Failure Pressure Of Pipelines Research Articles

Probabilistic burst pressure prediction model for pipelines with single crack-like defect

While several models have been developed to predict the failure pressure of pipelines with corrosion defects, relatively few models are available for pipelines with cracking defects. The goal of this study is to develop an unbiased and accurate probabilistic burst failure pressure model for thin-walled pipelines containing a single, longitudinally-oriented, crack-like defect. A comprehensive database is first established, consisting of experimental and numerical data collected from literature as well as numerical data obtained from the extended finite element method (XFEM) conducted in this study. The failure pressure prediction model is developed by adding a correction factor to the modified Ln-Secant method, a semi-empirical model previously developed. The correction factor is modeled using a multivariate linear regression that considers the pipe properties and defect characteristics as independent variables. The proposed model delivers unbiased and less variable failure pressure predictions. A case study of an example pipeline with a crack like defect shows that the failure pressure model plays a critical role in the risk management of pipelines through a life-cycle cost analysis.

Condition assessment of underground corroded pipelines subject to hydrogen damage and combined internal pressure and axial compression

In this work, a 3D finite element (FE) based model was developed to assess the condition of an underground hydrogen transmission pipeline containing a corrosion defect under combined internal pressure and soil movement-induced axial compression. The use of mechanical properties of X100 pipeline steel under different hydrogen charging time models the degree of hydrogen damage in pipelines. Parameter effects, i.e., axial compressive stress, hydrogen damage, defect geometries, and pipeline diameter-to-thickness ratio, were determined. The results demonstrated that the synergistic effect of axial compression, internal pressure, corrosion, and hydrogen damage can lead to a significant decrease in the failure pressure of pipelines. The failure pressure decreased with the wall thickness reduction and increased hydrogen damage, axial compressive stress, defect length, defect depth, and pipe diameter. The competitive effect was observed between the degree of metal loss and hydrogen damage in determining the burst capacity of pipelines. In situations where the pipeline integrity was severely compromised, the failure pressure exhibited minimal reduction despite the increasing severity of hydrogen damage. The stress distribution at the defect zone was influenced by axial compressive stress but remained unaffected by hydrogen damage under normal operating conditions (i.e., an internal pressure of 10 MPa). This work is expected to help operators understand the applicability of elder and in-service pipelines for hydrogen transmission.

Assessment of reliability for subterranean corroded pipelines in cold regions using Monte Carlo method and BP neural network

Due to the complexity and instability of the environment in which the buried oil pipeline is located in cold regions, the corrosion of the outer wall of the pipeline often occurs, and the corrosion poses a serious threat to the safety of the pipeline. In order to ensure the safe operation of buried oil pipelines, it is particularly urgent to study the reliability of operating pipelines. In this paper, the external temperature field and soil effect were taken into account, and the finite element method was used to calculate and analyze the results. The fitted formula which can predict the failure pressure of buried corroded pipeline was obtained. After that, the reliability of buried corroded pipelines was studied by using Monte Carlo method and BP neural network. The results show that the fitted formula for predicting the failure pressure of pipelines is more accurate than traditional code. The corrosion depth has the most significant impact on the reliability of pipelines, being 1.85 times that of the corrosion length. The impact of corrosion width, burial depth, frost-heaving rate, and length of the frost-heaving section on the reliability of corroded pipelines is relatively small. The frost-heaving section within 5000 mm can play a certain positive role in the reliability of corroded pipelines.

The prediction analysis of failure pressure of pipelines with axial double corrosion defects in cold regions based on the BP neural network

The conventional corrosion assessment codes show a certain conservatism in predicting the failure pressure of pipelines with double corrosion defects, which will lead to the failure of reasonable maintenance of pipelines. In addition, when the numerical simulation method is used to predict the failure pressure of the pipeline, the time cost is relatively large. To predict the failure pressure accurately and quickly, ABAQUS and MATLAB were used to analyze the failure pressure of pipelines with axial double corrosion defects in cold regions in this paper, and developed the BP (Back Propagation) neural network for predicting the failure pressure. The results show that the corrosion depth has the most obvious effect on the failure pressure, and the maximum failure pressure loss rate is 42.40%; corrosion length is second, 17.56%; and corrosion spacing is the smallest at 7.16%. Compared with the codes, the failure pressure value predicted by the BP neural network is the closest to the experimental data. The maximum error is 10% and the minimum error is 1%. It proves that it is reasonable to use the BP neural network to predict the failure pressure.

