Load carrying capacity
The load carrying capacity of a housing depends on many factors:
the housing material and design and, where applicable, cap bolt strength
the direction of the load
the strength of the attachment bolts and support structure
the condition of the support surface
SKF provides static housing load limits, either in the form of breaking loads or safe loads, for most housings. Where values are not provided, the load carrying capacity is higher for the housing than for the bearing.
Breaking loads can be used to calculate a permissible load, based on a selected safety factor. Safe loads already include a safety factor.
Special attention is required for split housings subjected to cyclic loads or dynamic imbalance. Under these conditions, cap bolt and housing cap strength (P180°) should be analyzed carefully. For additional information, contact the SKF application engineering service.
For most SKF housings, guideline values for the breaking loads P are provided in the relevant product section. To obtain the permissible load for a housing, the guideline value should be divided by a factor based on the safety requirements and operating conditions of the application. In general engineering, a safety factor of 6 is typical. The permissible load can only be exploited if the housing is mounted properly and all bolts are tightened to the specified torque values. For split housings, the strength of the cap bolts should also be considered. A minimum safety factor of 2 against cap bolt yield should be used.
The load Pa is the axial breaking load of the housing. If the incorporated bearing is mounted on a sleeve, check the permissible axial load for the sleeve (refer to Axial load carrying capacity for bearings on a sleeve, below).
In some regions, safe loads are used instead of breaking loads. These guideline values have been established using accepted engineering practices, taking safety and ultimate tensile strength of the materials into account. They reflect a safety factor of 5 against housing fracture, and where applicable, a minimum factor of 2 against cap bolt yield. The safe loads can only be fully exploited if the housing is mounted properly and all bolts are tightened to the correct torque values.
Axial load carrying capacity for bearings on a sleeve
When using a bearing on a sleeve on a plain shaft, the axial load carrying capacity is limited either by the bearing, sleeve or housing.
For the axial load carrying capacity of the bearing, refer to Bearings, units and housings. For the sleeve, the permissible axial load to safely prevent slippage on the shaft is determined by the friction between the shaft and sleeve. Provided the bearing is mounted correctly (→ skf.com/mount), the permissible axial load can be calculated from
Fap = 0,003 B d
|Fap||=||maximum permissible axial load [kN]
|B||=||bearing width [mm]
|d||=||bearing bore diameter [mm]
Information about the axial load carrying capacity of the housing is provided in the relevant product section.