Load carrying capacity
SNL housings are intended for loads acting perpendicularly toward the support surface. If the housing is supported over its entire base and the loads are purely perpendicular, loads are limited only by the bearing. If loads acting in other directions occur, or if the housing is not supported over its entire base, be sure that the magnitude of the load is permissible for the housing, the cap bolts and the attachment bolts. When housings are subjected to cyclic loads or dynamic imbalance, contact the SKF application engineering service.
Breaking loads and safety factorsGuideline values for the breaking loads P for housings made of grey cast iron are listed in the product tables for bearings on an adapter sleeve (with standard seals), for bearings on an adapter sleeve (with oil seals) and for bearings on a cylindrical seat.
To obtain the permissible load for a housing, the appropriate breaking load value should be divided by a factor based on the safety requirements. In general engineering, a safety factor of 6 is typical (→ Load carrying capacity).
The permissible load can only be exploited if the cap bolts are tightened at least to the torque values listed in the product tables for bearings on an adapter sleeve (with standard seals), for bearings on an adapter sleeve (with oil seals) and for bearings on a cylindrical seat.
The limits for P0° apply only when the housing is not supported over its entire base.
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.
For housings made of spheroidal graphite cast iron, the breaking loads and safe loads should be multiplied by a factor of 1,8.
Safe loadsIn some countries, safe loads are used instead of breaking loads. Approximate safe loads are listed in table 1. These guideline values have been established using accepted engineering practices, taking safety, ultimate tensile strength of the materials and working stresses into account. They reflect a safety factor of 5 against fracture, and a minimum factor of 2 against cap bolt yield.
Additional housing supportWhen the housing is subjected to loads acting parallel to the support surface, it may be necessary to pin the housing to the support surface or to provide a stop to counter the load. When loads act at angles between 55° and 120°, or when the axial loads are greater than 5% of P180° (table 1), the housing should be pinned to the support surface or a stop should be provided to counter the load. The dowel pins or stop should be sufficiently strong to accommodate the loads acting parallel to the support surface.
Recommendations for the position and size of the holes to accommodate dowel pins are provided in the product tables for bearings on an adapter sleeve (with standard seals), for bearings on an adapter sleeve (with oil seals) and for bearings on a cylindrical seat.
Load carrying capacity of the cap boltsApproximate values for the yield points for cap bolts are provided in table 2. The values in table 2 apply to 8.8 strength cap bolts, which are supplied with SNL and SNLD housings.
If a safety factor of 6 is used for the permissible load of grey cast iron SNL housings, the cap bolts do not need to be considered. In this case, the permissible load of the housing is less than the permissible load for the cap bolts.