Environmental Engineering Reference
In-Depth Information
figure 4.25 Low-pressure hose coupling.
Another type of metallic hose is used in ductwork. This type of hose
is usually made of aluminum, galvanized steel, and stainless steel and
is used to protect against corrosive fumes, as well as gases at extreme
hot or cold temperatures. The hose is also fire resistant and usually
does not burn.
4.11.4 hose Couplings
The methods of connecting or coupling hoses vary. Hose couplings
may be either permanent or reusable. They can also be manufactured for
the obvious advantage of quick connect or quick disconnect. Probably
the best example of the need for quick connect is fire hose—quick-dis-
connect couplings permit rapid connection between separate lengths
of hose and between hose ends and hydrants or nozzles. Another good
example of where the feature of quick connect and quick disconnect
is user friendly is in plant or mobile compressed-air systems, where
a single line may have a number of uses. Changes involve disconnect-
ing one section and connecting another. In plant shops, for example,
compressed air from a single source is used to power pneumatic tools,
cleaning units, paint sprayers, and so on. Each unit has a hose that is
equipped for rapid connecting and disconnecting at the fixed airline.
Caution:
Before connections are broken, unless quick-acting, self-clos-
ing connectors are used, pressure must be released first.
For general low-pressure applications, a coupling like that shown
in Figure 4.25 is used. To place this coupling on the hose by hand, first
cut hose to the proper length, then oil the inside of the hose and outside
of the coupling stem. Force the hose over the stem into the protective
cap until it seats against the bottom of the cap. No brazing is involved,
and the coupling can be used repeatedly. After the coupling has been
inserted in the hose, a yoke is placed over it in such a way that its arms
are positioned along opposite sides of the hose behind the fitting. The
arms are then tightly strapped or banded.
Caution:
Where the pressure demands are greater, such a coupling can
be blown out of the tube. Hose couplings designed to meet high-pressure
applications must be used.
A variation of this type uses a clamp that is put over the inner end
of the fitting and is then tightly bolted, thus holding the hose firmly. In
other cases, a plain clamp is used.
Each size clamp is designed for a hose
of a specified size (i.e., diameter). The
Key Point:
For large hoses of rugged wall construction,
it is not possible to insert push-on fittings by hand.
Special bench tools are required.
