OUTSIDE SEALS O018
These seals are designed to run without any metal parts in contact with the sealing fluid.
Most of them are hydraulically balanced and many of them are designed to prevent shaft fretting.
The main problem with outside seals is that centrifugal force throws solids and dirt into the lapped seal faces. A second problem occurs when solids build up in front of the seal preventing it from moving forward to compensate for wear.