Filled sealing rings – seals in a metal sheath for specific areas of application
Filled sealing rings consist of a core (e.g. fibre seal, graphite or mica), which is surrounded by a metal sheath (e.g. stainless steel or copper). The sheath can enclose the seal either partially or fully. It protects the interior from the negative effects of the medium to be sealed. The core has a support function and yields due to the contact pressure. This must be much higher than for a soft material seal in order to achieve adequate sealing properties. Accordingly, the counter pieces to be connected must also show a greater stability.
Sheathed seals – the advantages
In comparison with solid metal seals, filled sealing rings score points by providing very good sealing properties even with low tightening torques. They are capable of compensating for surface defects in the counter pieces to be connected, and maintain a certain elasticity when they are installed. Filled sealing rings are, for example, used to seal off valves, manometers and fluids.
One of the most important areas of application of metal-sheathed seals is apparatus construction, especially at temperatures of over 500 °C. Generally speaking, the sheath material should be as soft and flexible as possible. For corrosion reasons, however, stainless steel is also frequently used. The material is selected according to the flange imprecisions that are to be bridged. The more even the sealing surfaces are, the hard the outer material of the filled ring can be.
Depending on the circumstances, there are a wide variety of possible combinations. Particularly extreme combinations for materials include an aluminium sheath with a graphite insert or a stainless steel sheath with a mica insert.