threaded ports in pumps, valves, and other
components. Several of these thread combinations
are shown in figure 5-16.
Tubing used with flare connectors must be
flared prior to assembly. The nut fits over the
sleeve and when tightened, it draws the sleeve and
tubing flare tightly against the male fitting to form
The male fitting has a cone-shaped surface
with the same angle as the inside of the flare. The
sleeve supports the tube so vibration does not
concentrate at the edge of the flare, and distributes
the shearing action over a wider area for added
strength. Tube flaring is covered in Tools and
Their Uses, NAVEDTRA 10085 (series), and
other applicable training manuals.
Correct and incorrect methods of installing
flared-tube connectors are illustrated in figure
5-17. Tubing nuts should be tightened with a
torque wrench to the value specified in applicable
If an aluminum alloy flared connector leaks
after being tightened to the required torque, it
must not be tightened further. Overtightening may
severely damage or completely cut off the tubing
flare or may result in damage to the sleeve or nut.
The leaking connection must be disassembled and
the fault corrected.
If a steel tube connection leaks, it may be
tightened 1/6 turn beyond the specified torque in
an attempt to stop the leakage; then if it still leaks,
it must be disassembled and repaired.
Undertightening of connections may be
serious, as this can allow the tubing to leak at the
connector bemuse of insufficient grip on the flare
by the sleeve. The use of a torque wrench will
A nut should never be tightened when
there is pressure in the line, as this will tend
to damage the connection without adding
any appreciable torque to the connection.
Figure 5-17.Correct and incorrect methods of installing flared fittings.