Design considerations

Location of bearings

Deep groove ball bearings

The selection of shaft and housing fits depends on the bearing operating condition and bearing size. An appropriate fit is needed to locate the shaft, provide satisfactory support and allow for thermal expansion up to the stated maximum operating bearing temperature (table 1).

Insert bearings

For moderate loads (0,035 C < P ≤ 0,05 C), the shaft seats should be machined to an h7Ⓔ tolerance. For light loads and low speeds, an h8Ⓔ shaft tolerance is sufficient.

Symbols

Cbasic dynamic load rating [kN] (→ product tables)
Pequivalent dynamic bearing load [kN] (→ Loads for standard insert bearings)

Operating environment

SKF high temperature bearings are designed to provide solutions to common issues in high temperature applications. In addition to operations involving high temperatures and low rotational speeds, it is important to consider environmental conditions in the process area.

Since high temperature bearings are supplied without preservative oils and must be used without grease or oil lubrication, the anti-corrosion property of the bearings is limited. Therefore, the bearings should be used in a dry environment or with a proper sealing solution to keep the bearings dry.

Axial displacement

To accommodate axial displacement, the shaft at the non-locating bearing position of high temperature insert bearings should be provided with one or two grooves, 120° apart, to engage a modified grub screw:

  • Hexagon socket grub (set) screws with a dog point, in accordance with ISO 4028, but with a fine thread according to the product tables. The grub screw should be secured by a nut and a spring or star lock washer (fig. 1).

The screws and groove(s) accommodate changes in shaft length and prevent the shaft from turning independently of the bearing. The sliding surfaces between the shaft and inner ring and those in the shaft grooves should be coated with a lubricant paste suitable for the operating temperature.

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