The anti-extrusion rings

The anti-extrusion rings, also known as back-up rings are used in dynamic or static sealing rods or pistons applications. Under high pressures they prevent the penetration (gap extrusion) of the sealing element (O-Ring or X-Ring) in the sealing gap.

Advantages

In addition to improving the lifetime of an O-ring or a X-ring by protecting them from any impurities, the use of anti-extrusion rings widens their range of applications while remaining very cost effective in the following cases:

• Pressure >50 bars,
• Large tolerances and radial clearance,
• High speed,
• Pressure changes,
• Wide temperature influences.

Back-up ring versions

There are 3 standard profiles of back-up rings (BAE):

• AES: Back-up ring, spiral form
• AEM: Back-up ring, unslotted
• AEC: Back-up ring, concave

The profiles AEM and AEC are available in slotted design with an angle of 30 or 45°, or special version (20°) upon request.

Back-up ring type AES

• Rectangular cross section
• Material: PTFE
• Cut angle at 30° or 45°
• Static and dynamic use
• For reciprocating movements only
• Installation in closed grooves
• Can be adjusted by simple cuts in the case of non standard diameters
• Compensation of large temperature changes and tolerances through a screw-like elongation and contraction.

Back-up ring type AEM

• Rectangular cross section
• Material: virgin or filled PTFE-PU-PA-NBR90
• Reciprocating and rotating movements possible
• Installation in open grooves (possible in closed grooves for the type AEMF, Cut angle at 30° or 45 °)

Back-up ring type AEC

• Concave cross section
• Material: NBR90–FPM 90-virgin or filled PTFE-PU
• Static and dynamic use
• For reciprocating movements only
• The large contact surface protects the O-Ring against deformation in case of high pulsating pressures
• Installation in open grooves (possible in closed grooves for the type AEF, Cut angle at 30° or 45°)

Recommendations

The recommendations are identical to those of the installation of the O-ring, however for the non cut back-up rings, the installation in closed grooves should be made with a special tool. The ring must be expanded with a cone and recalibrated after assembly.

Materials