Cap Seal | Aerospace Digital Catalogue

CDI is trusted by the world’s major aircraft manufacturers for everything from flight control actuators to landing gear. Our industry-leading sealing systems are made from time-tested materials and are specifically built to meet any application need.


Operating Conditions



Cap Seal

The Cap Seal is the original slipper seal developed in the mid-1950s’s to improve the performance of O-Rings and Back-up Rings used in older versions of the MIL-G-5514 gland standard. The Cap Seal was originally designed to provide a cost-effective cap seal solution that prevents extrusion and eliminates O-ring spiral failure in dynamic applications. Each seal is a dual-acting seal that combines a cap made from Armorlene®, CDI’s PTFE material, and an Arylast™ elastomeric energizer which demonstrates excellent friction and sealing properties. The Cap Seal provides non-stick-slip starting and excellent dry running.

Features and Benefits

  • Lower friction and elimination of spiral failure, which leads to better system performance.
  • Surrounds the O-ring, protecting it from extrusion when under pressure.
  • Hardware (gland diameter) can be modified to improve seal friction without affecting leakage control.
  • Utilizes standard aerospace grade O-Rings.
  • Configuration includes a cap component with circumferential grooves (for better dynamic sealing and lubrication retention) and notches (reference SAE AIR1243 for blow-by protection)
    • Note that some sizes of the Cap Seal do not include grooves or radial notches
    • Alternate configurations are available upon request, including Seal Caps component without circumferential grooves and/or notches.
  • Designed for use in MIL-G-5514 and AS4716 glands.
Dash Size B Rod OD Min B Rod OD Max H Rod Bore Ø Min H Rod Bore Ø Max E Rod Gland Groove Ø Min E Rod Gland Groove Ø Max Share