The spring or springs should be located out of the sealing fluid to prevent clogging and corrosion. Stressed metal corroded at a rate faster than unstressed metal and the springs are under a constant stress. The elastomer must move to a clean surface as the seal face wears. Centrifugal force should be used to throw solids away from the lapped seal faces. The moveable portion of the seal must move to a clean area as the seal faces wear.
Vibration damping is necessary in all mechanical seals.
To prevent the faces from vibrating open. Back up seals or dual seals make sense in several applications. When there is no spare pump. To keep oxygen or air away from a product. To prevent a product pressure drop across the seal faces.