In most cases it is mandatory to discard and replace
seals and gaskets. You should ensure that seals and
gaskets are properly seated and that mating and align-
ment of flanges are fitted. This will prevent the exces-
sive torque required to close the joint, which imposes
structural loads on the clamping devices. Adjacent
support clamps and brackets should remain loose until
installation of the coupling has been completed.
Some of the most commonly used plain-band
couplings are shown in figure 3-26. When you install a
hose between two duct sections, the gap between the
duct ends should be a minimum of 1/8 of an inch and a
maximum of 3/4 of an inch. When you install the
clamps on the connection, the clamp should be 1/4 of an
inch from the end of the connector. Misalignment
between the ducting ends should not exceed 1/8 of an
Marman clamps are commonly used in ducting
systems and should be tightened to the torque value
indicated on the coupling. Tighten all couplings in the
manner and to the torque value specified on the clamp
or in the applicable maintenance instruction manual.
When you install flexible couplings, such as the
one shown in figure 3-27, the following steps are
recommended to assure proper security:
Figure 3-26.--Flexible line connectors.
Figure 3-27.--Flexible line coupling.