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
