there is axial force on a pillow block the the radial capacity is reduced to ________%

A

65

120
Q

Three types of loads on pillow blocks

A

Vertical

Horizontal

Axial

121
Q

Load capacity can be reduced on horizontally split pillow blocks anywhere from 1/3 to 2/3’a it’s radial capacity if pulled at a ______ degree angle

A

55 degrees

122
Q

Rule of thumb for grease fill in a pillow block is about ____ to _____ unless it is a total full application and can be filled to 80-90%

A

1/3 to 2/3 full

123
Q

Grease fitting on pillow blocks for re greasing need to be mounted on which side of the housing? Nut side or no nut side

A

No nut side

Nut will tear the grease fibres

124
Q

If only one big retaining ring is used on a pillow which side is it installed on and why?

A

On the retaining but side. So that the grease from the fitting has no restrictions into the bearings

125
Q

How come set screw locking style bearing reduce the speed rating of the bearing?

A

Because it pushes the shaft slightly off centre causing more vibration

126
Q

Strongest type of plain bearing pillow block?

A

Gib joint

Millwright Level 2 (15 decks)

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