A close interval survey (CIS) is a preventive action that can
help prevent this corrosion before it starts. CIS is one part of a
suite of tools used to identify conditions that cause corrosion,
allowing you to assess the effectiveness of the cathodic
protection (CP) system protecting your pipeline – ensuring it is
operating to NACE SP0169 specified standards.
before it starts.
Once corrosion is detected in a pipeline, extensive (and
costly) remediation programs must be implemented to
ensure ongoing safety of your assets, employees, neighbors
and the environment. These may include costly replacement
or repair of corroded sections of pipeline, a reduction in
maximum allowable operating pressure (MAOP) and throughput
or an increase in required assessments of your pipeline.
Pipeline operators estimate that the total cost of maintenance
of CP systems can be up as much as 15 times lower compared
to monitoring and repairing corrosion. A proactive, preventive
close interval survey program – including those that conduct
annual pipeline surveys – can be a fraction of the cost of a
program to survey and remediate corroded pipe.
Regulations prescribe how often pipeline operators
must perform an assessment of their transmission
pipelines. In the U.S., it is a minimum of every seven
years for transmission lines and every five years if the
pipe carries hazardous liquids.
Many operators, however, perform CIS assessments
more frequently so they can take action to prevent
corrosion. Once corrosion is detected, costly repairs
or a reduction in MAOP is required which leads to
reduced throughput and lower revenue for operators.