Pipeline Safety Evaluation Research Articles

Risk Assessment Method for the Safe Operation of Long-Distance Pipeline Stations in High-Consequence Areas Based on Fault Tree Construction: Case Study of China–Myanmar Natural Gas Pipeline Branch Station

The safe operation of natural gas long-distance pipeline stations is the critical link for its sustainable transmission. Therefore, station operation risk assessment and space-time expression in high consequence areas have become a critical problem that must be urgently addressed. The conventional way to assess the probability of gas pipeline failure cannot meet the requirements of the natural gas operating companies for the safety assessment of natural gas stations. Taking the example of the China–Myanmar natural gas pipeline branch station, based on the fuzzy fault tree model (FFT), a comprehensive pipeline safety evaluation method (CPSE-FFT) has been introduced, which evaluates the risk factor of pipeline operation in the station area and the social security risk brought by it. In this case study, the method is applied to a branch station of the China–Myanmar long-distance pipeline. In the results, the probability of pipeline accidents in the area of the station is 5.79×10−4 times/year, and six buildings with higher risk levels among the 37 buildings are also exposed on the risk distribution map. The overall social risk level is also expressed. CPSE-FFT is a practical, reasonable, and accurate assessment method that can quantitatively reflect the risks posed by the safe operation of natural gas stations. This method is suitable for most natural gas station risk assessments. The results of the risk assessment provide a reference for managers and decision-makers to reduce the risk of natural gas stations.

Analytical solution of overlying pipe deformation caused by tunnel excavation based on Pasternak foundation model

The existing tunnel construction causes stratum deformation, which in turn leads to additional deformation and internal force of the overlying pipeline, thus increasing the risk of pipeline accidents. Then, how to correctly calculate the deformation and internal force of pipeline is the key to pipeline safety evaluation. To this end, this study firstly used the Pasternak foundation beam model to simulate the interaction of pipeline and soil, and divided the pipeline into the void area (i.e., pipeline-soil detachment) and the coordination area (i.e., pipeline-soil is always deformed together) between pipeline and soil. The differential equation of pipeline deflection for the void area and the coordination area were established respectively, and the solutions of pipeline deflection, the internal force of pipeline and the width of pipeline-soil void area were presented. Subsequently, the accuracy of the proposed method was verified by comparing with the available model and field test data, and it is found that the calculation results are too conservative without considering the pipeline-soil voiding phenomenon. Finally, the detailed parametric analysis was conducted. The results show that the pipeline deflection decreases with the increase of the pipeline-tunnel spacing between pipeline and tunnel, the pipeline bending stiffness and the soil elastic modulus, but increases with the increase of the formation loss rate, and the width of pipeline-soil void area increases with the increase of the pipeline-tunnel spacing, the pipeline bending stiffness and the soil elastic modulus.

1-G experimental study of the collapse effects on buried steel gas pipelines

Collapse disasters are commonly occurring geological disasters around buried gas pipelines and severely threaten the safety of pipeline operations. In this study, to investigate the soil deformation characteristics and mechanical response law of the pipeline under collapse, an experimental box (6 m × 1 m × 1.2 m) was built, and 1-G collapse experiments with different pipe diameters and burial depths were performed. The soil deformation laws, change in earth pressure around the pipeline, and mechanical response of the pipeline during the expansion of the collapse range were obtained by comparing and analysing the experimental results. Pipeline collapse disasters can be divided into two stages: before and after large-scale collapse disasters. The burial depth has an influence on pipeline collapse disasters mainly in a small-scale collapse range. As the collapse range increases, the influence of the burial depth on the strain distribution of the pipeline gradually decreases. However, an increase in pipe diameter can lead to a significant increase in the large-scale collapse range. Large-diameter pipelines bear greater strain than small-diameter pipelines after a large-scale collapse. This study provides data support for further research and serves as a valuable reference for pipeline safety evaluation in collapse disasters.

