Strength Pipeline Research Articles

Importance sampling-based probabilistic performance modeling of low-, mid- and high-strength pipelines under coupling effect of hydrogen-induced damage and corrosion

In-service long-distance pipelines are a practical approach to implementing large-scale hydrogen transportation under the context of energy transition. However, the hydrogen-induced damage (HID) and corrosion would deteriorate the material properties and load-bearing capacity of the pipelines. In the present study, the coupling effect of HID and corrosion are probabilistically incorporated into the mechanical characterization models for low-, mid- and high-strength pipelines. Spatiotemporal stochastic growth is modeled using the stochastic gamma processes with significantly affected defect geometric parameters to facilitate the uncertain performance status of pipelines. All unknown parameters of the proposed method can be inferred by inducing in-line inspection (ILI) data. The computational framework for importance sampling (IS) has been developed to estimate the system failure probability of corroded natural gas pipelines considering HID. Apply several programs to conduct probability analysis to demonstrate the applicability and effectiveness of the proposed method. The results demonstrate that HID affects the failure behavior and safety probability state of pipelines containing corrosion defects. The performances of various strength pipelines have significant differences in deterioration paths due to HID, causing additional maintenance or potentially disastrous consequences. The proposed method has been proven to capture the potential uncertainties of HID and corrosion on different-strength steel pipelines, which is beneficial for the lifecycle management of blended hydrogen natural gas pipelines.

An Artificial Neural Network-Based Equation for Predicting the Remaining Strength of Mid-to-High Strength Pipelines with a Single Corrosion Defect

Numerical methods such as finite element analysis (FEA) can accurately predict remaining strength, with strong correlation with actual burst tests. However, parametric studies with FEA are time and computationally intensive. Alternatively, an artificial neural network-based equation can be used. In this work, an equation for predicting the remaining strength of mid-to-high strength pipelines (API 5L X52, X65, and X80) with a single corrosion defect subjected to combined loadings of internal pressure and longitudinal compressive stress was derived from an ANN model trained based on FEA results. For FEA, the pipe was assumed to be isotropic and homogenous, and the effects of temperature on the pipe failure pressure were not considered. The error of remaining strength predictions, based on the equation, ranged from −6.33% to 2.39% when compared to an unseen FEA dataset, with a correlation value (R2) of 0.9975. A parametric study was subsequently performed using the equation to determine the effects of material property, defect depth, defect length, and longitudinal compressive stress on the remaining strength of pipelines with a single corrosion defect. Defect depth reduced the failure pressure by more than 65% on average, longitudinal compressive stress by more than 20% on average, and defect length by more than 21% on average.

Application of 0.8 Design Factor in China Gas Pipeline

The paper reviews current situation of high design factor application abroad, and analyzes development of high-strength pipeline in China. It shows that related technology has greatly improved in China, such as manufacture of high strength pipe, inspection, quality control, pipeline construction and pipeline integrity management. So it is available to use 0.8 design factor for the class one location in China. And the paper also introduces trial section experiences in the third West-East pipeline on safety pre-assessment, design check, pipe specification, construction technology and integrity management plan. With relative specifications further perfected, it is promising to put the 0.8 design factor into a wide use in Chinese pipeline project.

Failure pressure analysis of corroded moderate-to-high strength pipelines

Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criterion is used to predict the failure pressure of finite element model of corroded pipeline under internal pressure. By considering the pipe steel grades and geometries of corrosion defects, a series of finite element analyses is conducted. The effects of corrosion depth, length and width on burst capacity are also discussed. A specific failure pressure solution for the assessment of corrosion defects in moderate-to-high strength pipeline is proposed on the base of numerical results. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods.

Microstructure Evolution and Alloying Features of a Developed High Strength and High Toughness Weld Metal Used for Pipeline Steels

ABSTRACT Lei, X.; Wu, K.; Wang, H., and Yu, L., 2015. Microstructure evolution and alloying features of a developed high strength and high toughness weld metal used for pipeline steels. The microstructure evolution and continuous cooling transformation curves of the simulated heat-affected zone of a developed high strength and high toughness weld metal was investigated by means of thermal simulation on a Gleeble 3,500. This weld metal was picked up from the welding joint of a high strength and high toughness pipeline steel which was welded with commercial welding materials. Results showed that fine acicular ferrite was the main microstructure during a wide range of cooling rates. Actual welding experiment was also carried out with the heat input of 21 kJ / cm. The yield strength of the weld joint in weld metal is 875 MPa. The average impact toughness are about 104 and 183 J at –30° C in weld metal and the fusion line, respectively. The observed results indicated that the developed weld metal had superior ...

Mechanical Properties and CO<sub>2</sub> Corrosion Behavior of High Strength and Toughness X80 Pipeline Steel

A type of X80 grade high strength and toughness pipeline steel was designed and researched. The strengthening mechanism of the steel was analyzed by SEM, TEM and XRD, and the CO2corrosion behavior of the steel was simulated by high-temperature and high-pressure autoclave. The result shows that the microstructure of the base metal is mainly acicular ferrite with a small amount of granular bainite. Acicular ferrite consists of laths which occlude and interweave with each other, and there are many dislocation and carbonitrides distributing in acicular ferrite, which made the pipeline steel have good strength and toughness. Under the simulation of the actual working conditions, the activity of reactants is low at 30°C, so the corrosion rate is smaller at this temperature; the maximum of corrosion rate occurs at 60°C; when the temperature increases to 90°C, the corrosion rate is lower than that of 60°C, that is because hindering corrosion effect which take by the acceleration deposit of corrosion product is better than the acceleration corrosion reactions.

Effects of Thickness and Delaminating on Fracture of High Strength and High Toughness Pipeline Steel

Effects of Thickness and Delaminating on Fracture of High Strength and High Toughness Pipeline Steel