Back-up rings

Aston Seal back-up rings for O-rings, for the most common cross-sections: 1.6, 1.78, 2, 2.4, 2.62, 3, 3.53, 4, 4.5, 5.33, 5.7, 6 and 6.99 mm.

With large clearances or high pressures, the pressure pushes the O-ring into the gap between the parts. The O-ring is nibbled (extrusion), starts to lose pieces and stops sealing. The harder back-up ring sits against the O-ring on the gap side and stops it being pushed in.

How to fit:

• With pressure from one side only: one ring on the side away from the pressure;
• With pressure from both sides (on a piston, for example): one ring on each side of the O-ring;
• The groove must be wide enough for the O-ring and the ring.

How to choose: the O-ring cross-section and the rod or groove diameter. The rings come solid or split (spiral or open), and the split versions fit without dismantling the part.

O-rings have their own category, and the seal finder searches by dimensions.

Technical guide: How to choose a hydraulic seal