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Bearings Flashcards

0
Q

What are the three main functions of bearings?

A 
(FLAW)
Reduce   Friction 
Support  Loads
Aid in Alignment 
Reduce  Wear
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1
Q

Name four functions of a bearing lubricant.

A 
It reduces friction
Cools
Reduces rust and oxidation
Seals out impurities
Removes Contaminants
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2
Q

What are five of the criteria in selecting a bearing lubricant?

A 
Rotational speed 
Load 
Size and type of bearing 
How the lubricant is applied
Environment including temperature, exposure to water or chemicals
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3
Q

What are two types of sliding type (plain) bearing?

A 
Journal
Split ( solid split, half, multi-part)
Thrust
Sleeve
Guide
Tilting pad
Three lobe
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4
Q

List three design features incorporated into sliding bearings to aid lubrication.

A

Grooves
Holes
Channels

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5
Q

What are five desirable characteristics of a journal bearing lubricant?

A 
It must: Maintain a full fluid film
             Prevent excessive friction
             Conduct heat
             Remain stable under severe operating conditions
             Be economical
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6
Q

The orientation of oil grooves in fluid-film journal bearings falls into two main categories. What are they?

A

Circumferential and axial

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7
Q

Channels are placed ______ _____ _____ _____ _____ in order to maintain the load carrying ability of plain bearings.

A

Away from the load zone

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8
Q

What are three advantages that plain bearings have over anti-friction bearings?

A 
Easy to install
Carry high loads
Less expensive
Repairable
Less sensitive to particle and water contamination
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9
Q

What are three advantages that anti-friction bearings have over plain bearings?

A

They may be sealed for life
can be used for high speeds
can accommodate misalignment
lower energy consumption

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10
Q

Where would anti-friction bearings be used where plain bearings would not be used?

A

High speeds

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11
Q

What is a Kingsbury thrust bearing?

A

A bearing with tilted shoes that form an oil wedge between the shoe and the collar.

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12
Q

What are five types of rolling element bearings?

A 
Ball bearings 
Cylindrical roll bearings 
Thrust or tapered roll bearings 
Spherical roll bearings 
Needle Roll bearings
Angular contact
Deep groove Conrad
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13
Q

Name five parts of a rolling element bearing.

A 
Cup (Outer ring) 
Cone (Inner ring) 
Rolling elements 
Cage (Retainer) 
Raceways
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14
Q

What are the five dimensions of a rolling element bearing?

A 
Outside diameter (OD)
Inside diameter (ID)
Pitch diameter
Width
Radial clearance
Operating clearance
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15
Q

Where there are two anti-friction bearings on a shaft, one should be ________ and the other should be _______.

A

Fixed ( or held )

Floating ( or loose )

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16
Q

What are the relative strengths and weaknesses of ball versus roller bearings?

A

Ball bearings are less expensive and can operate at higher speeds. Roller bearings carry higher loads.

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17
Q

Approximately what percentage of bearings fail prematurely?

A

90%

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18
Q

What are six causes of failures in babbitted bearings?

A 
Inadequate bonding of babbitt to sleeve
Misalignment
Incorrect oil grooving
Corrosion
Lack of lubrication
Abrasives
Lubricant deterioration
Shock loading
Loose bearing fastenings
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19
Q

What causes the eventual failure of a well-installed and lubricated anti-friction bearing?

A

Fatigue

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20
Q

What is False Brinelling?

A

The indentations in a race that formed by vibration, i.e. when bearings are in transit stored near vibration

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21
Q

What is Brinelling?

A

When a bearing race is marred by balls or rollers due to shock impact, often during handling and installation.

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22
Q

__________ Brinell and above have a tendency to show destructive pitting (spalling).

A

400

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23
Q

What is spalling?

A

Spalling (destructive pitting) results when normal loading is combined with sliding. It occurs when large wear particles are generated from subsurface cracks that are propagated from surface defects.

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24
Q

A sintered (also called porous or impregnated) metal bearing can contain up to ____% liquid lubricant impregnated between the metal pores.

A

35%

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25
Q

Various means are used to lubricate large bearings. What physical characteristics are incorporated into bearing assemblies to assure adequate lubrication?

A 
Channels
Holes
Grooves
Rings
Collars
Discs
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26
Q

What does a lubrication chain do in a bearing assembly?

A

It is a chain that is used to pick up lubricant from the sump and deposit it on the bearing.

27
Q

What is a bearing shield?

A

A metal disc fitted to the bearing outer ring with a small clearance with the inner ring.

28
Q

What are the advantages of a chamfered oil groove in a bearing?

A

It prevents oil from being scraped off.
It promotes cooling
Greater flow and better distribution of oil to the bearing
It is rounding of the edges

29
Q

What are four benefits of lubricating a bearing with grease?

A

It forms a better seal
It requires less frequent re-lubrication
The lubricant stays in place.
It can be used in sealed for life applications

30
Q

What are four benefits of lubricating a bearing with oil rather than grease?

