The Southeast Alabama Gas District (SEAGD) has been engaged with the development
of in-depth analysis, field data interpretation, validation and analysis pertaining to the
integrity of natural gas transmission pipelines. The integrity assessment of the subject
pipelines included urban and rural settings, and was complicated by pipelines under
asphalt and concrete at road crossings. The project attempted to utilize various AC
attenuation survey methods (specifically Pipeline Current Mapper (PCM) and Alternating
Current Voltage Gradient (ACVG)) and Long Range Guided Wave Ultrasonic Testing
(LRGWUT) technology to accurately identify, categorize and locate corrosion defects
along significant portions of the transmission portion of a regional distribution network.
This paper presents the main findings, conclusions and recommendations generated
over the period (2004-2006), carefully taking note of the latest Natural Gas Integrity
Rules (DOT49 CFR Part 192), drawing on practical experience, as well as the relevant
NACE Recommended Standard RP0502-2002 for ECDA. The potential impact of
corrosion failures on public safety and the environment is rationalized during the process
by the delineation of “Class 3 High Consequence Areas” and “Identified Sites” as applied
to the ECDA. The case study should be of value to other gas distribution companies as
lessons learned which could promote a common understanding and direction for the
benefit of all parties concerned.