Fuzzy Comprehensive Safety Evaluation of Pipeline Disaster in China-Russia Crude Oil Permafrost Region Based on Improved Analytic Hierarchy Process-Entropy Weight Method

Considering the difficulty in evaluating pipeline safety in permafrost region, the pipeline disaster safety evaluation index system in permafrost region is analyzed and established. A comprehensive weight determination method based on improved fuzzy analytic hierarchy process, entropy weight method and Lagrange algorithm is proposed, and a fuzzy comprehensive evaluation model of permafrost pipeline safety is established. Taking the disaster safety evaluation of pipeline in the China-Russia crude oil permafrost region as an example, the proposed method is used to determine the comprehensive weight of disaster safety index of permafrost pipeline and carry out comprehensive safety evaluation. The rationality of the comprehensive weight determination method is verified by comparing with the performance of the traditional AHP evaluation method.

New Methods for Predicting Strain Demand of Arctic Gas Pipelines across Permafrost under Frost Heave Displacement

With increasing gas resource development in the Arctic region, gas pipeline installations in permafrost regions are becoming important. Frost heave of pipeline foundation soils may occur when a chilled gas pipeline passes through unfrozen areas with frost-susceptible soils. The stress and strain behaviors caused by the differential frost heave will directly affect the safety of the pipeline. A nonlinear finite element model (FEM) computing the mechanical responses of the buried gas pipeline subjected to frost heave load was established and successfully validated with the results of a large-scale indoor pipe-soil interaction experiment carried out in Caen in France. Utilizing C# language and object-oriented visual programming techniques, a new customized parametric strain calculation software was developed. The effects of pipe diameter, pipe wall thickness, pipe internal pressure, and peak soil resistance on the longitudinal strain of X60, X70, and X80 steel pipes have been investigated quantitatively. For the first time, a fitting semiempirical equation and trained backpropagation neural network (BPNN) for predicting pipeline strain demand subjected to frost heave load were proposed based on 2688 groups of FEM results. The comparison results have proved their high accuracy and lower running time cost. The proposed new methods can be applied in the strain-based pipeline design and safety evaluation of pipelines in service. It is in the hope of supplementing existing theory and identifying new approaches for arctic gas pipeline installations.

Full-scale experimental investigation of the fracture behaviours of welding joints of APL X80 wide plate based on DIC technology

With the advances in material research and pipe manufacturing, the construction of oil and gas pipelines is developing continuously, and the evaluation of welding joints with defects has become the focus of pipeline safety research. In this study, two full-scale wide plate tensile tests were performed on Ø1422 mm × 25.7 mm X80 specimens with original and repaired welding joints. By comparing and analysing the experimental load–displacement responses, as well as the synchronous monitoring results of strain gauge and digital image correlation (DIC) system, the variation trend of the crack mouth opening displacement (CMOD) with distal strain, and the strain capacity of welding joints under different critical CMOD conditions were obtained. This way, the difference in bearing capacity between the original and the repaired welding joints was further determined. Under the same load condition, the driving force of the defect crack expansion at the repaired welding joint was smaller. When the critical CMOD was 0.5 mm and 1.0 mm, the strain capacity of the repaired welding joint was increased by 0.12% and 0.35%, respectively. Therefore, the repair operations of the welding joint effectively strengthen its deformation capacity. This research can provide a valuable data basis for the subsequent verification of numerical analysis models, and can also be referenced for the safety evaluation of pipelines with crack defects.

Dynamic behavior and failure of buried gas pipeline considering the pipe connection form subjected to blasting seismic waves

