Bearings for vibratory applications
For vibratory applications, SKF supplies spherical roller bearings with a cylindrical or tapered bore and surface-hardened stamped steel cages (series designations 223../VA405). These bearings have the same dimensions and performance characteristics as basic design bearings, but have C4 radial internal clearance as standard.
Bearings for vibratory applications are also available with a PTFE coated cylindrical bore (designation suffix VA406). These bearings are manufactured to VA405 specifications, with the exception of the bore. VA406 bearings are intended for the non-locating bearing position in vibratory applications with outer ring rotation. The PTFE coating prevents fretting corrosion between the shaft and the bearing bore. Therefore, shafts do not require special heat treatments or coatings.
PTFE coatings exposed to an open flame or temperatures above 300 °C (570 °F)
are a health and environmental hazard! They remain dangerous even after they have cooled.
Read and follow the safety precautions under Seal materials.
All bearings are equipped with an annular groove and three lubrication holes in the outer ring.
Depending on their size, SKF spherical roller bearings for vibratory applications are manufactured to one of following designs:
E/VA405 spherical roller bearings (fig. 1) have two surface-hardened stamped window-type steel cages, an inner ring without flanges and a guide ring centred on the inner ring or on the cages.
EJA/VA405 and CCJA/W33VA405 spherical roller bearings (fig. 2 and fig. 3) have two surface-hardened stamped window-type steel cages, an inner ring without flanges and a guide ring centred on the outer ring raceway.
Vibratory applications, such as vibrating screens or exciters, induce accelerations of rollers and cages in the bearings. This puts extra demands on the bearing design. SKF spherical roller bearings for vibratory applications can withstand considerably faster accelerations than corresponding standard bearings. The permissible acceleration depends on the lubricant and the mode of acceleration.
The bearing is subjected to a rotating outer ring load in combination with a rotating acceleration field, or an internally induced angular acceleration field due to rapid speed variations. These accelerations cause the unloaded rollers to generate cyclic loads on the cages.
The bearing is subjected to impact loads, which generate a linear acceleration in a constant radial direction, causing the unloaded rollers to “hammer” the cage pockets.
Typical examples for mode 1 are vibrating screens (fig. 4
), planetary gears and general arrangements subjected to rapid starts or rapid speed variations. A typical example for mode 2 is the acceleration generated when rail wheels roll over rail joints (fig. 5
). Road rollers, where the roller is vibrating against a relatively hard surface, are subjected to a combination of mode 1 and 2 acceleration.
Values for the permissible acceleration are listed in the product table and are valid for oil lubricated bearings. The values are expressed in multiples of g, where g is the acceleration of gravity (g = 9,81 m/s2).
System solutions for vibrating screens
In addition to single bearings for vibrating screens, SKF has developed fault detection and bearing systems that can improve performance, reduce maintenance and monitor machine condition in vibratory equipment. For additional information about the SKF Copperhead system solution for vibrating screens, contact the SKF application engineering service.