Statistical Soil Characterization of an Underground Corroded Pipeline Using In-Line Inspections

Rafael Amaya-Gómez,Emilio Bastidas-Arteaga,Felipe Muñoz,Mauricio Sánchez-Silva

doi:10.3390/met11020292

Abstract

Underground pipelines have a space-dependent condition that arises from various soil properties surrounding the pipeline (e.g., moisture content, pH, aeration) and the efficiency of protection measures. Corrosion is one of the main threats for pipelines and is commonly monitored with in-line inspections (ILI) every 2 to 6 years. Preliminary characterizations of the surrounding soil allow pipeline operators to propose adequate protective measures to prevent any loss of containment (LOC) of the fluid being transported. This characterization usually requires detailed soil measurements, which could be unavailable or very costly. This paper implements categorical measurements of soil properties and defect depth measurements obtained from ILI to characterize the soil in the surroundings of a pipeline. This approach implements an independence test, a multiple correspondence analysis, and a clustering method with K-modes. The approach was applied to a real case study, showing that more severe defects are likely located in poorly drained soils with high acidity.

Highlights

Suppose that we had J categoric soil features; the main objective was to describe the relationship between the features and the corrosion depth, which could be treated as a continuous quantitative variable or divided into categories to address non-linear behaviors [30]
The p-value under the null hypothesis of independence, considering 2000 Monte Carlo replicates for each soil feature and dataset
For the inner wall at the second inspection, the results indicate that the corrosion labels are almost independent of the soil features, as expected, except from a weak dependence with the fertility with a p-value of 0.0465

Summary

Introduction

Corrosion is one of the main threats for onshore pipelines, either at the inner or outer walls. The external wall condition is subjected to a space-dependent degradation process favored by the varied soil conditions surrounding the pipeline, the pipe installation (e.g., underground, aboveground), and protection barriers (e.g., coatings, cathodic protection), among others. Considering the role of soil corrosiveness for underground pipelines, different authors have studied certain soil features to characterize more aggressive locations and take adequate protective measures. In this regard, soils with a higher concentration of chlorides, an acidic pH, and the presence of bacteria or fungi have been recognized to influence the external corrosion significantly [1]

Methods

Results

Conclusion