Page 541 - Corrosion Engineering Principles and Practice

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of certain process parameters to mechanical integrity, and therefore
are not routinely monitoring them. This is often realized when there
is a loss of containment incident and root cause investigation reveals
that the failed equipment has been operating beyond one or more of
the key process parameter limits [3].
An RBI program can also serve as a helpful tool for quantifying
the risk associated with a change in the value of a key process
parameter. This can be an invaluable resource to the corrosion
engineer when addressing management of change issues in an
operating process unit. It also can serve as an aid to reaching
agreement on the desirable process monitoring and limits on
operating conditions, and in communicating with process unit
operators and management about the impact of changes on risk.

12.7 Industrial Example: Transmission Pipelines
The transmission pipeline industry is an irreplaceable component of
modern infrastructures. Pipelines have historically been the safest
means of transporting natural gas and hazardous liquids. However,
recent pipeline failures have heightened the awareness of transmission
pipeline systems. In particular, in many parts of the world cities have
grown and are now located close to pipeline systems that have been
operating for decades [18].
Many millions of kilometers of pipeline crisscross the globe,
carrying oil and natural gas. In the United States alone there are
approximately 3.5 × 10 km of transmission pipeline, 525,000 for the
6
transmission and gathering of natural gas, 260,000 for the transmission
and gathering of hazardous liquid and the balance for the distribution
of natural gas. Each system is unique with respect to potential integrity
threats and associated consequences in the unlikely event of a failure.
The probability of a release can be reduced through an effective
management program that addresses these integrity threats.
There are many causes and contributors to pipeline failures. The
U.S. Department of Transportation (DOT) Research and Special
Programs Administration, Office of Pipeline Safety (RSPA/OPS)
compiles data on pipeline accidents and their causes. Tables 12.4 to
12.6 summarize the results collected during a two-year period (2002
and 2003) for respectively, natural gas transmission and gathering,
hazardous liquid transmission, and natural gas distribution.
It is notable, in Tables 12.4 and 12.5, that corrosion was the most
common cause (37 percent) of natural gas transmission and gathering
pipeline incidents during that period, and the second most common
cause (24 percent) of hazardous liquid pipeline incidents. During the
same period over 60 percent of natural-gas distribution pipeline inci-
dents were caused by outside forces (e.g., excavation by the operator or
other parties, damage from natural forces, and the like) while only a
small fraction (0.1 percent) of the property damage was attributed