Rotor Seal, Vespel, Rheodyne 7725i

The rotor seal in the Rheodyne model 7125 is of a Vespel type seal. Slots in the rotor seal make a flow path between the adjacent stator ports and turning the rotor 60° switches the flow path. A Teflon sleeve is embedded in the rotor seal and the needle port tube pushes against the outer edge of the sleeve with spring tension just sufficient to compress the Teflon around the needle.