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Static Seals

Static Seals

Static sealing solutions are used for applications involving no movement between the sealing component and the surface. A distinction is made between static axial seals, where sealing occurs parallel to the seal centerline, and static radial seals, where the seal centerline has a radial seal orientation. The seals most often used for this kind of application are O-rings, which are standardized in their sizes and tolerances.

Gasket O-Ring Seal - Operating Pressure Always Looks for a Way Out

Cover Seals From FST Sealing Technologies

Even if machine elements under pressure are firmly bolted to one another, there is still a so-called static seal gap that must be sealed. O-Rings – or O-Rings with back rings for improved extrusion stability – are most commonly used. If the requirements are more specialized, one-piece sealing elements made of polyurethane come into use. For example, the requirements may involve gaps for breathing due to major pipe expansion, short pressure rise times or alternating operating pressures. Freudenberg Sealing Technologies offers the most suitable cover seal for any application. They stand for the highest possible operating security and extrusion stability.

Close-up of a Gasket O-Ring Seal from Freudenberg Sealing Technologies

Simple and Secure Mounting

Polyurethane material offers outstanding characteristics relating to robustness and form stability – above all, to resist extrusion. As a result, even complex geometries can be manufactured with injection molding or even with turning technologies if a quick delivery is needed. This characteristic makes it possible to use one-piece seals. This especially offers an advantage during mounting since any potential inverted position – as in an O-rings/back ring combination – can be precluded. The profile rings are designed in such a way that they can even be substituted in existing installation spaces for O-ring/back ring systems (Fig. 1).

Close-up of an installed cover gasket as a cross-section from Freudenberg Sealing Technologies

The high linear force on the seal edges of polyurethane seals also enables their use in related applications. Merkel® Pinmatic is produced with only slight changes in its geometry. It provides the best possible performance in virtually static applications such as knee lever systems or the bearing or joint bolts of injection molding machines (Fig. 2).

Our Products in Detail

FST Cover Seals Merkel Cover Seal PU 82

Merkel® Cover Seal PU 82

One-piece, dual-action compact seal made of polyurethane. Internal sealing. High operating reliability and extrusion stability. Suited to existing O-ring installation spaces as well as those for O-rings with a back ring.

FST Cover Seals Merkel Cover Seal PU 83

Merkel® Cover Seal PU 83

One-piece, dual-action compact seal made of polyurethane. Internal sealing. High operating reliability and extrusion stability. Suited to existing O-ring installation spaces as well as those for O-rings with a back ring.

FST Cover Seals Merkel Pinmatic

Merkel® Pinmatic

One-piece, dual-action compact seal made of polyurethane to seal joint bolts. Internal sealing. Insensitive to pressure peaks.

FST Cover Seals Merkel Stircomatic

Merkel® Stircomatic SRC

One-piece compact seal made of polyurethane for high operating pressures up to 80 MPa. High operating reliability and extrusion stability. Simple, secure mounting.

FST Cover Seals O-Ringe O-rings


Usage mainly for sealing stationary machine parts against liquid and gaseous media. Under certain conditions, their use as a dynamic sealing element is possible when the movements are axial, rotating and oscillating.

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