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availability of various pressure classes and diameters makes it easily
desirable to engineers and specifiers. The pipe itself is highly resistant
to chemical permeation. Also, there are various internal and external
corrosion protection systems available.
Ductile iron is susceptible to internal and external corrosion.
Although there are a variety of corrosion protection systems, they do
not all perform equally. Cathodic protection is too cost prohibitive for
use in the municipal systems. The internal cement-mortar lining pre-
vents the deflection of the pipe beyond 3 percent, even though ductile
iron is a flexible conduit. External polyethylene encasement is easily
damaged, for example during tapping, and is subject to careful instal-
lation. The heavy weight of ductile iron pipe raises the cost of labor.
Although the pipe itself resists chemical permeation, the gasket at the
joint does not.
Steel Pipe
Steel pipes, made from a versatile refinement of iron, have seen a wide
range of usage for more than a century and a half. The development
of high-strength steel pipes has made it possible to transport fluids
such as natural gas, crude oil, and petroleum products over long dis-
tances. Initially, all steel pipes had to be threaded together, which was
difficult for large pipes, and they often leaked under high pressure.
The development of electric arc welding machines in 1920s made it
possible to construct leak-proof, high-pressure, large-diameter pipe-
lines. One of the earliest steel water pipe installations in the United
States, still in service today, was in San Francisco in 1863. Develop-
ments in technology have given way to riveted steel pipes evolving
to the automatically welded steel pipes of today. Various other devel-
opments have resulted in the creation of different types of joints as
well as effective mechanisms for prevention of corrosion, making
steel more versatile for trenchless and open-trench applications.
In municipalities, steel pressure pipes are used today in large-
diameter potable water transmission applications. In municipal
trenchless construction, steel pipes are used as casing pipe in pro-
cesses such as microtunneling, jacking, boring, and pipe-ramming
because of their high stiffness and compressive strengths. There have
even been several large-diameter spiral-welded steel pressure pipe
installations in Texas, Washington, and Hawaii via horizontal direc-
tional drilling.
Corrugated Steel Pipe Corrugated steel pipes have been used for
more than a century in gravity applications such as drainage and
storm sewers. Though corrugated steel pipes have been used in
some sanitary sewers, this is not the case today. Due to their rela-
tively low-compressive and tensile strengths, corrugated steel pipes
are not used in trenchless or pressure applications. Therefore, a
detailed discussion of corrugated steel piping products has been