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Power Plant Operations > Basic Industrial Lubrication > Flashcards

Basic Industrial Lubrication Flashcards

1
Q

What is an important function of lubrication? What are purposes of lubrication?

A

To reduce friction between two surfaces that are in contact with each other. (Tribology)

  • reduce friction
  • reduce wear
  • provide cooling it to rubbing surfaces
  • prevent corrosion
  • flush contamination away
  • reduce shock due to impact between two surfaces
  • reduce safety hazards created by improper lubrication
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2
Q

Define a lubricant.

A

Any substance that is used to reduce friction and wear.

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3
Q

What different physical states can lubricants be classified under?

A
  • liquid
  • semi liquid
  • solid
  • gaseous
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4
Q

Define friction.

A

A restive force that resists relative motion between two bodies which are in contact with each other.

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5
Q

In order to move mechanical bodies and fluids we need to spend energy and apply force.The energy we spend is used up in what two ways?

A

To do useful work and to overcome friction. 30% of all energy spent is used in overcoming friction.

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6
Q

Define asperities.

A

Sharp irregular peaks on all surfaces, even polished ones. When two surfaces that are touching move relative to each other, these asperities get caught up, and the surfaces can only move if hey overcome each other or if they are broken.

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7
Q

Define frictional force

A

The force necessary to overcome hindrances posed by micro scopic irregularities (asperities) on the two surfaces which are in contact with each other

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8
Q

Describe how two surfaces come into contact with each other.

A

The area of contact is really the area where asperities come in contact with each other. This extra stress on the asperities caused him to overheat to an extent that they melt and fuse, during relative movement between these two surfaces, the welded points break and create debris.

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9
Q

What are the two main friction modes in mechanical applications.

A

Sliding friction and rolling friction

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10
Q

Describe sliding friction

A

When 2 surfaces in contact with each other, and force is applied on the top slab in one direction, the frictional force acts in opposite direction. The applied force has to overcome the frictional force before the top slab is able to move.

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11
Q

The magnitude of the frictional force depends upon what two key factors?

A
  • area of contact, the more contact area, the higher the resistive force
  • nature of the contact surface. Rough surfaces create a high frictional force.
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12
Q

Define rolling friction

A

When force is applied to a ball, it contacts the source only at one point, with a small contact area and very few asperities to cause friction force, but friction still happens.

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13
Q

How does mechanical load on a bearing cause more friction?

A

The ball is flattened, Increasing the contact area and friction.

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14
Q

Lubrication science is:

A

Technical discipline that deals
With the reduction of friction by the application of a suitable substance between two rubbing surfaces so that the opposing asperities don’t come into contact.

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15
Q

Hydrodynamic conditions are created by:

A

When two surfaces are moving in relation with each other, one surface (B) is positioned with a slight angel to the other (A). As B moves to he right, it goes over a film of lubricant. This flow of lube through a wedge shaped region creates an up force which pushes B away from C. Results:

  • no wear
  • low energy consumption
  • reduction in heat generation due to friction
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16
Q

What are the three main forms of lubrication action?

A
  • hydrodynamic lubrication
  • mixed-film lubrication
  • boundary lubrication
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17
Q

What is mixed film lubrication?

A

Load is carried partly by oil film and partly by asperities. Can occur during reduction in relative speed between surfaces, and increase in load which decreases the wedge and the height of the lubrication film, and decrease in oil viscosity.

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18
Q

Boundary lubrication

A

When lube adheres and sticks to the boundary regions, yet most of the film was squeezed out. This small amount does keep the surfaces separated slightly. Frictional force is high and wear takes place.

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19
Q

What is wear?

A

When two surfaces rub against eachother. Can include Adhesive, abrasive, corrosive, fatigue, fretting, and erosive wear.

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20
Q

Adhesive wear

A

When load is carried almost all by asperities, the sliding produces enough heat to weld the asperities together. But with the motion, on of the welded asperities from one surface breaks off breathing debris that contaminates the lube oil.

21
Q

Abrasive

A

When lubricating oil has solid debris that, as they flow, have an abrasive effect on the surfaces. Solution: filters.

