Hydrodynamic Bearing: What advantages do they have over roller bearings and how does the transition work?

Why do hydrodynamic bearings offer advantages over roller bearings?

Rolling bearings are the first choice in many machine designs. They are inexpensive, standardized and widely used. However, their performance can quickly be limited, especially in harsh operating environments.

A detailed comparison of hydrodynamic bearings and roller bearings shows where conventional roller bearings are at a disadvantage and what specific potential advantages hydrodynamic bearings can offer over roller bearings.

Typical weak points of roller bearings:

• Limited load capacity under high loads
  Localized force transmission via rolling elements can lead to material fatigue and premature wear under high loads.

• Large space requirements
  In most applications, the rolling bearing itself determines the available installation space for the entire system. The selection of a suitable bearing therefore has a significant influence on the dimensions of the installation space.

• Limited speed 

    At very high speeds, friction and heat generation can become a problem due to rolling elements and cages. Their maximum speeds are limited by their design.

• Sensitive to dirt
  In open or unprotected systems, the failure rate increases dramatically if environmental influences cannot be completely shielded. 

• Limited service life under dynamic loads & vibration
  The limitations of conventional roller bearings quickly become apparent, especially in applications with shock-like or alternating loads.

A practical example: Compressors and gearboxes are often subject to high loads and temperatures. These are ideal conditions for the use of robust hydrodynamic bearing solutions. In this article, we show how these can be successfully integrated: Successful use of hydrodynamic bearings in compressors

Higher load capacity with the same installation space

Hydrodynamic bearing have the advantage over roller bearings in that they transfer loads over a large area. Roller bearings, on the other hand, transmit loads at discrete points via balls or rollers. This means that hydrodynamic bearing can absorb significantly higher forces in the same installation space. This is a decisive advantage, especially for highly loaded bearing points.

Better heat dissipation and temperature resistance

Direct contact between the bearing and the housing allows hydrodynamic bearings to dissipate heat more efficiently.  Depending on the application, special bearing materials from Miba can also be used to improve heat dissipation.

Resistance to dirt, moisture and vibration

Compared to roller bearings, hydrodynamic bearings are significantly more robust against external influences such as particles, moisture or vibrations. In harsh environments, this is a decisive advantage that contributes to operational reliability.

High degree of design freedom and variety of materials

While roller bearings are standardized, hydrodynamic bearings can be individually adapted to the requirements of the respective application in terms of shape, material and design. This enables both more compact assemblies and additional functional benefits, for example through integrated damping elements.

How the transition works, step by step

Switching from a rolling bearing to a hydrodynamic bearing does not necessarily mean a complete redesign. In most cases, only minimal adjustments are required in terms of design.

Hydrodynamic bearings can often use the necessary oil that is already available in the immediate surroundings. Initial trials or qualification of the technology can therefore usually be carried out in the existing system with minimal adjustments.

Those who want to take advantage of the benefits of hydrodynamic bearings over roller bearings can significantly increase the service life and reliability of their application through a systematic switch. At Miba, we support our customers in this process as experienced engineering partners.

Hydrodynamic bearings in wind power: a successful model with a signal effect

A particularly impressive example of the successful switch to hydrodynamic bearing can be found in wind energy in main gearboxes of wind turbines, especially in planetary stages of higher power classes.

With minimal adjustments, initial tests and qualification of the technology were carried out in existing systems. This demonstrated that the limits of planetary gearboxes could be pushed with little effort and that the advantages of hydrodynamic bearings over roller bearings could be exploited:

• More compact designs
• Higher power densities
• Significantly reduced system complexity
• Increased service life
• Higher input torques

These findings were taken into account during the design phase of the next evolutionary stage of planetary gearboxes and the advantages of hydrodynamic bearings were fully exploited.

This experience from the wind power industry can be transferred as a blueprint to many other industries.