Mechanical seal is being used increasingly on fluid pump to replace packed gland and lip seal. Pump with mechanical seal perform more efficiently and generally perform more reliably for extended periods of time.

 

Mechanical seal is provided to prevent pumped fluid from leaking out along the drive shaft. The controlled leakage path is between two flat surfaces associated with the rotating shaft and the housing respectively. The leakage path gap varies as the faces are subjected to varying external load which tend to move the faces relative to each other.

 

The products require a different shaft housing design arrangement compared to that for the other type of mechanical seal because the mechanial seal is a more complicated arrangement and mechanical seal does not provide any support to the shaft.

 

In order for the mechanical seal to perform over an extended time period with low frictional the mechanical seal faces are generally hydrodynamically lubricated. The fluid film will need to carry substantial load. If the load becomes to high for the film surface contact will take place with consequent bearing failure. This lubricating film is generally of the order of 3 micrometres thick , or less. This thickness is critical to the required sealing function. Mechanical seal often have one face of a suitable solid lubricant such that the mechanial seal can still operate for a period without the fluid film.