Lubrication Flashcards
The 3 types of lubrication?
- Full Film
- Elasto-hydrodynamic
- Boundary
Lubrication reduces friction?
-separating the moving surfaces with a film that has less friction than the moving surfaces
Full Film
-thick enough to completely separate the surfaces with a continuous film
Elasto-hydrodynamic
- completely separates two surfaces and is a type of full film lubrication
- but the two surfaces are loaded to the extent that deformation takes place in the loaded zone
Boundary
- forms at low speeds
- forms when viscosity is too low to support the load
- forms if there is not enough lubricant
3 types of friction and anti-friction bearings?
- Sliding
- Rolling
- Fluid
Sliding Friction
-resistance as one surface slides over another
Rolling Friction
- the resistance to movement of one surface rolling over another
- the deformed ball and deformed carpet as it rolls over it
Fluid Friction
- resistance to flow within a fluid
- result of electromagnetic bonds
Oil Wedge
- supports the shaft and relocates it within the bearing clearances
- it forces a full film of fluid into the loaded area
- dependant on speed, load pressure and viscosity
1 cause of bearing failure
-improper Lubrication
Flash Point
-lowest temperature at which the vapour above an oil will ignite when a flame passed over it
Contaminants produced by lubrication breakdown.
Acid, sludge, varnish
Functions of a lubricant
- to reduce resistance
- reduces friction
- protects against corrosion
- carries away heat
- carries away contaminants
Viscosity Index
- a number that identifies the amount of change in the viscosity of a lubricant over a temperature range
- stability of the oil
Pour Point
- the lowest temperature at which an oil is observed to flow
- 3 degrees above the temperature of oil that doesn’t appear to be flowing
Absolute viscosity
Ash
-detergents leave this residue when oil is burned
Block Lubrication System
-divider valves are stacked to form distribution blocks to deliver oil
Oil Mist System
- Above atmospheric pressure which helps keep contaminants out of the system
- bad cause the oil turns into a mist and gets into the air
- small high speed
Viscosity
- how thick or thin the oil is
- measures the fluid friction
- decreases when temperature increases
- increases when pressure increases
- measured at 100 degrees C
Air Oil system
- Oil pump to inject very small amounts of into oil lines
- supplies droplets of oil along the walls of the oil lines
- pressurizes system to prevent junk from getting in
Oil starts to oxidize
55 degrees c
Wax
- in Paraffin based oil
- cause issues at high temperatures in pipelines
Petroleum based oil
- they do not wear out
- stable up to 55 degrees C
Synthetic oil
- made from at least 10 chemical based
- wide operating temp
- fire resistant
Additives
- 22% of the oil
- DO wear out
TBN/TAN
- TBN (total base number)
- TAN (total acid number)
- a drop or rise in either of these numbers indicates oxidation is happening
Grease
- liquid lubricant mixed with a thickener
- Never mix different greases with different thickeners
- thickeners are known as soaps
Drop point
-Lowest temperature at which lubricant will begin to drip from a grease
Molybdenum Disulphide
-additive of choice to make the film strong enough to support the load & separate the surfaces in a loaded zone
Proper grease levels.
-the housing should be 1/3 full after the bearing is packed
Proper oil levels in oil bath system?
-1/3 to 1/2 up the lowest rolling element
What is the proper condition a coupling should be in?
-perfect alignment
not to company specs because the company doesn’t know what the coupling is being used for.
More clearance between bearing and housing means what?
-less load on that bearing
Naphtha Based Oil
- base oil for grease
- imported
What is the best thickener for conventional grease at high temperatures?
-Sodium
Bottle Oiler
a bottle mounted on top of the bearing housing that rests on the surface of the shaft. Slight vibration causes oil to run down and lubricate the bearing
Oxidation with oil
-it doubles every 8 degrees over 55
CST or centistoke
-British unit of measure for viscosity accepted world wide
Functions of detergents
- keep out sludge and fine deposits
- clean up existing deposits
- control acid buildups
- act as an anti wear additive
- act as an anti scuff additive
- act as a rust inhibitor
