Freudenberg develops CO2 seals for power industry

Weinheim, Germany – Freudenberg Sealing Technologies (FST) has developed two new seals to for electric substations where carbon dioxide is used as quenching gas.

Regulations in Europe and the US have limited the use of fluorinated gases and a new alternative is the use of CO2 as a quenching gas – being 22,800 times less damaging than SF6 on the environment.

While being more climate-friendly than SF6, the CO2-based materials migrate “much too easily through the sealing material,” FST said in a 27 June release.

“It is like a balloon,” explained Robert Rotzoll, material developer at the company.  “At first, it is filled to bursting, but over time the air or the helium escapes through the rubber surface.”

Permeation, according to Rotzoll, is much greater for CO2 molecules, with their smaller sizes and different structures, than it is for SF6.

The two sealing solutions developed FST are claimed to contain CO2 molecules securely.

One material was developed from EPDM rubber, and the second solution, known as 70 CIIR 236460, uses a synthetic rubber based on chlorobutyl (CIIR).

The CIIR, which stands out for its low permeability to gases and liquids, is also used in the tire industry for its low permeability feature.

“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.

FST will test the new seals jointly with its customers as part of an effort to carry green electricity in the future.

Substations play an important role in the distribution of electric power. They connect transmission lines, which carry at least 110,000 volts, to local grids, which have between 10,000 and 30,000 volts.

Combined with a high current density, the difference in voltages leads to repeated electric arcs at the switches of transformers.

SF6 and the new alternatives are used as protective gases filling the switch under high pressure,. The gas then has very high dielectric strength as an insulating material.