Lubrication Flashcards
What are the three main types of friction?
Sliding, rolling, and fluid friction
This type of friction occurs when two surfaces slide over each other, such as in journal bearings, or pistons sliding in a cylinder
Sliding friction
This type of friction takes place when a spherical or cylindrical body rolls over a surface such as ball and roller bearings
Rolling friction
This type of friction occurs when there is no metal to metal contact and sliding occurs between the layers of oil within the film
Fluid friction
The reduction of friction to a minimum by the replacement of dry friction with fluid friction is called?
Lubrication
This theory thats that these forces cause unlike materials to stick together (polar attraction)
Adhesion
This theory states that these forces cause molecules of like materials to stick together
Cohesion
When the adhesive forces are strong in oil it’s said to be high in?
Oiliness or lubricity
What is the resistance to flow called?
Viscosity
Which viscosity is thicker and pours more slowly?
High viscosity
This is the most important property of lubricating oil
Viscosity
The higher the viscosity of the oil, the _______ the load it will carry
Greater
The higher the journal speed, the ______ the oil viscosity needed to carry a specific load
Lower
To minimize power losses, the oil should have the ______ viscosity able to carry the load on the bearing
Lowest
Choose the oil that has the desired viscosity at which temperature?
Operating temperature
Which two ways is viscosity measured?
Dynamic and kinematic
This viscosity is determined by measuring the force required to overcome fluid friction in a film or known dimensions. It’s used most frequently in bearing design and oil flow calculations
Dynamic or absolute viscosity
This viscosity is a measure of viscosity that is affected by the density of the oil. It is used to often compare lubricants when both are measured at the same temperature
Kinematic viscosity
The most common instrument used to measure viscosity is called?
Saybolt viscosimeter
The specific viscosity reaction of an oil whose temperature changes is indicated by what?
Viscosity index
The higher the viscosity index number, the ______ the change in viscosity due to temperature
Smaller
The _______ forms and forces the shaft up toward the centre of the bearing
Oil wedge
When the film of oil fails for a short time it is called?
Boundary or marginal lubrication
This occurs when you over-lubricate a threaded hole and it presses the liquid causing the casing to crack
Hydraulic lock
Additives are divided into these three main groups
Air control, water control, and load capacity
This is the ability of a petroleum oil to separate from water upon standing
Demulsibility
This is the ability of a petroleum oil to mix with water
Emulsibility
These are added to the oil to reduce the rusting of ferrous parts
Rust inhibitors
These additives are used for heavy load or shock load conditions
Extreme pressure (EP)
Load capacity additives are separated into these two groups
Anti-wear and Extreme pressure
What are the two types of oil lubrication systems?
Once-through/wasted oil system and Encloses
Squirt cans, wick-feed oiler, and drip-feed oilers are which type of lubrication system?
Once-through
Ring oiler, splash, oil bath, and re-circulating and which type of lubrication system?
Enclosed
This type of lubrication is recommended for high-speed bearings and high-velocity roller chain
Oil mist lubrication
This is usually made by thickening lubricating oils with a soap
Grease
Soap content for general use greases range from what percent?
7-18%
This type of grease is made by combining fatty acid with a base metal
Simple soap grease
What is the most commonly used soap grease
Lithium and barium
What type of grease is made by combining various types of soaps to extend the service life of grease
Mixed soap greases
These greases are made from special soaps and are multi-purpose
Complex soap greases
These greases are used to suit special conditions of temperature, environment or service life
Non-soap greases
These greases are designed to allow one grease to be used instead of three or four separate grades
Multi-purpose greases
This type of grease is designed for shock loading or high-local-pressure areas
Extreme-pressure (EP) greases
How is grease consistency measured
Penetration numbers
The NLGI ranges grease from softest to hardest with what numbers
000, 00, 0, 1, 2, 3, 4, 5, 6
The temperature at which grease becomes fluid enough to drip is called
Dropping point
Common grease dropping points range from
135 C (275F) to 182 C (360F)
How high should the oil bath cover the bearing
Covers the bottom of the outer race, but does not cover the centre point of the lowest ball or roller
What does over-oiling produce
Churning and a temperature rise
Should you use oil or grease for high speeds
Oil
Should you use oil or grease for heavy loads at low or medium speeds
Grease
What are the three types of cutting oils
Straight, emulsifiable, and chemical
