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Millwright Level 2 > Lubrication > Flashcards

Lubrication Flashcards

(65 cards)

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1
Q

Describe friction?

A

Friction is the resistance to movement between two surfaces.

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2
Q

What is lubrications main job?

A

Reduce friction

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3
Q

Why is friction bad?

A

Increase in power consumption
Causes wear
Causes heat

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4
Q

What are the three types of friction?

A

Sliding
Rolling
Fluid

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5
Q

What is viscosity?

A

Measurement of resistance to flow.

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6
Q

What is the most important property of a lubricant?

A

Viscosity

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7
Q

Higher viscosity equals?

A

Slower flow rate

Better sealing properties

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8
Q

What units are viscosity measured in?

A

Centistrokes

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9
Q

What is the viscosity index (VI)?

A

The amount of change of a lubricant over a temperature range. (40-100 degrees C)

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10
Q

Oil with very little change with temperature has a ________VI#?

A

High

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11
Q

What is the pour point of oil mean?

A

The lowest temperature which oil will flow

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12
Q

What is the flashpoint?

A

The lowest temperature at which the the Vapor above the oil will ignite.

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13
Q

What are the two SAE grade viscosity measures?

A

Low temp W (minus 5 to minus 30)

High temp: no letter (100 degrees C)

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14
Q

What does the two numbers mean in engine oil? 10w30

A

Flows like 10w in minus 30 degrees and still remains a film strength of 30 at 100 degrees c

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15
Q

How do lubricants reduce friction?

A

By separating moving surfaces and protect agains corrosion.

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16
Q

Why is full film lubrication better then elasticity-hydrodynamic film lubrication?

A

Offers the least friction resistance

Eliminates wear on the moving surfaces

Generates the least amount of heat

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17
Q

What are the 3 types of lubricant films?

A

Full film lubrication (thick enough to completely separate the surfaces with a continuous film)

Elasto- hydrodynamic film lubrication (similar to a full film but deformation still takes place in the loaded area)

Boundary lubrication (film does not completely separate the 2 surfaces

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18
Q

Describe an oil wedge?

A

Oil sticks to unloaded area of the shaft

As rotation begins the uncoated part of the shaft rolls up to the coated area

As the shaft hits the oil’s surface it slips back down reaping a layer of oil under it

As the shaft continues to turn it draws a wedge of oil under the loaded area slowly lifting it higher to form a full film.

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19
Q

How much oil do journal bearings need to avoid metal on metal?

A

At least 0.001”

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20
Q

What factor affect viscosity

A

Temperature
Pressure
Speed

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21
Q

What are the characteristics of petroleum based oil?

A

Oil does not wear out

Can be re-refined

Stable to 55 degrees C

Separate from water easily

Cheap

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22
Q

What is the characteristics of synthetic oil?

A

Last longer

More chemical additives for more specific conditions

Stable up to 250 degrees

Wider operating range

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23
Q

When are bio degradable oils used?

A

When there is a high chance of spills

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24
Q

What percent of oil can be additives?