Failure pressure prediction by defect assessment and finite element modelling on pipelines containing a dent-corrosion defect

Dent-corrosion defects are a typical combination of defects and pose a significant threat to the safety and integrity of energy pipelines. In general, the corrosion features rather than dents are considered the primary factor of fitness-for-service of pipelines containing a dent-corrosion defect. In this work, a finite element (FE) based model was developed to predict the failure pressure of pipelines containing a dent-corrosion defect and investigate its dominant factor. Parametric analysis results demonstrated that the presence of dents reduced the failure pressure of corresponding pipelines containing a single corrosion defect. The dominant factor of the failure pressure changed from corrosion feature to dent feature if (1) an increase in dent depth and a decrease in the pipe diameter-to-thickness ratio, (2) exceeding the critical dent depth by 8% of diameter (D), and (3) below the critical indentation radius by 10%D. Longitudinal dent gave a significant reduction of the failure pressure, making dent feature a dominant factor; Oppositely, the effect of the circumferential dent was marginal.

A generalized weighted yield criterion: Theoretical derivation and its application in the plastic failure analysis of pipeline with corroded defects

For the aim of predicting the failure pressure of pipelines accurately, a new yield criterion that embeds two physical parameters, i.e. the tension-compression ratio and the shear-tension ratio, is proposed by weighting the squares of the shear stresses. The yield criterion is proved to be universal and can convert into different yield criteria suitable for different materials. The experimental results show that the criterion can coincide well with the experimental data and can describe the yield characteristics of different materials very well. Base on the above research result, the mechanical analysis of a pipeline is executed based on the limit analysis method, and the analytical formulas of the burst pressures without and with defects are obtained by considering the strain-hardening behavior. The validation shows that both the theoretical values of burst pressures of pipelines with and without corroded defect based on the present yield criterion agree well with the experimental values. The sensitivity analysis is also carried out, which shows that the burst pressure of the uncorroded pipe decreases when the strain hardening exponent increases, while increases when the thickness-diameter ratio increases. In addition, the burst pressure of the corroded pipeline decreases when the defect depth or its length increases.

Empirical Failure Pressure Prediction Equations for Pipelines with Longitudinal Interacting Corrosion Defects Based on Artificial Neural Network

Conventional pipeline failure pressure assessment codes do not allow for failure pressure prediction of interacting defects subjected to combined loadings. Alternatively, numerical approaches may be used; however, they are computationally expensive. In this work, an analytical equation based on finite element analysis for the failure pressure prediction of API 5L X52, X65, and X80 corroded pipes with a longitudinal interacting corrosion defect subjected to combined loadings is proposed. An artificial neural network (ANN) trained with failure pressure obtained from finite element analysis (FEA) of API 5L X52, X65, and X80 pipes for varied defect spacings, depths and lengths, and axial compressive stress were used to develop the equation. Subsequently, a parametric study on the effects of the defect spacing, length, and depth, and axial compressive stress on the failure pressure of a corroded pipe with longitudinal interacting defects was performed to demonstrate a correlation between defect geometries and failure pressure of API 5L X52, X65, and X80 pipes, using the equation. The new equation predicted failure pressures for these pipe grades with a coefficient of determination (R2) value of 0.9930 and an error range of −10.00% to 1.22% for normalized defect spacings of 0.00 to 3.00, normalized effective defect lengths of 0.00 to 2.95, normalized effective defect depths of 0.00 to 0.80, and normalized axial compressive stress of 0.00 to 0.80.

Failure pressure estimation for an aged and corroded oil and gas pipeline: A finite element study

The mechanical behavior of an aged pipeline, affected by localized and generalized corrosion defects, is investigated using the finite element method. A sample of pipeline steel was aged artificially via an isothermal process (which represents the natural aging transformations), to obtain the mechanical characteristics. In real scenarios, oil and gas pipelines undergo deterioration owing to both aging and corrosion defects.Therefore, this research studies the assessment of failure pressure by combining these two types of deterioration using the finite element method. To calibrate the methodology proposed for estimating the pipeline failure pressure,data from real-scale burst tests published by the Pipeline Research Council International (PRCI) was used. Following the simulations, the initial failure region for each type of defect was determined and analyzed. Similarly, the estimated values of pipeline failure pressure were compared to assess the results obtained through finite element analysis, considering the changes in mechanical characteristics caused by the artificialartificial aging of the steel. In addition, these results were compared with those of certain well-known semiempirical models. Finally, for the different types of corrosion defects investigated in this study, the effects of volumetric loss on the estimation of pipeline failure pressure using finite elements are discussed. The main conclusion of this study is that failure pressure can be estimated more accurately by considering both corrosion defects characteristics and variations in the steel properties caused by aging.