A 
Better heat removal
Removal of contaminants
Ease of replacement
Reduced internal friction
Longer service life
31
Q

What are five types of bearing failure?

A

Normal fatigue Scoring Spalling
Glazing Fretting Smearing
Brinelling Electric Arcing Burn up
Bruising Water damage Corrosion

32
Q

What do the following noises sometimes signify in faulty bearing applications?

  1. Low pitched noise
  2. High pitched whine
  3. Rattle
  4. Low rumble
  5. Marbles rolling around
A
  1. Misalignment - Low pitched noise
  2. Overload - High pitched whine
  3. Inadequate interference fit - Rattle
  4. Poor finish - Low rumble
  5. Cavitation - Marbles rolling around
33
Q

Name two good methods to heat a bearing for installation.

A

Hot oil bath

Induction heating

34
Q

What is the “chain reaction” caused by abrasive wear?

A

Abrasive particles become work hardened.
Work hardened particles produce more particles.
New particles become work hardened.
Chain continues until removed by filtration.

35
Q

The operating or dynamic clearance of a bearing depends upon the __________ , _________ and lubricant ______________.

A

Load
Speed
Viscosity

36
Q

What is meant by the rated life of a bearing?

A

The number of revolutions, at a given constant speed, that 90% of identical bearings will complete before the first evidence of fatigue.

37
Q

What are two ways to remove a bearing from a shaft without damaging it or the shaft?

A

Bearing puller

Arbor press

38
Q

An__________________________ may be used to aid in mounting roller bearings.

A

Induction heater

39
Q

The outer race of a bearing should show normal wear in the _______ half of the race.

A

Loaded

40
Q

_________ _________ in the bearing case occurs when the shaft simply pushes the oil around within the internal clearances of the bearing.

A

Oil whirl

41
Q

What are four common causes of bearing failure?

A 
Lubricant
Installation
Contaminants
Improper selection
Maintenance practices
Fatigue
Overload
42
Q

What type of bearings support axial loads and restrain endwise movements?

A

Thrust bearings

43
Q

Name three causes of bearing failure in sliding bearings?

A 
Unsuitable materials
Incorrect grooving 
Unsuitable finish 
Insufficient clearance
Operating conditions 
Oil Contamination
44
Q

Name two ways in which sliding bearings are lubricated?

A

Lubrication holes

Lubrication grooves

45
Q

How is a radial load applied to a bearing, relative to the shaft?

A

Perpendicular

46
Q

How is an axial load applied to a bearing, relative to the shaft?

A

Parallel

47
Q

What are the five factors involved in bearing selection?

A

Available space Noise factor
Seals Cage design
Load Internal clearance
Precision required Materials
Speed

48
Q

What type of bearing is best suited for handling any thrust loads?

A

Tapered Roller

49
Q

What type of bearing is not suited for handling any thrust load?

A

Plain bearing

50
Q

What are two common housing styles for pre-mounted bearings?

A

Pillow block

Flange

51
Q

What are the three types of bearing mounting methods?

A

Cold mounting
Temperature mounting – Heat housing and/or bearing
Oil injection mounting (Hydraulic)

52
Q

What does normal fatigue mean in relation to bearings?

A

Bearing material simply can no longer take the operational stresses.

53
Q

What is dN, and how is it calculated?

A

It is the shaft diameter in mm times the rpm of a rolling contact bearing. It, along with operating temperature, is used to calculate the recommended viscosity of a lubricant.

54
Q

An anti-rotation dowel pin will keep a _________ bearing from spinning.

A

Journal

55
Q

What is a thrust bearing?

A

A bearing that prevents the lengthwise motion of a shaft.

56
Q

Which type of bearing offers the largest capacity and the smallest cross section obtainable for a given shaft size.

A

Needle bearings

57
Q

List three types of thrust bearings.

A

Tapered roller bearings
Kingsbury
Angular contact ball
Spherical roller thrust

58
Q

What is pre-loading a bearing?

A

Procedures employed during assemble and mounting to remove all looseness or play in a bearing, usually performed on shafts or spindles in machine tools and precision machines that must rotate without clearance in either the axial or radial direction.

59
Q

_______________ wash the original lubricant from a new bearing.

A

Don’t

60
Q

An electric motor bearing with a single lip seal positioned for lube retention in a high water environment is experiencing short bearing life. What two things would you recommend without changing the seal or grease type.

A

Reverse the seal to prevent water contamination and regrease more frequently.

61
Q

What kind of bearing does not have an inner race?

A

Needle bearing

62
Q

What type of bearing is suitable for handling heavy radial and thrust loads?

A

Tapered roller bearing

63
Q

Under constant load, the life of a bearing is inversely proportional to _________.

A

Speed

64
Q

A bearing manufacturer specifies a bearing specification of 2 u, rms. What does this mean?

A

RMS stands for root mean square, or average surface roughness. The manufacturer specifies that the average of the distance between the peaks and valley of asperities is no more than 2 u.

Study Questions (17 decks)

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