To ensure the safety of gas pipelines during tunnel blasting excavation, it is of vital significance to investigate the dynamic response of buried gas pipelines under blasting vibration. Based on a great number of engineering examples, a representative buried gas pipeline with a diameter of 1 m and a wall thickness of 10 cm in the urban area was taken as the research object, and a full-scale buried gas pipeline blasting experiment on basis of vibration monitoring and dynamic strain monitoring was designed and implemented Next, 3D numerical models were established to analyze the response characteristics of the buried gas pipeline based on the field experiment, and the reliability of the numerical model was verified by the field monitoring data. Considering the influence of pipeline connection form, the numerical calculation models of the buried gas pipelines with bolted flange joints were established under different blasting scaled distances to supplement the field experiment. The dynamic response characteristics of the pipeline without interface and pipeline with bolted flange joints were further analyzed, and the dynamic response characteristics of bolted flange joints were discussed emphatically. At last, based on the failure mode of pipeline connection and the results of dynamic strain analysis of pipeline in field experiment, the safety evaluation of pipeline with bolted flange joints and pipeline without interface was comprehensively proposed. By comparing the safety control vibration velocity of pipeline with bolted flange joints and pipeline without interface, it is concluded that the flange bolt connection is vulnerable to the harmful effect of blasting vibration and the safety evaluation of pipeline considering bolted flange connection is more reasonable.

Resource evaluation method for safe use of gas and oil pipeline sections under conditions of bifrequency loading

The article proposes a mathematical model for predicting gas and oil pipeline section resource under bifrequency loading. Mathematical model for pipeline safety evaluation is formulated. The authors offer a resource-predicting algorithm for gas and oil pipelines.

Formula for Calculating Pressure Distribution of Crude Oil Flowing through 180 Degree Bend

FLUENT software was used to analyze the distribution of internal pressure P of elbow with the variation of outlet pressure P0, inlet velocity v, fluid density ρ and the degree of curvature k=R/D during the flow of crude oil in 180 degree bend pipe, to establish 135 kinds of working condition of internal pressure P distribution database. According to the distribution law of the pressure of the inner wall of the elbow under different parameters (P0, v, ρ, k), calculation formula of the internal pressure distribution of the pipe is analyzed and fitted by 1stOpt software. Through the numerical simulation results of 11 kinds of working condition of FLUENT, the calculation precision of the formula was verified (Maximum relative error). It provides basis for design of bend pipe and safety evaluation of pipeline in high pressure, high flow rate and long distance petroleum pipeline.

Safety Evaluation of Pipelines Based on Probabilistic Approaches

The existing methods for assessing the reliability of pipelines take into account the mechanical characteristics of the pipe, the type and loading parameters, the number and size of defects, and a number of other factors affecting the operability of the pipeline. However, the precise definition of pipelines’ remaining life in a certain period by the method of experimental investigations is practically impossible to predict due to measurement errors, assembly technique, personnel qualification, etc. The modern in-line inspection revealed many inconsistencies of the results of the calculation methods and regulatory requirements. In this article the methodology on estimating reliability of pipelines on the basis of probabilistic approaches is elaborated, on the basis of which it is possible to determine the reliability of the pipeline systems and the effectiveness of measures aimed at eliminating the most dangerous defects by the process of repair. There is a proposition to replace expensive experimental investigations for numerical modelling of the deterioration process by using a set of random variables. The results of numerical computations of existing approach should define the destruction time caused by a defect. An example of calculating reliability of a pipeline section with defects in the operational period of 5 years is given. After the elimination of defects during the process of repair, the reliability of the pipeline section is 92%.

A Study on the Development and Applicative Estimation of Safety Evaluation Model for Water Supply Pipelines using Quantification Theory Type Ⅱ

Owing to time and cost constraints, new methods that would make it possible to evaluate the safety of the water supply pipeline in a less time- and cost-consuming manner are urgently needed. In response to this exigency, the present study developed a new statistical model to assess the safety of the water supply pipeline using the quantification theory type II. In this research, the safety of the water supply pipeline was defined as `a possibility of the pipeline failure`. Quantification analysis was conducted on the qualitative data, such as pipe material, coating, and buried condition. The results of analyses demonstrate that the hit ratio of the quantification function amounted to 77.8% of hit ratio, which was a fair value. In addition, all variables that were included in the quantification function were logically valid and demonstrated statistically significant. According to the results derived from the application of the safety evaluation model, the coefficient of determination () between K-region`s water supply pipeline safety and the safety inspection amounted to 0.80. Therefore, these findings provide meaningful insight for the measured values in real applications of the model. The results of the present study can also be meaningfully used in further research on safety evaluation of pipelines, establishing of renewal prioritization, as well as asset management planning of the water supply infrastructure.

