Sealing technology

Seals have the primary function of separating two functionally different spaces with the same or different pressures so that no exchange of solid, liquid or gaseous media can take place between them or the exchange is within permissible limits. Typical applications include preventing the loss of operating materials (e.g. oil leakage from rolling bearings, air from pneumatic seals), preventing the ingress of contamination (e.g. in rolling bearings) or preventing the mixing of different operating materials.

It is important for the achievable tightness whether sealing is required between two stationary sealing surfaces (static seals) or between two sealing surfaces that move relative to each other (dynamic seals).

In the case of stationary components, “technical tightness” is required for liquid and gaseous media.
lossless tightness is required, except for diffusion losses in the case of gaseous media. For moving components
three leakage paths are possible: between the housing and the seal (acts as a static seal), between the shaft and the seal.
seal), shaft and seal, and through the seal itself (diffusion losses). Between shaft and
and seal, a liquid film reduces friction and thus wear, and is therefore desirable, even though it can lead to low
it leads to low leakage loss (also referred to as leakage rate).

In order to achieve effective sealing, it is necessary to match the sealing surfaces to each other, at least on one sealing line. This results in requirements for adjacent components in terms of surface roughness, shape and position tolerances, and possibly installation tolerances and surface hardness. In addition, it must be taken into account that installation conditions can change under operating conditions (deflection of the shaft, different thermal expansion, wear of the seal running surfaces, elastic/plastic deformation of the components and seal).