Radial shaft seals that are primarily used for contaminant exclusion should be installed with the lip pointing outward. When additional protection is needed, SKF recommends a seal design that incorporates an auxiliary lip, for example the HMSA10 or CRWA1 seals.
For tough operating conditions, SKF WAVE seals (fig 1) with hydrodynamic features are recommended. To further enhance sealing efficiency, two single-lip seals can be arranged in tandem (fig 2) or a double-lip seal, like the HDSE1 seal, can be used (fig 3).
V-rings (fig 4) are used primarily to exclude contaminants. These seals, which act as flingers, rotate with the shaft and seal against a surface that is perpendicular to the shaft.
V-rings and axial clamp seals are often used as secondary seals to protect the primary seals from coarse contaminants.
None of these seal arrangements are intended for oil retention.