22
Q

Corrosive wear

A

Caused by corrosive chemicals, lubricants that get oxidized, creating acidic chemicals that attack metallic Surfaces.

23
Q

Fatigue

A

Metal subjected to pressure will break. This is metallic fatigue.

24
Q

Fretting

A

This damage is Caused by vibration between two surfaces.

25
Q

Erosive wear

A

Occurs when microscopic chunks of a surface are removed due to impingement of impurity particles.

26
Q

Selection of a lubricant for an application depends on:

A
  • is the machine designed for oil or grease
  • operational speed
  • magnitude of mechanical load
  • nature of bearings (plain or anti friction)
  • mechanical load on bearings
  • operational temperature
  • nature of possible contaminants
  • how long the lubricant is needed to stay in service before it is replaced
  • availability of continuous lubricant filtering and cleaning devices
27
Q

What are some lubricant properties?

A 
Viscosity
Specific gravity 
Pour point 
Flash and fire point 
Anti-wear properties
Ability to handle extreme pressure (EP)
Oxidation resistance
Foaming tendency
Penetration 
Dropping point
Shear stability
Grease pumpability
Resistance to water washout
28
Q

Viscosity

A

Is a measure of flow ability. The higher the viscosity the slower the flow, the lower the viscosity the easier the flow.

29
Q

ISO

A

International Standards Organization

30
Q

Specific Gravity

A

Ratio of two quantities

  • weight of a substance for a given volume
  • weight of water having the same volume

Water has a specific gravity of 1

31
Q

Pour point

A

Lowest temperature at which a substance is able to flow.

32
Q

Flash and fire points

A
  • The flash point indicates the lowest temperature at which sufficient vapor is released to allow ignition by a flame.
  • the fire point indicates the temperature at which the released vapor is sufficient to allow ignition and support fire for at least 5 seconds.
33
Q

Anti-wear (AW)

A

Factor depends on Ability of a lubricant to provide protection against metal wear.

34
Q

Extreme pressure (EP)

A

Factor that depends on the ability of a lubricant to provide lubrication service under heavy pressure conditions.

35
Q

Oxidation resistance

A

This factor quantifies the ability of a lubricant to resist oxidation.

36
Q

Oxidation

A

When ambient oxygen reacts with a substance, or causes a substance to react by changing the chemical structure of that substance.

37
Q

Foaming Tendency

A

This factor quantifies the ability of lubricating oils to resist foaming.

38
Q

Penetration

A

Factor reflects the consistency or hardness of grease. Use this for grease instead of viscosity

39
Q

Dropping point

A

The temperature at which the physical state of grease changes from semi solid to fluid

40
Q

Shear stability

A

This factor quantifies the ability of a grease to withstand repeated mechanical stress without any damage to its chemical structure

41
Q

Grease pumpability

A

Ability of a grease’s ability to be pumped easily

42
Q

Water washout

A

Ability of grease to withstand being washed away with water.

43
Q

What are two main types of lubricants?

A

Oils and greases

44
Q

What are the two types of lubricating oils?

A

Petroleum based and synthetic

45
Q

Greases offer the following advantages over oils:

A
  • where oil can’t stay in place, grease will
  • grease is used to keep contaminants such as dirt out
  • sometimes more economical
  • grease can handle better shocks
  • grease can be used in locations which are not easy to access.
46
Q

Bearings are used for the following purposes:

A

-support the rotating elements in equipment
-reduce friction between the moving and stationary parts
-hold the rotating elements in proper place
(Prevent longitudinal movement)

47
Q

Radial load

A

This load acts in the transverse direction, consists of the weight of the shaft and other components attached to it. Most Bearings are designed to support this type of load. (Radial or journal bearings)

48
Q

Thrust

A

This type of load acts longitudinally along he length of the shaft. Thrust bearings are used to hold the bearings in place.

49
Q

Bearings are classified in two main categories:

A
  • Plain bearings-“sleeve or bush bearings” where sliding action takes place
  • antifriction bearings- where rolling action takes place

Power Plant Operations (2 decks)

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