Module 7.11

Question 1

slow rotation of bearings highlights what?

Answer 1

roughness due to damage, corrosion or wear

Question 2

bearing tests are usually restricted to rotational checks for excessive backlash or free play, what direction is freeplay in?

Answer 2

axial or radial

Question 3

if a bearing shows a fault or defect, what must be done?

Answer 3

remove or replace

Question 4

how is preservation oil removed?

Answer 4

solvent bath

Question 5

how is heavy grease, carbon or oil removed ?

Answer 5

in a soak bath

Question 6

what is the final cleaning method?

Answer 6

ultrasonic bath

Question 7

what must be done to the bearing if it us not going to be used immediately?

Answer 7

coated with rust preventing oil

Question 8

what is likely to be grounds for any replacement of a bearing?

Answer 8

any flaw of defect

Question 9

what properties must a lubricant have?

Answer 9

-reduces friction and abrasion
-reduces heat from friction
-prolongs life
-prevents rust
-keep foreign objects away from rollers

Question 10

what lubricant is a better choice than grease for high rotational speeds?

Answer 10

oil is for high RPM. grease gets very hot at high RPM

Question 11

how is loss of lubricant stopped?

Answer 11

retaining device
-labrynth seals
-felt
-rubber washers

Question 12

most bearings are shielded or sealed, what must be done if evident lubricant has been washed out or lost?

Answer 12

replaced

Question 13

grease nipples are provided for some bearings, what must be done before applying through the nipple?

Answer 13

wiped clean to prevent dirt ingress

Question 14

what type of bearing is on a wheel hub? how is this regreased?

Answer 14

tapered roller bearing, usually regreased by hand

Question 15

what is hydrodynamic lubrication?

Answer 15

load carrying surfaces separated by a thick film of lubrication to reduce friction

Question 16

what is hydrostatic lubrication? and what does it not require?

Answer 16

high pressure oil or air to separate surfaces. Doesn’t require relative motion

Question 17

what is boundary lubrication and why is it important?

Answer 17

thin layer of lubrication between mating parts. Viscosity is not important, however lubricity is

Question 18

what is solid film lubrication? how is it applied and what are the benefits?

Answer 18

paint like coatings are applied by spraying, dipping or brush. film repels water, reduces friction and increases wear life.

Question 19

what is true brinelling?

Answer 19

regularly spaced indents with a vibraion increase

Question 20

cause of true brinelling?

Answer 20

-loads from incorrect mounting
-debris
- excessive static overload or impact loads

Question 21

rectification of true brinelling?

Answer 21

avoid unnecessary shock or impact loads

Question 22

what is false brinelling?

Answer 22

hollow spots on the raceway that resemble true brinelling

Question 23

what is the cause of false brinelling?

Answer 23

vibration in a static state, which causes metal to metal contact. poor luibrication

Question 24

how is false brinelling rectified?

Answer 24

reduce vibration by preloading,
use proper lubrication

Question 25

what is burnishing?

Answer 25

splits or cracks in rolling elements or bearing rings

Question 26

what causes burnishing?

Answer 26

-insuffcient lube
- excessive loads and impacts
- overheating by movement and rapid cooling
- very loose fits

Question 27

what does overheating look like?

Answer 27

discolouration of elements from gold to blue

Question 28

how is burnishing rectified?

Answer 28

• prevent movement
• correction of fit
• correct lube

Question 29

what causes overheating?

Answer 29

poor lube, heavy electrical loads and insufficient cooling

Question 30

how do you rectify overheating?

Answer 30

prevent overload, serviceable lubricant system, supplemental cooling.

Question 31

what does galling look like? and caused by?

Answer 31

metal to metal contact, metal transfer. looks like skidding due to overspeed

Question 32

what is the rectification of galling?

Answer 32

prevent overload and have a serviceable lubing system

Question 33

what is spalling?

Answer 33

breakdown of surface due to cyclic loading

Question 34

what is wear caused by?

Answer 34

worn surface and dimensions are reduced component to other portions, caused by FOD, poor lube ect.

Question 35

what bearings are more suceptible to damage?

Answer 35

moving bearings

Question 36

what is one way to rectify electric damage?

Answer 36

prevent current from passing through

Question 37

how does electric damage appear?

Answer 37

dark brown, greyish black corrugating or craters on raceway, balls have dark discolouring only.

Question 38

what does corrosion on bearings look like and what is it caused by?

Answer 38

black pitting marks or reddish brown marks, caused by moisture and contamination.