A method to evaluate the corrosive environment of annular spaces within casings of natural gas transmission pipelines using commercially available, “off the shelf” equipment has been devised and implemented. Three separate locations were selected for test monitoring of corrosion rates on steel carrier pipelines operating within these environments. The locations were monitored for 22-26 months and average corrosion rates were established for a variety of representative conditions. Test results confirmed the initial hypothesis that cased pipeline segments exist in relatively benign environments as long as cathodic protection/coating systems and electrical isolation status between carrier and casing are maintained. These results lend further credence to the position that cased segments are inherently safer than uncased segments due to the extra layer of protection from third party damage which remains the most significant threat to pipeline integrity.

Subject
Humidity, Carrier pipes, External corrosion direct assessment, Piping, Cathodic protection, Corrosion rate, Probes, Pipelines, Installation, Equipment, Corrosion data, Corrosion probes, Oxygen
Keywords:
corrosion rate, casings, cased pipeline segments, annular space, direct assessment, high consequence areas, natural gas transmission pipeline, external corrosion direct assessment, ECDA, electrical resistance (ER) corrosion rate probes
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2011
Association for Materials Protection and Performance (AMPP)
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