When installing seals, care must be taken so they are not stretched
Any twists or strains to the seal can lead to its
early failure and must be prevented by gently working the seal into
A gasket is a piece of material placed between two parts where there
is no movement.
The gasket is used as a filler to compensate for
irregularities on the surfaces of the two mating parts permitting
Many different materials are used for making
gaskets. For use in hydraulic systems the gaskets may be made from
treated paper, synthetic rubber, copper, or aluminum.
O-Ring Gaskets. The most common type of gasket used in aircraft
hydraulic systems is the O-ring.
When used as a gasket the O-ring
has the same advantage as when used as a seal, as explained in a
Crush Washers. The second most commonly used gasket is the crush
washer, used in hydraulic systems and made from aluminum or copper.
Fittings using these washers have concentric grooves and ridges that
bear against or crush the washer. These grooves and ridges seal the
washer and fitting as the connecting parts are tightened together.
Some types of gaskets can be field-fabricated as long as the bulk
material conforms to the required military specifications. When you
cut replacement gaskets from bulk material, the most important
consideration is the exact duplication of the thickness of the
Like seals, gaskets must be examined before installation to ensure
their serviceability. The component surfaces to be connected must be
thoroughly cleaned. During assembly, care must be taken not to crimp
or twist the gaskets.
When tightening the components, the gaskets
must not be compressed into the threads where they can be cut,
damaged, or block mating surfaces from being flush.
STORING SEALS AND GASKETS
Seals and gaskets must be stored in accordance with the same
specifications outlined for hose and hose assemblies in a previous
paragraph. By way of review, those specifications