Jianping Liu’s research while affiliated with China University of Petroleum, East China and other places

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Publications (7)


Figure 1. Schematic of the FAD.
Figure 2. FAD Evaluation Process based on BS 7910-2019.
Figure 3. X65 line-pipe steel stress-strain curve.
Figure 4. Schematic diagram of cracks at the girth weld.
Figure 5. Option 1 and 2 evaluation curves of the Ø813 × 17.5 mm X65 pipe base metal.

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Ultimate Axial Load Prediction Model for X65 Pipeline with Cracked Welding Joint Based on the Failure Assessment Diagram Method
  • Article
  • Full-text available

December 2021

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409 Reads

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3 Citations

Applied Sciences

Jianping Liu

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Shengsi Wu

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Crack defects in the girth welds of pipelines have become an important factor affecting the safe operation of in-service oil pipelines. Therefore, it is necessary to analyze the factors affecting the safe operation of pipelines and determine the ultimate load during pipeline operation. Based on the failure assessment diagram (FAD) method described in the BS 7910 standard, the key factors affecting the evaluation results of the suitability of X65 pipeline girth welds are analyzed, and the effects of crack size, pipe geometry, and material properties on the evaluation results are investigated. The results indicate that the crack depth is more crucial to the safe operation of the pipeline than the crack length. While the effect of wall thickness is not significant, the misalignment can seriously aggravate the stress concentration. In general, the higher the yield ratio and tensile strength of the pipe material, the more dangerous the condition at the weld. The ultimate axial load that a crack-containing girth weld can withstand under different combinations of the above factors was determined. Furthermore, a data driven model via the optimized support vector regression method for the ultimate axial load of the X65 pipe was developed for engineering application, and the comparison results between the FEM results and the predicted results proved its accuracy and reliability.

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An Accurate and Efficient Fitness-For-Service Assessment Method of Pipes with Defects under Surface Load

September 2021

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506 Reads

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1 Citation

Energies

With continued urbanization in China, the construction of urban gas pipelines is increasing, and the safety of gas pipelines are also increasingly affected by urban development and the increased scope of buildings and roads. Pipes with defects are more likely to fail under the surface loads. In this study, uniaxial tensile tests of high-density polyethylene (HDPE) pipes were carried out to obtain the real material parameters of pipe. A pipeline-soil interaction finite element model of HDPE pipeline with defects under surface load was established. The failure mechanism of the urban gas pipeline was studied and the influence of parameters such as internal pressure, defect position, defect depth on the mechanical behavior, and failure of pipelines were analyzed. A failure criterion for HDPE pipes with defects under surface load was proposed based on the limit-state curves obtained under different working conditions. Furthermore, an accurate and efficient fitness-for-service assessment procedure of pipes with defects under surface load was proposed. The results showed that maximum Mises stress of the pipeline gradually increased with increasing surface load and the position of maximum stress changed from the top and bottom of the pipe to the defect position and both sides of the pipe. Finally, when Mises stress of the HDPE pipe exceeds the yield limit, failure will occur. Internal pressure, defect location, and defect depth were found to influence the failure process and critical surface load of the pipeline. Safety evaluation curves of the gas pipeline with defects under surface load were obtained by calculating the critical failure load of the pipeline under various working conditions. Finally, a nonlinear fitting method was used to derive a formula for calculating the critical surface load under different defect parameters. The proposed method provides a useful reference for urban gas pipeline safety management.


Digital Twin of Buried Oil Pipe in Permafrost Regions: A Multi-Source Monitoring and Numerical Simulation Model

July 2021

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43 Reads

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3 Citations

Geohazards have become one of the major threats for pipeline safety as catastrophic consequences can be induced by the ground displacement. To prevent pipe failure, multi-source monitoring technics have been adopted by pipeline operators in engineering practice. While the strain gauge monitored strain results are discretely distributed along the pipeline, which makes the most dangerous pipe section might be not derived directly via sensors. Therefore, it is of great significance to establish an accurate numerical simulation model based on digital twin technology in the geological disaster areas to predict the actual stress and strain status in pipelines. In this paper, an automatically generated parametrical finite element model was established by combining using the general nonlinear finite element software package ABAQUS and the numerical calculation software MATLAB. Numerous numerical strain results were generated as database for a multi-layer backpropagation artificial neural network regressing pipe’s strain state and the geohazard loading conditions (i.e. soil displacement, length of the geohazard areas etc.). Finally, particle swarm optimization algorithm was employed to obtain the most fitting geohazard loading conditions based on monitoring data. An actual case of a buried X65 crude oil pipeline in northeast China was considered as an example, results show that after 5 iterations a relatively accurate strain distribution along the pipe was obtained via the optimization results. The proposed method can be adopted in the integrity management of pipeline crossing geohazard areas.


