Whenever an object moves against another object, friction will be present, turning kinetic energy into heat and causing equipment to wear. Using lubricants helps to reduce this friction, allowing more work to be done for the same amount of energy input, lowering the temperatures of the materials in contact, and greatly extending the lifespan of the moving equipment.
Kinematic viscosity
Test Number & Name: ASTM D-445 Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids.
- Measure of internal resistance to flow.
- It is measured in Centi Stokes (CSt).
- Kinematic viscosity decreases with increase in temperature.
- Kinematic viscosity also Important in lubricant selection.
- Increase in used oil indicates oxidation.
- Specified at 40 degree C and 100 degree C.
Lubricity
Some lubricants are said to have high lubricity, or oiliness. This property comes from the chemical compositions of the oils, which reduce wear and friction even in extreme conditions.
Pour Point
- Test Number & Name: ASTM D-97 Standard Test Method for Pour Point of Petroleum Oils.
- Lowest temperature at which the fluid will flow is known as pour point.
- It indicates lowest operating temperature.
- It measured in Degree C.
Cloud Point
Petroleum-based lube oils contain dissolved wax. At a low enough temperature, referred to as the cloud point, this wax will separate from the oil and form wax crystals. These crystals can clog filters and small openings, deposit on surfaces such as heat exchangers, and increase the viscosity of the oil.
Viscosity index
Test Number & Name: ASTM D-2270 Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40°C and 100°C.
- It measure of fluids change of viscosity with temperature.
- Higher the Viscosity index lower will be the change of viscosity with temperature.
- Viscosity index Indicator of temperature range of operations.
Oxidation and Corrosion
When lubricants are exposed to oxygen and certain metals or compounds at temperatures above 160 degrees Fahrenheit, they can be prone to oxidation. Oxidation of lubricants can lead to several undesirable consequences, such as increased oil viscosity, formation of corrosive acids, and sludge buildup. Preferred lubricants are those that have a high resistance to oxidation and inhibit corrosion by protecting components from water, oxygen, and chemical attacks.
Aniline Point
Aniline point of the lubricant oil is defined as the minimum equilibrium solution temperature for equal volumes of aniline and lubricant oil samples. It gives an indication of the possible deterioration of the lubricant oil in contact with rubber sealing; packing, etc.
Aromatic hydrocarbons have a tendency to dissolve natural rubber and certain types of synthetic rubbers. Consequently, low aromatic content in the lubricant oil is desirable. A higher aniline point means a higher percentage of paraffinic hydrocarbons and hence, a lower percentage of aromatic hydrocarbons.
Total Base Number (TBN)
- Test Number & Name: ASTM D 664
- Total Base Number measured the acid neutralizing reserve in oil.
- Total Base Number measured in Mg KOH/gm of oil.
- TBN is Important for deciding discard of oil.
- TBN is decreases due to Oxidation of oil, Water contamination and Fuel contamination.
Flash Point and Fire point
- Test Number & Name: ASTM D-92 Standard Test Method for Flash and Fire Points by Cleveland Open Cup.
- Lowest temperature at which the vapor above the liquid will ignite under flame is known as Flash point.
- Fire point is the lowest temperature at which a specimen sustains burning for five seconds.