Lubrication Flashcards
What is lubrication trying to accomplish?
Reduce:
-friction
-amount of mechanical energy to do work
-energy dissipated as heat
-reduce wear and corrosion
Dampen Shock
-shock loading is mainly a concern in gears.
-Viscosity increases with a pressure increase.
How does lubrication reduce corrosion?
- Acts as a preservative for non-operating equip.
- Provides a protective film for operating equip.
Examples of ‘Seal Outs’
-seal oil
-Gland sealing steam on main turbine
2 Different types of Lubrication Films characteristics?
-Adhesion
-Cohesion
What’s dry film?
-Natural lube (gasses,water vapor)
- NOT IDEAL
What’s mixed film?
-Some lube & some metal-to-metal contact
-single layer of lube
-high friction (bad)
What’s boundary film?
-Thicker lube and some metal-to-metal contact
-Common during startup/shutdown
-when components start to move, will draw lube between them.
What’s full film?
-Surfaces completely separated
What are two types of full film?
-Hydrodynamic: maintains separation of loaded surfaces due to exerting a higher psi and viscosity undue increased loads
-Hydrostatic:
•provided from an outside source
•used for slow, heavy loads
What is friction?
-The microscopic roughness on materials
What’s static friction?
-Exists between a body at rest and the surface upon which it rest.
-Must be overcome to START a body in motion.
What’s kinetic friction?
-Exist between moving bodies or between one moving body and one stationary body
-Must be overcome to KEEP a body in motion.
What’s different types of Kinetic friction?
-Sliding friction (bad)
-Rolling friction (better)
-Fluid friction (Good!)
What’s adhesion wear?
-Where metallic surfaces slide against each other under pressure.
-Bonds form and then break away
What’s abrasive wear?
-adhesive wear can cause this.
-When loose material is caught between sliding surfaces, causing gouging.
What’s an oil wedge?
-A layer of oil formed around a journal when it starts rotating.
-‘Full film layer’ at full speed
-Created with cohesion,adhesion and viscosity
Liquid Oil
-Mineral oils made from crude oil (most common)
-Also oils made from animal or veggie fat.
How are lubricants chosen for specific applications?
-Based on physical and chemical properties.
What’s Viscosity?
-The tendency of a fluid to resist flow.
How does viscosity change?
Temperature: Hot=runny
-inverted
Pressure: ‘heavy’/high psi=slow/thick
-Directly affects
What are light oils used for?
-High speed
-Low pressure
-Low temp.
What are heavy oils used for?
-Low speed
-High pressure
-High temp.
Viscosity Index (VI)
-Keep it 100%/ 100(Vi) = never changes
-0(Vi)= changes the most
Pour Point
-The lowest temp. at which oil will flow from a container
-High viscosity, high pour point.
Flash Point
-The temp when oil is vaporized enough to ignite momentarily
-Need a spark.
-Low flash point= oil easily vaporized.
Fire Point
-The temp when oil will continue to burn
-Higher temp than flash point.
Auto-Ignition Point
-when the flammable vapors from oil will burn
-No spark required
Demulsibility
-A measure of ability for oil and water to separate.
What is grease?
-Semi-solid
-oil as basic lubricant
-thickener that supplies body(soap)
-additive that enhance properties
(Graphite,asbestos,zinc)
Properties of Grease?
-Hardness
-Dropping point(melting point)
-Pumpability
-Water resistance
-Stability
Type of solid lubricants?
-teflon tape
-graphite tape
Gas lubricants
-required for high separation or high temp. conditions.
-Examples: jet engines or furnaces
What are forms of manual lubrication
-Oil can
-Hand pump
-Grease gun
What are forms of Gravity/drip feed?
-Container holding lubricant above equip.
-Adjustable needle valve
-Vibrating pin
-Wick oiler
-Trico bubbler
How can over filling occur in Trico bubblers?
-repeated removal and replacement of bubbler
side note
-only add oil when level is less than 1/3 of the bubble level.
Methods of natural lubrication?
-Splash oilers
- Ring oilers
Methods of pressure/force feed lubrication?
-Wet sump (internal to system)
-Dry sump (separate from system)
-Air line lubricators (enters by Venturi as a mist)
Lubrication failures occur due to?
-Chemical decomposition
-Contamination (particle)
-temperature (creates varnish/lacquer)
-inadequate flow
-water/air in oil
Telltale symptoms of improper lubrication:
-High temp
-vibration
-noisy components
-component failure
Gravity settling
-oil purification
-simple and slow process
-can reduce time by heating it.
