SKF NJ305 ECP/C4 Zylinderrollenlager (25x62x17)

As a cylindrical roller bearing, this bearing carries high radial loads with limited axial capacity. The dynamic load rating of 46.5 kN characterises this bearing. The static load rating is 36.5 kN. The limiting speed is 15000 rpm. This variant features greatly increased radial clearance (C4). Strongly increased clearance (C4) is intended for bearing positions where mounting alone consumes a substantial part of the radial play and operation consumes the rest.

Strongly increased clearance (C4) does not describe a different bearing but a larger initial radial play for the same rolling geometry. It makes sense wherever the known consumers of play bite particularly hard: with a tight seat on both rings, with an inner ring drawn onto a tapered shaft or a sleeve and deliberately expanded in the process, and with a sustained heat flow from the shaft into the bearing, as occurs on drying cylinders, hot-running fans or in rolling mill arrangements.

In these cases a standard clearance leads on paper to an operating play near zero, and the result would not be a particularly accurate guide but a preloaded roller set with rising frictional torque and rising temperature. Strongly increased clearance (C4) moves the starting point up far enough that a workable residual play remains after fitting and heating.

Its downside is to be seen in the cold, unloaded state: the bearing then runs with noticeable play, the load zone is narrow, and the most heavily loaded roller carries a larger share of the radial force. For the layout this means assessing the operating clearance rather than the mounted clearance, and considering fits, drive-up distance, temperature profile and load direction together in order to do so.

The open form presupposes sealing and lubricant supply by the surrounding construction, which in hot service must also carry part of the heat dissipation.