Structural Integrity of Steel Pipeline with Clusters of Corrosion Defects.

Maciej Witek

doi:10.3390/ma14040852

Abstract

The main goal of this paper is to evaluate the burst pressure and structural integrity of a steel pipeline based on in-line inspection results, in respect to the grouping criteria of closely spaced volumetric surface features. In the study, special attention is paid to evaluation of data provided from the diagnostics using an axial excitation magnetic flux leakage technology in respect to multiple defects grouping. Standardized clustering rules were applied to the corrosion pits taken from an in-line inspection of the gas transmission pipeline. Basic rules of interaction of pipe wall metal losses are expressed in terms of longitudinal and circumferential spacing of the features in the colony. The effect of interactions of the detected anomalies on the tube residual strength evaluated according to the Det Norske Veritas Recommended practice was investigated in the current study. In the presented case, groups of closely-spaced defects behaved similarly as individual flaws with regard to their influence on burst pressure and pipeline failure probability.

Highlights

A lot of studies deal with investigation of strength and structural integrity of steel pipelines with wall metal losses and longitudinally-oriented grooves similar to cracks using different methodologies, for instance, the latest publications applying a finite element method [4] and a linear elastic fracture failure mode [5]
The aim of the present study is to calculate the failure probability of the steel pipeline failure based on the in-line inspection data containing groups of indications
Due to the limit of circumferential spacing for the considered pipelinelim = 271.5 mm and a value of longitudinal spacing along the pipe axis less than sL≤lim = 172.8 mm of each pair, only the two flaws C3D3 and C3D4 can be considered as interacting with the combined length of lnm = 33.5 mm and maximum depth of 22% of pipe wall thickness which corresponds to the value of 2.42 mm

Summary

Introduction

A corrosion rate of high pressure steel pipelines needs to be controlled by their operators during the maintenance. A lot of studies deal with investigation of strength and structural integrity of steel pipelines with wall metal losses and longitudinally-oriented grooves similar to cracks using different methodologies, for instance, the latest publications applying a finite element method [4] and a linear elastic fracture failure mode [5]. A rupture pressure prediction model for steel tubes affected by the stray current corrosion based on artificial neural network was applied in [6]

Objectives

Methods

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Conclusion