Lubrication Fundamentals Flashcards
0
Q
What does STLE stand for?
A
Society of Tribologists and Lubrication Engineers
1
Q
What does ASTM stand for?
A
American Society for Testing and Material
2
Q
What is tribology?
A
Tribology is the science of the interactions between surfaces moving relative to each other; the fields include the study of friction, wear and lubrication.
3
Q
What is lubrication?
A
Control of friction and wear by introduction of a film between moving surfaces in contact.
4
Q
What is hydrodynamic lubrication?
A
Lubrication between two surfaces with the development of a full lubricating film.
5
Q
What is mixed film lubrication?
A
The transient lubrication regime in which boundary and hydrodynamic lubrication both occur. (i.e some fraction of both)
6
Q
What is boundary lubrication?
A
Lubrication between two rubbing surfaces in the absence of a full fluid lubricating film. Boundary lubrication is often accomplished with the use of extreme pressure additives.
7
Q
What does EHL stand for, and how does it work?
A
Elasto-Hydrodynamic Lubrication is the lubrication between two surfaces with a full lubricating film under high loads and speed. The mating surfaces deform elastically due to the incompressibility of the lubricant film under the load. This regime occurs in rolling element bearings.
8
Q
What is the primary function of a lubricant?
A
The primary function of a lubricant is to control friction and wear.
9
Q
What are five secondary functions of a lubricant?
A
1) Transfer Heat
2) Prevent corrosion
3) Scavenge Debris
4) Seal
5) Transfer force / energy
10
Q
Name three types (physical phases) of lubricant films.
A
Liquid
Solid
Gas
(Also Plastic) also boundary (chemical), hydrodynamic, and elastohydrodynamic
11
Q
Improper lubrication contributes to approximately ________ percent of machine failures.
A
Greater than 40
12
Q
One inch approximately = ________ microns
25 microns approximately = ____________ inch
A
25,000
.001
13
Q
Convert 0.05% to ppm.
A
500 ppm
1% = 10000 ppm So x(ppm) = 10000 x (%)
Move decimal 5 places to the right
14
Q
What does the abbreviation ISO VG mean?
A
International Standards Organization Viscosity Grade
15
Q
What is an approximate conversion from cSt at 40°C to SSU at 100°F?
A
5 x (cSt at 40° C) approximately = SSU at 100° F
16
Q
What are the units of Kinematic viscosity?
A
cSt (Centistoke)
17
Q
What are the units of Absolute viscosity?
A
cP (Centipoise)
18
Q
What is VI?
A
Viscosity Index
The resistance of an oil’s viscosity to change with temperature.
19
Q
As the temperature of a lubricating oil increases, what effect does this have on the oil’s viscosity and density?
A
Both decrease
20
Q
When pressure increases the viscosity of an oil ________ .
A
Increases
21
Q
Name the five “rights” of lubrication.
A
(PAT QT)
1) Right place
2) Right amount
3) Right type
4) Right quality
5) Right time (Frequency)
22
Q
What is viscosity?
A
Measurement of a fluid’s resistance to flow.
23
Q
What is friction?
A
Friction – the resistance to motion of one object over another
24
List three harmful effects of friction.
1) Wear
2) Heat
3) Power loss and vibration
25
What is the most common type of wear mechanism?
Abrasive wear is the most common type of wear.
26
What are asperities?
Asperities are the roughness or harshness of a surface (tiny peaks and valleys on the surface).
27
Name three types of synthetic oils.
1) PAO (polyalphanolefin)
2) Diester
3) Polyolester
4) Silicone
5) Polyglycols
6) Phosphate ester
28
What does NLGI mean?
National Lubricating Grease Institute
29
What specifications are unique to grease?
```
NLGI rating (penetration)
Dropping point
Consistency
Soap base
Oil separation
Water washout
Wheel bearing leakage
```
30
Name three soaps used to thicken oil.
1) Lithium 7) Calcium Complex
2) Calcium 8) Aluminum Complex
3) Aluminum 9) Barium Complex
4) Sodium 10) Lithium/calcium
5) Barium and other mixed soap bases
6) Lithium Complex
31
What are three types of thickeners used in greases?
Soaps
Inorganic thickener (i.e. clay, carbon black)
Organic such as polyureas
32
Name the NLGI grades.
```
000 3
00 4
0 5
1 6
2
```
33
What are considered the 3 most basic and important characteristics of grease to consider when selecting the right grease for an application?
1) Soap type
2) Base oil viscosity
3) Consistency as measured by penetration
34
What are H1 lubricants?
USDA approved lubricants for incidental food contact. USDA recently stopped testing and issuing approvals, but they still set the standards. Manufacturers must now self-certify that their product is suitable for incidental food contact.
35
What are the three basic types of lubricant films?
1) Boundary
2) Mixed
3) Hydrodynamic
36
What is specific gravity?
The density of a substance divided by the density of water at the same temperature.
37
How is API gravity calculated from specific gravity?
Degrees API = 141.5 / (Specific gravity @ 60° F) – 131.5
38
The lowest temperature at which oil will flow is known as its___________________________.
pour point
39
What is a squeeze film?
