Unit 18 Lubrication

Question 1

Relative to lubrication, one place where wear is beneficial is

Answer 1

on new babbit bearing surfaces which wear smooth

Question 2

Grease is not a suitable lubricant

Answer 2

if a large amount of cooling is desired

Question 3

If an oil’s viscosity changes much with little temperature change, it will have

Answer 3

a low viscosity index

Question 4

If you desire an oil to flow at a much lower temperature you would most likely add

Answer 4

pour point depressants

Question 5

High capacity steam turbine oils should

Answer 5

fire resistant

Question 6

4 properties that affect the type of lubricant that should be chosen for an application

Answer 6

Nature of surfaces to be lubricated
load to be carried
speed of sliding surfaces
operating temperatures

Question 7

A common method of determining viscosity of an oil

Answer 7

A given quantity of oil is placed in a Saybolt viscosimeter at a controlled temperature. The time for the oil to pass through a standard small diameter tube is measured and this indicates viscoity in Saybolt Seconds universal

Question 8

Grease is a mixture of

Answer 8

mineral oil and soap

Question 9

3 classes of lubricants

Answer 9

Solid- graphite, soapstone used in extreme temps
Semi-solid - greases used where oil could leak away, where dirt and moisture is to sealed out
Liquid- mineral oils, synthetic oils and fixed oils used in service where maximum lubrication is required and heat and dirt is to be carried away from bearings

Question 10

a measure of the resistance of a liquid to internal deformation and indicates a fluids ability to flow

Answer 10

Viscosity

Question 11

temperature at which an oil will give off enough vapors to ignite momentarily

Answer 11

flash point

Question 12

temperature at which wax in the oil begins to separate out

Answer 12

Floc point

Question 13

Determines the amount of carbon an oil will form when subjected to a high temperature

Answer 13

Carbon Residue

Question 14

A measure of how much an oil’s viscosity changes with temperature

Answer 14

Viscosity index

Question 15

Define boundary lubrication

Answer 15

when a microscopic layer of lubricant separates the surfaces. Used when lubricant supply is intermittent

Question 16

Fluid film lubrication

Answer 16

when the bearing is flooded with oil and a film built up that is thick enough to completely separate the surfaces

Question 17

Describe the construction of shell or sleeve type bearings

Answer 17

bearing surface is made of white metal called babbit, which is soft enough to conform to load and debris will become embedded. Bearing housing is made of cast iron or steel. Bearings have grooves to distribute oil to the surfaces.

Question 18

Describe the procedure for cooling an overheated bearing

Answer 18

increase oil flow to bearing to carry away heat
slacken off bearing caps if shaft is expanded, in slow moving bearings.
apply water to shaft but not directly at the bearing

Question 19

Allows a wedge of oil to build up between the revolving thrust collar and the stationary pads

Answer 19

Tilting pads

Question 20

Roller or ball type bearings are known as

Answer 20

antifriction bearings

Question 21

A loose fitting ring hanging on the rotating shaft inside the bearing that lifts oil from the reservoir and distributes it to the bearing and shaft

Answer 21

Oiling ring

Question 22

The ring assembly within which the balls or rollers of an antifriction bearing rotate.

Answer 22

Bearing Inner race

Question 23

A device using a threaded spindle which is rotated to apply force on a bearing to remove it from a shaft

Answer 23

Bearing puller

Question 24

The outer race of an anti friction bearing

Answer 24

Bearing shield

Question 25

Indents created in the bearing race of antifriction bearings under the balls or rollers

Answer 25

Brinelling

Question 26

4 main purposes of lubricating bearings

Answer 26

To protect the surfaces of the balls, rollers and raceways from corrosion; to provide a seal against dirt and other impurities into the housing; To serve as a heat transfer medium; To provide lubrication and reduce friction

Question 27

Which type of thrust bearing does not utilize the oil wedge principles of lubrication

Answer 27

Collar

Question 28

To clean a bearing

Answer 28

Drain old oil, remove dirt and grease from around it
fill bearing with solvent, run machine without load for a short period. Drain solvent and impurities. Continue this process until clean solvent is drained out.
Fill with a light oil and run to remove solvent.
Drain oil and fill bearing with normal lubricant

Question 29

When stationary bearings are exposed to vibration causing the rollers or balls to form indentations in the bearing inner race or sleeve race

Answer 29

False brinelling

Question 30

What to check when inspecting an antifriction bearing

Answer 30

pitting or flaking of balls, rollers or races
cracked ball, rollers, races shields or separators
rusting or corrosion
discoloration indicating overheating