Function of the Heavy Duty Face Seals

The two halves of the seal are mounted in separate housings facing one another. The housing's bore, where the O-ring is located, is tapered, with the taper increasing with the depth of the bore. The cast iron Seal Ring is also tapered on its outside diameter to locate the O-ring. This area is known as the "ramp". When a Seal Ring and an O-ring are axially compressed in the housing the O-ring deforms between the two tapers producing a radial force as well as an axial one. The axial component of this force can be calculated and it is this force, known as "Face Pressure" that is most important for proper operation. The rubber O-rings serve three functions: 1. They generate pressure on the axial face because of their elasticity. 2. They become a static seal between the outer diameter of the Seal Ring and the inner diameter of the housing. 3. They transmit torque from the rotating half of the assembly through the faces to the static half. It is important to understand that only one of the seal halves is rotating. The interface between the rotating and non-rotating half are the finely lapped faces of the seal. The Seal Ring should never rotate relative to the O-ring nor should the O-ring rotate relative to the housing. In order to obtain a "leak free" seal the contact band of the faces are lapped with a surface finish of R max 1.8 micrometers. The tapered portion of the face forms a 1-3mm tapered gap at the ID of the seal set. The whole purpose of this tapered gap is so the lubricant is allowed to feed the sealing faces. It also enables new faces to be continuously formed as wear will take place through time. This ability to form new faces considerably enhances the service life of the seal. The lifespan of the seal is determined, however, by the time it takes the sealing band to move from the OD to the ID of the face. Special care should be taken so as to not damage the face area of the seal set.