The viscous fluid layer between two surfaces formed as the fluid is forced out from between a pair of approaching surfaces. Pressures are developed which resist the tendency of the surfaces to come together.
40
What is DN, and how is it calculated?
dN is the pitch diameter (ID - OD/2) x speed (RPM). Speed factor which is used to calculate minimum viscosity required at the operating temperature.
41
When choosing the viscosity of a lubricant for a particular application, the most important factor to take into account is ________.
Speed and operating temperature are equally important.
42
In a specific family of lube oils, if a higher flash point is desired, then the ______ of the oil must be increased.
Viscosity
43
In general, an oil’s_____________ should be about 20°F below the lowest temperature to which the fluid will be exposed in service.
Pour point
44
Name three elements/compounds used in additives to enhance EP/anti-wear properties of lubricants.
The principal EP additives are compounds of sulfur, phosphorus, zinc, chlorine, molybdemum, and graphite.
45
Name two negative effects that occur if EP additives are too active or in too great a concentration.
Increased corrosion
| Reduced oxidation stability
46
What NLGI consistency grade is a grease with a worked penetration of 320?
NLGI 1
47
List three grease properties that need to be taken into consideration for high temperature applications.
1) Dropping point
2) High temperature thickener
3) High base oil viscosity
4) Good oxidation resistance
48
List two grease performance capabilities that can be degraded when two incompatible greases are mixed.
Incompatible grease usually softens or stiffen. The mixture may lower the dropping point or change shear stability. There may be increased oil separation.
49
What type of lubricant is described by the following set of specifications? ISO VG = 32; VI = 105; RBOT = 600 minutes; SSW Rust Test = Pass; Neutralization Number = 0.05; 4-Ball wear scar = 0.8mm.
High quality turbine oil
50
What type of lubricant is described by the following set of specifications?
ISO VG = 68; VI = 48; Pour Point = -35°F;
Aniline Point = 180°F; Water = 10ppm; Cu Corrosion = 1A.
Naphthenic, low pour point, very dry, non-corrosive refrigeration oil
51
What is the term used to refer to the ability of a grease to restore itself to its original NLGI grade penetration value after it has been severely worked?
Thixotrophy
52
Draw a Stribeck Curve
do not know
53
What is the most commonly used NLGI grade?
NLGI 2
54
What is the "center line average" of a surface?
The average departure of the surface profile above and below the centerline.
55
What is the coefficient of friction?
Defined as the ratio of the friction force to the normal force between two bodies in contact.
56
What are the three most commonly encountered wear mechanisms?
1) Abrasion
2) Adhesion
3) Fatigue
57
What are the two basic types of lubrication?
1) Flooded - Full Film
| 2) Boundary
58
What is the "duty parameter" of a lubricant?
Lubricant velocity times sliding viscosity of the system divided by pressure on the system, which defines performance requirements of bearings.
ZN/P Z=Velocity N=Sliding Velocity P=Pressure
59
Briefly describe the difference between Newtonian and Non-Newtonian fluids?
A Newtonian fluid obeys the relation of a constant ratio of shear stress to shear rate at a constant temperature and Non-Newtonian fluids do not.
60
Briefly describe the difference between kinematic and absolute viscosities?
Kinematic viscosity is defined as the ratio of Absolute Viscosity divided by the Density. Kinematic viscosity is measured in capillary tubes with gravity flow and Absolute is measured using concentric cylinders with the inner cylinder rotating.
61
Name the three main factors that affect a lubricant's viscosity?
1) Base Stock - Composition
2) Temperature
3) Pressure
62
What happens to viscosity under pressure?
Viscosity increases significantly under high pressure.
63
How does multi-grade motor oil experience temporary viscosity loss? Permanent?
1) Temperature loss occurs when polymer molecules become oriented in direction of flow, which results in less internal friction & less on viscosity of lube.
2) Permanent loss occurs when some of the polymer molecules break down under high shear rates & smaller polymer molecules have less interaction with base oil molecules.
64
List three base oil components?
a. Paraffin’s
b. Naphthenes
c. Aromatics
65
Name and briefly describe an application where a naphthenic base stock is desirable?
Refrigeration oils due primarily to the low pour points ad good oxidation stability.
66
Name the two most common synthetic base stocks?
Esters
| PAO ‘s
67
List ten lubricant additives.
1) VI Improver 6) Detergent
2) Antioxidant 7) Dispersant
3) Pour paint Depressant 8) Anti – Wear Agent
4) Corrosion Inhibitor 9) Extreme Pressure
5) Anti – Foam Agent 10) Friction Modifier
68
What is the ISO equivalent of a SAE 140 gear oil?
460 or 680 cSt
69
The oil analysis report for a piece of equipment shows some indications of wear. Other than changing the viscosity of the oil, since the OEM recommendations are being followed, what else could be done to insure the equipment is being operated as close as possible to a full fluid lubrication regime?
Use an oil with higher VI
Decrease Temperature
Increase Speed
70
What additives do you expect to find in a turbine oil?
Rust, oxidation and foam inhibitors
71
What are emulsifiers?
