Lubrication Flashcards
Which type of friction would produce the greatest heat?
Sliding friction
What are three kinds of friction and provide examples of each one?
Sliding- is the resistance to me that is produced when one so if the slides across another
Rolling- is the resistance to movement of one surface rolling over another
Fluid- is the resistance to flow within the fluid
what is the definition of viscosity?
Is a measurement of fluid friction. fluids that flow easily like Water have low viscosity
How would an increase in viscosity city affect the load strength of a lubricant
The higher the viscosity, the Higher the load capacity of the film
How would an increase in temperature affect viscosity?
As temperature increases viscosity decreases. As temperature rises molecular actively increase, breaking some of the electromagnetic bonds
What is the world wide excepted unit of measurement of oils viscosity?
Centistoke (CST)
How is pour point of oil determined?
Pour point in 3°C above the temperature at which the oil shows no movement from a container held horizontally for five seconds
A lubricants main job is ?
Reduce resistance
Viscosity is a measurement of?
The fluids resistance to flow
What offices the least resistance
Fluid friction
If a fluid flows easily we say it has a
Low viscosity
As the temperature of oil increases, viscosity…….?
Decreases
The amount of change in viscosity over a temperature change is referred to as……?
Viscosity index
An oil with very little change in viscosity as it is heated from 40°C to 100°C is referred to as having a………. Viscosity index?
High viscosity index
The lowest temperature at which an oil will float is known as……?
Pour point
In oil designation, the W stands for
Winter (cold weather starting ability)
Chemicals added to the oil to give properties for various special uses are….?
Additives
Where there are heavy loads with metal to metal contact possibilities, protection against the asperities welding there surfaces is prevented by adding chemicals with which designation
EP= Extreme pressures
Are Detergent oil is recommended for high temperature applications
No they are not
What does viscosity index of oil indicate?
Identifies the amount of change in the viscosity of a lubricant over a temperature range
Why is it important to know the pour point of oil?
Because it determines the lowest temperature at which oil will flow into bearings, etc
What is the flashpoint of oil and what is its importance?
Flashpoint is the lowest temperature at which the vapor above an oil will ignite when a flame is passed over it.
Flashpoint indicates the file or explosion hazard of the lubricant
List three stages of lubrication
Boundary film
Partial film
Full film
What percentage of an industrial lubricant oil would be additives?
22%
The oxidation rate of petroleum based oil doubles for every……. Degrees Celsius temperature rise above…….. Degrees Celsius
The oxidation rate of petroleum based oil doubles for every 8°C temperature rise above 55°C
What is friction?
Friction is the resistance to movement of two surfaces in contact with each other
What the effects of friction?
It’s resistance to movement increases power consumption
It causes wear
It generates waste that can reduce the life of components
What is sliding friction?
Sliding friction is the resistance to movement that is produced when one slides across another
The resistance is produced by interlocking, tearing and momentarily molecular welding of the peaks of the asperities of two surfaces
What is rolling friction?
Rolling friction is the resistance to movement of one surface rolling Over another
Mainly a result of the resistance of the material to being deformed
What is fluid friction?
Fluid friction is the result of electromagnetic bonds ( attraction ) between the molecules of a fluid
Note: A fluid is anything that flows and can be either a liquid or a gas
What are the functions of a lubricant?
To reduce friction, to protect against corrosion of the surfaces, to carry away heat, to carry away contaminants, to help seal
What is full film lubrication?
Full film lubrication is thick enough to completely separate the surfaces with a continuous film
What are the good characteristics of full film lubrication?
Offers the least friction resistance
Eliminates wear on moving surfaces that separates
Generate the least amount of heat
What is Elasto-hydrodynamic film lubrication?
A type of full lubrication, however two surfaces are loaded to the extent that deformation takes place in the lighted area.
The fluid film is extremely thin (1/4 micron to 3 microns thick)
This type of film forms at high speeds as well as high pressures
What is boundary film lubrication?
Boundary film lubrication is some of the tips of asperitties I touching.
Boundary fill forms at low speeds
When the viscosity of the lubricant is too low to support the load
That is not enough
What is the oil wedge theory?
Hydrodynamic principles, which active as the shaft rotates,create an oil wedge that supports the shaft and relocate it with in the bearing clearances
The following points should be noted about the hydrodynamic lubrication?
Minimum speed required, depends on the load Pressure and the viscosity of the fluid, film thickness increases with speed, it is important to rotate the shaft above the minimum speed for full film lubrication as soon as possible
how does the total clearance affects the load capacity of a bear?
The shaft is not centered in the bearing because the fluid film is thinner under the loaded area, when the clearance is large, the area of supporting is very small, when the clearance is small, the area of support is much greater
What are the two petroleum based Oils
Paraffin base and naphtha based
What characteristics does paraffin based oil have? Where is it produced?
Produced in North America, most commonly used oil base in North America.
They have the high wax content, most soluble, have a high viscosity index, less solvency
What is naphtha based oil stock and what characteristics does it have?
Are imported into North America, used mainly as the base oil in cold temperature grease and lubricants, low viscosity index, low pour point, greater solvency’s
What applications would you use petroleum based oils
Petroleum based oil is the most widely used type for the lubrication of bearings and gears.
What synthetic oil’s
Synthetic oils have been developed to solve lubrication problems that petroleum miles on able to overcome. They are made from at least 10 chemical basis
What applications would you use synthetic oil
Gas turbins all the drying section of papermaking machines, extreme temperature ranges, aircraft hydraulics, fire resistance is important
What is the oxidation rate?
The oxidization rate of petroleum based oil doubles for every 8°C temperature rise above 55°C
What is the function of antioxidants
Anti-oxidants improve the oils oxidatio suitability by anywhere from 10% to 150%
What are two types of corrosion damage
Rust (due to water) and acid attack
What can EP additives tend to corrode
Copper and bronze
Proper level of lubricant in a rolling element bearing is
Half way up the lowest rolling element
A measurement of Greece stiffness is referred to as
Consistency
Thinners for Grease can be made from compounds that are classified chemically as
Soaps
The system which offers advantage with their large number of lubrication points is the?
Centralized lubrication system
