Natural Gas Pipelines:

Greater Use of Instrumented Inspection Technology Can Improve Safety

RCED-92-237: Published: Sep 28, 1992. Publicly Released: Sep 28, 1992.

Additional Materials:


Kenneth M. Mead
(202) 512-2834


Office of Public Affairs
(202) 512-4800

GAO provided information on the inspection techniques available to determine and maintain the structural integrity, safety, and condition of natural gas transmission pipelines, focusing on: (1) the use, capabilities, limitations, and costs of instrumented inspection technology, commonly referred to as smart pigs; (2) federal smart pig inspection regulations and guidelines; and (3) the Department of Transportation's (DOT) Research and Special Programs Administration's (RSPA) compliance with the Pipeline Safety Reauthorization Act of 1988.

GAO found that: (1) DOT is responsible for developing, issuing, and enforcing natural gas transmission pipeline safety regulations; (2) from 1985 to 1991, natural gas pipeline incidents totalled 1,726, involving 131 fatalities and 634 injuries; (3) causes for pipeline failure include outside-force damage, corrosion, and defective materials; (4) smart pig inspections have the potential to detect internal and external corrosion, provide information on metal integrity, and detect other pipeline flaws, without pipeline excavation; (5) companies use smart pigs to determine the source and location of internal or external pipe problems, locate anomalies, and establish existing pipeline conditions; (6) smart pig use enables companies to minimize pipeline downtime, plan effective maintenance, ensure operational safety, and perform condition appraisals prior to pipeline sales; (7) smart pigs' operational limitations include their inability to negotiate sharp bends, detect longitudinal cracks, and locate potential pipe seam failures and circumferential weld metal loss; (8) the cost of using smart pigs depends on the pig type, pipeline diameter, pipeline cleanliness, pipeline length, pig vendor competition, amount of corrosion, amount of excavation needed, and extent of data interpretation required; (9) the two types of magnetic-flux smart pig technologies are first-generation, which is about 25 years old, and the more recent second generation, which has advanced capabilities for flaw detection; (10) RSPA has not completed the legislative requirements to improve pipeline safety, including a study discussing smart pig requirements and mandatory regulations requiring new and replacement pipelines to be capable of accommodating smart pigs; (11) companies do not use smart pigs frequently because of a lack of federal regulations; and (12) pending legislation would initiate regulations and require smart pig inspections in densely populated areas.

Recommendations for Executive Action

  1. Status: Closed - Implemented

    Comments: DOT provided Congress with its final report from the smart pig feasibility study in November 1992.

    Recommendation: The Secretary of Transportation should act to expeditiously provide the Congress with the final report from the smart pig feasibility study mandated by Public Law 100-561, or notify the Congress when it will be available.

    Agency Affected: Department of Transportation

  2. Status: Closed - Implemented

    Comments: In April 1994, DOT issued the final regulations mandated by Public Law 100-561 requiring that new or replacement pipelines transporting natural gas, hazardous liquids, and carbon dioxide, where practicable, be designed to accomodate smart pig inspection devices.

    Recommendation: The Secretary of Transportation should act to expeditiously issue the regulations mandated by Public Law 100-561.

    Agency Affected: Department of Transportation


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