Regardless of this movement the lapped seal faces must remain in contact. The seal is normally set screwed to the shaft or sleeve causing the metal case to follow any and all shaft movement. This means that there is a constant relative movement between the Teflon wedge and the shaft sleeve. We see evidence of this rubbing when we observe the frett mark on the sleeve caused by the removal of the sleeve's protective oxide layer. This passivated oxide layer forms on all corrosion resistant metal parts and can easily be rubbed or polished off exposing the base active metal.
Most fluids contain a certain amount of suspended solids.
If the lapped faces open, these solids will penetrate between the seal faces, imbed or stick into the softer carbon face, and cause a scoring or damaging to the hard face. This is the most common seal failure that you will experience. In addition to suspended solids there are other problems with fluids that can cause the premature opening of the lapped faces. Solidify in the springs, or between sliding seal components causing the faces to open as the shaft or sleeve moves. Become viscous causing the seal faces to be pulled open as the springs are not able to rapidly respond to the shaft movement.