Stress Analysis of Buried Pipelines Under Thaw Settlement of Permafrost Zone Based on Moisture-Heat-Stress Coupled Analysis

September 2020

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29 Reads

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1 Citation

Permafrost thawing caused by the hot crude pipeline is a major threat to the safe operation of buried pipelines in permafrost zone. In this paper, the process of thawing and consolidation of frozen soil is considered, and a three-dimensional (3D) finite element model of buried pipelines in permafrost zone is established using ABAQUS. The calculation of thaw settlement displacement of frozen soil based on moisture-heat-stress coupled was carried out, and the deformation and stress of buried pipelines were analyzed. The effects of ground temperature, oil temperature, thermal conductivity of insulation material and soil distribution along the pipeline on the vertical displacement and longitudinal stress of buried pipelines in frozen soil were studied. Research results show that in thaw-unstable soil, the vertical displacement and stress of the pipeline increase significantly with the increase of the average ground temperature, and change on ground temperature amplitude has a little effect on the vertical displacement and longitudinal stress of the pipeline in thaw settlement zone. It is 1/3 of the vertical displacement of the pipeline without a heat insulating layer. When the thermal conductivity of the insulation material is less than 0.4 W/m °C, the vertical displacement of the pipeline in the thawing zone can be further reduced by reducing the thermal conductivity of the insulation material. When clay and sand appear alternately along the pipeline, the vertical displacement and longitudinal stress of the pipeline can be reduced by reducing the length of clay section. This study has certain reference value for optimizing the design parameters of buried pipelines in permafrost zone and reducing the impact of differential thaw settlement of frozen soils on the safe operation of pipelines.


An Improved Analytical Strain Analysis Method for Buried Steel Pipelines Subjected to Abrupt Permanent Ground Displacement

September 2020

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42 Reads

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1 Citation

Abrupt permanent ground displacement is a typical loading condition for pipelines crossing geotechnical hazard areas. An improved analytical method for calculating longitudinal strain of buried pipeline under tension combined with bending load induced by permanent ground displacement (PGD) was proposed, in which, the pipe steel was considered as a bilinear material and the soil constraint on pipe was considered as a series of elastic-plastic nonlinear soil springs. Effects of elastic deformation of axial soil springs on pipe strain was derived accurately. Effects of axial force in pipe on pipe’s bending deformation was considered directly in the governing equation of pipe. Equilibrium between the section stresses in the large deformed pipe sections near fault trace and the section force and moment at the same position derived by the beam theory was used to obtain the nonlinear stress distributions in the pipe section and furtherly to obtain the equivalent modulus describing the locally decreased pipe stiffness. This method makes it possible to accurately derive the pipe longitudinal strain considering the effects of pipe material nonlinearity induced locally decreased pipe stiffness in large bending deformed pipe segments. A three dimensional nonlinear finite element model was also established by general software package ABAQUS to serve as a benchmark to validate the accuracy of proposed analytical method. Shell and pipe elements were employed to simulate pipes in large deformation and small deformation regions respectively. Distributed nonlinear soil spring elements were employed to simulate nonlinear soil constraints on pipe. Various loading conditions were performed to compare the efficiency and accuracy of the proposed analytical method comparing with the FE method. Results show the proposed analytical method can predict accurate longitudinal strain results even large plastic deformation appears in pipe. And comparing with FE method, analytical method has advantages in calculating efficiency, which is more suitable for application in engineering practice.


Establishment and Application of the Pipeline Monitoring System in Permafrost Regions in China

