Direct Assessment of Pipeline
It is possibly by using cathodic protection principles
to determine whether a metallic structures coating
breakdown has occurred. This is conducted by
measuring the structure-to-electrolyte potential and
examining the results with respect to a standard
reference criteria. The results then highlight potential
coating breakdown areas and respective severity. Given this information localised excavations
can be conducted, at the most onerous locations, to determine the remaining wall thickness and
enable fitness-for-service evaluations to be conducted to indicate the integrity of the pipeline. This
approach is commonly referred to an external corrosion direct assessment and is incorporated into
many international standards.
The assessments normally are conducted to the requirements of ASME B31.8S which covers the risk assessment, inspection and integrity assessment methods for gas pipelines. For other parts of the assessment, eg external assessment of the pipeline coating, the relevant international codes and standards will be applied, eg NACE RP 0502. TWI’s participation on the NACE committees enables a thorough understanding of any compliance requirements.
This coupled with the company’s long range ultrasonic inspection technique is a powerful tool in determining the safety and long term integrity of a pipeline.
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