Purpose and mode of bearings lubrication

For bearings, lubrication is an important issue that affects their performance. Whether the lubricant or lubrication method is suitable or not will greatly affect the life of bearings.

The function of lubrication is as follows:

1) lubricate all parts of the bearing to reduce the rotary friction between the raceway surface and the steel ball, the sliding friction between the steel ball and the retainer, and the sliding friction between the retainer and the raceway guide surface.

2) Take away the heat generated by internal friction inside the bearing and other heat transmitted from the outside to prevent the bearing from heating and the deterioration of lubricant.

3) Make the rolling contact surface of the bearing often form an appropriate oil film to relieve the concentrated stress of impact load and prolong the fatigue life of the bearing; 4) Prevent the corrosion of steel balls, grooves and retainers, the intrusion of garbage, foreign objects and moisture, and prevent the bearing from rust and dust.

Lubrication methods of bearings are mainly divided into grease lubrication and oil lubrication, and their general comparison is as follows:

Project fat oil

The sealing device is simple and complicated, so attention should be paid to maintenance.

Good lubrication, very good.

Low-medium speed can also be used for high speed.

Torque is relatively large and relatively small.

The replacement of lubricant is more troublesome and simple.

The life of lubricant is short and long.

The cooling effect is not good (circulation is needed)

It is difficult and easy to filter out impurities.

Lubricant leakage, oil leakage and less pollution are not suitable for places where oil leakage is not allowed.

Grease lubrication

Grease lubrication can be filled with grease for a long time, and its sealing device has a simple structure, so it is widely used.

Grease lubrication includes the sealing method of filling grease in sealed bearings in advance, and the filling grease supply method of filling proper amount of grease in the shell and supplementing or replacing it every once in a while.

In addition, for machinery with multiple bearings that need lubrication, centralized grease supply is also adopted by connecting pipes to each lubrication place.

1) Filling amount of grease

The filling amount of grease in the shell varies with the structure and volume of the shell, and it is generally appropriate to fill it to 1/3-1/2 of the volume.

When the filling amount is too much, the grease will deteriorate, age and soften due to heating during stirring, which should be paid attention to.

However, when used in low-speed bearings, it is sometimes filled to 2/3-1 of the volume to prevent foreign bodies from invading.

2) Supplement and replacement of lubricating grease

The replenishment and replacement of lubricating grease are closely related to the lubrication method. No matter which method is adopted, clean lubricating grease must be used, and attention should be paid to preventing the invasion of external foreign bodies.

Supplementary grease should be the same brand number of grease.

When replenishing grease, it is particularly important to ensure that new grease really enters the bearing.

oil lubrication

Oil lubrication is suitable for high-speed bearings and can withstand a certain degree of high temperature, but also effective in reducing vibration and noise, mostly used in occasions where grease lubrication is not applicable.

Oil lubrication can be roughly divided into:

(1) Oil bath lubrication (2) Drip lubrication (3) Splash lubrication

(4) Circulating lubrication (5) Jet lubrication (6) Oil mist lubrication

(7) Oil-gas lubrication

Standard lubricant

Grease is a semi-solid lubricant composed of base oil, tackifier and additive, so it is necessary to choose the grease suitable for the purpose according to their combination.

(1) Base oil

Mineral oil is generally used as the base oil of grease, but synthetic oil such as silicone oil is also used to improve heat resistance and low temperature fluidity.

(2) tackifier

There are various kinds of tackifiers, which are used to control mechanical stability, water resistance, temperature range and other characteristics.

(3) Additives

Add various additives according to the purpose of use.

Extreme pressure additives make the impact load and heavy load characteristics upward.

Oxidation additives prevent oxidation deterioration when there is no replenishment for a long time.

Anti-rust additives prevent the bearing and its surroundings from rusting.

(4) Viscosity

The degree of hardness of grease is the physical quantity (expressed by 0.1mm) that is poured into a metal cone with a specified weight within 5 seconds. The larger the value, the softer it is.

(5) Dropping point

After heating, the oil becomes a flowing state, and the temperature at which it drips from a specified hole is called the dropping point. The higher the value, the higher the use temperature.

(6) Mixing of heterogeneous oils and fats

When tackifier and additive are mixed, the properties of oil change, so in principle, it is best to avoid mixing different oils.

(7) Sealing amount of grease

(8) Life of grease

(9) Supplementary clearance of grease

Even if high-quality grease is used, due to the influence of long-term use and surrounding environment, the performance of grease is degraded and its lubrication performance is low, so it is necessary to supplement and replace grease in time. Generally, the operating temperature is about 50℃ once a year, and even if it exceeds 100℃, it is best to exchange it 2~3 times a year.

Unless otherwise specified, the standard lubricants are as follows: Grease brand Basic types of lubricating grease Working temperature application range

Chevron SRI-2 mineral grease -30~180 is resistant to high temperature and water.

Shell Alvania 2 mineral grease -35~120 has long service life and wide application.

Shell Doliun R stone grease -40~150 is corrosion-resistant and water-resistant.

Cooperate with Kyodo Yoshi SRL to synthesize fat -40~150 with low noise and low torque.

Mobil Mobil HP lithium chromium synthetic grease -30~110 is vibration-resistant and corrosion-resistant.

Dupont Krytox240AC fluorinated ester -35~290 has high temperature resistance and good characteristics.

Esso Exxon Beacon 325 synthetic grease -55~120 universal grease

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