One of the most interesting uses of shaft seals is in washing machines. Though it might at first glance seem simple, sealing a washing machine tub is a demanding application. Water must be contained, but the water, bleaches, detergents, and other washing products can easily corrode the metallic portions of the seal—the case and the spring.

What allows a tub seal to function effectively has everything to do with lip design. A comparison between the contact point of a normal seal and that of a tub seal is shown in Figures 196 and 197. Note that the contact angles and the “R” value on the sprung lip of the tub seal are reversed compared to standard seal designs. This reversal is what allows a tub seal to prevent water and suds from getting into the machine’s grease-filled bearings. And even as it keeps water out, the sprung lip also helps keep grease in. The reversed contact angles and “R” value also place the garter spring on the air side of the application, so water cannot reach it. This helps protect the garter spring from corrosion. Figures 198 and 199 show two different tub seal designs.

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