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Second Year Millwright > Bearings > Flashcards

Bearings Flashcards

0
Q

What is an axial or thrust load?

A

A load that is parallel to the shaft axis

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1
Q

What is a radial load?

A

A load that is perpendicular to the shaft axis

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2
Q

What is a plain bearing?

A

A bearing that has no rolling elements

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3
Q

What is the name for the plain bearing that supports radial loads?

A

Journal bearings

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4
Q

What is the name of the plain bearing that supports axial loads?

A

Thrust bearing

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5
Q

What are the main functions of the journal bearing?

A

To hold a journal in it’s required location, to support the intended radial load, and minimize friction

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6
Q

Name the three types of radial loads

A

Stationary load, oscillating load, and reciprocating load

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7
Q

Define a stationary load

A

The load generally acts in one direction and on one area of the bearing

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8
Q

Define an oscillating load

A

The load shifts through an arc less than 180°

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9
Q

Define reciprocating load

A

A load shifts 180° from one side of the bearing to the other

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10
Q

What happens with the clearance and bearings that support oscillating loads?

A

They have much smaller clearances

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11
Q

What are some features of a thin shell type split bearing?

A

They have a thin shell, the shell is flexible, shell consist of a thin overlay on the still backing, the shell must be seated in a strong housing and has a very accurate bore

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12
Q

What are the advantages of split bearings?

A

Hi load capacity because they are high precision, more compact housing, relatively inexpensive to replace, quick to change out, available in oversizes and under sizes, and consistent quality

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13
Q

What are some applications for thick wall split bearings

A

Gearboxes, turbines, fans, dynamic compressors

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14
Q

What are the two types of seats for thick wall split bearing?

A

A plain seat, or spherical seat

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15
Q

What is a bushing?

A

A type of plain bearing that has not been split and can be designed to handle radial or axial loads

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16
Q

What is a wrapped bushing?

A

A bushing that consists of a thin steel shell lined with the soft bearing material such as lead bronze

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17
Q

What is an advantage of a wrapped bushing

A

They have high fatigue strength

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18
Q

What is a solid bushing?

A

A bushing that is bored out of his solid piece of Bearing material such as lead bronze or Teflon

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19
Q

What is a limitation of the solid bushing

A

They do not have the fatigue strength of wrapped bushings

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20
Q

What is a floating bushing?

A

A bushing that consists of an outer bushing with a loosely fit inner bushing

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21
Q

Where are water lubricated bushings used?

A

They are used in situations where water is continually flushing the bearings and makes it impossible for the mechanism to retain any other lubricant

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22
Q

What type of applications are water lubricated bushings used for?

A

They are suitable for only very light loads on journals of corrosion resistant material like stainless steel

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23
Q

What is a pre-lubricated bushing

A

A bushing that is either made of a porous material soaked with lubricant or have a lining made with pockets filled with lubricant

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24
Q

What is the range of porosity in a porous bronze bearing?

A

3-30% it’s volume in oil

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25
Q

What are some other names of porous bronze bearings?

A

Oilite, or sintered bronze

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26
Q

What materials are used for a dry lubricated nearing?

A

A bronze matrix containing graphite, or Teflon. Teflon is self lubricating.

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27
Q

What is a hydrodynamic bearing?

A

A bearing that at operating speed, develops a full film of lubricant, called an oil wedge.

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28
Q

What determines the minimum speed for hydrodynamic bearing rotation?

A

The load determines the speed. Oil viscosity and surface area of the bearing also are factors

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29
Q

What type of oil would you use in a high speed, light load application?

A

Low viscosity oil

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30
Q

What is done differently in hydrodynamic lubrication under a reciprocating or oscillating load?

A

It may include a circumferential oil distribution groove in the middle of the bearing

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31
Q

What plain bearing is good for heavy radial loads?

A

The pivoting shoe

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32
Q

When is a hydrostatic bearing used?

A

In equipment that operates too slow to create a hydrodynamic oil wedge

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33
Q

Where is oil admitted in a hydrostatic bearing?