Finite element analysis of the failure of high-strength steel pipelines containing group corrosion defects

Corrosion defects in steel pipes can lead to pipeline failure, and such failures can have severe impacts; thus, developing appropriate corrosion mitigation schemes to prevent them can be beneficial. To this end, the influences of variables such as the depth, length, and group spacing of corrosion defects on the failure of X80 steel pipes containing group corrosion defects were analysed in this study. Abaqus, a simulation software, was used for non-linear finite element analyses, and 52 groups corresponding to corrosions under different geometric factors were prepared. Furthermore, a pipeline failure pressure prediction model was established using 138 sets of simulations to determine the maximum von Mises stresses of pipelines subjected to internal pressures under different working conditions. Actual blast test data and error comparisons with various existing evaluation standards were conducted to verify the accuracy of the proposed model. The results revealed that an increase in the internal pressure and the changes in the depth, length, and group spacing of group corrosion defects impact the maximum von Mises stress in the pipe. Among the group corrosion defects considered, the depth of the deepest defect was found to be the most critical factor in determining the form of damage and the failure pressure of pipes containing corrosion defects. The length of corrosion defects and the axial spacing between groups of defects were found to be the secondary factors that affect the failure pressure. In an actual pipeline, group corrosion defects are expected to cause a reduction in the wall thickness and, thus, pose a threat to safety, an issue that warrants substantial attention. The results of this work can serve as a reference for assessing the failure of X80 steel pipelines containing group corrosion defects.

A probabilistic approach to estimate the remaining life and reliability of corroded pipelines

Considering corrosion rate during the remaining life assessment of aging pipelines is fundamental to calculate the interval between two consecutive inspections. A total of 798 internal and external corrosion defects have been detected, using the Magnetic Flux Leakage intelligent inspection tool, over 48 km of a pipeline length located in the west region of Algeria. The statistical analysis has shown that there is a strong correlation between the corrosion defect length and the corrosion defect circumferential width, with a significant correlation coefficient equal to 82.87%. A probabilistic methodology is presented for the assessment of the remaining life of a corroded pipeline transporting gas, and a finite element method (FEM) was used to assess the pipeline failure pressure. The numerical FEM modeling results were compared with the commonly used codes-models for calculating limit pressure to establish a more realistic and accurate engineering model. The reliability analysis of an API 5L X60 steel made Algerian natural gas pipeline, in service for thirty years, and exposed to active corrosion attack, is presented. The sensitivity analysis of the basic random variables within the nonlinear limit state function was carried out to bring out the relative contribution of each variable affecting the remaining life of corroded pipelines. The reliability analysis is carried out by using Breitung's formula, based on the second-order reliability method (SORM). The reliability assessment of the corroded pipeline is based on the usage of the notched failure assessment diagram (NFAD), different codes for the calculation of the failure pressure, and the numerical results using the finite element analyses (FEA) software ANSYS.

Fast and accurate prediction of failure pressure of oil and gas defective pipelines using the deep learning model

Determining the failure pressure of defective pipelines is an important part in pipeline reliability engineering, which affects the assessment of pipelines residual service life. In this work, a fast and accurate method for predicting the failure pressure of defective pipelines using the deep learning model is developed. The calculation results of ASME-B31GM, DNV, PCORRC codes and finite element method (FEM) are compared and analyzed in detail to obtain high-quality sample data. 150 groups of validated FEM simulation data and 142 groups of burst pressure test data are selected for the training and validation of deep learning model. In the training process, influences of key model parameters of deep neural network (DNN) on the prediction accuracy are investigated. Prediction results indicate that the used deep learning model can offer high prediction accuracy. In addition, the calculation of deep learning model is accelerated by at least two orders of magnitude compared with that of FEM simulations under same calculation conditions. Finally, the influence of defect sizes on pipeline failure pressure is analyzed by the DNN. This work is expected to shed a light on efficient and accurate predictions of failure pressure of oil and gas defective pipelines.

