PU seal from Freudenberg-NOK replaces PTFE seals in hydraulic piston accumulators

Test comparisons with other products have shown that Freudenberg-NOK’s Simko 300 seal ring offers distinct advantages over frequently used polytetrafluorethylene (PTFE) seals with regard to operating life, form stability and sealing characteristics.

The durability of sealing rings in piston accumulators is a crucial parameter for operating life. For this reason, piston accumulators undergo accelerated load tests at the Hydratech test centre in Sikeborg, Denmark, that simulate 20 years of service life. During the testing process, the behaviour of the seals under pressures greater than 200 bar and temperatures ranging between –104 °F to +140 °F is measured – conditions that exceed actual stresses.

Based on its form stability, high hardness and low abrasion, Hydratech now uses Simko 300 from Freudenberg-NOK. The sealing solution “fully meets our expectations and is impressive due to its long service life,” said Jimmi Wenderby, Hydratech research and development manager.

Most sealing systems in piston accumulators work with two seals, one for oil and another for gas. This leads to increased wear due to the extreme load, especially in PTFE seals. By contrast, the Simko 300 is a single seal (consisting of a seal ring and a pressure ring) and is made of polyurethane. Polyurethane’s hardness grade of 98 Shore A corresponds to that of PTFE but is much more robust. Its susceptibility to potential surface damage during installation is also lower. The pressure ring creating the necessary pre-tension is made of an elastomer.

The Simko 300 seal’s high form stability, its surface firmness, and its long operating life make it especially appealing for use in hydraulic pitch controllers in wind power facilities. They are an important component of the security technology in wind power facilities, as the piston accumulator must not merely function reliably under extreme weather conditions but also withstand the high differential pressures that are also produced. The accumulator must be able to operate leak-free over very long periods of time.

The Simko 300 is a cost-effective and reliable solution for use in piston accumulators, and it provides a long service life for the wind power station due to its outstanding sealing qualities, says Freudenberg-NOK.