Industrial seal self study guide - SKF.com

SEAL DESIGN GROUPS (cont.)
All HS seals require a cover plate
for proper fit (fig. 3t).
HS3
The HS3 all-rubber seal has a spring
held in an open groove, permitting
easy access to the garter spring (fig. 3u).
HS4
The HS4 all-rubber seal’s spring is
secured by a Spring-Lock (fig. 3v).
HS5
HS5 is the same as HS4, but with
a Spring-Kover to provide added
protection (fig. 3w).
Cover Plates
All HS type seals, split and solid, require the end-user to fabricate and
use a cover plate for proper fit (fig. 3t). The cover plate provides axial
compression and supplements radial press-fit to ensure a leakproof
seal. Refer to Large Diameter Split Seal Installation section for details.
Solid Designs (HS3, HS4, HS5)
The differences between these three designs lie in the shape of the
sealing element and the method of retaining the garter spring.
HS3
HS3 is an all-rubber seal with a single spring-loaded element (fig. 3u).
The spring is held in an open groove which permits easy access to the
garter spring. This design is recommended for vertical and horizontal
shafts (Split version: HS9). Limited availability. All new machine
designs, and field replacements, should be made with HS4 or HS5.
HS4
HS4 is an all-rubber seal with a single spring-loaded element (fig. 3v).
The Spring-Lock secures the spring during installation regardless of
the direction of shaft entry. It is recommended for vertical and
horizontal shafts and for use with a cover plate. It is used in steel mills,
work rolls and other applications requiring frequent shaft removal
and installation. (Split versions: HS6).
HS5
HS5 is identical to HS4, except that it also has a Spring-Kover (fig.
3w). HS5 is recommended in applications where materials could affect
the garter spring or when installation can cause the spring to pop
out (Split versions: HS7 and HS8). It can be used for vertical shaft
assemblies in flooded conditions.
Split Designs (HS6, HS7, HS8, HS9)
Split seals are recommended in applications where downtime is
critical and shaft disconnection is impractical. The split seal design
offers a distinct advantage over solid seal types. It is placed around
the shaft, the spring connected and then the seal is pushed into the
seal bore. A cover plate provides axial and radial compression
and butts the split ends together.
Split seals perform best in grease applications or on well-lubricated
horizontal applications where the oil is below the shaft centerline.
Split seals generally have poor pressure sealing capability.
20