Sealing solutions

SKF supplies all Y-bearings capped with a seal or shield on both sides. In typical Y-bearing applications, no additional external protection is necessary. Therefore, Y-bearings are available with several sealing arrangement designs to meet the demands of a wide range of operating conditions.
Standard seals
The standard seals for Y-bearings consist of a stamped sheet steel washer with a seal lip made of NBR, vulcanized to its inner surface (fig. 1, designation suffix VP274 for bearings with a standard inner ring and no designation suffix for other Y-bearings). The non-contact sheet steel washer forms a narrow gap with the cylindrical surface of the inner ring shoulder and protects the seal against coarse contaminants.
Standard seals with additional flingers
For more contaminated environments, SKF recommends Y-bearings equipped with a standard seal and an additional plain flinger on both sides (fig. 2, designation suffix 2F). The flinger, made of sheet steel or stainless sheet steel, has an interference fit on the inner ring to considerably improve the effectiveness of the seal without increasing friction. These seals are only available for bearings with an inner ring extended on both sides.
Multiple seals
For very contaminated environments, SKF recommends Y-bearings equipped with the highly effective multiple seal on both sides (fig. 3, designation suffix 2RF). This sealing arrangement consists of a standard seal and a flinger with a vulcanized NBR lip. The flinger lip seals axially against the standard seal. The space between the flinger lip and the shaft is filled with grease to provide additional protection. These seals are only available for bearings with an inner ring extended on both sides.
5-lip seals
For extremely contaminated environments, such as agricultural applications, SKF recommends Y-bearings equipped with the patented 5-lip seal on both sides (fig. 4). The seal consists of a sheet steel insert with a vulcanized 5-lip contact seal made of a low-friction NBR compound. The steel insert, which protects the seal from solid contaminants, is held in place by a groove in the bearing outer ring. Each seal lip has a different design to provide superior sealing performance in response to different operating conditions, including dynamic misalignment. The outermost and innermost lips act as a labyrinth to prevent contaminant ingress and grease leakage respectively. The three inner lips make constant contact with the inner ring shoulder.
RS1 seals

Y-bearings with a standard inner ring are equipped as standard with an RS1 seal on both sides. These NBR contact seals, developed for standard SKF deep groove ball bearings, are reinforced with a sheet steel insert (fig. 5, designation suffix 2RS1). They are fitted in a recess on the outer ring and ride against the inner ring shoulder.

Y-bearings with a standard inner ring with designation suffix VP274 are equipped with standard seals.

On request, Y-bearings can be supplied with a shield on both sides. The sheet steel shields are fitted in a recess on the outer ring and do not make contact with the inner ring, but form a narrow gap (fig. 6, designation suffix VP076). They are designed for applications where the contamination level is low and additional friction should be avoided. Bearings with shields should not be used if water, steam or moisture can enter the bearing.
Greases for capped bearings

Y-bearings are filled with one of the following greases:

  • zinc-coated and stainless steel Y-bearings
    → food-grade grease GFJ
    This grease fulfils the requirements listed in the Guidelines of section 21 CFR 178.3570 of the FDA (US Food and Drug Administration) regulations. It is approved by the USDA (United States Department of Agriculture) for Category H1 use (occasional contact with food stuffs).
  • all other Y-bearings
    → standard grease VT307

The technical specifications for the various greases are listed in table 1.

Grease life for Y-bearings

Grease life for Y-bearings should be estimated according to the procedure described in this section. The grease life for Y-bearings is presented as L10, i.e. the time period at the end of which 90% of the bearings are still reliably lubricated. When relubrication is required, the method to estimate relubrication intervals is described on under Relubrication intervals. For additional information, refer to Relubrication.

The grease life for Y-bearings depends on the operating temperature and the speed factor. It can be obtained from diagram 1.

The grease life for each is valid under the following operating conditions:

  • horizontal shaft
  • very light to moderate loads (P ≤ 0,05 C)
  • stationary machine
  • low vibration levels

If operating conditions differ, the grease life obtained from the diagrams has to be adjusted:

  • For vertical shafts, use 50% of the value from the diagram.
  • For heavier loads (P > 0,05 C), use the reduction factor listed in table 2.

The values for adjusting the grease life are estimates. Vibration can have a negative influence on grease life. The extent cannot be quantified, and the influence increases with increasing operating temperature. For additional information, refer to Lubrication or contact the SKF application engineering service.


Y-bearings do not need relubrication when the grease life (→ Grease life for Y-bearings) exceeds the SKF rating life of the bearing (→ Selecting bearing size).

Relubrication can extend bearing service life under any of the following conditions:

  • The bearings are exposed to high humidity or severe contamination.
  • The bearings accommodate normal or heavy loads.
  • The bearings operate for extended periods at high speeds or at temperatures above 55 °C (130 °F).
  • The bearings are subjected to high vibration levels.

To relubricate Y-bearings, the following greases can be used:

  • zinc-coated and stainless steel Y-bearings
    → food-grade grease SKF LGFP 2
  • all other Y-bearings
    → SKF LGWA 2, LGMT 2 or LGMT 3 grease

If relubrication is needed, the relubrication intervals can be estimated following the method explained under Relubrication intervals.

When relubricating, the shaft should be turned and grease should be pumped slowly until fresh grease starts to escape from the seal(s). Excessive pressure from pumping too quickly can damage the seals. When machines and equipment are used for a limited period of time, SKF recommends relubricating each bearing at the end of the operational period, i.e. immediately before being laid up.

Relubrication features

SKF Y-bearings are designed to facilitate relubrication. They have two lubrication holes in the outer ring as standard, one on each side, positioned 120° apart. Bearings without lubrication holes can be supplied on request (designation suffix W).

The following bearings do not have the standard relubrication features:

  • Stainless steel Y-bearings with grub screws have a lubrication groove in the outer ring located on the side opposite the locking device and one lubrication hole within this groove.
  • Y-bearings with a standard inner ring without designation suffix B and Y-bearings with 5-lip seals are lubricated for life and cannot be relubricated. They do not have any lubrication holes.
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