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Sealing solutions

SKF supplies the single row deep groove ball bearings with filling slots shielded on one or both sides. Details regarding the suitability of shields under various operating conditions are listed in table 1. However, these guidelines cannot substitute for testing a seal in its application. For additional information, refer to Sealing solutions.
When shielded bearings must operate under certain extreme conditions, such as very high speeds or high temperatures, grease may leak at the inner ring. For bearing arrangements where this would be detrimental, special design steps must be undertaken. For additional information, contact the SKF application engineering service.
Bearings shielded on both sides are lubricated for the life of the bearing and should not be washed or relubricated. They are filled with the appropriate amount of a high-quality grease under clean conditions. The bearings are considered virtually maintenance-free. If they are to be hot mounted, an induction heater should be used.
SKF does not recommend heating shielded bearings above 80 °C (175 °F). However, if higher temperatures are necessary, make sure that the temperature does not exceed the permissible temperature of the grease.

Bearings with shields are primarily intended for applications where the inner ring rotates. Shields are fitted in the outer ring and do not make contact with the inner ring, but form a narrow gap with it. Shields are made of sheet steel.

Shields for SKF single row deep groove ball bearings with filling slots are identified by the designation suffix Z. Typically they have an extension in the shield bore to form a long, narrow gap with the inner ring shoulder (fig. 1). Some shields do not have the extension (fig. 2).

Greases for shielded bearings

Single row deep groove ball bearings with filling slots shielded on both sides are filled as standard with the high temperature grease GJN.

On request, bearings can be supplied with the following special greases:

  • wide temperature range grease HT or WT
  • wide temperature range and silent running grease LHT23
  • low temperature grease LT

The technical specifications of the various greases are listed in table 2. The standard grease is not identified in the bearing designation (no designation suffix). The special grease is indicated by the corresponding grease suffix. Check availability of bearings with special grease prior to ordering.

Grease life for shielded bearings

Grease life for shielded bearings should be estimated according to the procedure described in this section. The grease life for shielded bearings is presented as L10, i.e. the time period at the end of which 90% of the bearings are still reliably lubricated. The method to estimate relubrication intervals (→ Relubrication intervals) represents the L01 grease life and should not be used.

The grease life for shielded bearings depends on the operating temperature and the speed factor. It can be obtained from diagram 1. The grease performance factor (GPF) is listed in table 2.

The grease life is valid under the following operating conditions:

  • horizontal shaft
  • inner ring rotation
  • light load (P ≤ 0,05 C)
  • operating temperature within the green temperature zone of the grease (table 2)
  • stationary machine
  • low vibration levels

If the operating conditions differ, the grease life obtained from diagram 1 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 3.
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