Assessment of Interaction Between a Dent and an Adjacent Corrosion Feature on Pipelines and the Effect on Pipeline Failure Pressure by Finite-Element Modeling

AbstractDents and corrosion are two types of defects commonly found on pipelines. Although major efforts have been made to assess the defects of each type, there is a limited understanding of inter...

New evaluation method of failure pressure of steel pipeline with irregular-shaped defect

• Failure pressure analysis of pipeline with irregular-shaped defect is conducted. • The effect of deep defects size on the failure pressure is considered. • The evaluation length of irregular-shaped defect is obtained. • A new failure pressure evaluation method for corroded pipeline is proposed. • The accuracy of the new evaluation method is verified by experimental tests. The relation between the failure pressure of pipeline with irregular-shaped defect and the characteristic geometric parameters is more complex than regular-shaped defect. Therefore, it is necessary to study the evaluation method of failure pressure of pipeline with irregular-shaped defect. This paper presents a case study on the failure pressure of irregular-shaped defect based on finite element model and experimental tests. The case is composed of shallow patch and deep defect included in the shallow patch. The effect of the length, depth and the longitudinal spacing of deep defects on the failure pressure of irregular-shaped defect are analyzed. Based on the limit longitudinal spacing between deep defects, the evaluation length of irregular-shaped defect is obtained. According to the irregularity of the depth profile of irregular-shaped defect, the axial projection shape of defect is equivalent to different regular shape. Combined with the effective depth of equivalent shape and the evaluation length, a new evaluation method for predicting failure pressure of steel pipeline with irregular-shaped defect is proposed, and the accuracy of the new method is verified by comparing with the experimental results for different steel grades.

Predicting the Burst Pressure of High-Strength Carbon Steel Pipe with Gouge Flaws Using Artificial Neural Network

AbstractPredicting the failure pressure of pipelines is of paramount importance in design and integrity management in order for pipes to operate safely, efficiently, and cost-effectively in terms o...

Failure pressure prediction by defect assessment and finite element modelling on natural gas pipelines under cyclic loading

In this work, a 3-dimensional finite element (FE) model was developed to investigate the effect of cyclic loading, which is induced by vibration during operation of in-line inspection (ILI) tools, on local stress and strain distributions and failure pressure of an X80 steel natural gas pipeline containing a corrosion defect. Modelling was also conducted on a low-grade X60 steel pipe for comparison. Parametric effects, including internal pressure, R-ratio, cyclic frequency and dimension of the corrosion defect (primarily the defect depth), were determined. The cyclic loading greatly increases the von Mises stress and strain at the corrosion defect and reduces the threshold internal pressure to cause plastic deformation at the defect. As the internal pressure increases, both the von Mises stress and the strain increase and the high stress/strain zones expand along the defect length direction. The local stress and strain at the corrosion defect increase with decreased R-ratio and cyclic frequency, resulting in a reduction of failure pressure of the pipeline. An increased defect depth enhances local stress and strain concentrations, reducing failure pressure of the pipeline. A novel method is developed to assess corrosion defect during ILI tool operation and predict the failure pressure of pipelines under cyclic loading for the first time of its kind.

Effects of depth in external and internal corrosion defects on failure pressure predictions of oil and gas pipelines using finite element models

This study presents, for the first time, the mechanical behavior of API 5L pipeline steels X42, X52, X60, X70, X80, and X100 with external and internal corrosion defects as well as a combination of both defects that has been named external–internal corrosion defects. The conventional methods to predict failure pressure in corroded pipes, such as B31G, RSTRENG-1, SHELL, DNV-99, PCORRC, and FITNET FFS, have also been discussed in this article. In addition, pipeline failure pressure has been estimated using the finite element method, considering that it is the best approach to calculate actual failure pressure. The external and internal corrosion defect investigated in this research manifests as a rectangular shape with spherical ends at the edges. When the external–internal corrosion defect appears, failure pressure data decrease dramatically because of severe damage. This is due to the decrease in the ligament (effective area) caused by the corrosion defect. To have a good estimation of the pipeline failure pressure with an external–internal corrosion defect, DNV-99 method can be used with acceptable certainty.

