OIL SEALS- often called grease, fluid or dirt seals - close spaces between stationary and moving components in mechanical equipment, helping prevent lubricant escape. They also stop harmful contaminants from entering machinery, particularly in severe environments. Vital components of practically every type of machine and vehicle in operation, oil seals protect all types of precision-constructed, close-fitting ball, sleeve and roller bearings.
A Mechanical Seal has 3 primary design characteristics:-
SEAL FACES- which are lapped flat to within 2 - 3 light bands. Making the seal face flat within millionths of an inch. Since both faces are lapped flat and then pressed together it effectively seals our any fluid (other than a very thin film) from leaking between them.
An Energizer - It's done using a single spring, multiple springs, wave springs, metal bellows or even o-rings or internal pressure, but one of the above must be used to create a force pressing seal faces together preventing leakage from between the seal faces.
Secondary Seals - While seal faces seal perpendicular to the shaft, secondary seals are necessary to seal parallel to the shaft. Those seals include rubber boots, common to industry standard type 1, 2, 21, 6 and 6A seals. O-Rings made of a variety of elastomers including Buna-N, Viton, Aflas, Kalrez, Chemrez, Amerirez, PTFE, SBR, Neoprene, and FEP encapsulated o-rings. Gaskets made or the same elastomers as above, along with Flexible Graphite, and Compressed non-asbestos materials. In the case of high temperature metal bellows seals Flexible Graphite wedges are used to seal the pump sleeve/shaft.