When and wherever fluids are being pumped, it is the face seal rings and plain bearings that undergo the most punishment, particularly if the medium is corrosive or abrasive. In fact, the durability and profitability of may items of plant and equipment hinge largely on the wear and corrosion resistance of these parts. Materials engineering therefore plays a major role in the seal ring industry.
Whereas 20 years ago, steel or gray cast rings were used for such purposes, nowadays it is high-performance ceramics that do the same job. With their outstanding material and application properties, such ceramic parts have a service life extending many times over, even in aggressive media.
Leakproof Face Sealing Rings
The job of a face seal ring is to plug the gap between the housing and the rotating shaft so tightly that no liquid or gas may escape. This leakproof seal is achieved by means of a rotating sealing surface at the point of shaft entry.
With their outstanding thermal conductivity, low heat expansion coefficient and high Young's modulus, high-performance ceramics minimize any deformation to the face seal or packing ring under mechanical and thermal loads. Alongside such resistance to corrosive media it is the tribological properties of the sealing system that figure predominantly in the selection of ceramics for these demanding applications.
Materials Selection and Lubrication Considerations for Face Seal Rings
The important factor is whether or not the seal gap is lubricated by a fluid medium (be it liquid or gas). For this reason there is a standard combination of materials. If there is lubrication in the system, ceramic to ceramic matings are possible. In other instances, one of the two components must possess lubricating properties. One well proven combination consists of ceramics to carbon graphite.
By mating alumina and silicon carbide we are able to tune the sliding and sealing properties exactly to the actual operating environment. Combined bearings in high-performance ceramics are remarkable for their lightness, stiffness, low centrifugal forces, function and dry-running properties.
CeramTec engineers develop face seal rings and bearings ranging up to 900 mm in diameter.