Environmental Engineering Reference
In-Depth Information
4.9.1.3 Plastic Pipe
Plastic pipe has been used in the United States for about 60 years,
and its use is becoming increasingly common. In fact, because of its
particular advantages, plastic pipe is replacing both metallic and non-
metallic piping. The advantages of plastic piping include:
•
High internal and external corrosion resistance
•
Rarely requires insulating or painting
•
Light weight
•
Ease of joining
•
Freedom from rot and rust
•
Resistance to burning
•
Lower cost
•
Long service life
•
Easy to maintain
Several types of plastic pipe are available; still, where plastic pipe
is commonly used in wastewater service, polyvinyl chloride
(PVC) is the
most common plastic pipe for municipal water distribution systems.
PVC is a polymer extruded (shaped by being forced through a die) under
heat and pressure into a thermoplastic that is nearly inert when exposed
to most acids, fuels, and corrosives. PVC is commonly used to carry cold
drinking water because PVC is nontoxic and will not affect the taste of
the water or cause an odor. The limitations of PVC pipe include its lim-
ited temperature range (approximately 150°F to 250°F) and low-pressure
capability (usually 75 to 100 psi). Joining sections
of plastic pipe is accomplished by welding (solvent,
fusion, fillet), threading, and flanges.
Key Point:
The strength of plastic
piping
decreases
as the temperature
of the materials it carries
increases
.
4.10 Tubing
Piping by another name might be tubing?
A logical question might
be “When is a pipe a tube, or a tube a pipe?” Does it really matter if we
call piping or tubing by two distinct, separate, and different names? It
depends, of course, on the differences between the two. When we think
of piping and tubing, we think of tubular, which infers cylindrical prod-
ucts that are hollow. Does this description help us determine the differ-
ence between piping and tubing? No, not really. We need more—a better,
more concise description.
Maybe
size
will work. When we normally think of pipe, we think
in terms of either metallic or nonmetallic cylindrical products that are
hollow and range in nominal size from about 0.5 inch (or less) to several
feet in diameter. On the other hand, when we think of tubing, we think
of cylindrical, hollow products that are relatively smaller in diameter
compared to many other piping materials.
