SKF engineers have made significant improvements to two common bearing designs, resulting in a new bearing family with broad industrial applications. They can offer energy savings of one third compared with standard bearings. With growing concern for the environment and a desire to adopt greener technologies, these new products represent a significant step towards reducing energy use and saving resources.
After intense development efforts, SKF has launched a new family of bearings that can deliver significantly lower energy consumption.
SKF’s new Energy Efficient Bearings family includes the two most commonly used bearing types: the deep groove ball bearing and tapered roller bearing.
Both new bearing designs offer energy savings of almost a third for most applications. SKF engineers wanted to make sure that any energy saving could be achieved without compromise to load-carrying capacity and service life expected for standard bearings.
The new tapered roller bearings developed by SKF consume 30% less energy than standard products in an example case of a wind turbine gearbox. (See graphs below.) The first products related to this bearing type target industrial segments where applications consume more high power such as wind turbines, heavy-duty industrial gearboxes and railway applications as well as gear units used for material handling equipment, extruders and ships. These industrial segments typically have to transmit heavy loads and frequently use bearings with outside diameters of between 200 and 600 mm (7 7/8 to 23 5/8 inches). As a general rule, the larger the diameter, the greater the potential energy saving – up to 50% in the best possible case.
Improvements to the design of tapered roller bearings included modification of the flange geometry, reducing the recess and extending the inner ring raceway. Special raceway profiles and roller topographies were created and the surface roughness of the raceway and flange of the rings was reduced. Another design feature was a special cage with reduced bore diameter – made of PEEK (polyetheretherketone), or, for special demands, of sheet steel.
PEEK is an outstanding cage material because it offers excellent forming characteristics as well as stability of form and dimension. It has particularly good thermal stability over a very wide temperature range, being capable of performing from minus degrees Celsius up to a permanent operating temperature of 160°C and peak temperatures up to 200°C (320° to 392°F).
A further contribution to energy savings was achieved by reducing the number of tapered rollers. In the case of the 32230 tapered roller bearing type, reducing the number of rollers and replacing a steel cage by a PEEK cage, means decreasing the rotating mass by approximately 10%, and this has a positive effect on the required drive energies. This adds up to a lighter bearing that is inherently more energy efficient because it takes less power to move the rolling elements. As the moving parts have a lower inertia, the chance of skidding and smearing is reduced therefore avoiding problems that might affect performance and service life.
The new tapered roller bearings have been designed to dimensions according to ISO standards and they can be easily incorporated into existing solutions. Potentially substituting a conventional bearing for the new version could add up to huge energy savings in every industrial sector, from pulp and paper, metals and mining to hydrocarbon processing, food, textiles, and wastewater.
Energy efficient deep groove ball bearing
The single row deep groove ball bearing is the most widely used bearing type. Deep groove ball bearings can accommodate radial and axial loads under various speed conditions.
For the new deep groove ball bearing designs, the focus has been on developing products that would suit light- and medium-load applications such as industrial electrical motors that drive machines such as pumps, compressors, fans and conveyors in a broad range of applications. Here the products initially launched target-shielded deep groove ball bearings with an outside diameter ranging from 52 to 130 mm (about 2 to 5 1/8 inches).
To achieve minimum 30% energy savings for deep groove ball bearings, SKF engineers made improvements to three aspects of the design: the internal geometry, cage and grease. The bearing internal geometry has been optimized, a novel polymer cage has been developed and a low-friction grease has been introduced. These improvements have enabled friction losses to be cut by minimum 30% and result in improved service life. Only the combination of these three design parameters, deeply optimized for the application conditions, make it possible to achieve such performance.
The benefit for end users include lower energy consumption and lower total cost of ownership with extended bearing service life. In addition, the new design facilitates the construction of machinery of higher efficiency.
For the industrial motor manufacturer, the use of energy efficient deep groove ball bearings will help the manufacturer to build motors of higher efficiency. Efficiency regulations in the US and EU are going to be more strict in the coming years, and the use of energy efficient bearings will contribute to meet these new requirements.
For the end user (motor user), the direct benefit is of course the lower energy consumption, and thus a lower total cost of ownership. Over a period of 10-15 years, depending on the motor size, the total cost of ownership is expected to make up 95 to 99% of the energy bill (the remaining percentage being purchasing and maintenance cost). In addition, the developments of energy efficient deep groove ball bearings demonstrate that a longer service life can be achieved by a better usage of the lubricant and by a lower operating temperature. This makes the energy efficient deep groove ball bearings even more attractive, because it leads to longer machine life.
For more information about SKF’s new energy saving bearings – or any of their other wide range of bearings, ask your IBT sales rep or write to us.