Asperity theory


This is one of the more popular seal face lubrication theories. It was proposed in the early 1960s as a result of testing done at Battelle Memorial Institute in Ohio, USA. The testing was sponsored by a majority of the seal companies supplying hardware to the aircraft industry along with a high percentage of the aircraft engine manufacturers.

A conventional mechanical seal face is manufactured from a combination of carbon and graphite. Testing showed that during seal operation, the graphite was removed from the carbon/ graphite face and deposited on the hard face. The pits or holes that remained in the carbon filled with lubricant and the seal faces were observed running on this film.

The asperities are the carbon peaks that remain when the graphite is deposited on the hard face. All of this means that carbon vs, graphite is the conventional face combination. The hard face is used to give the graphite a place to deposit.

Testing also showed that moisture had to be present for this transformation to take place, hence the problem with some dry running seals. Today we use carbon/ graphite faces impregnated with organic materials that will release the graphite in dry running applications.

See “Seal Face Lubrication”.