The Department of Transportation’s Office of Pipeline Safety(OPS) has issued an industry-wide bulletin advising operators andowners of gas transmission pipelines to review their monitoringprograms and operations for detecting the presence of internalcorrosion on their systems.

The OPS took this action two weeks after an investigation by OPSand the National Transportation Safety Board (NTSB) revealedcorrosion inside the El Paso South Mainline pipeline (Line 1103)that ruptured.

OPS said its review of incident reports and inspections”indicated that better industry guidance is needed to determine thebest practices for monitoring the potential for internal corrosionin operator pipelines.” It advised gas pipelines to refer to therecommended corrosion-monitoring practices of the nationalconsensus standards organizations, including the American PetroleumInstitute, the National Association of Corrosion Engineers, and theGas Piping Technology Committee (GPTC). The OPS said that the GPTCis considering modifying its “Guide for Gas Transmission andDistribution Piping Systems” to address design considerations,corrective measures and detection techniques for internalcorrosion.

It recommended that gas pipelines give “special attention” to anumber of specific conditions, including flow characteristics, pipelocation (especially drips, deadlegs and sags, which are on-linesegments that are not cleaned by pigging or other methods),fittings and/or “stabbed” connections which could affect gas flow,operating temperature and pressure, water content, carbon dioxideand hydrogen sulfide content, carbon dioxide partial pressure,presence of oxygen and/or bacteria, and sediment deposits.

The OPS further urged gas pipelines to focus their review onsegments downstream of gas production and storage fields, where itsaid corrosive elements most often accumulate. Also, “reviewconditions in pipeline segments with low spots, sharp bends, suddendiameter changes, and fittings that restrict flow or velocity, andsegments in unusual terrain. These features can contribute to theformation of internal corrosion by allowing condensates to settleon the gas stream.”

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