Corrosion Assessment Models for Predicting Remaining Strength of Corroded Thick-Walled Pipelines

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Abstract Corrosion is a major threat to pipeline integrity. Over the past half century, many corrosion assessment models have been developed for determining the remaining strength of corroded pipelines, including the traditional industry codes of ASME B31.G, Modified B31.G and PRCI RSTRENG, and numerous newer corrosion criteria of LPC, PCORRC and their modified models. However, all available corrosion assessment models are applicable to large diameter, thin-walled line pipes with a diameter to wall thickness ratio D/t ≥ 20. In practice, there are many small-diameter, thick-walled pipelines with a D/t ratio < 20, and thus an adequate corrosion assessment model is needed for predicting remaining strength for corroded thick-walled pipelines. This paper first reviews the burst pressure models for defect-free thin and thick-walled pipelines and a variety of corrosion assessment models for thin-walled pipelines. On this basis, three corrosion assessment models are developed for thick-walled pipelines in terms of the average shear stress yielding theory. A large set of burst pressure test data is employed to evaluate and validate the proposed corrosion assessment models for thick-walled pipelines in a wide range of pipeline steel grades. The comparison shows that the proposed thick-wall corrosion models can more accurately predict the remaining strength for both thin and thick-walled pipelines with corrosion defects.