Known container-treatment devices include rotating machines with processing positions on a periphery thereof. In these machines, container treatment involves applying treatment medium while the containers are moving. This requires some kind of rotary joint to bring treatment media from a stationary reference frame into a rotating reference frame.
A typical rotary joint has one stationary part and one rotating part. There are also flow channels for both media. These are sealed from each other and from the exterior by mechanical seals that extend through both parts of the rotary joint.
To suppress entry of bacteria or other contaminants into these flow paths, it is usual to provide barrier spaces between the joint's two parts and to fill these barrier spaces with a barrier medium that differs from the treatment medium. The barrier medium is often a hot vapor.
The need to use a barrier medium is a disadvantage. First, it is one more consumable to supply and pay for. Second, it creates the need for a complex design that prone to failure. Additionally, its pressure must be monitored constantly to detect leakage.
To make matters worse, the barrier medium is usually heated. This heat stresses the various seals, thus reducing their service life.