Spring energized lip seals

Components:

Normally, spring energized seals consist of a jacket made of highly stressable plastic/plastic compounds and an embedded preloading element made of different materials.

Among other plastics, polytetrafluoroethylene, or PTFE for short, is the most suitable material for the seal jacket. Also known as Teflon, this polymer has special properties due to its chemical structure. The arrangement of the fluorine atoms around the carbon atoms creates a kind of protective layer, which generates almost universal chemical resistance. Only a few media, such as elementary fluorine or alkali metals, can affect the plastic. Furthermore, PTFE has a low friction coefficient, which makes it predestined for use in dynamic applications. In addition to high temperatures up to 300°C, PTFE is also used in cryogenic applications. By admixing additives, the properties of PTFE can be modified and adapted to the respective application. PTFE is a sintered material which is brought into the desired shape by machining. This allows a wide range of variants to be produced without tooling costs.

Different variants and materials are available as preloading elements or springs, which are also adapted to the respective application. In addition to corrosion-resistant stainless steel, alloys for higher requirements are available. The use of elastomeric materials is also possible. The preload elements essentially determine the force characteristics of the seal and will be adapted to the respective application. Due to the in-house production of the spring elements we have a wide range of different materials and special dimensions.

The behaviour of a spring energized seal follows the functional principle of an elastomer O-ring.

During installation, the seal is compressed and creates a pressure on the sealing surfaces primarily by the spring. As a rule, the higher the force of the spring, the higher the tightness. The actual system pressure increases the contact pressure and thus the sealing effect.

Depending on the required force application, different spring variants can be selected. These differ in the ratio between the pressing stroke and the pressing load as shown in the following diagram.

The gap behind the seal is decisive for the effect and the service life. This gap occurs primarily in radial seals or is necessary for design reasons. Since plastics tend to flow, this gap must be kept as small as possible to avoid extrusion into the gap. This phenomenon is significantly intensified with increasing pressure or temperature.

To counteract the cold flow, different arrangements of support rings made of pressure-resistant material are used.

Our technical department will be pleased to advise you on this.

Spring energized lip seals require a comparatively high standard of surface quality for the sealing surfaces. In general, the better the surface, the better the sealing effect and also the service life of the seal due to less wear. The best possible surface quality should be aimed for, especially when sealing gases and in the cryogenic area.

In addition, the surface hardness of the sealing surfaces also determines the wear resistance of a dynamic seal. Soft sealing surfaces can be damaged by abrasive particles, which must also be considered when selecting the correct seal material. A hardness of approx. 55-60 HRC should be maintained as a guide value.

More than 250 compounds are available for the material of the seal jacket for a wide range of applications. A selection of these can be found here in the table.

In addition, individual compounds suitable for your application are also possible.

Please contact our application technology department.

The specifications provided are only valid with explicit confirmation from GFD. All application parameters must be checked on a case-by-case basis.

In addition to the following standard materials, other materials are also available. Please contact our technical department.

Besides springs as preload elements, elastomer O-rings made of FKM, NBR or silicone are also possible, depending on the application.

Apart from the standard shapes listed below, we develop variants customized to the respective application.
Our technical department will be pleased to advise you.

In addition to the standard shapes listed below, we also develop customized versions for specific applications. Our technical department will be pleased to advise you.

Solutions for valves

Valves that have to function at low temperatures of e.g. -196°C or in the desert, that have to be resistant to aggressive media, hot gases and pressures of several hundred bar, and at best with a long service life, require special solutions. We at GFD check your application individually and offer you a variety of solutions.

We supply solutions for a wide variety of valves such as ball valves, butterfly valves or control valves. We offer materials, which are tested and certified according to NACE/NORSOK/BAM.

If you have any questions, please feel free to contact our technical department. We have the right solution for your application.

Solutions for the food and pharmaceutical industry

This area ideally combines the material properties of chemical-resistant plastics and acid-resistant spring steel. The preloading element guarantees a high and permanent elasticity, which is not affected by cleaning or sterilization processes. We offer FDA and USP VI certified materials. If you have any questions, please feel free to contact our technical department. We have the right solution for your application.