Figure 2-41.—Series 320 (Aeroquip) quick disconnect.
NOTE: Do not use a wrench to couple or
uncouple series 145 or 155 quick disconnects
unless a modified union nut is incorporated.
Modified union nuts may be identified by the
letter C preceding the part number on the nut.
On these modified union nuts, a wrench may
be used to assist in tightening the coupling.
Torque values for the various size couplings
may be found in the aircraft MIM, and should
be strictly complied within all instances.
A newer type of quick-disconnect coupling is the
series 3200 (Aeroquip). This is an improved version
and is simple to operate. This series is designed for
use in hydraulic systems up to 3,000 psi operating
pressure. Figure 2-41 shows the quick disconnect in
both the disconnected and connected positions. To
connect, align the tabular valve of the hose-attaching
half with the recess in the bulkhead-coupling half.
The nut is then brought forward to engage the threads,
and rotated in a clockwise direction until the hex nut
engages the hex on the coupling body. This may be
done in one continuous turn of the union nut, about
one-quarter of a revolution. The quick-lead Acme
thread allows the coupling to be connected by hand,
against pressures up to 300 psi.
The connection may be inspected by three
different methods as follows: If the nut can be turned
by hand in a clockwise direction, the coupling is not
locked. A slight tug on the hose will separate the
halves if the couplings are not locked. Inspect the
locking male hex on the 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
possibly an O-ring and two backup rings. Hydraulic
seals used internally on a sliding or moving assembly
are normally called PACKINGS. Hydraulic seals
used between nonmoving fittings and bosses are
normally called GASKETS. Most packings and
gaskets used in naval aircraft are manufactured in the
form of O-rings.
An O-ring is circular in shape, and its cross
section is small in relation to its diameter. The cross
section is truly round and has been molded and
2-30
