Page 78 - SKF-bearing-housings

Split plummer block housings SNL 2, 3, 5 and 6 series

Breaking loads and safety factors Load carrying capacity of the cap bolts
G uideline values for the breaking loads of Approximate values for the yield points for cap
housings made of grey cast iron are listed in bolts are provided in table 10 on page 77. The
table 8. To obtain the permissible load for a values in table 10 apply to 8.8 class cap bolts,
housing, the appropriate breaking load value which are supplied with SNL housings made of
should be divided by a factor based on the grey cast iron. SSNLD housings made of spher-
safety requirements. In general engineering, oidal graphite cast iron are supplied with 10.9
a safety factor of 6 is typical († Load carrying class cap bolts. For these cap bolts, the values
capacity, page 44). The permissible load can obtained from table 10 should be multiplied by
only be exploited if the cap bolts are tightened a factor of 1,4.
according to the torque values listed in If a safety factor of 6 is used for the permis-
table 10 on page 77. sible load of grey cast iron SNL housings, the
The limits for P 0° apply only when the hous- cap bolts do not need to be considered. In this
ing is not supported over its entire base. case, the permissible load of the housing is less
The load P a is the axial breaking load of the than the permissible load for the cap bolts.
housing. If the incorporated bearing is
mounted on a sleeve, check the permissible
axial load for the sleeve. Operating temperature
For housings made of spheroidal graphite The permissible operating temperature
cast iron, the values obtained from tables 8 is mainly limited by the seals († table 3,
and 9 on pages 75 and 76 respectively should page 65) and the lubricant in the bearing.
be multiplied by a factor of 1,8. For temperature limits of SKF bearings and
lubricants, refer to the product information
Safe loads available online at skf.com/bearings.
In some countries, safe loads are used instead The housing material does not have any
of breaking loads. Approximate safe loads are additional temperature limits, except for very
listed in table 9 on page 76. These guideline low temperature applications where impact
values have been established using accepted strength could be a factor.
engineering practices, taking safety, ultimate The housing paint is heat resistant up to
tensile strength of the materials and working 80 °C (175 °F) material temperature or 100 °C
stresses into account. They reflect a safety (210 °F) ambient temperature. When tem-
factor of 5 against fracture, and a minimum peratures outside the permissible range are
factor of 2 against cap bolt yield. expected, contact the SKF application engin-
eering service.
Additional housing support
When the housing is subjected to loads acting
parallel to the support surface, it may be Operating speed
ne cessary to pin the housing to the support All seals, except non-contact labyrinth seals,
surface or to provide a stop to counter the limit the permissible operating speed. Speed
load. limits for seals are provided in table 3 on
When loads act at angles between 55° and page 65 and in table 7 on page 70. For
120°, or when the axial loads are greater than speed limits of the bearing, refer to the
5% of P 180° († table 8), the housing should be product information available online at
pinned to the support surface or a stop should skf.com/bearings.
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 table 13 on page 82. For FSNL
housings, refer to table 1 on page 62.

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