The majority of damage to the broken shaft seal is due to overheating (thermal attack). When a shaft seal is operating without lubrication at the contact point between the seal and the shaft (dry running), the buildup of friction leads to very high temperatures. The time needed to reduce the generated heat within the safe limit for the material is too short.

Take a look at this picture of a melted connection rod.  We know that aluminium melts at approximately 660°C. How is it possible that an aluminium rod is melting in a situation where the oil temperature is a maximum of 50°C?

It happened due to a buildup of heat that rose above 660°C and resulted in the melting of the rod.

A similar situation can happen with the shaft seal. When there is no lubrication between the two faces, friction leads to a very high temperature that makes the carbon surface (standard face of a shaft seal) burst.

The faces become uneven and the shaft seal starts leaking uncontrollably.  This means that the shaft seal is broken and needs to be replaced..

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