Failure mechanism and integrity assessment of a cracked piping elbow in an oil transport system

Purpose This study investigates the failure mechanism of a cracked piping elbow in a crude-oil transport system after approximately 20 years of service, with the aim of identifying the dominant degradation mechanisms and assessing structural integrity using numerical and risk-based approaches. Design/methodology/approach The study combines field inspection, non-destructive testing, wall-thickness measurements, fracture-mechanics concepts, finite element method (FEM)/extended finite element method (XFEM) numerical simulations and American Petroleum Institute: API 581-based risk-based inspection (RBI) analysis. Findings The results showed that the failure was caused by the combined action of erosion–corrosion, naphthenic acid corrosion, localized corrosion and pressure transients. Numerical simulations identified the elbow–pipe transition as the critical stress region, consistent with the observed crack location. Research limitations/implications The analysis was based on a real industrial case study and limited by the absence of experimentally determined fracture toughness data. Nevertheless, the integrated methodology provides useful insight into localized degradation and failure development in aging pipeline systems. Practical implications The study demonstrates the importance of combining inspection data, numerical analysis and RBI methodologies in the integrity assessment of geometrically sensitive pipeline components. The results support complete elbow replacement as the most reliable remediation strategy. Social implications The study contributes to improved operational safety and reliability of aging oil-transport infrastructure by supporting earlier identification of locally critical damage mechanisms that may lead to leakage and environmental incidents. Originality/value The study presents an integrated analysis of a real pipeline elbow failure combining field observations, FEM/XFEM simulations, fracture-mechanics concepts and RBI methodology. The study highlights how multiple moderate degradation mechanisms can interact to produce locally critical conditions that may be underestimated by global risk assessments.