Oil and gas transmission pipelines are subject to internal and external agents that can cause corrosion affecting their safety, integrity, and profitability. Restoring pipelines to a safe operating condition is the
main goal of inline inspection (ILI) using state-of-the-art Smart Pigs. These tools travel through the full length of pipelines gathering detailed information that is used for the assessment of both the internal and
the external surfaces of the line. Ultrasound ILI tools perform direct measurements of the remaining wall thickness of the pipe. The
analysis of an ultrasound ILI run determines the residual strength of the pipeline at the time of the inspection. Furthermore, the comparison of recurrent ultrasound runs establishes patterns of defect growth. Under this light the interpretation of the data leads to an assessment of the dynamics of the corrosion phenomena occurring in pipelines.
This paper presents the results of applying remaining strength criteria for the evaluation of corrosion defects detected by an ultrasound tool in transmission lines. The impact of defect growth on the integrity of transmission pipelines is illustrated by comparisons of sets of data collected from recurrent ultrasound inline inspections of a pipeline system.
Key words: pipeline, smart pig, in-line inspection (ILl), ultrasound wall-thickness test, metal loss, corrosion, integrity, maximum allowable operating pressure (MAOP), maintenance.