Classification Of Grease Oil

Lubricating substance, which is formed by the addition of thickening chemicals and reacting at certain temperatures to a lubricating liquid, is called grease or grease oil, which has different physical properties from semi-fluid to solid.

- The structure of the grease is similar to a sponge

- Cavities are filled with oil

- Additives are added to these oils.

Oil is released during operation

The Structure Of The Grease?

70 to 95% mineral or synthetic oil

5 to 30% constituent transmitter

Contributions from 0 to 10%

Tasks of grease

Separating friction surfaces

- Creating a lubricating film layer

- Pushing eroded particles and dust out of the lubrication area

- To reduce the friction coefficient

- To provide sealing in the bearings

- Use in a wide temperature range

NLGI No. Hard greases such as 2-3;

* They resist centrifugal forces at high speeds,

* They resist the penetration of external pollutants,

* They maintain their consistency at high temperatures.

NLGI No. Soft greases such as 0-1;

* They provide easy operation and good lubrication at low temperatures,

* They facilitate the correct flow and pumping to the pump mouth,

* They are economical in terms of low energy consumption.

Low viscosity thin oil containing greases;

* They are suitable for high speeds,

* They do not cause internal heating problems.

Greases with high viscosity thick oil;

* They are suitable for medium and low speeds,

* They have high load carrying properties.

General Rules in Grease Selection;

- at higher speeds

- Harder greases with lower viscosity (thinner) oil

- at higher loads

Softer greases with higher viscosity oil

- at higher temperatures

- Harder greases with higher viscosity (thicker) oil

For example; For 2500-3000 rpm (for high speed bearing):

Base oil viscosity ISO 100-150 (cSt / 40oC)

Soap consistency NLGI No. 2-3

Some Tests Performed On Greases

PENATRATION (ASTM D217 - TS 1799 ISO 2137)

It is used to measure the viscosity of greases.

It is also known as the NLGI (National Lubricating Greases Institute) degree.

Measurements are made according to ASTM (American Standard Test Method) and TSE standards.

Penetration value in greases can be kept in mind as follows:

When you throw a teaspoon into 1 glass of water, the spoon will immediately go down, but when you put the same spoon into 1 glass of honey, it will come down very slowly. Here, water represents soft grease, honey represents a harder grease than water. Sealing is a result of penetration. The higher the hardness of the greases, the higher the sealing ability. For example, gear greases are soft, so their sealing ability is low.

DROPPING POINT (ASTM D 2265)

The dropping point is used to determine the temperature at which a grease transforms from solid to liquid. In lithium soap greases, 60 ° C below the dropping point gives information about the operating temperature of that grease. For example, a grease with a dropping point of 200 ° C can work up to 130 ° C. But this only applies to Lithium greases. For other greases, it should definitely be consulted.

SEPARATION FROM OIL (ASTM D'6184 - IP 121)

It is often described as "bleeding or vomiting" in enterprises. When greases are stored for a long time or used at high temperatures, the oil they contain exhibits separation behavior. Refers to the separation of oil from soap. Partial separation from oil is desired in bearing lubrication. But above the standards, it creates excess soap at the point of separation from oil. This causes flow strain and insufficient rainfall in the lubrication line. Some greases are separated from oil under pressure in central lubrication systems, these should be considered. (these greases are usually calcium and calcium complex greases)

FOUR BALL (FOUR BALL TEST) (ASTM D2596 - TS EN ISO 20623)

This test contains the load from which the grease begins to originate. The highest load without starting welding is the biggest load that the grease lubricating film can carry. There is a driven ball at the top and three fixed balls below it. Balls are placed in a pyramid shape. Testing is made according to ASTM D2596. At the same time, the wear diameter under load is determined. It is a very important test for heavy industry and greases working under high pressure.

WATER SPRAY TEST (ASTM D'4049)

It is the measurement of the separation stability of greases from metal surface under water pressure. Water at 38 ° C is sprayed on the grease at 40 psi pressure for 5 minutes and the amount of grease separated is calculated as%.

EMCOR (ASTM D6138)

It aims to evaluate the corrosion prevention ability of oils and greases in bearings. Oil or grease is tested with distilled water and sea water at 80 rpm and unloaded in aqueous environment for 110 hours.

What Should We Consider When Choosing Grease Oil?

When very well-processed metal surfaces are viewed under a microscope, it is seen that they are actually rough.

Oil Free Movement of Surfaces:

When two metal surfaces are moved mutually without oil;

* Surfaces get hot

* Boiling points break off

* Surfaces wear out.

The first rule of lubrication;

• With the right lubricant,

• In the right place and time,

• To make the right amount of lubrication.

Selection of Greases

• Working Speed / Revolution (In terms of base oil viscosity and thickener type)

• Working Load (Pulsed, continuous, variable etc.) (Base oil viscosity, in terms of additives)

• Operating Temperature (in terms of base oil viscosity, dropping point, thickener type)

• Application place and form (Central or singular, etc.) (Thickener type, in terms of penetration)

• Bearing, Bearing Type (in terms of penetration)

• Compatibility (in terms of thickener type, base oil, additives)

Results of Improper Grease Selection

• The grease cannot be applied, does not reach the bearings (hardness level or soap type)

• Inability of grease to bear load, bearing distribution (Base oil viscosity, Thickener, EP additives)

Grease bleeding, bearing dispersion, (fibrous structure being short, soap type)

Insufficient additives (rust, abrasion, scratches etc.) (EP, Aw, AO, Anti corrosion, dry lubricants etc.)

• Under load, temperature and cycle, the grease quickly ages, its consistency decreases, becomes gummy, discoloration, and flows rapidly from the seals. (Soap type, additives, hardness)

• Loss of grease consistency due to low dropping point (soap type, additives).

• Taking the water in the environment in excess, formation of rusting (soap type, additives)

• Not resistant to high operating temperature (soap type, base oil type)

• Formation of tearing, oxidation and rusting on felt, copper parts, aluminum parts, pump elements. (Soap type, base oil type, additives)

• Leaving away from the bed by cooling water pressure (water resistance, soap type)

• Heating of the grease under high speed, losing its consistency over time, thinning (speed factor, hardness degree, base oil viscosity)

What Can We Gain With The Right Lubrication?

• According to the acceptance of the lubrication unions (room, board, R&D), 60% of machine failures are due to insufficient or inappropriate lubrication practices.

• According to the data of the Lubrication Industry, proper lubrication extends the machine life three times more.

Saving:

• 7.5% due to reduction in energy consumption, reduced friction