Thermal shaft expansion is over compressing an outside seal design, or one of the seals in a dual seal application. The open impeller adjusting technique can over compress some seal designs. The stuffing box is running in a vacuum because the supply tank is not vented properly or cold weather is freezing the tank vent. Water hammer, pressure surges and cavitation will all alter seal face loading. O-rings and other elastomer designs to extrude and jam the sliding components.
Lapped seal faces to distort and go out of flat.
A stuffing box vacuum can blow open unbalanced seals. A differential pressure across the elastomer can cause ethylene oxide to penetrate into the elastomer and destroy it as it expands in the lower pressure side. If you are monitoring temperature and pressure in the stuffing box area you will note the changes mentioned and depending upon your knowledge of the above, you will have time to react before seal failure occurs. An increase in the bearing case oil temperature is significant because the life of bearing oil is directly related to the oil temperature. It is these formed solids that will destroy the bearing.