A

In the loaded and unloaded zones

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34
Q

How is oil pressure adjusted in a hydrostatic bearing?

A

The inlet holes or slots are fitted with restrictors to regulate the pressure

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35
Q

What is the minimum speed in a hydrostatic bearing?

A

There is no minimum speed It can start on a full film of oil with no dry rubbing friction. The result is no wear at start up

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36
Q

What is the load limitations of hydrostatic bearings?

A

Loads are generally lower than hydrodynamic, but very high loads can still be supported if the speed is zero or a few feet per min (fpm)

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37
Q

What is an oil lift bearing?

A

The oil lift journal bearing is a hydrostatic bearing with pressurized oil entering under the loaded area only

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38
Q

What is the name of the oil in a oil lift journal bearing?

A

Jacking oil.

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39
Q

Where are hybrid bearings used?

A

In situations where there is an imbalance, such as eccentric weight on the rotor that causes the radial load to increase as the speed increases

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40
Q

Which type of plain thrust bearing can support the most load?

A

The tilting pad thrust bearing. It is also referred to as a Kingsbury, or Mitchell bearing

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41
Q

Where is the area of greatest wear on a tilting pad bearing?

A

On the trailing end of the pads

42
Q

What is a gas lubricated bearing?

A

Pressurized gas (air) can support a loaded journal in lightly loaded high speed applications

43
Q

What is compressive strength?

A

The bearing material must be strong enough to support the shaft loads at maximum operating temperature

44
Q

What is fatigue resistance?

A

The resistance of the bearing material to cracking and flaking by loads that increase and decrease in rapid cycles

45
Q

What is high embeddability

A

How well a material will handle contaminants without failing

46
Q

What is deformability?

A

Deformability allows the material to yield to misalignment or imperfections in the shaft

47
Q

What is wettability?

A

It is the ability to retain a film of lubricant

48
Q

What is good thermal conductivity?

A

Allows for rapid transfer of heat

49
Q

What is compatibility?

A

It must not seize or weld to journal under rubbing conditions such as during start up

50
Q

What are some things that bad it can be made of?

A

Tin,lead, Copper, antimony

51
Q

What are some advantages of Babbitt?

A

It has high imbedability, high conformability, High wetability, good thermal conductivity, good corrosion resistance, an excellent bondability

52
Q

What is bearing crush?

A

It is the distance that a new insert protrudes above the split line of the bearing housing

53
Q

What is bearing spread?

A

The spread is the amount that the insert diameter is wider than the bearing housing diameter

54
Q

What is the purpose of locking tabs and dowels?

A

They are anti-rotation devices

55
Q

Why is Babbitt scraped after being poured?

A

They are scraped so that the proper surface area is supporting the journal. You should get a pattern over at least 85% of the surface

56
Q

What are the three types of friction?

A

Sliding, rolling and fluid

57
Q

What are the three purposes of the cage or separator?

A

To prevent the rolling elements from rubbing against each other, to push the rolling elements through the unloaded zone, and to guide the rolling element with a minimum amount of friction

58
Q

What is a bearing that starts with the number one

A

Self aligning ball bearing

59
Q

What is the Bearing type that starts with the number four?

A

Deep groove double roll ball bearing

60
Q

A bearing that starts with number five is what?

A

Thrust ball bearing

61
Q

A bearing that starts with the number six is what?

A

Deep groove single row ball bearing

62
Q

What is a bearing that starts with the number seven?

A

Single row angular contact ball bearing

63
Q

What is a bearing that starts with the number two?

A

Spherical roller bearing

64
Q

What is a bearing that starts with the number three?

A

Tapered roller bearing

65
Q

What is a bearing that starts with the number eight?

A

Cylindrical roller thrust bearing

66
Q

What are the three most common bearings?

A

Number two, spherical roller bearing number six deep groove single row ball bearing, number seven angular contact ball bearing single row

67
Q

Which type of bearing gives the best load support?

A

Needle bearings

68
Q

What is the area of contact called under a ball bearing?

A

Point contact

69
Q

What is the area of contact called under a needle bearing or spherical roller bearing?

