Some performance indicators and parameters of industrial lubricants

1. Density and relative density

Relative density refers to the ratio of the normal density of a substance at a given temperature to the density of a standard substance at a standard temperature. For petroleum liquids, the standard material is water.

2. Viscosity

The measure of internal friction when a liquid flows is called viscosity, and the viscosity value decreases as the temperature increases. Most lubricants are graded based on viscosity. There are generally five ways to express viscosity, namely dynamic viscosity, kinematic viscosity, Engler's viscosity, Wright's viscosity and Saybolt viscosity.

Dynamic viscosity: represents the measurement of internal friction when a liquid flows under a certain shear stress. Its value is the ratio of the shear stress applied to the flowing liquid and the shear rate. The legal unit of measurement in my country is pascal/second (Pa·s). It is customary to use centipoise (Cp) as the unit, 1cp=10-3Pa.s.

Kinematic viscosity: represents the measurement of the internal friction force when a liquid flows under the action of gravity. Its value is the ratio of the dynamic velocity of the liquid to its density at the same temperature. In my country's legal measurement unit, it is expressed in 0/s. It is customary to use centistokes (cst), 1cst=1mm2/so

Engler viscosity: Under specified conditions, the ratio of the time (s) required for a sample of a certain volume to flow out of the small hole of the Engler viscometer to increase the volume of 200 mL to the value of water measured by the viscometer, expressed in 0Et.

Ray's viscosity: under specified conditions, the amount of time required for a certain volume of sample to flow out of a 50mL sample from the Redwood viscometer.

The unit is s.

Saybolt viscosity: Under specified conditions, the time required for a certain volume of sample to flow out of the Saybolt viscometer, measured in s.

Saybolt viscosity is divided into Saybolt universal viscosity (expressed in SUV) and Saybolt heavy oil viscosity (expressed in SFV).

3. Viscosity index

Viscosity index is an agreed quantitative value that expresses the change of oil viscosity with temperature. A high viscosity index indicates that the oil's viscosity changes less with temperature, and vice versa.

4. Flash point

Under specified conditions, the lowest temperature when a mixture of vapor and air escaped from heated oil contacts a flame and an instant fire occurs is called the flash point, represented by "C". The methods for measuring flash point are divided into open cup method and closed cup method. The open cup method is used to measure the flash point of heavy lubricating oil; the closed cup method is used to measure the flash point of fuel and light lubricating oil.

5. Freezing point

The highest temperature when the test oil is cooled to stop moving under specified conditions is called the tipping point, represented by "C". Condensation point is an item to evaluate the low-temperature performance of oil.

The pouring point of oil is directly related to the wax content. The more wax content in the oil, the higher the pouring point. Therefore, the freezing point can guide the dewaxing process operation in petroleum product processing technology.

6. Pour point

Pour point refers to the lowest temperature at which cooled test oil can flow under specified conditions, expressed as "C". Pour point, like pour point, is an indicator of the low-temperature flow properties of petroleum products.

7. Moisture

Moisture refers to the water content in the oil, expressed as a weight percentage. There are several moisture measurement methods in the petroleum product analysis standards, generally expressed as first, and less than 0.03M is a trace. For oils with special requirements, the moisture content is expressed in 10-6 (ppm).

8. Mechanical impurities

All impurities present in oil that are insoluble in specified solvents are called mechanical impurities.

9. Water-soluble acid or alkali

Water-soluble acid or alkali refers to the general term for acidic or alkaline substances present in oil that are soluble in water.

10. Residue charcoal

Under specified conditions, the residue formed during the cracking of oil is called residual carbon. Expressed as weight percent.

11. Ash content

The inorganic substance obtained by simmering the residue after the oil is carbonized under specified conditions is called ash, expressed as a weight percentage. Ash is mainly naphthenate salts contained in oil. Usually the ash content in oil is very small. When certain high-ash additives are added to lubricating oil, the ash content of the oil will increase.

12. Demulsification value

A measure of the ability of an oil to separate from an oil-water emulsion is called the demulsification value, expressed in min. It is a major specification item for turbine oil. During use, turbine oil sometimes comes into contact with, or even mixes with, water and air leakage, forming temporary emulsification. Therefore, it must have the ability to quickly separate from water to ensure normal oil circulation and lubrication of mechanical parts.

13. Oxidation stability

The ability of petroleum products to resist the action of air (or oxygen) without permanently changing their properties is called the oxidative stability of the oil.

14. Shear stability

Shear stability is specified. The ability of a petroleum product to resist shear and maintain viscosity-related properties under certain conditions.

15. Ditch point

The groove formation point is to store the test oil sample at the specified temperature for 18 hours, cut the test oil into a groove with a metal piece, and then determine whether the test oil flows together and cover the bottom of the oil test container within 10 seconds. If the oil sample flows back and completely covers the bottom of the oil test container within 10 seconds, it is reported that the oil sample is not grooved; otherwise, it is reported that the oil sample is grooved. The channeling point is used to measure the channeling performance of gear oil (low temperature).

16. Drop point

The lowest temperature at which a solid or semi-solid petroleum product reaches a certain fluidity under specified conditions is called the dropping point, expressed in °C. The dropping point of a grease has a lot to do with its composition. The approximate range of the dropping point of commonly used greases is as follows:

The dropping point of alkylene grease is generally 40~80℃

The dropping point of calcium-based lipid is about 75, 95c

The dropping point of calcium sodium based grease is approximately 120~135℃