Since the seal face is the only sacrificial part of the mechanical seal, a worn out seal is identified as one that has no carbon nose piece left at the time it started to leak. A failed seal is identified by the fact that it has substantial carbon remaining at the time it started to leak.
Three Main Causes:
1. Seal faces opening
When repairing mechanical seals, 85% of the failure is found not caused by abrasion. Leaking has already occurred before abrasion. Seal faces open due to locking of axial movement of the dynamic seal ring. Axial movement is needed to compensate for thermal and pressure-induced axial expansion. In addition, if solid particles, such as sodium hydroxide crystals, precipitate out of liquid across sliding faces, it will also cause the open of seal faces.
Seal faces are running dry, resulting in overheating. High torque on seal faces made of hard materials can generate heat that can be transmitted to elastomers, resulting in hardening and burning.
3. Over-error Tolerance
Correct assemble tolerance is indispensable to fastening mechanical seals properly. Seal is not built into the correct assembly length, resulting in no contact between seal ring and seat.