A

Line contact

70
Q

What is the load called if it has both axial and radial loads?

A

A combination load

71
Q

What is another name for a number six bearing?

A

Conrad bearing

72
Q

A single row deep groove ball bearing supports what as its main function?

A

A radio loadbearing since that is the main function it tolerates very little angular misalignment

73
Q

What is the maximum capacity Deep grove ball bearing?

A

It has loading slots to put more ball bearings in. It’s axial load capacity is less because of the loading slots, but it has a higher radio load capacity than a regular deep groove ball bearing of the same size

74
Q

What is a double row deep grove ball bearing?

A

It’s designed provides a higher radial load capacity without increasing the radial dimensions

75
Q

What is an externally self aligning ball bearing?

A

A deep groove ball bearing that has a spherically ground outer ring that mounts in a special housing

76
Q

What are some features of a single row angular contact bearing?

A

They support substantial thrust loads in one direction only (against the high shoulder on both races) and must have some axial load as well

77
Q

What are the arrangements when you mount two angular contact bearings together?

A

Face to face, back to back, and tandem.

78
Q

What is the stiffest combination of tandem arrangements?

A

Back to back

79
Q

What is a double row angular contact bearing?

A

It can handle heavy radial and axial loads in both directions, but cannot tolerate any misalignment

80
Q

What is a four point angular contact bearing?

A

It can be used for only combination or axial loads, has Gothic arch shaped raceways, is a separable bearing and occupies much less axial space than a pair of single row contact bearings.

81
Q

What are the four types of roller bearings?

A

Cylindrical, needle, tapered, spherical

82
Q

Describe cylindrical roller bearings?

A

They are separable in both directions, so they can only support pure radial load

83
Q

What are the three more common needle bearings?

A

No cage or inner ring, drawn steel cup, machined inner and outer rings

84
Q

What differentiates between a cylindrical roller bearing, and needle bearings?

A

Needle bearings are 2.5-10 times as long as their diameter

85
Q

What are the two parts of a tapered roller bearings?

A

The inner and outer ring are known as cone and cup

86
Q

What are some features of a tapered roller bearing?

A

They are the best bearing for combination loads, you can use them in pairs to accommodate reversing loads

87
Q

What is the rule of thumb for clearance when installing a spherical roller bearing?

A

1/2 the bench clearance

88
Q

What is the rule of thumb for clearance when installing ball bearing applications?

A

When there is a slight drag when outer race is rotated

89
Q

What is a CARB bearing?

A

Compact aligning roller bearings. It’s shape is compact like a needle bearing, but with the misalignment capability of a spherical bearing

90
Q

What do the last two digits of a bearing represent?

A

The number X5 is the ID of the bearing

91
Q

What do the last two digits 00, 01, 02, 03 represent?

A

10,12,15,17 mm ID

92
Q

What is the ID of these two bearings
222/07
222/950

A

07 mm

950 mm

93
Q

What is a K and a K30 designation?

A

K is a 1:12 taper

K30 is a 1:30 taper

94
Q

What things are considered that affect speed of a bearing?

A 
Type of rolling element
Size of rolling element
Precision of bearing
Type of cage
Method of lubrication
Type of lube
Type of seal
95
Q

What is a z or rs designation?

A

Z is a shield

RS is a rubbing seal

96
Q

What are the three types of ring loading?

A

Rotating load, stationary load, indeterminate load

97
Q

What should you do if you are cleaning a bearing and using compressed air?

A

You should hold both races to prevent high-speed spinning

98
Q

What is the proper oil level in that antifriction bearing with an oil bath

A

Between the third and halfway up the lowest rolling element

99
Q

What is the correct grease level in a housing?

A

Approximately one third full after the bearing is fully packed

100
Q

What is the number one cause of bearing failure?

A

Improper lubrication

101
Q

What is the name of arc damage in a rotating bearing and in the stationary bearing?

A

In a rotating bearing it is called fluting in the stationary bearing it is called pitting

102
Q

What are the two most common causes of vibration?

A

Imbalance and misalignment

Second Year Millwright (8 decks)

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