SHAFT SEALS TAKE A SEAT AND SOLVE A PROBLEM
Installing a shaft seal into a housing can be a problem if there is
no counterbore to help align and seat the seal. Even if the initial installation
is perfect, the absence of a counterbore makes it easy for the seal to
become cocked when the shaft is slipped into place (see upper drawing).
Seal cocking is most common in blind designs that prevent the assembly
team from seeing whether the seal is properly seated.
Cocking increases the temperature at the interface between the shaft and the seal lip. High temperature hastens hardening and cracking of the seal. Cocking also can lead to the development of a pumping action. If the leading edge of the incoming shaft has splines, additional problems are possible. If the shaft is not installed properly, the splines can easily tear the seal's wiper lip and/or dent the metal can. The end result of any of these problems is leakage and premature seal failure.
RL Hudson, Tulsa, offers a solution to the problems associated with seal cocking – the TAY shaft seal. The TAY design has a flange on the OD of the seal (see lower drawing). This flange helps ensure that the seal seats properly against the housing face during initial installation. Because the flange's presence also helps prevent the possibility of subsequent misalignment, seal cocking concerns can be eliminated.
This article was published in the June, 2000 edition of Hydraulics and Pneumatics magazine.
