Needle roller bearings with machined rings in the (R)NA 49 series are available with a contact seal on one (fig. 2) or both (fig. 3) sides. The NBR seals are effective at keeping the lubricant in and contaminants out of the bearing.
The inner ring of sealed bearings is 1 mm wider than the outer ring. This maintains the effectiveness of the seals and simplifies the bearing arrangements even when small axial displacements occur.
In addition to integral bearing seals, SKF also supplies an assortment of external seals that can be used for needle roller bearing arrangements. Appropriate power transmission seals are listed in the product table, when available. For information about these seals, refer to the product information, available under Seals.
Greases for capped bearings
Needle roller bearings with one or two seals are are supplied greased. They are filled with high-quality grease under clean conditions.
The relatively large quantity of grease in the bearings means they can be operated for long periods before relubrication is required. SKF recommends SKF LGWA 2 grease, if relubrication is required.
The technical specifications for the initial grease fill and the grease for relubrication are listed in table 2.