The Perfect Wave

Wave-shaped sealing lip instead of a rotation-symmetrical design

Freudenberg Sealing Technologies has developed a new rotary seal, the “Gerromatic,” for wet-running applications and pressures up to 8 bar. It is equipped with a wave-shaped sealing lip, not a rotation-symmetrical design. This results in a sinusoidal contact pattern. As the shaft rotates, each point of the seal lip repeatedly coats a different area of the shaft, moistening it with the medium. This reduces friction and the usual temperature rise at the sealing area. The contact zone of the undulated seal lip, alternating between flat and linear, has the ability to distribute high pressure so the seal lip’s performance is maintained. It lies securely against the shaft and does not fold down, even across a wide range of pressures. Furthermore, the sinusoidal path provides self-cleaning: If small particles, perhaps from the process material, settle under the seal lip at times, they are quickly rinsed out of the contact zone. This reduces wear and increases the operating life of the seal.

In a Freudenberg Sealing Technologies testing facility, experts have already demonstrated the new seal’s special features. In a test, the Gerromatic displayed a temperature rise that was 20°C less than the increase for a standard seal. The test was a standard wet-running trial that ran for 96 hours at 5 bar and a circumferential speed of 5 meters per second. Its leakage behavior is even more impressive: Under the same conditions, only a vanishingly small leakage rate could be detected over the entire test route of more than 1,700 kilometers.

High resistance to cleaning and sterilizing media

The new Gerromatic rotary seal from Freudenberg Sealing Technologies is made of PTFE and produced in various versions. PTFE is a thermoplastic polymer consisting of fluorine and carbon and is available with food authorizations in accordance with EU 10/2011 and FDA as well as pharmaceutical approvals in accordance with the U.S. standard USP Class VI.

The material stands out for its resistance to temperatures ranging from -80°C to +200°C. Another advantage of the PTFE materials now being used is their high resistance to the media usually used for cleaning and sterilizing closed equipment in the process industry. With a pressure resistance of up to 8 bar and a circumferential speed of up to 25 meters per second, the new seal is especially suited for partially and fully immersed applications with aqueous media where above-average pressure development must be taken into account.