Environmental Engineering Reference
In-Depth Information
Various heat treatments can be used to manipulate specific prop-
erties of steel, such as hardness and ductility (meaning it can be fash-
ioned into a new form without breaking). One of the most common heat
treatments employed in steel processing is annealing.
annealing
(some-
times referred to as
stress relieving
) consists of heating the metal and
permitting it to cool gradually to make it softer and less brittle.
Note:
Steel is one of the most important basic production materials of
modern industry.
nonferrous
metals, unlike ferrous metals, do not contain iron. A
common example of a nonferrous metal used in piping is brass. Other
examples of nonferrous materials used in pipe include polyethylene,
polybutylene, polyurethane, and polyvinyl chloride (PVC). Pipes of these
materials are commonly used in low-pressure applications for trans-
porting coarse solids (Snoek and Camey, 1981).
In addition to the more commonly used fer-
rous and nonferrous metals, special pipe materials
for special applications are also gaining wider use
in industry—even though they are more expensive.
Probably one of the most commonly used materials that falls into this
category is aluminum pipe. Aluminum pipe has the advantage of being
lightweight and corrosion resistant with relatively good strength charac-
teristics. Lead is another special pipe material used for certain applica-
tions, especially where a high degree of resistance to corrosive materials
is desired. Tantalum, titanium, and zirconium piping materials are also
highly resistant to corrosives.
Key Point:
Although aluminum is
relatively strong, it is important
to note that its strength
decreases
as temperature
increases
.
Note:
Piping materials selection for use in water treatment and distri-
bution operations should be based on commonly accepted piping stan-
dards such as those provided by the American Society for Testing and
Materials (ASTM), American Water Works Association (AWWA), American
National Standards Institute (ANSI), American Society of Mechanical
Engineers (ASME), and American Petroleum Industry (API).
Piping systems convey many types of water including service water,
city water, treated or processed water, and distilled water. Service water,
used for flushing and cooling purposes, is untreated water that is usu-
ally strained but is otherwise raw water taken directly from a source
(e.g., lake, river, or deep well). City water is treated potable water. Treated
water has been processed to remove various minerals that could cause
deterioration or sludge in piping. Distilled water is specially purified.
4.8.5.1.1 Cast Iron Pipe
“There are more miles of [cast iron pipe] in use today than of any
other type. There are many water systems having cast-iron mains that
are over 100 years old and still function well in daily use” (AWWA, 1996).
Cast iron pipe has the advantages of strength, long service life, and
being reasonably maintenance free. Its disadvantages include its being
subject to electrolysis and attack from acid and alkali soil and its heavi-
ness (Gagliardi and Liberatore, 2000).
