Module - Lubrication - Part A

Question 1

The 3 types of friction are?

Answer 1

1. Sliding
2. Rolling
3. Fluid

Question 2

What is Friction?

Answer 2

Friction is the resistance to movement of two surfaces in contact with each other.

Question 3

What are 3 negative effects of friction?

Answer 3

1. Increased power consumption
2. Causes wear.
3. Generates heat.

Question 4

What are 4 positive effects of friction?

Answer 4

1. Provides a means of polishing.
2. Provides a means of starting, stopping, most machines.
3. Accurate tracking in bearing raceways.
4. Provides traction. Ensures rolling instead of skidding in anti-friction bearings.

Question 5

What are 5 functions of a lubricant?

Answer 5

1. To reduce friction.
2. Protect against corrosion.
3. Carry away heat.
4. Carry away contaminants.
5. Help seal.

Question 6

What are the three types of Lubricant Films?

Answer 6

1. Full film lubricaiton
2. Elasto-Hydrodynamic film lubrication
3. Boundary film lubrication

Question 7

Define: Full Film Lubrication.

Answer 7

Full film lubrication is thick enough to completely separate the surfaces with a continuous film.
+ offers the least friction resistance
+ eliminates wear on the moving surfaces
+ generates the least amount of heat

Question 8

Define: Elasto-Hydrodynamic Film Lubrication

Answer 8

An elasto-hydrodynamic film completely separates two surfaces and is therefore a type of full film lubrication. However, in this case the two surfaces are loaded to the extent that deformation takes place in the loaded area.
+ fluid film in extremely thin
+ fluid film offers low friction resistance
+ type of film forms at high speeds as well as high pressures.
+ example: Hydroplaning

Question 9

Define: Boundary Film Lubrication

Answer 9

A boundary film does not completely separate the surfaces, so some of the tips of the asperities touch.
+ forms at low speeds
+ forms when the viscosity of the lubricant is too low to support the load
+ forms if there is not enough lubricant

Question 10

Why does a reduction in clearance increase the load capacity of a journal bearing?

Answer 10

A reduction in clearance will increase the arc of the load supporting film.
+ Smallest total clearance gives largest support area.

Question 11

Define: Viscosity

Answer 11

Viscosity is a measurement of fluid friction (resistance to flow). Fluids that flow easily, like water, have low viscosity. Fluids that flow very slowly, such as tar, have high viscosity.

Question 12

Define: Viscosity Index

Answer 12

Viscosity index (VI) is a number that identifies the amount of change in the viscosity of a lubricant over a temperature range. This means that an oil that shows very little change in viscosity as it is heated from 40C to 100C would have a high viscosity index.

Question 13

Define: Pour Point

Answer 13

Pour point is the lowest temperature at which an oil is observed to flow.

Question 14

Define: Flash Point

Answer 14

Flash point is the lowest temperature at which the vapour above an oil will ignite when a flame is passed over it.

Question 15

What 5 things does viscosity affect in the performance of a lubricant?

Answer 15

1. load capacity
2. flow rate
3. fluid friction
4. heat generation
5. sealing effect

Question 16

A lubricant’s main job is to

a) reduce power consumption.
b) reduce resistance.
c) reduce heat.
d) reduce rolling friction.

Answer 16

b) reduce resistance.

Question 17

Which of the following offers the least resistance?

a) fluid friction
b) rolling friction
c) sliding friction
d) asperity welding

Answer 17

a) fluid friction

Question 18

Viscosity is a measurement of

a) the fluid pour point.
b) the capacity of fluid film.
c) the fluid’s flash point.
d) the fluid’s resistance to flow.

Answer 18

d) the fluid’s resistance to flow.

Question 19

If a fluid flows easily we say it has a __________ viscosity.

a) low
b) high

Answer 19

a) low

Question 20

As the temperature of an oil increases, viscosity

a) increases.
b) decreases.

Answer 20

b) decreases.

Question 21

Which of the following is the accepted worldwide measure of viscosity?

a) SUS
b) AGMA
c) CST
d) ISO

Answer 21

c) CST

Question 22

The amount of change in the viscosity over a temperature change is referred to as

a) pour point.
b) flash point.
c) penetration number.
d) viscosity index.

Answer 22

d) viscosity index.

Question 23

An oil with very little change in viscosity as it is heated from 40 degrees C to 100 degrees C is referred to as having a __________ viscosity index.

a) low
b) high
c) graded
d) neutral

Answer 23

b) high

Question 24

The lowest temperature at which an oil will flow is knows as

a) flash point.
b) full film lubricant point.
c) oil wedge theory point.
d) pour point.

Answer 24

d) pour point.

Question 25

In the oil designation, the W stands for

a) water soluble.
b) winter (cold weather starting ability).
c) wax ingredients.
d) wedge theory of lubrication.

Answer 25

b) winter (cold weather starting ability).

Question 26

Chemicals added to the oils to give properties for various special uses are

a) additives.
b) emulsifers.
c) solubles.
d) biodegradeable.

Answer 26

a) additives.

Question 27

Where there are heavy loads with metal to metal contact possibilities, protection against the asperities welding their surfaces is prevented by adding chemicals with which designation?

a) W
b) AS
c) SUS
d) EP

Answer 27

d) EP

Question 28

Detergent oils __________ recommended for high temperature applications.

a) are
b) are not

Answer 28

b) are not