Designs and variants
SKF manufactures four-row tapered roller bearings in the TQO and TQI designs in the following variants:
-
TQO design bearings (face-to-face arrangement, fig. 1):
- open or sealed
- with cylindrical or tapered bore
-
with or without inner ring extension on both sides
- with or without helical groove in the bore
-
basic design or SKF Explorer bearings
-
TQI design bearings (back-to-back arrangement, fig. 2):
- with cylindrical or tapered bore
-
with or without inner ring extension on one side
TQO design bearings have two pairs of tapered roller and cage assemblies. The two rows of rollers of each pair are arranged face-to-face. Because TQO is the most widely used four-row tapered roller bearing design, SKF manufactures this design in many variants, such as:
| Design variant | Characteristics |
TQON
 |
|
TQO
 |
|
TQON.1
 |
|
TQO.1
 |
|
TQOEN
 |
|
TQOE
 |
|
TQOT
 |
|
TQOSN
 |
|
TQOSNP
 |
|
TQOS
 |
|
TQOSN.1
 |
|
TQOESN
 |
|
TQOES
 |
|
TQI design bearings have two pairs of tapered roller and cage assemblies. The two rows of rollers of each pair are arranged back-to-back. These bearings provide relatively stiff bearing arrangements, which can also accommodate tilting moments. In those applications the bearings are generally mounted with an interference fit on the roll neck by applying a bearing design with a tapered bore.
TQI design bearings are also used for vertical rolls of universal mills. In this case a bearing with a cylindrical bore is required because the inner rings have a loose fit on their seat and the outer rings are mounted with an interference fit in the chocks.
Examples of TQO design variants:
| Design variant
| Characteristics |
TQIN
 |
|
TQI
 |
|
TQI.1
 |
|
TQIT
 |
|
-
provide, compared to open bearings, the following general advantages:
- extended bearing service life
-
improved reliability
-
reduced maintenance
- reduced lubricant consumption (by up to 90%)
- reduced environmental impact
-
less surplus grease to contaminate the milling emulsion, to improve both the rolling process and product quality
-
are the preferred solution for rolling mills
- are a simple replacement for open bearings because they have the same external dimensions and, depending on the seal design, even have the same load carrying capacity (→ SKF Explorer bearings)
-
have grooves with an O-ring in the bearing outside surface, which prevents any contaminants from entering between the outer rings and the chock bore
-
are fitted on both sides with one of the following seal designs:
-
standard FKM seal design (fig. 3)
-
standard HNBR seal design for SKF Explorer bearings (fig. 4)
-
upgraded HNBR seal design for SKF Explorer bearings (fig. 5)
-
standard FKM seal design (fig. 3)
-
are identified by the design suffix S
WARNING
Seals made of FKM (fluoro rubber) 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.
SKF manufactures SKF Explorer and optimized SKF Explorer four-row tapered roller bearings. The following features are valid for both:
-
Higher load carrying capacity and significantly extended bearing service life
The optimized internal geometry and tighter tolerances provide an optimal load distribution over all four rows of rollers.
Optimized surface finish of all contact surfaces supports the formation of a hydrodynamic lubricant film.
-
Improved wear resistance
Extremely clean and homogenous steel in combination with an advanced heat treatment result in bearing rings with an optimized balance between high surface hardness and core toughness.
-
Separable mounting and simpler inspection
These bearings are available as four-cup design bearings (four separate outer rings) with or without intermediate rings. Designs without intermediate rings facilitate mounting and dismounting as well as inspection routines. Both designs have identical dimensions and are also interchangeable. -
Improved sealing performance
-
Helical groove in the bore
SKF manufactures these bearings with a helical groove in the bearing bore as standard (→ Design considerations).
-
Total bearing interchangeability
Identical external and internal dimensions as well as equal load carrying capacity between open (designation suffix E8) and sealed (designation suffix E81) bearings make them interchangeable. -
Equally high load carrying capacity for sealed and open bearings
The optimized and compact seal design allows the same roller dimensions (fig. 6) between sealed and open bearings and, therefore, equal load carrying capacity
-
Improved sealing performance
The upgraded seal design (designation suffix E8(X)1, → Sealed bearings) ensures high protection against external contamination, keeps friction and frictional heat low and extends lubricant life. This seal design also provides a better retention of lubricant, minimizes environmental impact and reduces maintenance costs. -
Easy-to-assemble sealing kit
This allows open bearings (designation suffix E8) to be converted into sealed bearings at a later stage. -
No cage protrusion
Bearings with the designation suffixes E8 have no cage protrusion at their side faces.
Sealed four-row tapered roller bearings can be relubricated via the following relubrication features or a combination of them:
- lubrication holes in the outer ring and in the intermediate rings between the outer rings (fig. 7)
- lubrication grooves in the ring side faces:
-
lubrication groove and holes in the inner ring and gap between the inner rings (fig. 10)
-
lubrication holes in the inner ring shoulders next to the seals (fig. 11)
Sealed bearings with the designation suffix VA902 or E2 have no relubrication features (fig. 12).
SKF manufactures TQO and TQI designs in different variants with different features. Bearing related design variants and features are identified in the product tables (→ product tables TQI and TQO designs) under Design variant/feature. For sizes or design variant and feature combinations not listed in the product tables, contact SKF. Design variants and features are identified by the following characters:
Design variants
| E | Extended inner rings
|
| EN | E + N
|
| ESN | E + S + N
|
| N | Without intermediate rings
|
| N.1 | N + .1
|
| S | Sealed bearing
|
| SN | S + N
|
| SN.1 | S + N + .1
|
| .1 | Steel pin-type cages and pierced rollers
|
Features (fig. 13)
| G | Helical groove in the inner ring(s) bore (→ Design considerations) |
| GW | G + W |
| GWI | G + WI |
| GWISI | G + WI + SI |
| GWSI | G + W + SI |
| GWOY | G + WO + Y |
| LS | Lubrication holes in the inner ring shoulder, usually of bearings intended for vertical application with rotating outer rings |
| W | Lubrication grooves in the side faces of the bearing rings |
| WI | Lubrication grooves in the side faces of the inner ring(s) |
| WILS | WI + LS |
| WO | Lubrication grooves in the side faces of the outer ring(s) |
| SI | Seal fitted between the two inner rings |
| Y | Lubrication groove and holes in the inner ring and gap between the inner rings |
