Test rig for rod seals contact pressure measurement

The sealing efficiency and the extent of the friction force in an elastomeric seal – counterpart sliding contact depend highly on the contact characteristics at the interface. In particular, a deep knowledge of the interface contact pressure is needed. The work herein described deals with the design of a new test bench for an indirect contact pressure measurement. In particular, the radial force exerted by a rod seal sliding on a sensor-equipped portion of a cylinder rod is measured; during the seal displacement, the contact area between the seal and the sensorequipped rod increases, so that the radial force trend during time can be acquired. Taking the sliding velocity at a low constant value, contact pressure can be indirectly computed by differentiating the force signal. This way it is possible to perform measurements without introducing a third body between the seal and its counterpart, so avoiding any modification of the contact surface. Initially, the test bench working principle is described, highlighting all critical aspects related to the radial force transmission from the seal to the load sensor; subsequently, the test bench requirements were defined. Finally, the design solution was presented.