Good equipment lubrication is an effective way to reduce equipment wear, improve equipment efficiency Scope Of Application and save materials and energy. The lubrication of the bearing is to enable the bearing to operate normally,
avoid the direct contact between the raceway and the surface of the rolling element, reduce the friction and wear inside the bearing, prolong the service life of the bearing, enhance the performance of the bearing, and prevent rust and corrosion caused by foreign matters invading into the bearing.
This paper introduces the function of bearing lubrication, common lubrication methods, advantages and disadvantages and comparison of application scope. Only by doing a reasonable and correct lubrication can we give full play to the performance of bearing and prolong its service life.
1、 About bearing lubrication
1. Role of lubrication
a. Bearing lubricating oil film
b. Circulating oil can dissipate heat
c. Sealed to prevent the invasion of external pollutants
d. Damping effect, reduce bearing rotation noise
e. Rust prevention
2. Oil lubrication
Oil lubrication is suitable for high- Scope Of Application speed working conditions, with high requirements for seal design and maintenance
2、 7 ways of bearing lubrication
1. Drip lubrication of oil cup
Drip lubrication of oil cup is a Scope Of Application lubrication method of dropping oil to the bearing through the oil saving port in the oil cup.
Advantages: simple structure, convenient use and fuel saving. Moreover, the oil supply can be adjusted by the oil saving port. Scope Of Application Generally, the oil drop should be one drop every 3 ~ 8 seconds, because too much oil will increase the bearing temperature rise.
Disadvantages: there are certain requirements for the viscosity of lubricating oil. Lubricating oil with Scope Of Application high viscosity cannot be used and has no heat dissipation function.
Application: oil cup drip lubrication is suitable for low speed, light load and low working temperature.
2. Oil bath (oil immersion) lubrication
It is a lubrication method that immerses the bearing part into the lubricating oil and brings the oil into other parts of the bearing after the Scope Of Application bearing runs. Oil bath lubrication is one of the most common and simple lubrication methods.
Considering the mixing loss and temperature rise during oil bath Scope Of Application lubrication, the height of the bearing part invading the lubricating oil shall be limited for the horizontal shaft.
Generally, the oil level shall be controlled near the center of the rolling element below the bearing. Oil bath (oil immersion) lubrication is sufficient, but the oil supply is not easy to adjust. If there is no filter device in the oil tank, it is easy to bring impurities into the bearing and damage the bearing.
Application: oil bath (oil immersion) lubrication is generally applicable to low-speed or medium speed Scope Of Application occasions, and it is widely used on low-speed bearings.
Experience: separable reinforcing ribs can be installed at the bottom of the bearing pedestal to reduce agitation Scope Of Application and / or heat dissipation. The static oil level shall be slightly lower than the center of the low rolling element of the bearing applied to the horizontal axis.
For the vertical axis, the static oil level shall cover 50% – 80% of the rolling Scope Of Application element. If the bearing temperature of the oil bath system is relatively high, it can be changed to drip, splash or circulating oil system.
It is a kind of lubrication method that splashes oil into the bearing through other running parts. The oil supply of splash lubrication is not easy to adjust, and the lubricating oil level cannot be too high, otherwise it is easy to produce mixing loss and temperature rise, and it is also easy to bring impurities in the oil tank into the bearing to damage the bearing.
In splash lubrication, the oil splashes onto the bearing through the rotating body (impeller or “oil throwing ring”) installed on the shaft, and the bearing is not immersed in the oil.
Experience: in the gearbox, the gear and bearing often share the same oil tank with the gear as the oil slinger. Since the viscosity of the gear oil may be different from the bearing requirements, and the oil contains wear particles from the gear, a separable lubrication system or method can be used to improve the bearing life.
4. Circulating oil lubrication
The lubricating oil is sucked from the oil tank through the oil pump and transported to the parts of the bearing that need lubrication, and then returned to the oil tank from the oil return port for reuse after filtration. The oil supply system consists of oil pump, cooler, filter, oil tank, oil pipeline, etc.
The circulating oil is fully lubricated, the oil supply is easy to control, and the heat dissipation and impurity removal ability are strong. Circulating oil lubrication is an ideal lubrication method. However, an independent oil supply system is required, and the manufacturing cost is relatively high.
Circulating oil lubrication can be divided into injection lubrication, forced lubrication and spray lubrication. They are classified from different angles.
Application: circulating oil lubrication is applicable to occasions for the purpose of heat dissipation or impurity removal, as well as occasions with high speed, high temperature and heavy load, with high reliability.
5. Oil mist lubrication
The lubricating oil is mixed with a small amount of lubricating oil by compressed air in the oil mist generator to form oil mist, which is then transmitted to the lubricating part of the bearing. The oil mist lubrication has the advantages of small stirring loss and temperature rise, oil saving,
less impurities in the oil, and the air flow generated during oil mist injection has a certain cooling effect, which can also effectively prevent impurities from invading or discharging impurities. However, the cost of the lubricating device is high, and there are certain requirements for the viscosity of the used oil.
Generally, it should not be higher than 340 mm2 / s, otherwise the atomization effect will not be achieved. In addition, if the seal is not tight during lubrication, some oil mist may escape into the air and pollute the environment. If necessary, an oil-gas separator should be used to collect oil mist.
Application: oil mist lubrication is suitable for high-speed occasions.
6. Oil injection lubrication
It is a kind of lubrication method that uses high-pressure injection method to spray lubricating oil into the bearing to lubricate the bearing. When the bearing runs at high speed, the rolling element and cage also rotate at a fairly high speed, thus forming an air vortex around the bearing.
If the general lubrication method is adopted, the lubricating oil is not easy to reach the lubrication part. On the other hand, due to the centrifugal force generated by high speed, the lubricating oil is difficult to maintain in the lubricating part.
In order to ensure that sufficient but not excessive lubricating oil is supplied to the high-speed bearing, the lubricating oil must be forcibly sprayed from one end of the bearing for lubrication, and then re flows into the oil tank from the other end.
When designing the lubrication system, the position of the high-pressure nozzle shall be located between the inner ring and the center of the cage, and the lubricating oil shall be thrown out of the raceway through centrifugal action.
In order to effectively lubricate the bearing, the injection speed of lubricating oil shall not be less than 15m / s. In terms of running speed, oil injection lubrication is often used for bearings running at higher speed under low or medium load;
From the bearing force direction, oil injection lubrication is often used for bearings on vertical or inclined shafts, and the lubricating oil is usually injected directly into the bearings.
7. Oil air lubrication
Oil air lubrication is usually suitable for occasions with high bearing running speed. The oil air lubrication system mixes a small amount of lubricating oil with a certain pressure of gas, and then supplies it to the bearing.
Applicable: this method is suitable for high-speed applications, such as machine tools, oil refining and chemical industries.