Signal processing and defect analysis of pipeline inspection applying magnetic flux leakage methods

Corrosion, stresses and mechanical damage of oil and gas pipelines can result in catastrophic failures, so pipeline safety evaluation is an important problem of oil and gas transmission. To evaluate the pipeline safety, this paper described a novel magnetic flux leakage (MFL) inspection device, and the designing MFL intelligent inspection pig was used to multi-radius pipelines and variational work condition. At the same time, because signal processing and defect recognition technique is one of the most important techniques in offshore pipeline inspection MFL system, the paper also discussed its signal processing procedure. Time-frequency analysis, median and adaptive filter, and interpolation processing are adopted to preprocess MFL inspection signal. In order to obtain high sensitivity and precision, we adopted multi-sensor data fusion technique. A wavelet basis function neural network was used to recognize defect parameters. The main contribution of the article is that we presented a novel method to evaluate and predict oil pipelines' condition through combining neural network, data fusion and expert system techniques, and through constructing a knowledge-based off-line inspection expert system, the system improved its defect recognition capability greatly.

Based on ANASYS with Finite Element Analysis and Calculation of Cracked Pipeline

Pipeline in the entire oil and gas transportation industry play an important role and in the soil is corroded in order to produce the stress corrosion crack. The topic analyzes and calculates cracked pipeline with finite element method by use of ANSYS software mainly, and provides the theory basis for safety evaluation of pipeline.

Oil and Gas Pipeline Residual Strength Research Based on Reliability Analysis

Strength of residual wall thickness reliability was studied by Monte-Carlo and finite element method, based on 40in X70 steel and 48in X80 steel which were often used in oil and gas transport pipeline. Pipe with defects in different residual wall thinkness, calculated the critical residual value of wall thickness, and analysed the defect depth and width of influence on pipe reliability. The results provide basis for pipeline safety evaluation and reasonable replacement.

Research on a Recognition Algorithm for Offshore-Pipeline Defects during Magnetic-Flux Inspection

Pipeline-safety evaluation is an important problem for industry. On the basis of the magnetic-flux-leakage (MFL) method, this paper presents an automated inspection device for inspection of pipeline defects, analyzes the MFL-inspection theory and some defect-feature parameters, and gives a recognizing algorithm based on a dynamic wavelet-basis-function (WBF) neural network. This dynamic network utilizes a multiscale and multiresolution orthogonal wavelet and backward-propagating through signals and has more significant advantages than BP or other neural networks used in MFL inspection. It also can control the accuracy of the predicted defect profiles, possessing high-speed convergence and good approaching features. The performance that applies the algorithm based on the network for predicting a defect profile from experimental MFL signals is also presented.

Research on Recognition Algorithm of Offshore Oil Pipeline Defect Inspection Based on Magnetic Flux Leakage Method

Pipeline safety evaluation is an important issue in the industry. Based on magnetic flux leakage (MFL) method, this paper presents an automated inspection device to inspect pipeline defects, analyzes the MFL inspection theory and some defect feature parameters, and gives a recognizing algorithm based on the dynamic wavelet basis function (WBF) neural network. The dynamic network utilizes multiscale and multiresolution orthogonal wavelet, through signals backwards propagation (BP), has more significant advantages than BP or other neural networks used in MFL inspection. It can also control the accuracy of the predicted defect profiles, possessing high-speed convergence and good approaching features. The performance applying the algorithm based on the network to predict defect profile from experimental MFL signals is also presented.

Safety Assessment Of Offshore Pipelines Anchor Damage By Means OfSimulation Method

This paper presents the simulation method of underwater pipeline safety evaluation in the aspect of emergency anchoring vessels. The simulation model is a probabilistic one based on the Monte Carlo simulation principle including a simplified human decision algorithm and mechanics of ship anchoring. The results achieved with the use of the presented model can be applied for determination of underwater pipelines safety and as guidelines for pipeline protection. The paper also presents an example case study of safety determination of sub-sea gas pipeline located on the Baltic Sea.