Determination of Folias Factor for Failure Pressure of Corroded Pipeline

AbstractCorrosion assessment and burst pressure prediction of line pipes with corrosion defects are essential for the integrity assessment of steel transmission pipelines. The failure assessment methods proposed in codes or handbooks may be overly conservative or exhibit significant scatter in their predictions. In this paper, the effects of two key parameters—the flow stress and Folias bulging factor, on predicting the failure pressure of pipelines with defects are studied. The Folias bulging factor is suggested by fitting the results from finite element (FE) analysis. Then, a new prediction method for the failure pressure of pipelines with defects is proposed. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods such as B31G, MB31G, Det Norske Veritas (DNV), and rectangular parabolic area (RPA).

On the Influence of the Corrosion Defect Size in the Welding Bead, Heat-Affected Zone, and Base Metal in Pipeline Failure Pressure Estimation: A Finite Element Analysis Study

In this study, failure pressure prediction was conducted in a pipeline with localized corrosion in base metal (BM), heat-affected zone (HAZ), and welding bead (WB) by finite element (FE) analysis. In the gas pipeline industry, there are methods (B31G, RESTRENGH, Shell, DNV, PCORR, and Fitnet FFS) and authors' approaches (Choi and Cronin) to determine the failure pressure. However, one disadvantage of these methods is that their equations do not consider damage corrosion at the HAZ or WB. They consider corrosion only in the BM. The corrosion shape is rectangular with a radius at the edges. In this study, the corrosion defect depth (d) was varied. The corrosion defect length (L) and the corrosion defect width (W) were equal. A type of rectangular corrosion defect with a radius at the edges in the longitudinal and circumferential directions was proposed. True stress–strain curves for BM, HAZ, and WB of an API 5 L X52 were introduced in the FE program. The results show that the pressure decreases as d, L, and W increase. This is because the damage corrosion is more severe as it grows, which causes the failure pressure to decrease.

Assessment by finite element modeling of the interaction of multiple corrosion defects and the effect on failure pressure of corroded pipelines

Determination of the failure pressure of pipelines containing multiple corrosion defects is critical to the integrity and safety of the pipeline infrastructure. In this work, finite element models were developed to determine the failure pressures of X46, X60 and X80 steel pipelines containing multiple corrosion defects with varied geometries and orientations by assessing the mutual interaction of the defects and the effect on pipeline integrity. Generally, the failure pressure of corroded pipelines decreases with the increasing interaction effect between corrosion defects. The interaction effect mainly depends on the mutual orientation of the defects and their geometry and spacing, rather than the steel grade. For longitudinally and circumferentially aligned corrosion defects present on a pipeline, the interaction effect between them does not exist when their spacing is larger than 2.5Dt and 5.3 t, respectively, where D and t are diameter and wall thickness of the pipeline. As a result, the multiple defects can be assessed individually. Compared to circumferential corrosion defects, the longitudinal defects are associated with a larger spacing where the interaction effect between corrosion defects exists. The circumferential spacing of corrosion defects has a less impact on the failure pressure of corroded pipelines compared with the longitudinal spacing. For pipelines containing overlapped corrosion defects, the failure pressure is lowered, compared to that in the presence of a single top layer defect only. An increase in the depth of either top or bottom layer corrosion defect reduces the failure pressure of the pipeline. The increased length of the defect also increases the interaction effect between the overlapped defects, lowering the failure pressure of the pipeline.

Nanofillers Reinforced Polymer Composites Wrap to Repair Corroded Steel Pipe Lines

This paper presents the analysis of repair of pipelines using nanofiller dispersed composites. Steel pipe with part wall loss as per ISO 24817 is repaired using glass/epoxy composites with and without nanoclay reinforcement and burst test is performed in order to assess the performance and effectiveness of nanocomposites-based repair system. A simple methodology is developed to find out the failure pressure of pipelines and is compared with the experimental and ISO 24817 repair code results. The thickness of the composite wrap is predicted analytically for 1–5% nanofiller dispersion in the epoxy for 30–80% of pipe wall loss and live pressure of pipe. The results are analyzed to find effectiveness of clay dispersion and effect of live pressure for 30–80% of pipe wall loss. It is observed that the dispersion of nanofiller improves the bursting resistance of composite wrapping over outer surface of pipe.