Figure 8-10.--Series 320 (Aeroquip) quick disconnect.
possibly an O-ring and two backup rings. Hydraulic
A newer type of quick-disconnect coupling is the
seals used internally on a sliding or moving assembly
series 3200 (Aeroquip). This is an improved version
are normally called PACKINGS. Hydraulic seals used
and is simple to operate. This series is designed for use
between nonmoving fittings and bosses are normally
in hydraulic systems up to 3,000-psi operating
called GASKETS. Most packings and gaskets used in
pressure. Figure 8-10 shows the quick disconnect in
naval aircraft are manufactured in the form of O-rings.
both the disconnected and connected positions. To
connect, align the tabular valve of the hose-attaching
An O-ring is circular in shape, and its cross section
half with the recess in the bulkhead-coupling half. The
is small in relation to its diameter. The cross section is
nut is then brought forward to engage the threads, and
truly round and has been molded and trimmed to
rotated in a clockwise direction until the hex nut
extremely close tolerances. In some landing gear struts,
engages the hex on the coupling body. This may be
an elliptical seal is used. The elliptical seal is similar to
done in one continuous turn of the union nut, about
the O-ring seal except for its cross-sectional shape. As
one-quarter of a revolution. The quick-lead Acme
its name implies, its cross section is elliptical in shape.
thread allows the coupling to be connected by hand,
Both the O-ring and elliptical seals are shown in figure
against pressures up to 300 psi.
8-11.
The connection may be inspected by three different
Advances in aircraft design have made new O-ring
methods as follows: If the nut can be turned by hand in a
composition necessary to meet changing conditions.
clockwise direction, the coupling is not locked. A slight
Hydraulic O-rings were originally established under
tug on the hose will separate the halves if the couplings
AN (Air Force-Navy) specification numbers (6227,
are not locked. Inspect the locking male hex on the
6230, and 6290) for use in fluid at operating
bulkhead coupling half; if the coupling is not
connected, the red male hex of the bulkhead half will be
visible.
HYDRAULIC SEALS
Hydraulic seals are used throughout aircraft
hydraulic systems to minimize internal and external
leakage of hydraulic fluid. They prevent the loss of
system pressure. A seal may consist of more than one
component, such as an O-ring and a backup ring, or
Figure 8-11.--Hydraulic seals.
8-22
