SKF has launched an improved and expanded range of Explorer single row angular contact ball bearings for use in applications such as compressors and screw pumps, including industrial vacuum screw pumps. These bearings can help increase power density and improve machine performance and efficiency by enabling operation at higher speeds and with lower friction while providing cost competitiveness as well as global availability and support.
Compressed air is often referred to as the “fourth utility”. The reliability and efficient performance of compressor systems are essential for most manufacturing facilities. A common type of compressor in industrial plants is the twin-screw compressor. In addition to compressed air, an increasing number of modern production processes require atmospheres with varying degrees of vacuum. Vacuum pumps, generally very similar to air compressors, are common in many industries, including the food and beverage and packaging industries, the optical, electronics, and semiconductor industries, and the chemical, pharmaceutical, and glass industries, where they are used in industrial coating processes. such as PVD (physical vapor deposition) and CVD (chemical vapor deposition). Vacuum pumps are even found in large-scale scientific experiments,
Screw vacuum pumps, like twin screw compressors, work with two geared screw shafts that rotate in opposite directions. This gas is trapped between the screws and transported to the discharge side, while on the inlet side the gas is removed and the pressure is reduced to the expected vacuum level. The bearings that support screw rotors are critical components: they support loads created by gas pressure and provide precise radial and axial positioning of the shaft, which is a key criterion for the efficiency of screw machines.
In the future, the compressor and pump markets expect higher speeds, compact designs, even more precise axial shaft positioning and robust performance from so-called original bearings. Support bearings, which support reverse loads and control the axial clearance of the bearing arrangement and therefore the clearance between the shafts and housing, can suffer from a combination of high speed and low loads. For screw vacuum pumps, speed, efficiency (through tight sealing gaps) and low heat generation are key.
Improved design
SKF is already responding to these new needs. It has introduced numerous improvements to bearing design and developed a completely new range to ensure that the SKF Explorer single row angular contact bearing can meet current and future performance needs. The first innovation was a new cage with significantly improved geometry and a new brass material, which allows faster operation with reduced friction.
Additionally, SKF has added a 25° contact angle variant to the standard range of angular contact ball bearings. Both bearing designs include the new improved cage design. Compared to the 40° contact angle variant, the smaller 25° contact angle allows the bearing to operate at higher speeds and at the same time offers better performance as a backup bearing under light loads. 25° bearings also provide greater radial load capacity than 40° bearings, which can be used, for example, to downsize machines in specific cases. Offering a standard catalog design also ensures global availability with short delivery times.
Another important advantage of this 25° series is that these bearings are universally compatible with other 25° and 40° bearings, meaning they can be mounted in duplex or triplex arrangements without the need for a measuring operation.
Project example
A customer requested technical support to validate a proposed design for a new generation of screw vacuum pumps. SKF carried out a comprehensive analysis of the bearing system using the SimPro 3D simulation program. The simulation highlighted some performance risks if 40° angular contact ball bearings were used, such as lower calculated service life, high contact angle variations and higher friction losses. Note that at very high speeds the centrifugal forces acting on the spheres will become relevant; a smaller contact angle will provide better kinematics in such conditions.
The speeds of the analyzed vacuum pumps were higher than those of screw compressors of similar size, while the axial loads were slightly lower. Analysis showed that the best design choice was a duplex bearing arrangement incorporating new SKF Explorer bearings with a 25° contact angle and light backlash. The calculation results shown in the graphs below clearly demonstrate the differences in performance when it comes to calculated service life and reduced energy losses.
Benefit from the latest improvements
With the latest improvements to the SKF Explorer range of single row angular contact ball bearings, customers can enjoy a wide range of benefits, including the savings of having a standard range available from stock. In terms of performance, the 25° angular contact ball bearing range can operate at higher speeds and also perform better as support bearings under light loads. The increased radial load capacity can also be used to reduce the size of machines. The new and improved machined brass cage design helps ensure quieter operation and lower friction losses. Design options are highly flexible, with three clearance classes and three preload classes. Because 40° and 25° bearings are universally compatible, logistics, inventory management and machine assembly are very simple.
