In high-pressure hydraulic systems, extreme mechanical loads and high fluid pressures create a severe risk of seal extrusion. As pressure spikes, softer elastomeric piston seals are forcibly squeezed into the microscopic extrusion gap between the piston and the cylinder bore. Once forced into this clearance, the seal material quickly nibbles, deforms, and fails.
To prevent this mode of failure under heavy loads, engineers rely on backup rings. Positioned adjacent to the primary piston seal on the low-pressure side, a backup ring acts as a rigid mechanical barrier that physically blocks the clearance gap. Materials like hard thermoplastics or PTFE are commonly used because they retain their shape under immense stress.
When system pressure rises, it pushes the main seal against the backup ring. The backup ring bridges the clearance space, preventing the softer seal from flowing into the gap while still allowing it to maintain an effective radial seal.
Incorporating backup rings is an essential engineering practice for high-load hydraulic cylinders, significantly enhancing system reliability, extending component lifespan, and preventing catastrophic fluid failure under intense operational pressures.
