What are the Characteristics and Requirements for Good Lubricants? [Explained] (2022)

Your machinery wears out prematurely if it is not lubricated. Lubricants reduce friction. By using good lubricants, you will be able to reduce maintenance, reduce energy consumption, increase production, and extend the life of your assets.

Best lubricants are considered based on their specific characteristics. Below are some of the most useful characteristics and requirements for good lubricants:

  • Viscosity
  • Flash Point and Fire Point
  • Cloud Point and Pour Point
  • Aniline Point
  • Corrosion Stability

What is Viscosity?

The property of liquids that prevents them from flowing freely (this resistance to flow is known as viscosity).

The pose is the unit of viscosity. A lubricating oil’s operating characteristics are mainly determined by this property, which is the most important. Oil films cannot form between moving surfaces if their viscosities are too low.

In contrast, excessive friction occurs when the viscosity of the oil is too high. A higher operating temperature result in thinner lubricating oil because the viscosity of liquids decreases as the temperature rises.

Good lubricating oils should be able to maintain their viscosity under varying temperatures without much change in viscosity. Viscosity Index (V.I.) measures the change in viscosity of lubricating oil with temperature.

A low viscosity index means that lubricating oil’s viscosity decreases as the temperature rises. Conversely, lubricating oil’s viscosity index is high if its viscosity is only slightly affected by temperature changes.

Related Guide: Mechanisms of Lubrication (2022)? [Explained]

What are Flash Point and Fire Point?

A flash point is the lowest temperature at which lubricant oil emits enough vapors for a tiny flame to ignite them for a moment.

If a tiny flame is brought near the lubricant oil vapors, they will burn continuously for at least five seconds.

There is usually a 5°C to 40°C difference between the fire points and flash points. When oil is exposed to high temperatures, flash and fire points have little to do with oil’s lubricating properties.

In order to be effective, lubricants need flash points above their operating temperatures. During use of lubricant, prevents fire risk.

What is Cloud Point and Pour Point?

In lubricant oils, the cloud point occurs when they cool slowly to a point where they become cloudy or hazy in appearance.

When lubricant oil reaches its pour point, it stops flowing or pouring. Oils that are suitable for cold conditions are distinguished by their pour points and cloud points.

The lubricant oil used in machines working at low temperatures should have a low pour point to avoid jamming caused by solidification. Lubricant oils with waxes have been found to have higher pour points.

What is Aniline Point?

As for equal volumes of aniline and lubricant oil samples, the aniline point is the minimum equilibrium solution temperature. When lubricant oil is in contact with rubber sealing, packing, etc., it shows signs of possible degradation.

Synthetic rubber and natural rubber can be dissolved by aromatic hydrocarbons. Therefore, lubricant oil should have a low aromatic content. When the aniline point is higher, there is a greater proportion of paraffinic hydrocarbons, resulting in lower aromatic hydrocarbon content.

Lubricant oil samples and aniline are mixed mechanically in equal volumes in a test tube to determine the aniline point. A homogeneous solution is obtained by heating the mixture.

Afterward, the tube is cooled at a controlled rate. The aniline point can be recorded as the temperature when the two phases (lubricant oil and aniline) separate.

What is Corrosion Stability?

In order to determine the corrosion stability of the lubricant oil, corrosion tests are conducted. For a specified period of time at a specific temperature, polished copper strips are immersed in lubricant oil.

The strip is removed after the stipulated time and examined for corrosion. Having tarnished copper strips indicates that the lubricant oil contains chemicals that cause the copper strip to corrode.

Copper strips should not be affected by good lubricant oil. Certain inhibitors are added to lubricant oils to retard corrosion. P, As, Cr, Bi, and Pb are common organic compounds used as inhibitors.

What are the Characteristics and Requirements for Good Lubricants?

Essential characteristics and requirements for good lubricants are as follows:

  • The viscosity index should be high.
  • The flash point and fire point of the machine should be higher than the operating temperature.
  • High oiliness is desirable.
  • It is always advisable to use lubricants that have cloud and pour points that are below the operating temperature of the machine.
  • Oils that are low in volatility should be used for lubrication.
  • A minimum amount of carbon should be deposited during use.
  • The aniline point should be higher.
  • Corrosion and oxidation resistance should be higher.
  • Detergent quality should be good.

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