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Pipeline integrity management is one way of addressing integrity and environmental concerns in high-consequence areas. For liquid pipelines, the U.S. Department of Transportation addresses pipeline integrity management in the U.S. Code of Federal Regulations (CFR) Title 49 Part 1995. Currently under development are the rules for gas pipelines in 49 CFR Part 192. The most prevalent time-dependent threat to a pipeline is corrosion. Corrosion can occur both externally and internally. When a pipe is excavated, external corrosion can be obvious; however, internal corrosion can remain undetected.
Corrosion is a time-dependent phenomenon. External corrosion can be caused by soil conditions, elevated or depressed pH, microbiological activity, moisture concentration, salts, stray current, and much more. Variations in weather and tides can change the corrosion conditions. Internal corrosion can be caused by components such as water, carbon dioxide (CO2), and hydrogen sulfide (H^sub 2^S) and can be aggravated by microbiological activity. High-performance pipeline coatings and cathodic protection (CP) are often used to combat external corrosion. Inhibitor programs are used to fight internal corrosion. When all else fails, a corrosion allowance is used to provide "sacrificial" metal and allow for corrosion losses during the design life of a pipeline.
The 2001 U.S. Office of Pipeline Safety (OPS) (Washington, D.C.) Hazardous Liquid Pipeline Accident Summary by Cause shows that 28.9% of accidents were attributed to corrosion.' The OPS data indicate that 14.06% of the accidents were caused by external corrosion, 12.5% by internal corrosion, and 2.34% by unspecified corrosion. The total reported cost of property damage was $6,436,200, or 25.17% of the total cost of damage caused by pipeline accidents.
For gas transmission pipelines, the 2001 OPS data indicate that 8.33% of the incidents were caused by external corrosion and 9.52% by internal corrosion, producing a total of 17.85% of incidents caused by corrosion.2 The cost of property damage amounted to $4,962,550, or 21.71% of the total cost of damage caused by gas transmission incidents.
New regulations for Hazardous Liquid Pipeline Operators (U.S. Code of Federal Regulations [CFR] Title 49 Part 1953) require written integrity management programs. These regulations are given in the "Implementing Integrity Management-Final Rule" Section of the OPS Web site: ops.dot.gov.4 Pipeline operators who own or operate >=500 miles (804 km) of pipeline subject to 49...