Page 19 - Reliability and Maintainability of In service Pipelines

8 Reliability and Maintainability of In-Service Pipelines

as compared to concrete and clay pipes, steel pipes are often used for pipe repla-
cements when concrete and/or clay pipes fail.
The different types of pipes, along with their use, function, and viability status
are reviewed in the following sections.

1.3.1 METALLIC PIPELINES

1.3.1.1 Nonferrous Pipes

Nonferrous metals, including aluminum, nickel, lead, tin, brass, silver, and zinc,
are known for their tensile strength and present characteristics that hold an
advantage over ferrous metals, mainly by their malleability, lighter weight, and
corrosion resistivity. As iron content is absent in nonferrous metals, the probabil-
ity of rust and corrosion occurring also is fairly low. Also these types of pipes
can be used in pipe networks that are prone to highly corrosive environments,
such as carrying corrosive chemicals and sewerage. Therefore, usage of nonfer-
rous metals in water pipes and gutters are very common. However, the only
difference lies in accessibility of these materials, recycling efficiency, and costs.
Recycling of nonferrous metals, including aluminum, copper, brass, and lead,
is relatively common due to its scarcity. Therefore, there is a heavy dependence
on recycling of scrap materials in order to create new nonferrous metals. In fact,
aluminum is known to be the most recycled metal, ranking third in the world. It
is also this reason that the cost of nonferrous metals is also more expensive than
ferrous metals, with stainless steel often being used instead, due to its cheaper
cost and versatility. Consequently, nonferrous metals are mainly used in fittings
of pipes, and other small applications that require strength where needed.
Nonferrous materials, can be combined to create alloys, including brass,
bronze, and solder, for increased strength and flexibility without resulting in the
effects of heavier weight compared with ferrous metals. The high malleable state
of nonferrous metals, makes them ideal for usage as they can be easily pressed
into thin sheets without breaking.

1.3.1.2 Ferrous Pipes

Ferrous pipes are derived from ferrous metals consisting of iron. Different types
of ferrous metals exist for different uses and are differentiated by the iron content
percentage. Below is a list of the different types of ferrous metals:
Mild steel: containing an iron content of 99.7% 99.9% and carbon content of
0.1% 0.3%.