Page 7 - SKF-Food-Line-ball-bearing-units

Housings The composite material for the blue range Table 1
housings is reinforced polypropylene – a Chemical resistance ratings for
The SKF blue range housings are strong, yet material chosen for its dimensional stability polypropylene
lightweight and chemically resistant Their and chemical resistance to detergents and
hygienic design features make them ideal for contaminants (table 1) Importantly, poly- Strong alkalies Excellent
following the highest food safety standards propylene is hydrophobic, distinguishing it
from conventional composite housing Weak acids Excellent
The housings remain highly stable dimen- materials Strong acids Good
sionally and maintain their expected physical
Alcohol Good
properties despite repeated operational and The housings feature 40% long glass fibres
washdown cycles reinforcement This reduces the tendency of
the housings to creep under temperature
Particularly in wet environments, the hous- and load
ings are more reliable compared to polyam-
ide (PA) and Polybutylene terephthalate
(PBT) PA (not geometrically stable) and PBT
(subject to hydrolysis if washed down with
hot water) are the main two materials com-
monly utilized in the market

The blue range housings are available in the following six designs – all covered by design protection:

Plummer block Short base Oval flanged 3-bolt flanged Square flanged Take-up
plummer block

Back seal

The primary purpose of the back seal is to
protect the bearing unit from “shaft-side”
contamination

The external face of the back seal has been
designed to provide sealing against cut-outs Static: Interference of small rubber undu-
This could for instance mean an enclosure lations or waves, against a matching
wall or panel that has been drilled to allow groove in the SKF blue range housing
clearance for the shaft to pass through to the
bearing unit

On a flanged unit this can be used to seal the
shaft access or clearance hole in order to
avoid the creation of a cavity behind the
panel, where food debris could otherwise
collect
The composite blue housing is the only Dynamic: A twin lip seal with sufficient
housing that can host a back seal It can only interference to cope with 1-degree
be mounted in a unit with a dedicated misalignment
bearing

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