Graphics Programs Reference
In-Depth Information
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The pipes must not be so far underground that it is cost prohibitive
to install them.
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Appurtenances such as valves and hydrants must be included in the
design to allow the lines to be controlled, accessed, and maintained.
These requirements relate to three basic types of pressure pipe design compo-
nents: fittings, pipes, and appurtenances. This chapter describes these components
as well as their relationship to each other when represented in a Civil 3D pressure
network.
understanding Fittings, Angles, and Appurtenances
Pressure pipe fittings serve two purposes. The first, like structures in gravity sys-
tems, is to enable two or more pipes to connect. For example, a tee or wye fitting
provides a connection for three pipes, whereas a crossing fitting provides a connec-
tion for four. The second purpose of a fitting is to create a bend in the direction of
the pipeline, the angle of which is typically dictated by manufacturing standards.
For example, elbows are commonly available in 90°, 45°, 22.5°, and 11.25° versions.
For this reason, bend angles are a big part of pressure pipe design.
In addition to bend angles, a slight amount of deflection is allowed within
connections. This deflection angle varies depending on how the pipes or fittings
have been manufactured and is part of the design. This allowable deflection also
enables a series of pipes to form a curve by providing a little deflection at each
joint. Therefore, pressure pipes can be laid out on a curve, with the radius deter-
mined by the allowable deflection.
Another factor that can be incorporated into the design is the allowable bend-
ing radius of the pipes. Bending the pipes is another way a system can be laid
out along a curve. The allowable bending radius is a function of the size, mate-
rial, and manufacturer specifications of the pipe.
Because of available fittings, allowable deflection angles, and allowable bend
radius, each bend in a pressure pipe is a design in itself. As a designer, you'll be
required to choose the right combination of fitting, deflection angle, and bend
radius to make each bend in the pipeline.
Appurtenances are another component of pressure pipe designs. The challenge
with appurtenances is that they usually require consideration for human access.
For example, a fire hydrant must be properly located at ground level so that fire-
fighters or maintenance personnel can access it.
understanding Pressure Pipes
Like gravity pipes, pressure pipes are used to convey a substance; but the main dif-
ference, of course, is that the substance is moved by pressure rather than gravity.