Modifies surface tension of liquid droplets to keep them from coalescing. This allows the droplets to stay suspended in an otherwise immiscible liquid.
72
How do surfactants affect surface tension?
Reduces
73
Name a test to measure the amount of fatty acid in an oil.
Saponification
74
What two applications preclude the use of hydraulic oil with zinc based anti-wear additives?
Where incidental food contact is possible. Systems with silver componets.
75
Name at least three negative aspects the presence of water can have on the properties of lube oil in service.
Promote corrosion
Promote oxidation
Lower dielectric strength
Cause freezing of refrigeration
76
What is considered the most significant and basic property of a lubricating oil?
Viscosity
77
The viscosity of mineral oils is dependent on, or is affected by, what two factors? What additional factor affects the viscosity of grease and multigrade oils?
1) Temperature
2) Pressure
3) Shear rate
78
What is crude oil and where is it found?
Hydrocarbon oil formed by conversion of organic matter under pressure over time. It is found around the world.
79
What should be the primary source of lubrication recommendations?
The OEM recommendation in conjunction with the lubricating oil supplier.
80
What are synthetic base oils?
Human made base stocks made up of chemical elements selected for the properties imparted to the finished synthetic base stock.
81
What is distillation?
Distillation is a heat dependent process used to purify or separate a fraction of a complex mixture.
82
In most lubricant applications, what is better, high VI or Low VI? Explain
Most applications require a high VI to give adequate lubrication over a wide temperature range.
83
What is meant by group II base stocks?
Base stocks that contain greater than 90% saturates and less than .03% sulfur with a VI between 80-120, produced by hydrocracking and other processes.
84
Can air, water or kerosene be used as lubricants?
Yes, All can
85
The standard ISO VG grades for lubricants range from ISO VG _________ to ISO VG _________.
ISO VG 2 to ISO VG 1500
86
A plant has standard ISO 32, 46 and 68 AW Hydraulic oils in stock. How would you suggest consolidation?
Check OEM recommendations, use an ISO 46 AW fluid with a high viscosity index.
87
The viscosity of mineral oils in service is dependent on what two factors?
1) Temperature
| 2) Shear stability and pressure
88
For every ________ degrees F that oil rises above 160° F, it’s useful life is cut in half.
20
89
Name the three most important factors to consider when selecting the correct viscosity lubricant for any given application.
Temperature
Speed
Load
90
What are the 12 most common lubrication errors?
Wrong lubricant Quantity
Viscosity Amount
Properties Temperature
Flow rate Water
Air Particulates
To adequately survey To keep adequate records
Contamination with another lubricant
Failure to assign lubrication to one person
To investigate all mechanical malfunctions
To prevent unauthorized personnel from lubricating equipment
To update and refine lubrication program
91
Name three factors that favor hydrodynamic lubrication.
High speed
Light loads
Oil of high enough viscosity
92
What is apparent viscosity?
Viscosity measured at a given shear rate.
93
The viscosity of used industrial oils is typically measured at ________ C.
40° C
94
API gravity is one way of expressing a lubricants ___________.
Density
95
When is an oil wedge formed?
In a journal bearing under hydrodynamic conditions.
96
What is a TLV?
Threshold Limit Value - the maximum concentration that may be inhaled over an 8-hour work day, 40 –hour work week with minimal hazard to health.
97
What is aniline point?
The lowest temperature at which a solvent will become completely miscible with an equal amount of aniline. The lower the aniline point, the greater the solvency.
98
Define Wear?
The loss of material due to motion between two surfaces in contact.
99
What is Spalling?
Spalling ( destructive pitting ) results when normal loading is combined with sliding. It occurs when large wear particles are generated from cracks that are propagated from surface defects.
100
What is fretting corrosion?
Combination of corrosion and abrasive wear. The corroded material leads to abrasive wear.
101
Define erosive wear and fatigue wear.
Erosive wear – removal of material from surfaces due to momentum effects.
Fatigue wear – repeated bending stresses.
102
What are various types of wear?
Abrasive Wear: Hard particles bridging two moving surfaces scraping one or both.
Adhesive Wear: Loss of oil film allows metal to metal contact between moving surfaces.
Fatigue Wear: Particles bridging a clearance cause a surface stress riser or micro crack that expands into a spall due to repeated stressing of the damaged area.
Erosion Wear: Fine particles in a high-speed stream of fluid eat away a metering edge or critical surface.
Cavitation Wear: Restricted inlet flow to pump causes fluid voids that implode shocks that break away critical surface material
Aeration Wear: Air bubbles in the fluid implode breaking away surface material
Corrosive Wear: Water or chemical contamination in the fluid causes rust or a chemical reaction that degrades the surface.
103
List the various viscosity grades.
```
150 1500
100 1000
68 680
46 460
32 320
22 220
```
104
If you have a 1500 SUS gear oil what is the ISO Grade?
ISO 320 gear oil
If you see SUS, you divide that number by 5
1500 divided by 5 equals 300
ISO Grades have a + or -10%
So the range for an ISO 320 is 288 through 352 cSt
So you would use an ISO 320 gear oil
