The structure of non-contacting gas face seals assumes the operation of such elements with a slight leak.
It means that a characteristic feature of non-contacting face seals is to maintain a stable (set, assumed) clearance which restricts the leak between the faces of cooperating rings. On the basis of the papers of the diagram of a non-contacting gas face seal type FMS (flexibly mounted stator) was shown in The seal consists of two rings, one of which (stator) (1) is mounted flexibly in the casing, while the other one (rotor) (2) turns together with a shaft (6) of a rotor machine. The radial clearance between the cooperating faces is filled with the sealing medium and creates a small gas pillow (of several micrometers).
The fluid film has specific elastic and damping properties which cause the transfer of vibrations from the rotor onto the stator.
If faces of rings are parallel to each other, it means that they move synchronously and the clearance has a virtually constant value close to the nominal value h.
However, usually performance or installation errors or bending of the shaft during operation create some misalignment of the sealing rings .
In consequence, they generate additional vibrations (axial and angular) which come from the rotor.
Such vibrations cause disruptions which move on to the stator and as a result, the operation of the seal may be unstable.
In extreme cases an undesired effect might take place, namely the rings may hit each other. The purpose of this paper is to conduct a comparative analysis of the vibrations of the ring that is mounted flexibly in the casing.
The analysis refers to chosen types of surface modifications (of that ring) and various assumptions of the
operating and geometrical conditions.