Choosing a sealing system is essential in order to ensure the correct and long-lasting operation of a bearing; it is therefore important to ensure that the bearing is always well-protected from any impurities and external agents, such as dust, water, corrosive fluids or even used lubricants.
This choice depends on the type of lubricant, the ambient conditions and therefore the type of contamination , the fluid pressure and the rotation speed. To give you a good place to start, the fluid pressure is a determining factor in the choice of sealing system. If the pressure is high in the range of bars for example a mechanical seal is ideal. Otherwise, the choice will be directly linked to the type of lubricant, grease or oil. For example, for grease lubrication the most commonly used solutions are: deflectors or washers, narrow passages that are machined or with grooves; in the case of oil lubrication the sealing system is often accompanied by the presence of a groove for oil recovery.
Conditions of use can also influence your choice, especially when it comes to assembling the bearing. The rigidity and precision that your use requires must also be taken into account. In some cases, you can provide for the application of a preload in the assembly of your bearing to increase its rigidity. Additionally, the preload will have a positive impact on the bearing life and noise level of your system. Be careful, in order to choose the preload radial or axial you must know the rigidity of all parts through software or experimentation.
In your selection criteria, you must also consider the ideal material for your bearing. Bearings can be made out of metal, plastic or ceramic. The bearing material depends on its intended use. We recommend that you choose the most compression-resistant bearing. Keep in mind however that the material used affects the price of the bearing.
Ball bearings are often optimized for radial contact : this means that they will be very useful if the force you want to bring into contact with the bearing is perpendicular to its axis of rotation. However, double row ball bearings are optimized for angular contact. Additionally, if you want to use a ball bearing for an axial load, it should be noted that this device only supports moderate axial loads.
However, this flaw can be avoided by using a double-row ball bearing construction. As well as being low-cost, ball bearings are also the most compact, making them the most widely used type of bearing. Cylindrical roller bearings are able to support significant radial loads , or even very significant ones.
There are several types of cylindrical roller bearings. They vary according to the number of rows of rollers one, two or four and whether or not there is a cage. A cage allows the bearing to support significant radial loads and a high speed. The absence of a cage allows the bearing to have more rows of rollers and therefore to support even heavier radial loads. The only disadvantage is that cylindrical roller bearings without cages do not tolerate as high speeds as the ones with cages.
Cylindrical roller bearings are also very robust and have a long bearing life. Additionally, some bearings can also support an axial load, provided that they do not have a shoulder on the inner and outer rings. If this is the case, you will not be able to use your bearing to support an axial load. Tapered roller bearings can support radial, axial and combined loads both at the same time.
The loads can be very heavy, due to their high rigidity. If you are unsure between a ball bearing and a tapered roller bearing, be aware that a tapered roller bearing of equivalent dimensions can support heavier loads. We therefore recommend this type of bearing for uses such as machine spindles, vehicle transmissions from car to boat, helicopter , or the steering of car or truck wheels.
Like cylindrical roller bearings, needle bearings can come with or without a cage. Roller bearings are standardized like ball bearings, albeit to a lesser degree. Mounted Bearings are mechanical assemblies that consist of bearings housed within bolt-on or threaded mounting components and include pillow blocks, flanged units, etc.
They provide means of supporting rotating shafts and minimizing friction between shafts and stationary machine members. Mounted bearings are used primarily in machinery with exposed rotating shafting. They are used as take-up devices on the ends of conveyors and as flanged units along intermediate points. The bearings can be rolling element or journal bearing configurations.
Mounted bearings are designed for bolt-on mounting and ease of replacement. Other varieties of mounted bearings include rod end bearings and cam followers. Linear Bearings are mechanical assemblies that consist of ball or roller elements captured in housings and used to provide linear movement along shafts.
Linear bearings are used primarily in machinery that requires linear movement and positioning along shafts. They also may have. Slide bearings are mechanical assemblies designed to provide free motion in one dimension between structural elements. Slide bearings are used primarily in the structural support of bridges as well as commercial and industrial buildings. These parts accommodate thermal movement, allow for end-beam rotation, and isolate components of the structure against vibration, noise, and shock.
Other types of slide bearings include those used on truss base plates, heat exchangers, and process equipment. Jewel bearings are mechanical devices used in light rotating applications such as watches, meter movements, gyroscopes, etc. Jewel bearings are constructed from a range of synthetics, with ruby and sapphire being particularly common. Frictionless bearings are mechanical or electro-mechanical alternatives to conventional bearings that provide controllable shaft support through air, magnetic fields, etc.
Bearing applications span across virtually every industry which employs moving components and equipment. For example:. While bearings are used nearly everywhere, there are some industries that use so many or have specific requirements for durability, cleanliness, etc. Some of these industries are:. When selecting a bearing for a particular application, there are several considerations to keep in mind, including bearing friction, temperature, and lubrication.
Along with the specific design and construction of the bearing, these three interacting factors can affect the overall performance. Radial ball bearings are used primarily for radially loaded shafts and those with light axial loads. Angular contact ball bearings are designed to take higher axial loads in one direction in addition to their radial capacities.
Ball thrust bearings are available which are specifically intended to take axial loads alone. The most common configuration for radial ball bearings is the single row version, which could be shielded or sealed depending on whether it is to be used within a housed area—a transmission, say—or in an exposed environment such as on a bicycle wheel. The seals and shields keep lubricant in the bearing and dirt and debris out of it. Ball bearings are usually fitted with retainers which space the balls evenly between and around the perimeters of their outer and inner races.
Roller bearings employ a host of different shapes for their rolling elements, including straight rollers, needle rollers, tapered rollers, spherical rollers, etc. Roller bearings are able to take higher radial loads than their ball bearing counterparts due to the higher contact area between the rollers and the races. Some roller bearings are designed to take high thrust loads using tapered elements and races.
Mounted bearings are ball, roller, or sleeve bearings which are furnished in housings, flanges, etc. Common mounting styles include pillow blocks, flanges, take-ups, etc. They are often used on conveyors where take-up assemblies provide adjustment for conveyor belt tension. In selecting rolling element bearings, either ball or roller or as mounted units, designers usually consider a number of factors including loads, both their quantities and directions, the accuracy requirements of the shaft system, misalignment factors, speeds, noise, and friction.
Where radial loads are high, a designer may opt for a roller bearing over a ball bearing and might do the same where high axial loads are anticipated. Ball bearings are the most common type of rolling element bearing.
These bearings can handle both radial and thrust loads but are usually used where the load is relatively small. Because of its structure, there is not a lot of contact with the balls on the inner and outer races.
If the bearing is overloaded the balls would deform and ruin the bearing. Instead, they have cylinders allowing more contact between the races, spreading the load out over a larger area. However this type of bearing is not designed to handle much thrust loading.
Jewel bearings are plain bearings with a metal spindle that turns in a jewel-lined pivot hole. They carry loads by rolling the axle slightly off-center and are usually used in mechanical watches or clocks. This is due to their low and predictable friction that improves watch accuracy. Fluid bearings support their load using a thin layer of gas or liquid and can be classified into two types: fluid-dynamic bearings and hydrostatic bearings.
Fluid-dynamic bearings use rotation to form the liquid into a lubricating wedge against the inner surface. In hydrostatic bearings, the fluids — usually oil, water, or air — rely on an external pump.
Magnetic bearings support moving parts without physical contact, instead relying on magnetic fields to carry the loads. They require continuous power input to keep the load stable, thus requiring a back-up bearing in the case of power or control system failure.
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