An innovative materials combination consisting of two distinct polyurethanes provides Freudenberg-NOK Sealing Technologies (Freudenberg-NOK) new HDR-2C rod seal with special extrusion stability at high pressures and great flexibility at temperatures down to -50 °C. This innovative materials combination is particularly well suited to address environmental challenges encountered in the fluid power industry.
Seals in hydraulic cylinders must withstand major stresses. They are exposed to severe pressure and temperature fluctuations as well as the hydraulic fluid in use. But they still must ensure reliable leak tightness across a wide performance spectrum over the entire period of use. The two-component technology of the HDR-2C handles the stresses on the different functional areas of a rod seal.
The individual sections of rod seals are exposed to very different stresses and must meet requirements that in part demand conflicting material characteristics. For this reason, standard seals are frequently manufactured with a medium-hard material – a compromise that decreases the seals’ reliability and service life. The reason: On one hand, with the help of an excellent press fit, the seal back must prevent a seal’s axial shift due to pressure and frictional forces. And it must be as extrusion-resistant as possible on the gap side. On the other hand, the seal lips require a softer, more flexible material. This is the only way a static lip can reliably seal the ground of the groove and that a dynamic seal can ensure high leak tightness and resistance to wear even at low temperatures despite significant axial and radial stresses. The conflicting requirements of the different functional areas thus range from high rigidity and higher extrusion resistance (hard material) to less permanent deformation and greater elasticity (soft material).
The company’s groove ring combines the advantages of two high-performance materials with different physical characteristics in just one element. The seal back is made from polyurethane 98 AU 928, a material with a hardness grade of 98 Shore A, which stands out for great stability under high operation pressures. The seal lips made of polyurethane 92 AU 21100 have very good dynamic sealing properties due to the material’s high elasticity and low compression set. Compared to a standard seal, the HDR-2C’s two-component technology offers a significantly improved performance range as well as much easier installation. Greater gap dimension tolerances, reliable use at operating pressures up to 500 bar and the high leak tightness in the temperature range from -50 °C to 110 °C make the new rod seal from Freudenberg-NOK an extremely high-performance sealing solution offering outstanding value for the money.