SHAF T. Grooves or pits at the seal dynamic elastomer location. Concentrated cell corrosion. The set-screws slipped on a hardened shaft or were not tightened properly. The seal faces stuck together causing the shaft to rotate inside the static elastomer. Salt-water applications are particularly troublesome when a static elastomer or clamp is attached to the shaft.
Pitting caused by the chlorides and the low pH of salt water are the main problems.
Rubbing at the wear ring location. The shaft is bending. Excessive temperature causing a thermal growth. Sleeve is not concentric with the shaft, or the seal with the sleeve. Unbalanced impeller or rotating assembly.