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

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 variantCharacteristics
TQON


  • two double row inner rings
  • four single row outer rings
  • without intermediate rings
  • steel window-type cages
TQO


  • two double row inner rings
  • one double row and two single row outer rings
  • intermediate rings between the outer rings and between the inner rings
  • steel window-type cages
TQON.1


  • two double row inner rings
  • four single row outer rings
  • without intermediate rings
  • steel pin-type cages (pierced rollers)
TQO.1


  • two double row inner rings
  • one double row and two single row outer rings
  • intermediate rings between the outer rings and between the inner rings
  • steel pin-type cages (pierced rollers)
TQOEN


  • two double row inner rings, extended on one side
    • inner ring extensions on both sides of the bearing are designed as counter-surfaces for radial shaft seals
  • four single row outer rings
  • without intermediate rings
  • steel window-type cages
TQOE


  • two double row inner rings, extended on one side
    • inner ring extensions on both sides of the bearing are designed as counter-surfaces for radial shaft seals
  • one double row and two single row outer rings
  • intermediate rings between the outer rings and between the inner rings
  • steel window-type cages
TQOT


  • two double row inner rings
  • one double row and two single row outer rings
  • intermediate rings between the outer rings
  • steel window-type cages
  • tapered bore, taper 1:12
    • if an interference fit is required on the roll neck
TQOSN


  • two double row inner rings
  • four single row outer rings
  • without intermediate rings
  • steel window-type cages
  • sealed on both sides
TQOSNP


  • two double row inner rings
  • four single row outer rings
  • intermediate rings between the two inner rings and the two middle outer rings
  • steel window-type cages
  • sealed on both sides
TQOS


  • two double row inner rings
  • one double row and two single row outer rings
  • intermediate rings between the outer rings and between the inner rings
  • steel window-type cages
  • sealed on both sides
TQOSN.1


  • two double row inner rings
  • four single row outer rings
  • without intermediate rings
  • steel pin-type cages (pierced rollers)
  • sealed on both sides
TQOESN


  • two double row inner rings, extended on one side
    • inner ring extensions on both sides of the bearing are designed as counter-surfaces for radial shaft seals
  • four single row outer rings
  • without intermediate rings
  • steel window-type cages
  • sealed on both sides
TQOES


  • two double row inner rings, extended on one side
    • inner ring extensions on both sides of the bearing are designed as counter-surfaces for radial shaft seals
  • one double row and two single row outer rings
  • intermediate rings between the outer rings and between the inner rings
  • steel window-type cages
  • sealed on both sides

TQI design bearings

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


  • one double row and two single row inner rings
  • two double row outer rings
  • without intermediate rings
  • steel window-type cages 
TQI


  • one double row and two single row inner rings
  • two double row outer rings
  • intermediate ring between the outer rings
  • steel window-type cages
TQI.1


  • one double row and two single row inner rings
  • two double row outer rings
  • intermediate ring between the outer rings
  • steel pin-type cages (pierced rollers)
TQIT


  • one double row and two single row inner rings
  • two double row outer rings
  • intermediate ring between the outer rings
  • steel window-type cages
  • tapered bore, taper 1:12 or 1:30
    • if an interference fit is required on the roll neck

Sealed bearings
  • 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)
    Table 1 provides an overview of these seal designs.
  • 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 Explorer bearings

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).
Optimized SKF Explorer bearings provide additional features such as:
  • 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.
Relubrication features

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:
    • via the outer rings only when a seal is fitted between the inner rings  (fig. 8), e.g. designation suffix VA901 or E(8)1
    • via the outer and/or inner rings when fitted without a seal between the inner rings (fig. 9), e.g. designation suffixes VA903 or E3
  • 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).

Variants/features

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
EExtended inner rings
ENE + N
ESNE + S + N
NWithout intermediate rings
N.1N + .1
SSealed bearing
SNS + N
SN.1S + N + .1
.1Steel pin-type cages and pierced rollers


Features (fig. 13)
GHelical groove in the inner ring(s) bore (→ Design considerations)
GWG + W
GWIG + WI
GWISIG + WI + SI
GWSIG + W + SI
GWOYG + WO + Y
LSLubrication holes in the inner ring shoulder, usually of bearings intended for vertical application with rotating outer rings
WLubrication grooves in the side faces of the bearing rings
WILubrication grooves in the side faces of the inner ring(s)
WILSWI + LS
WOLubrication grooves in the side faces of the outer ring(s)
SISeal fitted between the two inner rings
YLubrication groove and holes in the inner ring and gap between the inner rings
Cages

SKF four-row tapered roller bearings are fitted with either four pressed steel window-type cages (fig. 14) or four steel pin-type cages (pierced rollers, fig. 15).

For information about the suitability of cages, refer to Cages and Cage materials.

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