A

22 percent

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25
The oxidation rate doubles every _____degrees C at temperatures above _____ degrees C with no additives.
8 55
26
What do chemical inhibitors do?
Form a protective layer on the metal by reacting with it
27
What do foam depressants do?
Reduce the surface tension on the bubbles causing them to burst
28
What is the purpose of extreme pressure additives?
Protect against welding of surfaces
29
What are detergent additives for?
To keep sludge and deposits off metal surfaces
30
What does a demulsifier do
Help oils separate from water
31
What is the purpose of the lubrication system?
Distribute oil to the moving parts of the machines to reduce friction.
32
In an oil bath, how far up the lowest bearing should the oil be?
1/3 to 1/2 Any higher and excessive heat is caused
33
What are some different lubrication systems?
Bottle lubrication Wick feed oilers Drop feed lubrication Ring or chain oilers
34
What are the applications for a bottle lubricator?
Low surface speeds of 250feet/min
35
What are the applications for a wick feeder?
Bearings with a 2” or smaller shaft that require small amounts of oil
36
What are the applications for a drip feed lubricator?
Shafts up to 3” Maximum speed of 3600 RPM Only intermittent oiling is required
37
What are the applications for a ring/chain oiler?
Shafts smaller then 4” Max speed 3600rpm Good for friction and anti friction bearings Chain can be used on larger shafts with lower speeds
38
What is a pressure lubricating system?
Forces oil into engine bearings
39
What are the components of a pressure oil lubrication system?
Reservoir - holds oil and allows cooling Filter - removes contamination Pump - delivers oil Relief valve - bypass excess oil Distribution valve - sends oil to various lube points Metering valve - controls amount of lube delivered to each point Nozzles or ports
40
What are the applications of a pressure lubrication system?
Engine Gas/steam turbines Large reciprocating compressors Medium and large vane compressors Centrifugal compressors
41
What are the parts of an oil mist system?
Compressor - supplies air Moisture trap - removes moisture Pressure regulator - delivers right pressure of oil Bottle of lubricant Nozzles
42
What are the applications for a air activated lube system?
Small high-speed bearings Air tools Chain drives Gear sets Machine tool ways
43
What are air-oil lubrication systems used for?
Medium to high speed anti friction bearings
44
When is the block lubrication system used?
When elements are hard to access
45
What are the two main concerns when handling and storing oil?
Cancer Fire
46
What safety precautions should be taken when dealing with oil?
Read MSDS sheet Protect you skin Provide proper ventilation in storage area Avoid inhalation of lubricant fumes Do not carry a rag covered in oil in your pocket Report skin problems immediately
47
What precautions should be taken to prevent fire from lubricants?
Avoid open flame around them Have fire watch and ABC fire extinguisher around if welding or cutting near lubricants Do not store lubricants near heat Post no smoking sign near lubricants Make sure solvent drums are properly grounded
48
How do you protect lubrication from contamination?
Keep gloves clean when working with lubricants Keep lubricant dispensers such as oil cans funnels and grease guns immaculate. Store lubricant drums on their sides with the bungs at 3 and 9 o’clock If possible use a filter cart Keep storage area and lubricant containers very clean Clearly identify barrels
49
What happens in hot weather to lubrication?
Oxidation (indicated by darkening oil) Separation of the thickener from oil from grease Evaporation of water from fire resistant fluid Burst containers from expansion
50
What can happen to lubrication in cold weather?
Fire resistant fluids can be be damaged Water/oil emulsion can freeze Fluctuations above and below freezing can cause the pour point to be raised. (Pour point reversion)
51
What is grease?
Grease is a liquid lubrication mixed with a thickener that controls the flow of grease to the area being lubricated
52
How are greases classified?
By type of thickener By a distinguishing characteristic By its NLGI consistency # By the Viscosity of the base oil By its application
53
Proper grease selection depends on what two factors?
Temperature Load
54
What grease is good for low temps?
Low consistency (NLGI 0 or 1) Must have low base oil viscosity (about 15 centistrokes)
55
What grease is good for medium temps?
(Multi purpose) Consistency should have a NLGI of 2 or 3 Base oil viscosity should be between 75-200 at 40 degrees C
56
What grease is good for high temperature operation?
Grease must be suitable for up to 150 degrees. Consistency should be NLGI 3 Base oil viscosity should be 110 Centistrokes Base oil should contain additives to improve oxidation stability
57
What grease additive should be used for heavy loads?
Ep additives or molybdenum disulphides
58
What is most important when applying grease?
The right amount of grease is being applied at the right intervals
59
What are some of the main methods for applying grease?
Single point methods such as: Grease cups Grease guns Centralized systems: Automatic Manual
60
How do you grease a high speed bearing? Higher Than 500 rpm
House should not be more then 1/3 full Housing should be fitted with vents to allow excess grease to flow out On high speed applications over 3600 rpm refer to manufacturers instructions
61
When should you check a bearing for temp after new grease has been installed? What should the temperature of the bearing be?
After 3 hours Should not be above 60 degrees C
62
63
For proper lubrication plain bearings need minimum of ________ “ of clearance.
.001” To much clearance can move the shaft out of alignment
64
Why should EP lubricants not be used in worm wheel gear boxes with bronze in them?
EP additives tend to corrode copper and Bronze
65
Why should you treat maintenance of the lubrication system the same as you would for any critical component of the machine?
Improperly maintained lubrication system will cause the rest of the machine to fail

Millwright Level 2 (15 decks)

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