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Are you facing the challenge of choosing between a hydrodynamic bearing or a rolling bearing?
Hydrodynamic bearings contain no roller elements and rely on a sliding motion between the bearing and shaft.
Rolling bearings, on the other hand, have mechanical components like balls or cylinders and races, where the relative motion of the races causes the rolling elements to roll.
Find out which bearing technology best suits your needs in this blog article.
Specifically in hydrodynamic bearings, the lubricant forms a pressure film under the influence of relative motion between the bearing and the shaft. It separates the two surfaces and minimizes friction and wear. As a result, higher loads and speeds can be achieved.
Find out more about hydrodynamic bearings on our axial and radial bearings product pages.
In contrast to hydrodynamic bearings, rolling bearings support the entire load with rolling elements. As the shaft rotates, balls or rollers move between an outer and an inner ring. This rolling motion is a combination of rolling and sliding. The service life of the rolling elements is limited by material fatigue.
To select the right bearing for your application, it is important to understand its specific requirements. The following factors are key considerations for making a good decision:
| Hydrodynamic Bearings | Rolling Bearings | |
| Load Capacity | Hydrodynamic bearings have a larger contact area compared to roller bearings, which leads to an even load distribution and helps them to withstand higher loads. The lubricating film in hydrodynamic bearings ensures effective separation between the bearing and shaft. This makes them particularly suitable not only for high loads, but also for high speeds. | In roling bearings, the load is distributed across fewer contact points. They are suitable for medium to high loads but can be overstrained and fail prematurely under extreme loads. |
| Noise Generation and Friction | As there is a lubricating film between the bearing and the shaft instead of moving parts, there is no metallic contact, which means that these bearings operate almost silently. The lubricating film also minimises friction in hydrodynamic operation. Friction losses can be kept to a minimum by matching the lubricating oil (viscosity behaviour), speed range and bearing selection accordingly. | The direct, concentrated metallic contact in rolling bearings has lower noise-damping properties compared to hydrodynamic plain bearings. Due to the rolling contact, friction is usually low at operating conditions near standstill, approaching zero as speed decreases. However, as speed increases, additional effects such as cage friction can occur due to the more complex design, significantly increasing friction and potentially exceeding the sliding friction of bearings. |
| Space Requirements | If space is limited or there are strict weight requirements in your application, a hydrodynamic bearing is the perfect solution. With wall thicknesses of just a few millimeters, these hydrodynamic bearings require less space than roller bearings. This leads to weight savings that streamline the overall system, increase power density, and reduce material costs. | In most applications, the rolling bearing itself determines the available space for the entire system. Therefore, the selection of the appropriate bearing significantly influences the dimensions of the available space. |
| Vibration Behavior | In these hydrodynamic bearings, the lubricant film dampens vibrations, resulting in good vibration behavior. Thus, hydrodynamic bearings are ideal for applications with dynamic loading. | In contrast, rolling bearings transmit vibrations directly. These vibrations must be dampened to avoid noise. |
| Maintenance and Service Life | In hydrodynamic operation, there is no direct contact between the bearing surface and the shaft. By using a suitable lubricant and adhering to the application limits adapted to the system and the hydrodynamic bearing, the bearings operate wear-free. To ensure their optimum performance over the long term, it is only necessary to regularly check the lubricant for contamination and quality. Apart from this, hydrodynamic bearings are extremely low-maintenance. | In contrast to hydrodynamic bearings, the service life of rolling bearings can be precisely calculated under normal operating conditions. Material fatigue limits their lifespan. When considering the total cost over the entire service life, the decision for plain bearings often proves to be more advantageous, as they tend to be more durable. |
Replacing traditional rolling bearings with hydrodynamic bearings can provide both technological and competitive advantages in many applications. With these bearings, you can save weight and space while also handling greater loads. Reduced maintenance requirements and effective vibration damping make bearings a more attractive option. For example, engineers have already replaced roller bearings in pumps, compressors, and transmissions with these bearings.
In the following application areas, Miba’s hydrodynamic bearings have already proven themselves over rolling bearings:
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Not sure whether hydrodynamic bearings are suitable for your system? Find out in just a few clicks with our bearing calculator.
