Seals for Climate-friendly Switching Stations

But this protective gas has a major disadvantage – it is 22,800 times as damaging to the climate as carbon dioxide. Regulations in Europe and in the United States that limit the use of fluorinated greenhouse gases like SF6 have set off a search for substitutes. Today a handful of potential materials based on carbon dioxide have been identified. They are far more climate-friendly than SF6, but they have a huge disadvantage as well: They migrate much too easily through the sealing material. “It is like a balloon,” said Dr. Robert Rotzoll, material developer at Freudenberg Sealing Technologies. “At first, it is filled to bursting, but over time the air or the helium escapes through the rubber surface.” Permeation is the process by which a gas penetrates or migrates through a solid body. And it is much greater for CO2 molecules, with their smaller sizes and different structures, than it is for SF6.

For this reason, the material experts at Freudenberg Sealing Technologies have developed two new materials. They meet carbon dioxide’s higher requirements for permeation, without declines in temperature or media resistance. For example, the seals must withstand a temperature of 100°C as well as -50° C, so they can function in switching stations in colder regions. The sealing material must also have a long service life and thus be resistant to aggressive media, such as ozone, that act on the seal from outside.

While one material was developed from EPDM rubber, the second solution, known as 70 CIIR 236460, uses a synthetic rubber based on chlorobutyl (CIIR), which stands out for its low permeability to gases and liquids. It is also used in the tire industry for this reason. “The new seals for climate-friendly alternative gases are fully developed. We have already installed the 70 CIIR 236460 version based on chlorobutyl in prototype switches,” Rotzoll said. Freudenberg Sealing Technologies will test the new seals jointly with its customers – so green electricity can be transported in an even more climate-friendly way in the future.