September 2020

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19 Reads

Buried pipelines in permafrost regions are inevitably subjected to some typical geohazards, such as frost heave, thaw settlement and thaw slumping. The bending or/and longitudinal strains will be induced in pipe under these types ground movement, which is the potential cause of weld joint rupture. Thus, in order to prevent pipe failure, a comprehensive monitoring system was designed and used in the Mohe-Daqing oil pipeline in the permafrost region in northeast China. The Mohe-Daqing oil pipeline is built for importing oil from Russia and its north part of 440km lays in permafrost. The monitoring system includes soil temperature field monitoring system, ground displacement monitoring system and pipe strain monitoring system. The soil temperature field monitoring system, which uses fiber brag grating sensors, can monitor the distribution of surrounding soil temperature in radial direction of pipe in order to detect the change of active ring of permafrost. The ground displacement monitoring system, which is based on a total station, can discover any subsidence or heave of the pipe itself and the embankment along the pipeline. The pipe strain monitoring system, which includes pipe stress monitoring system based on fiber brag grating sensors and inertial measurement unit (IMU) mapping, can inspect the real-time change of pipe stress and the bending strain periodically respectively. Using the comprehensive monitoring system, the important parameters that affect pipeline integrity such as pipeline temperature, stress, strain and displacement of Mohe-Daqing oil pipeline can be supervised timely and effectively. And the accuracy and reliability of the monitoring system have been verified in practical application. In this paper, detail about how these systems are designed and installed on the Mohe-Daqing oil pipeline is elucidated and the monitoring data is analyzed. Through these data, the present mechanical situation of Mohe-Daqing oil pipeline is safe, but the long-term change is critical because of the soaring oil temperature that is far high than the design temperature. The monitoring system is of great significance to ensure the safe operation of Mohe-Daqing pipeline and can provide reference for the pipeline operation in permafrost areas.


An ANN‐based failure pressure prediction method for buried high‐strength pipes with stray current corrosion defect

November 2019

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294 Reads

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42 Citations

With continued increasing construction of both electrified facilities and buried high‐strength pipelines in China, stray current corrosion defects have become an nonignorable threat for these pipelines. A comprehensive investigation on a new failure pressure prediction model for high‐strength pipes with stray current corrosion defects was conducted in this study. The mechanism of stray current corrosion in steel pipes was firstly elaborated in brief. After that, a parameterized finite element model for stress analysis of pipes with external corrosion defects was programmed by APDL code developed by general software ANSYS. By comparing numerical results with full‐scale experimental results, both the numerical model and the failure criteria for pipe burst were proven to be reasonable. Based on the finite element model, parametric analysis was performed using a calculation matrix set by orthogonal testing method to investigate the effects of three main dimensionless factors, that is, ratio of pipe diameter to wall thickness, nondimensional corrosion defect length, and nondimensional corrosion defect depth on pipe's failure pressure. Utilizing the parametric analysis results as database, a multilayer feed‐forward artificial neural network (ANN) was developed for failure pressure prediction. By comparison with experimental burst test results and results of previous failure pressure estimation model, the ANN model results were proven to have both high accuracy and efficiency, which could be referenced in residual strength or safety assessment of high‐strength pipes with corrosion defects.

Citations (4)


... For the technical staff, in the daily process of large diameter long distance pipeline construction, they need to pay more attention to the process of the welding process. In the process of welding to promote defects or quality problems, corresponding technical researchers need to take timely remedial measures to remedy defects, to ensure that the daily use of large diameter long-distance pipeline safety performance will not be affected [1][2][3][4][5][6][7]. In order to be able to make the use of large diameter long distance pipelines play a more important role in the process, in order to ensure the use of large diameter long distance pipeline safety performance, technology researchers tried on large diameter long-distance pipeline daily use process, quality inspection and safety performance on a regular basis to check, large diameter long distance pipeline transportation quality can gain greater protection. ...

Reference:

Performance Test and Cause Analysis of Girth Weld with Defects
Ultimate Axial Load Prediction Model for X65 Pipeline with Cracked Welding Joint Based on the Failure Assessment Diagram Method

Applied Sciences

... The process of weight adjustment is the process of network learning and training. This process will not stop until the network output error is reduced below the preset threshold or exceeds the maximum training times [20], [21]. ...

Digital Twin of Buried Oil Pipe in Permafrost Regions: A Multi-Source Monitoring and Numerical Simulation Model
  • Citing Conference Paper
  • July 2021

... The physical properties of HDPE may vary depending on the casting process that is used to make a specific sample. To some extent, a determining factor is the international standardized test methods used to identify these properties for a given process [18][19]. ...

An Accurate and Efficient Fitness-For-Service Assessment Method of Pipes with Defects under Surface Load

Energies

... Bayesian network [100], [101], [102], [103], [104], [105], [106], [107], [108] Identify the critical pipelines in a high consequence area; Prediction of failure probability; Quantify the health state of the pipeline over time. ANN [78], [79], [82], [86], [87], [89], [109], [110], [111], [112], [113], [114], [115], [116], [117], [118], [119], [120], [121], [122] Predict the condition of existing oil and gas pipelines; Estimate the failure cause of oil pipelines; Classify different natural gas pipeline failures. Fuzzy Petri Net [123] One can to verify that the risk evaluation in the longdistance oil and gas transportation pipelines. ...

An ANN‐based failure pressure prediction method for buried high‐strength pipes with stray current corrosion defect