Axial support ring

For functional and material reasons, the gap between a seal face and the adjoining machine parts (shaft, shaft sleeve or housing) must be relatively large. The pressure to be sealed tries to extrude the secondary seal through this gap. A support ring positioned on the side of secondary seal facing away from the pressure prevents this extrusion. The preferred choice of material for axial support rings is PTFE with (reinforcement) fillers such as glass fibre, carbon powder or metal powder. The fillers increase the PTFE's resistance to flow and hence raise its thermal limit of application under pressure. Pressure, temperature and materials (coefficient of friction) are the primary factors needing to be taken into account when deciding on the size of the support ring and gap. For assembly reasons, axial support rings are preferably installed in open grooves (cf. types of groove).

Radial support ring

Metallic radial support rings are used to give radial support to relatively soft face materials (e.g. carbon) so as to counteract pressure induced deformation of the sliding faces (under external pressure loads: A-gap formation). Encasing a non-metallic seal face in metal on both sides lends it the geometrical stability and expansion characteristic of the metallic parts.