news

There are 6 factors to consider when selecting bearings for refrigeration equipment

 

All kinds of rolling bearings have different characteristics and are suitable for different use cases of various machinery. Under normal circumstances, thrust bearings and angular contact bearings are selected when bearing thrust loads;

 

Ball bearings are typically used for high-speed applications, and roller bearings are used for heavy radial loads.

 

1. The space and position of the machinery occupied by the bearing

 

In mechanical design, the size of the shaft is generally determined first, and then the rolling bearing is selected according to the size of the shaft. Ball bearings are usually used for small shafts and roller bearings for large shafts. However, when the bearing is limited in the diameter direction of the machine, needle roller bearings, ball or roller bearings of the extra light and ultra-light series are selected; When the axial position of the bearing in the machine is restricted, narrow or extra-narrow series of ball or roller bearings are available.

 

2. The magnitude, direction and nature of the load on the bearing

 

Load is the most important factor in the selection of bearings. Roller bearings are used to withstand heavier loads, ball bearings are used to withstand light or moderate loads, and bearings made of carburized steel or bainite quenched are designed to withstand shock and vibration loads.

 

In terms of the direction of action of the load, when bearing pure radial loads, deep groove ball bearings, cylindrical roller bearings or needle roller bearings can be selected. When bearing small pure axial loads, thrust ball bearings can be selected; Thrust roller bearings are available for large pure axial loads. When the bearing is subjected to a combined radial and axial load, angular contact ball bearings or tapered roller bearings are generally used.

 

3. The self-aligning performance of the bearing

 

When the centerline of the shaft is different from the centerline of the bearing housing, there is an angular error, or because the spacing between the two supports of the shaft is large and the rigidity of the shaft is small, it is easy to bend or tilt under force, the self-aligning ball or self-aligning roller bearing with good self-aligning performance and the outer ball bearing can be selected. These bearings remain in normal operation when the shaft is slightly tilted or bent.

 

The quality of the bearing self-alignment performance is related to the different axiality it allows, and the larger the value of different axiality, the better the self-alignment performance.

 

4. Rigidity of the bearing

 

The rigidity of a bearing refers to the amount of force required for the bearing to produce a unit deformation. The elastic deformation of rolling bearings is very small, and it is not necessary to consider it in most machinery, but in some machinery, such as machine tool spindles, bearing rigidity is an important factor, and cylindrical and tapered roller bearings should generally be selected. Because these two types of bearings are in point contact with the raceway when they are under load, the rigidity is poor.

 

In addition, all kinds of bearings can also be preloaded to achieve the purpose of increasing the rigidity of the support. For example, angular contact ball bearings and tapered roller bearings, in order to prevent the vibration of the shaft and increase the rigidity of the support, a certain axial force is often applied in advance during installation to make them compress each other. It is important to note here that the amount of preload should not be too large. When it is too large, the friction of the bearing will increase, the temperature rise will increase, and the service life of the bearing will be affected.

 

5. The rotational speed of the bearing

 

Each bearing model has its own limit speed, which is determined by physical characteristics such as size, type and structure, the limit speed refers to the maximum working speed of the bearing (usually r/min), exceeding this limit will cause the bearing temperature to rise, the lubricant to dry up, and even make the bearing stuck. The speed range required for the application helps to determine what type of bearing to use. Most bearing manufacturers provide the ultimate speed value of their products in their product catalogs, and practice has proved that it is better to work in a state below 90% of the limit speed.

 

Generally speaking, in the working occasion of higher speed, it is advisable to choose deep groove ball bearings, angular contact bearings, and cylindrical roller bearings; At lower speeds, tapered roller bearings are optional. The ultimate speed of tapered roller bearings is generally about 65% of that of deep groove ball bearings, 70% of cylindrical roller bearings, and 60% of angular contact ball bearings. Thrust ball bearings have a low limit speed and can only be used at lower speeds.

 

6. It is convenient for the installation and disassembly of bearings

 

When selecting the type of bearing, it is also necessary to consider whether the bearing is convenient to install and disassemble, especially for the installation and disassembly of large and extra-large bearings. The general angular contact ball bearings, tapered roller bearings, cylindrical roller bearings and needle roller bearings with separable outer rings are easy to install and disassemble, and their inner and outer rings can be installed on the shaft or in the housing bore respectively. In addition, spherical roller bearings with tapered bore and adapter sleeve, double row cylindrical roller bearings and spherical ball bearings are easier to install and disassemble.