The so-called gas lubricated bearing refers to the interactive bearing lubricated by gas lubricant. Our common gas lubricant is air. In use, the mechanism of bearing gas film formed by gas lubricated bearing is the same as that of liquid lubricated bearing. Therefore, glubricated bearings have the following advantages and disadvantages.
Advantages of gas lubricated bearings,Advantages and Disadvantages of Gas lubrication Bearing
The rotating speed of small helium turbine expander has reached 650000 R / min, the linear speed is 238m / s, and it has reached 455x106mm · R / min according to DN value.Advantages and Disadvantages of Gas lubrication Bearing
The gas film has the function of error homogenization, its accuracy is two orders of magnitude higher than that of rolling bearing, and has small vibration and low noise.
Low friction loss
The gas viscosity is only one thousandth of the viscosity of lubricating oil, so the friction torque caused by friction in the gas film is three orders of magnitude lower than that of the oil film.Advantages and Disadvantages of Gas lubrication Bearing
It is applicable to a wide temperature range and can resist atomic radiation
The high temperature resistance can reach 300-500 ℃, and the gas bearing can still work when the temperature is as low as 10K.Advantages and Disadvantages of Gas lubrication Bearing
The lubricating gas is generally air or inert gas, which will not cause pollution when discharged into the atmosphere. The bearing has small vibration, low noise and no pollution to the environment.Advantages and Disadvantages of Gas lubrication Bearing
Aerostatic bearing has no direct metal contact and its theoretical life is infinite. Considering other conditions, it should be more than 104H.
There is friction between metals at the moment of start and stop of dynamic pressure gas bearing, and the service life is affected to a certain extent, but it is also more than 3000h.Advantages and Disadvantages of Gas lubrication Bearing
Disadvantages of gas lubricated bearings
.Low bearing capacity
Compared with similar oil lubricated bearings, the bearing capacity of gas lubricated bearings is about 1 ~ 2 orders of magnitude lower. According to the bearing capacity per unit area, oil lubricated bearings are generally (0.5 ~ 2) MPa, while gas lubricated bearings are only (0.02 ~ 0.04) MPa.
On the one hand, gas lubricated bearings are easy to lose stability, resulting in common air hammer vibration and whirl instability. On the other hand, the phenomenon of gas lubricated bearing jamming, shaft holding or seizing also occurs from time to time.
High precision, high cost
Because the gas film is very thin, generally between a few microns and tens of microns, it requires high manufacturing accuracy and improves the cost. In addition, there are special process requirements for processing spiral grooves, throttling holes and porous materials, which increases the manufacturing difficulty and cost.Advantages and Disadvantages of Gas lubrication Bearing
Demanding working conditions
Gas lubricated bearings need a clean working environment and strictly abide by the operating procedures to ensure the normal operation of the bearings without accidents. Therefore, its wide application and commercialization are limited to a certain extent.
The sealing of bearing is divided into self sealing and external sealing. The external seal mainly adopts the combination of labyrinth and contact design. The more stages of the labyrinth (not lower than the two poles), the smaller the gap, and the better the sealing effect.
The clearance of labyrinth is 0.6 ~ 1.5mm on one side of radial direction according to the size of bearing; Axial 4 ~ 6mm.Advantages and Disadvantages of Gas lubrication Bearing
Contact skeleton oil seal: it is widely used in rolling mill. In order to increase the effect, two or three oil seals can be used in parallel. The oil seal is directional and cannot be installed reversely.
The hot rolling mill is generally equipped with two oil seals, and the lips of the two oil seals shall face outside the bearing seat to prevent the immersion of external dirt. Advantages and Disadvantages of Gas lubrication Bearing
The cold strip mill is generally equipped with three oil seals, and the lip of one oil seal close to the bearing shall be inward to prevent the overflow of lubricating grease and affect the quality of rolled products.
Be careful when using the oil seal to avoid damaging the lip when installing the roll and affecting the sealing effect.Advantages and Disadvantages of Gas lubrication Bearing
RBR seal ring: This is a special rubber lip seal ring for rolling mill bearing, which has been widely used in recent years. Advantages and Disadvantages of Gas lubrication Bearing
The RBR sealing ring adopts the axial sealing method, and its lip is attached to the base surface of the gland, which is not affected by the roll runout. Advantages and Disadvantages of Gas lubrication Bearing
The old grease inside the bearing can overflow, and the external cooling water, iron oxide scale and impurities are prevented from entering by the lip, which has a good sealing effect.
Moreover, it is easy to use. When changing the roll, the roll is installed into the bearing seat without any influence.Advantages and Disadvantages of Gas lubrication Bearing