Page 272 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

250 CORROSION CONTROL AND PREVENTION

receivers, removal of appurtenances that could cause the pig to become lodged), pos-
sible reduced throughputs during the pigging operation, cost of pigs, solvents, and
the cost of disposal of the material from the pipe.
Rehabilitation of internally corroded pipelines is somewhat more difficult to man-
age than external corrosion. Internally corroded pipes require cutting out and replac-
ing the affected sections of the pipeline. Other methods of internal rehabilitation
consist of pulled liners and epoxy flood coating. Cost estimates for these options
can vary greatly and predominantly dependent on the extent of cleaning required to
prepare the internal surface for coating.

4.11.5 Cost of Operation and Maintenance (Corrosion Control)
The most effective way to account for all of the related operating and maintenance
costs associated with corrosion is to examine the total operating and maintenance
budgets for representative companies (Table 4.22).
The three specific conditions that make replacement/rehabilitation necessary are:
(i) severe corrosion damage of a pipeline not cathodically protected; (ii) severe
coating deterioration leading to increased CP requirements, and (iii) SCC along
a large area of pipeline. Pipeline integrity management programs are used by
pipeline operators to determine the locations in which corrosion defects pose a
threat to safe operation. Repairs at these locations can vary from the installation
of a reinforcing sleeve to the implementation of a large-scale pipe rehabilitation
or replacement program. For localized corrosion flaws, the repair process can
include composite sleeves, full-encirclement steel sleeves, or replacement of a pipe
segment. For local flaws, the repair process can be handled by company procedures
and criteria. For large-scale corrosion and/or coating deterioration issues, the
replacement/rehabilitation decisions must consider both operational and economic
factors.
In-line inspections (ILI) are useful in obtaining a profile of defects in a pipeline.
High-resolution UT and MFL ILI tools can be used to determine the geometry and
orientation of corrosion defects.
These inspections can be used to determine the number and locations of
near-critical flaws that should be examined by a dig program to verify and repair
the flaw. Using appropriate growth models, predictions can be made on future
dig/repair and/or reinspection requirements for the ULI inspected line. If the density

TABLE 4.22 Estimated Costs for Operation and Maintenance Associated with
Corrosion and Corrosion Control

Company Miles of Pipe Total Costs Corrosion Costs Corrosion Cost Per Mile
A 11 × 10 6 359 × 10 6 15% $4894
B 10 × 10 6 707 × 10 6 15% $10605
C 5 × 10 6 192 × 10 6 15% $5760
Average cost $7086