How to inspection the flexible rubber impellers still can work or not!

Normally the flexible rubber impellers need to be replaced annually,or if any of the below conditions exist.
1.Flexible rubber impeller's blades(vans) bead worn to flat.
2.Flexible rubber impeller's blades(vans) pitting.
3.Flexible rubber impeller's blades(vans) tear.
4.Flexible rubber impeller's blades(vans) cavitation.
5.Flexible rubber impeller's blades(vans) bowed(set)
Flexible rubber impeller's blades(vans) ripped.