Back-Up Rings & Polyurethane O-Rsing

Back-Up Rings & Polyurethane O-Rings

Back-up rings are essential components used to prevent seal extrusion in high-pressure applications. They support O-rings by minimizing the “E” gap between metal parts that could otherwise lead to seal failure. Polyurethane (HPU) O-rings and PTFE rings are among the most widely used solutions due to their resilience, chemical compatibility, and wide operating ranges.

Key Features

Back-Up Rings

• Designed to prevent extrusion in high-pressure environments

• Compensate for loose-fitting parts and large extrusion gaps

• Made commonly from PTFE (scarf or spiral cut)

• Available in PEEK and Nylon for higher pressure or larger gaps

• Resistant to oils, solvents, and have a broad temperature range

Polyurethane (HPU) O-Rings

• Exceptional abrasion resistance

• High resilience and low compression set (better than nitrile)

• Can eliminate the need for back-up rings in certain applications

• Resistant to:

  • Water up to 100°C

  • Sea water

  • Mineral & vegetable oils

  • Silicone oils

  • Ozone and cold oxygen

  • HFA, HFB fluids

  • Diluted acids and lyes

• Available in standard or custom sizes, injection-moulded or lathe-cut

Importance

• Prevents seal failure: Back-up rings block O-rings from entering clearance gaps during pressure spikes, which avoids nibbling and seal damage.

• Ensures longevity and reliability: By supporting the primary sealing element, they extend seal life in extreme service conditions.

• Essential for high-pressure systems: Especially where pulsation or sudden pressure surges occur.

• Reduces downtime and maintenance costs: Effective sealing means fewer leaks and replacements.

• Ideal for heavy-duty use: HPU O-rings perform well under high dynamic loads, making them suitable for industrial and hydraulic systems.

• Enhances system safety: Prevents catastrophic failures due to seal extrusion or degradation.