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).
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 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 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.