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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
This seat allows the bearing to align it's bore with the sag in the shaft of a heavy rotor during installation
Spherical seat
26
This must be done to solid bushings after install
Reamed to their final diameter
27
Advantage of wrapped bushings
High fatigue strength
28
These bushings support lightly loaded high-speed shafts such as in turbo-chargers
Floating bushings
29
Porous bronze can hold up to __% of it's volume in oil
30%
30
Bushings made of slippery material such as graphite or PTFE
Dry lubricated bushings
31
One of the most widely used types of plain bearings, develop full film lubricant
Hydrodynamic bearing
32
An unsteady load at high speeds can cause this
Oil whirl
33
These bearings are found on equipment that operate too slowly to form a hydrodynamic film
Hydrostatic bearings
34
This is a special type of hydrostatic bearing with pressurized oil entering under the loaded area only
Oil lift journal bearing
35
Depend on both hydrodynamic and hydrostatic lubrication, used in situations of imbalance
Hybrid bearings
36
Three types of thrust bearings
Flat plate, tapered land, tilting pad
37
This is required on thrust bearings supporting heavy loads on vertical shafts
Oil lifts
38
This allow the material to yield to misalignment or imperfections in the shaft
Deformability (conformability)
39
What is the limitation of babbitt
Low fatigue resistance
40
What are the three basic rolling elements in anti-friction bearings
Ball Roller (cylindrical, tapered, spherical) Needle
41
What types of load do anti-friction bearings endure
Radial, thrust, and combination of both
42
What speeds can ball bearings handle
Up to 40,000 RPM
43
What is the normal speed range of roller bearings?
2000-20,000 RPM
44
What indicates the bore size of an anti-friction bearing?
The last two digits in the bearing number
45
Most bearing codes give these three pieces of information
Type of rolling element Service weight The bore in millimeters
46
How are ball bearings marked for clearance?
C1-C5 (lowest clearance to highest)
47
What gives further subdivisions of the C clearance markings?
P numbers (P2 to P6)
48
Anti-friction bearings have these two types of fit
Push fit and interference fit
49
This is the very slow rotation of of a push fit bearing race
Creep
50
The purpose of this fit is to hold the bearing ring in position and reduce clearance to a specified amount
Interference fit
51
What temperature should you not heat a bearing past?
120C (250F)
52
A device to hold a bearing in place is called
Positive keeping
53
For standard clearance of spherical roller bearings the rule of thumb is to reduce the initial clearance by
50 percent
54
Another name for a cup puller
Inside puller
55
The loaded section of the raceways is called this
Degrees loaded zone
56
The most common type of ball bearing
Deep groove ball bearing (Conrad)
57
The two types of self-aligning ball bearings
Internally and externally
58
Difference between internal and external self-aligning ball bearings
External - accommodates angular misalignment in mounting | Internal - Used when alignment is impossible to maintain (shaft wobbles)
59
Angular contact ball bearings are used to accommodate this
Both radial and thrust loads in one direction
60
The shapes of roller bearings
Cylindrical, needle, tapered, spherical
61
Needle bearings support these types of loads only
Radial
62
Needle rollers are this much longer than cylindrical rollers
2.5 to 10 times
63
These bearings are used for carrying heavy combined radial and thrust loads in one direction
Tapered roller bearing (mount in pairs for both directions)
64
This letter indicates a tapered bore
K (K30 on large bearings 1:30 ratio)
65
What do the letters Z and RS indicate
Z - Shield (can exclude only coarse contaminants) | RS - Rubbing seal (factory sealed, restricts running speed)
66
The total permissible variation for it's size is called
Tolerance
67
The range of permissible tightness or looseness of mating parts is called
Fit
68
What are the three types of ring loading
Rotating load, stationary load, intermediate load
69
How do you determine the difference between shaft fits and housing fits
Shaft fits are lower case letters, housing fits are uppercase
70
Never heat a sealed bearing above this temp
80 C (175 F)
71
You should cold mount bearings with these size bores only
1.5 inches or less (tapered bores under 4 inches)
72
This is the load the rolling elements are under before any external load is applied
Preload
73
To ensure the pillow block does not get pulled out of alignment stops should be installed at this many degrees
55-120 degrees
74
When there is axial force on a pillow block it's radial capacity is reduced to this
65% of the capacity at 90 degrees
75
Where should you install locating rings
Only one one bearing on a shaft (usually the drive end)
76
At what temperature is the lubricant oxidizing and inadequate?
55 C (131 F)
77
When a new bearing is installed it will run at this many degrees above normal for the first few hours
15 C (27 F)
78
Unsealed bearings temperature is too high when it exceeds
``` 125 C (257 F) 80 C (176 F) for sealed bearings ```
79
The surface temperature of the bearing housing is this many degrees cooler than the rolling elements
20 C (36 F)
80
This is the biggest cause of premature bearing failure
Contamination (most abrasive contaminants are smaller than 40 microns)
81
If a shaft shows more than this amount of runout it must be straightened or replaced
0.001"
82
This is impact denting and makes the bearing useless
Brinelling
83
How high should the oil be for an anti-friction bearing
One third to one half way up the lowest rolling element | One third full for grease
84
How much energy consumption can be saved by proper balancing?
20-50%
85
Misalignment accounts for how much of vibration problems
40%
86
When should a bearing be packed with grease
After it has been mounted
87
The most secure and effective puller
Bearing splitter
88
What are the service weight in order?
``` 0 - Ultra light 1 - Extra light 2 - Light 3 - Medium 4 - Heavy Duty ```
89
What does 6208 represent?
6 - Single row deep groove ball bearing 2 - Light service weight 08 - 40mm bore
90
What does 22208 represent?
22 - Double spherical roller bearing 2 - Service weight light 08 - 40mm bore
91
A loud hollow noise indicates this
Too much internal clearance
92
A high pitch scream or whine indicates this
The clearance is too small
93
A growling noise indicates this
The surfaces of the rollers and raceways are deteriorating

Millwright Level 2 (10 decks)

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