The limiting speed of a thin-walled bearing is the highest speed that the bearing can reach when it is running. It mainly depends on the relationship between the heat generated by friction and the heat dissipated when the bearing is running. It is closely related to factors such as bearing material, structural size, clearance, load, cage material and structure and guidance method, lubrication method, lubricant amount, bearing cooling status and other factors.
Generally speaking, bearing samples give the limit speed of a single set of bearings under grease lubrication and oil lubrication. The applicable conditions for thin-walled bearings are: open bearings with standard structure, ordinary level accuracy, and basic set clearance; sufficient lubrication conditions; equivalent dynamic load is less than the rated dynamic load of the bearing. 10% of load; 20℃ At ambient temperature, the temperature rise of the bearing is 50℃; radial bearings only bear radial load, and thrust bearings only bear axial load.
If the actual operating conditions of thin-walled bearings are different from the above applicable conditions, the actual higher operating speed will be lower than the reference limit speed value given in the sample. The limit speed of double or triple bearings can generally reach 60%-80% of a single set of bearings.
Improving the accuracy of thin-walled bearings and appropriately increasing bearing clearance can increase the bearing's limit speed to a certain extent, but the specific increase is difficult to quantify; using lightweight materials to make cages or designing cages with special structures, and using more effective lubrication methods can greatly increase the bearing's limit speed, which can reach 3 to 4 times the limit speed given in the sample.
What measures should be taken when the temperature of thin-walled bearings is high?
When using thin bearings, if the temperature is found to be high, the problem must be solved from the following aspects:
The bearing box should be refueled regularly according to the requirements of the work. Thin-walled bearings sometimes experience high temperatures after refueling, mainly due to excessive refueling. At this time, the phenomenon is that the temperature continues to rise. After reaching a certain point (generally around 10℃~15℃ higher than the normal operating temperature), it will remain unchanged and then gradually decrease.
An unsuitable lubricating grease makes it difficult to form a uniform lubricating film, so a suitable grease should be selected. Unsuitable grease cannot reduce internal friction and wear in thin-section bearings, leading to inadequate lubrication and higher bearing temperatures. Mixing different types of grease may cause chemical reactions that degrade and harden the grease, reducing its lubricating effect. Grease contamination also increases temperature. Dust entering during grease application contaminates the grease, causing it to deteriorate inside the bearing housing, impairing bearing lubrication, and raising temperature.
Cooling is not possible
Check whether the pipeline is blocked and whether the inlet oil temperature and return water temperature exceed the limits. If the cooler is inappropriately selected and the cooling effect is poor and cannot meet the application requirements, the temperature of the thin-walled bearing will also be high. At this time, a new cooler should be replaced in time or installed side by side. The axial flow induced draft fan should also check the insulation and sealing performance of the core barrel.
Confirm that there are no above problems and then check the coupling
The alignment of the coupling must comply with the process specifications. When aligning the axial flow induced draft fan, hydraulic coupler, etc., the thermal expansion of the equipment during operation should also be considered. The impeller side of the induced draft fan expands due to heat, and the thin-walled bearing box rises; when the temperature of the hydraulic coupling increases during operation, the bearing box expands and the bearing rises. Therefore, the timing of the motor should be higher, and the size of the reserve should be determined according to the characteristics of the equipment and the temperature parameters during operation.
Thin-walled bearings are mainly used to bear radial loads, but when the bearing radial clearance is increased, they have certain angular contact bearing performance and can bear combined radial and axial loads. When the rotational speed is high and thrust bearings are not suitable, they can also be used to bear pure axial loads. Compared with other types of bearings of the same size, this type of bearing has a small friction coefficient and a high limit speed. But it is not impact resistant and not suitable for bearing heavy loads.
In order to obtain low friction torque, high rigidity and good rotation accuracy of the bearing, steel balls with small outer diameter are used. The use of hollow shafts ensures lightweight and wiring space. Thin-wall bearings achieve extremely thin bearing cross-sections and also achieve product miniaturization and lightweight. The variety of products expands their range of uses. In any bearing series, the cross-section is constant and the bore diameter can vary. Typical cross-sections are twice the ball diameter, and nominal dimensions are often inches.
What are the advantages of thin-walled bearings over ordinary bearings?
The accuracy level that 1 and thin-walled bearings can achieve is much higher than that of ordinary slewable bearings, and the radial runout and axial runout that can be achieved are much higher than that of ordinary slewable bearings.
2, thin-walled bearings are much more rigid than ordinary slew bearings, and their running noise is smaller than crossed roller bearings. Therefore, in a low-noise working environment, it is better to choose crossed roller slew bearings.
3. In terms of structure, the structure of thin-walled bearings is relatively simple. Through a row of cylindrical rolling elements arranged crosswise on a single raceway, considerable bearing directional and radial bearing capacity and overturning moment can be obtained. However, ordinary slew bearings must have three rows of cylindrical rolling elements arranged sequentially on three rows of raceways to achieve the same effect.
In comparison, thin-wall bearings take up much less space and are lighter than ordinary three-row roller slew bearings. And because the structure of thin-walled bearings is much simpler than that of traditional bearings, considerable axial and radial bearing capacity and overturning moment can be obtained through multiple rows of cylindrical rolling elements. The structure is relatively simple, while traditional bearings must be arranged in sequence through multiple sets of bearings to achieve the same effect. This brings great convenience in design, assembly and installation.
And because the single-row raceway structure takes up much less equipment space than traditional bearings, the assembly difficulty is also greatly reduced.
(Source: Lambo Precision Bearing)