Sealed four-row tapered roller bearings
SKF supplies many sizes of four-row tapered roller bearings with integral radial shaft seals at both sides (fig 1). They are available in several designs depending on bearing size as well as on the open (non-sealed) basic design.
Whenever possible, sealed bearings should be used for rolling mills. Compared with open bearings they offer the following advantages
- longer service life
- reduced grease consumption (by up to 90%)
- extended maintenance intervals
- grease is retained within the bearing
- less surplus grease to contaminate the milling emulsion, to improve both the rolling process and product quality
- reduced environmental impact.
Sealed bearings can simply replace open bearings as part of a rebuild or refurbishment because the boundary dimensions are the same.
Sealed bearings are fitted with specially designed, C-shaped, radial shaft seals on both sides (fig 2). This enables the bearing to incorporate rollers that are equal to, or just slightly shorter than the rollers used in an open bearing. Consequently, the load carrying capacity of a sealed bearing is the same or very similar to an open bearing. The seals permit high sliding velocities and are intended for operating temperatures between –20 and +140 °C.
SKF Explorer four-row tapered roller bearings have sheet steel reinforced radial shaft seals made of hydrogenated acrylonitrilebutadiene rubber (HNBR) that are snapped into the groove in the outer ring.
Standard bearings contain sheet steel reinforced seals made of fluoro rubber (FPM) that must be staked into a groove in the outer ring. Fluoro rubber seals require special handling.
O-rings inserted in grooves in the outer ring outside surface prevent dirt or water from entering between the outer rings and the chock bore that otherwise would contaminate the lubricant.
Standard TQOSN design sealed bearings are supplied with window-type, stamped steel cages, without spacer rings (fig 3, fig 4, fig 5). However, spacer rings are available in the TQOS design (fig 6 + seals).
Larger size sealed bearings in the TQOSN.1 design are for applications that require extremely high load carrying capacity. These bearings have a special pin-type steel cage that uses pierced rollers (fig 7 + seals). Sealed four-row tapered roller bearings are also produced with extended inner rings which can serve as counterfaces for radial shaft seals. These bearings are supplied as standard without spacer rings in the TQOESN design (fig 8 + seals) or with spacer rings in the TQOES design.
Depending on the relubrication needs, sealed four row-tapered roller bearings can be supplied to three standard design variants
- Designation suffix VA901 (standard bearings) or E1 (SKF Explorer bearings) These sealed bearings (fig 9) can be relubricated via vertical slots in the outer rings. Bearings without spacer rings have a steel reinforced acrylonitrile-butadiene rubber seal between the two inner rings. Bearings with spacer rings have two O-rings that act as seals between the inner rings, similar to those shown in fig 10. The O-rings have a permissible operating temperature range from –40 to +100 °C
- Designation suffix VA902 (standard bearings) or E2 (SKF Explorer bearings). These sealed bearings (fig 11) have no lubrication slots and cannot be relubricated. Otherwise they have the same features as bearings with designation suffix VA901 or E1.
- Designation suffix VA903 (standard bearings) or E3 (SKF Explorer bearings) These sealed bearings (fig 12) have vertical lubrication slots in the outer rings. They do not have a seal between the inner rings.