Gas seals or dry gas seals of the type defined in the introduction are already known from various publications. Examples of these are WO2014/037150 and WO2014/023581.
Dry gas seals of said type generally comprise components composed of ceramic, in particular manufactured from silicon carbide or tungsten carbide. The ceramic components are normally the stationary and/or rotating slide rings and, if appropriate, adjoining elements. A further example from the patent literature is given by DE 39 25 403 C2.
Features of the shaft seal defined in the introduction are already known from DE 202 17 983 U1, DE 20 2007 012050 A1, DE 10 2011 007071 A1, WO 96/04497 A 1.
In addition to the primary sealing of the gas seal, in particular dry gas seal, it is required that both the rotating sealing ring and the stationary sealing ring are sealed off with respect to the rotor or stator (housing and possibly connected components) by means of a substantially static seal. Owing to the possible axial vibrations, it is necessary for at least one of these seals to be axially movable. This is generally at least the stationary seal because the mobility is easier to realize at this component. Owing to the high dynamics of the movements, this secondary seal is subjected to extreme loading.
It has been found that, in conventional designs, the secondary seal, which generally has to ensure an axial movement, was cumbersome, relatively ineffective and susceptible to defects.