Friction of hydraulic rod seals at high velocities

• Measurement of seal friction was performed up to a sliding velocity of about 10 m/s.
• Step seals can be full hydrodynamically lubricated at high velocities and low pressurisation.
• PU compact seal show a similar friction level than a PTFE step seal.

Hydraulic cylinders are preferred if a large power density and high dynamics are required because of the low mass which has to be accelerated. Maybe the most critical machine element in fluid power devices is the rod seal. A failure leads to a contamination of the environment and the friction is dominated by the seals. A test rig was developed to measure the seal friction at high accelerations and velocities. In an experimental study the influence of acceleration, sealed pressure and temperature was captured for a polytetrafluoroethylene (PTFE) step seal. Furthermore, the friction of different seal types was measured and the principle suitability of compact seals made from a polyurethane (PU) compound is highlighted.