Back-up rings are are designed to prevent O-ring extrusion under pressure.
Back-up rings also known as anti-extrusion rings are commonly used with O-rings, when high pressure is exerted on the O-ring, its soft rubber material can be forced into the clearance gap causing the O-ring to extrude. Back-up rings keep the O-ring material from flowing into the gap which prevents premature failure by providing resistance in minimising the risk of extrusion. Though back-up rings are not designed to have any sealing function in their own right.
At Chain & Drives, we stock AMAANDO’s high quality range of AS568, BS, JIS and standard metric sizes back-up rings in PTFE and NBR rubber to suit both O-rings or X-rings.