PTFE back-up ring

rubber

The mission of the back-up or anti-extrusion rings is to prevent the static seal from entering the existing gap between the two parts to be sealed and damaged when extruded due to the pressure of the system. The back-up rings are used as auxiliary elements of O-rings or other sealing seals, especially in high pressure applications for the sealing of rods and pistons in axial movement. They are manufactured in flat or convex cross-sections, depending on the geometry of the part to be protected. Depending on the extrusion gap between the two sliding parts, O-rings with back-up rings can work up to 250 bar pressure under dynamic loads, and up to 400 bar pressure, under static conditions. The back-up rings must be on the opposite side of the pressure. In double-acting assemblies, it is recommended to place back-up rings on both sides of the sealing seal. The back-up rings in stock are in PTFE and 90 NBR materials. Polyurethane (AU) and other technical plastics can also be manufactured, such as polyamide (PA) and polyacetal (POM). They are flat, concave section elements with a cross section and are used as auxiliary elements of the O-rings to prevent them from being introduced through the extrusion groove when sealing pistons and rods. On request, spiral rings can be supplied for very specific working conditions, such as sudden temperature fluctuations. Even if the ring shrinks, there is always a spiral protecting the O-ring from extrusion.