Industrial seal self study guide - SKF.com

SEAL DESIGN GROUPS (cont.)
Hydrodynamic Seals
One of the most significant developments in sealing technology
occurred in the 1950’s with the introduction of hydrodynamic seals.
Hydrodynamic seals have molded projections added to the seal lip
which enables the seal to pump oil into the oil pump, improving
lubricant retention.
Standard hydrodynamic seal designs
feature helical ribs, parabolic ribs or
triangular pads (fig. 3e).
There are a variety of molded projections used in hydrodynamic
seals. Standard designs have a series of helical ribs, parabolic
triangular pads molded to the lip (fig. 3e). However, these designs
are not without their problems. As dirt builds up against the seal lip,
the lip wears, eliminating the hydrodynamic projections. They can also
become clogged with carbon or dirt. Some hydrodynamic designs are
uni-directional, and can actually pump lubricant out if installed incorrectly.
SKF developed a new type of hydrodynamic seal in the early 1970’s.
Called “Waveseal”, this design features a sealing lip molded with a
sinewave pattern. This traces a wavy path over the surface of the
rotating shaft.
Low Angle
Steep Angle
Scraper
Waveseal
In technical terms, the SKF Waveseal is a smooth lip,
bi-rotational hydrodynamic, molded radial lip seal. More simply, it is a
shaft seal that pumps lubricant back into the sump while sealing out
contaminants no matter which way the shaft is turning.
Low Angle
Permits Oil
To Slide
Under Lip
Steep Angle
Scrapes Oil
Inward
Shaft
Rotation
The Waveseal by SKF
• Offers longer, more dependable performance and service life than
conventional trimmed lip seals and other hydrodynamic designs.
• Has almost universal applications
• Is the first standard line of shaft seals incorporating hydrodynamics
Static
Contact
Path
Air Side
Oil Particles
Dynamic
Contact
Path
Oil Side
The SKF Waveseal touches the shaft
in wide ‘sine’ or wave pattern. Due to
this unique design, contact pressure
and grooving are minimized, heat
generation and friction are reduced.
Lubricant is pumped back to the
bearing while dirt is pushed away
from the lip/shaft interface (fig. 3f).
How Waveseals Work
The Waveseal by SKF makes a sweeping contact with the shaft. Its
unique, specially molded lip rides the shaft forming a sinusoidal or
wave pattern around the shaft surface (fig. 3f).
This unique pattern generates less heat, reduces shaft wear and
provides greater lip lubrication than standard lip designs. Its pumping
power is maintained at the same level throughout its service life.
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