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Industrial Mechanic (Millwright) > Lubrication - Part A (160201fA) > Flashcards

Lubrication - Part A (160201fA) Flashcards

1
Q

What is friction?

A

Friction is the resistance to movement of one surface across another.

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2
Q

Name three kinds of friction:

A
  • Sliding
  • Rolling
  • Fluid
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3
Q

What type of friction exist within a lubricant?

A

Fluid friction

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4
Q

What are three negative effects of friction?

A
  • Increases power consumption
  • Causes wear
  • Generates waste heat
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5
Q

What are four positive effects of friction?

A
  • Provides traction between the raceways and the rolling elements of anti-friction bearings which ensures rolling instead of skidding
  • Promotes accurate tracking in bearing raceways
  • Provides a means of starting, stopping and accelerating most machines
  • Provides a means of polishing
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6
Q

How does a lubrication reduce friction?

A

It produces a film of liquid between components which lubricates and reduces the friction. The metal surfaces are separated and sliding friction (highest) is replaced with fluid friction (lowest)

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7
Q

Name four functions of a lubricant

A
  • To reduce friction
  • To protect against corrosion
  • To carry away heat if the lubricant is a fluid
  • To carry away contaminants if the lubricant is fluid
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8
Q

What type of lubricant film forms under a loaded rolling element?

A

Elasto-hydrodynamic lubrication

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9
Q

Does elasto-hydrodynamic lubrication provides complete separation of the rolling elements and the raceway

A

Yes

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10
Q

Does a boundary film provide a complete separation of surfaces?

A

No

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11
Q

What type of film has the most friction?

A

Boundary film

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12
Q

Under what conditions does a boundary film form?

A
  • At low speeds
  • When the viscosity is too low to support the load
  • When there is insufficient lubrication
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13
Q

Why is it important to bring the shaft rotation up to speed as soon as possible?

A

To establish full film lubrication which prevents wear

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14
Q

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

A

It increases the arc of the load supporting film

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15
Q

What are the two conditions necessary to ensure full film lubrication?

A
  • The shaft must rotate above the recommended minimum speed

- The viscosity must be high enough to support the load

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16
Q

What is viscosity?

A

Resistance to flow

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17
Q

How does an increase in viscosity affect the load-carrying capacity of a lubricant film?

A

It increases the load-carrying capacity

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18
Q

What is the most important property to consider when selecting oil?

A

Viscosity

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19
Q

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

A
  • Load capacity
  • Flow rate
  • Fluid friction
  • Heat generation
  • Sealing effect
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20
Q

How does an increase in temperature affect viscosity?

A

It decreases viscosity

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21
Q

Does an increase in speed affect the viscosity in many of the commonly used oils?

A

No

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22
Q

How does an increase in speed affect the oil containing polymer additives?

A

An increase in speed decreases viscosity

23
Q

What is the viscosity in centistokes of Telus 68 oil at 40°C?

A

68 centistokes

24
Q

What units of viscosity are used by the AGMA?

A

SUS units

25
Q

What does the viscosity index of an oil indicate?

A

It indicates how much the viscosity changes between 40°C and 100°C

26
Q

What viscosity index is considered good in today’s society?

A

150

27
Q

What is meant by the pour point of an oil?

A

It is the lowest temperature at which oil is observed to flow

28
Q

What is the practical importance of knowing the pour point of an oil?

A

It determines the lowest temperature at which an oil can be used for low temperature start-up

29
Q

What is the practical importance of knowing the flash point of an oil?

A

It indicates the explosion or fire hazard of a lubricant

30
Q

Were SAE standards developed for automotive or industrial oils?

A

For automotive oils

31
Q

What do the SAE grade numbers indicate?

A

Viscosity at 30°C and 100°C

32
Q

How is the low temperature viscosity SAE grade indicated?

A

With the letter W

33
Q

Would SAE grade 20 be suitable for winter start-up?

A

No

34
Q

What is the purpose of multigrade oils?

A

To accommodate start-up at low temperatures and adequate film strength at running temperature

35
Q

Is re-refined oil slightly substandard, or is it top quality?

A

Top quality

36
Q

What is the most widely used crude oil base stock in North America?

A

Paraffin base stock

37
Q

What does a pour point depressant do?

A

It hinders the formation of wax crystals at low temperatures in order to make the oil flow more easily

38
Q

How does a viscosity index improver work?

A

It thickens the oil at high temperatures, but has little effect at low temperatures.

39
Q

What does a demulsifier do?

A

It separates the water from the oil

40
Q

Where are naphtha-based oils mainly used?

A

In cold temperature grease in refrigeration systems

41
Q

What additive can be substituted for detergents?

A

Ashless dispersants

42
Q

Why are high-detergent oils not suitable for high-temperature applications?

A

They leave an ash deposit

43
Q

Why are EP additives unsuitable for some worm wheel reducers?

A

The EP additives would corrode the bronze worm wheel in some worm wheel speed reducers.

44
Q

Why are anti-wear additives unstable for extreme temperatures conditions?

A

The high temperatures produced in extreme pressure conditions would destroy the
anti-wear additives

45
Q

What is the temperature limit for anti-wear additives?

A

100°C

46
Q

How can foam be suppressed?

A

Spray silicon into the oil from an aerosol can

47
Q

What two things increase the tendency to foam?

A
  • Contaminants

- Most additives

48
Q

What are three results of rusting?

A
  • Surface pitting
  • Abrasion
  • Oxidation acceleration
49
Q

What are four results of oxidation in mineral oil?

A
  • Produces acid
  • Produces sludge
  • Produces varnish
  • Thickens the oil
50
Q

Why were synthetic oils developed?

A

To solve lubrication problems that cannot be overcome by petroleum-based oils

51
Q

Which wears out, the base oil or the additives?

A

The additives

52
Q

Why have biodegradable oils proved to be impractical?

A

They are unstable and unable to meet the normal operating requirements of industry.

53
Q

What are three common problems that synthetic oils can overcome?

A
  • Oxidation at high temperatures.
  • Waxes that hinder flow at low temperatures.
  • Thinning of oil at high temperatures.

Industrial Mechanic (Millwright) (11 decks)

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