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Deformation is one of the leading causes of oil and gas pipeline accidents, affecting pipeline transportation efficiency and operational safety. This paper proposes a pipeline deformation detection method and prediction models based on alternating current magnetisation (ACM) technology. Firstly, the mechanism of pipeline deformation detection based on ACM technology is introduced and mathematical models are proposed to evaluate the deformation length and height using magnetic detection signals. Next, finite element models of detection signals for deformations with various lengths and heights are analysed and original signal waveforms are obtained. Furthermore, linear and polynomial fitting mathematical models are developed to invert the deformation length and height using the measured peak signal and L' (distorted signal length) value. Finally, experiments are conducted to demonstrate that the length and depth of a deformation can be estimated by linear and polynomial models with tolerable errors. The proposed approach combining ACM and a prediction model is verified to size deformation in pipeline inspection quantitatively.

The ability to characterise corrosion and gouging associated with metal loss and the identification of gouge type from metal loss defect types are two of the primary obstacles affecting magnetic flux leakage (MFL) internal inspection technology. Gouges in pipelines are not extraordinarily severe; however, the depth of corrosion increasing due to a certain corrosion rate can be quite serious. In this paper, a novel theoretical model combined with a new approach for the analysis of the signals that distinguish gouging and corrosion using a low magnetisation level is presented for MFL detection, since the traditional MFL internal detection tools are insensitive to stress characteristics in the case of saturation magnetisation. A two-stage finite element (FE) model for the prediction of magnetic flux leakage resulting from two types of defect is built. In the first stage, the stress distribution associated with gouging is obtained from a solid mechanics model and, in the second stage, the stress distribution is incorporated into a magnetic finite element model by mapping the stress levels to permeability. The possibility of detection and identification of corrosion and gouging using the MFL technique at low-level magnetisation was confirmed by experimentally comparing the characteristics of the MFL signals for each defect type.

Conventional magnetic flux leakage technology is unable to identify the stainless steel-lined defects of bimetallic composite pipe. In this paper, the in-line inspection technology of a 316L liner based on the eddy current flaw detection principle is studied with the aim of solving this problem. A printed circuit board (PCB) coil is designed and parameters such as the external diameter, the number of turns, the number of layers and the shape of the eddy current testing coil are determined. The impedance changes that occur under the influence of different factors of the coil are analysed according to finite element simulation. The contribution of each influencing factor during eddy current testing is investigated to optimise the coil parameters and excitation parameters. An eddy current flaw detection model for the stainless steel liner is finally established and numerical calculation is carried out on the impedance response of the defect, which is detected by parameterised scanning with the coil swept. The coil impedance is obtained under the ideal state and then verified by the experimental tests. The results show that the eddy current array testing coil has good applicability in the detection of surface defects on the stainless steel liner, which can provide references for the development of a bimetallic tube composite probe.

Purpose The corrosion of buried steel pipelines is becoming more serious because of stress corrosion, stray current corrosion and other reasons. This paper aims to study the various alternating current (AC) interference densities on the stress corrosion cracking behaviors of X80 steel samples under cathodic protection (CP) in the simulated soil electrolyte environment by using an electrochemical method. Design/methodology/approach The change of corrosion rate and surface morphology of the X80 steel samples at various AC current densities from 0 to 150 A/m2 or CP potential between −750 and −1,200 mV in the soil-simulating environment was revealed by the electrochemical methods and slow strain rate testing methods. Findings The results revealed that with the increase of interference density, the corrosion potential of the X80 steel samples shifted to the negative side, and the corrosion pitting was observed on the surface of the sample, this may cause a danger of energy leak. Moreover, the corrosion rate was found to follow a corresponding change with the stress–strain curve. Besides, with the introduction of the CP system, the corrosion rate of the X80 steel working electrode decreased at a low cathodic potential, while showed an opposite behavior at high cathodic potential. In this study, the correlation between AC stray current, cathodic potential and stress was established, which is beneficial to the protection of oil and gas pipeline. Originality/value Investigation results are of benefit to provide a new CP strategy under the interference of AC stray current corrosion and stress corrosion to reduce the corrosion rate of buried pipelines and improve the safety of pipeline transportation.

The detection and characterization of cracks is one of the key issues in oil and gas transmission pipeline inspection. The weak degree of spatial magnetic field distortion caused by the small size of the crack creates great difficulties for signal extraction. In this paper, we propose an ACM crack detection probe with poly-magnetic structure, and investigate the influence of the core, shield on the detection signal through numerical simulations. The results show that the crack detection probe with the core and shield can effectively improve the distorted magnetic field component in space acquired by the magnetic element, increasing the distorted magnetic field signals in the vertical and horizontal directions by a factor of 2.10 and 1.76 respectively. Verification that ACM probe with poly-magnetic structure can effectively increases the crack-induced magnetic field distortion signal and reduce the probability of misses.

The development of fast response, highly accurate methane sensor becoming an important target for their indispensable role in the detection of methane during the coal mine and natural gas transportation, supply and use. In this cut-edge review, we summarized the development of gas sensors in these years in both technology and materials aspects. We believe this review could inspire scientists, inventors, researchers and engineers in this field. The methane sensors can be divided into semiconductor resistive-type gas sensors, optical fiber gas sensors and mass-sensitive gas sensors according to their functions. For example, the typical methane gas-sensing materials can be divided into semiconductor metal oxides, nanocomposites, organic polymer composites, cryptophane-A, carbon nanotubes and their doping materials etc. Semiconductor metal oxide nanomaterials such as SnO2, ZnO, In2O3, Fe2O3, Co3O4 are the most used methane gas-sensing materials. In a certain temperature range, the resistance of the gas sensor can be changed by the adsorption and desorption of methane molecules with the surface of semiconductor metal oxide film. In order to promote the sensitivity and lower the working temperature of methane sensors with semiconductor metal oxides, noble metal nanoparticles, carbon nanotubes or graphene were doped into metal oxides to form nanocomposites. The methane sensor prepared by doped polymer composites could work at room temperature which made it more applicable in closed, flammable and explosive places. Cryptophane-A has an amazing affinity for methane. When cryptophane-A was exposed to the methane gas, the methane molecules would enter the cavity of the cryptophane-A. Furthermore, some studies have shown that CNTs doped with noble metals were sensitive to methane but remain controversial. The future challenges and opportunities in this field are also discussed in the perspective section. The exploitation of high-response, high sensitivity and selectivity methane-sensing materials which can work at room temperature remains a major challenge. The properties of methane sensors can be improved from grain size, porosity and thickness of gas-sensing materials. With the development of preparation process of gas-sensing materials and intelligent control technology, the intelligent gas sensors which could monitor many kinds of gas would be one trend in development of methane gas sensor.

The application of pulse eddy current detection (PECT) to quantitative detection of oil and gas pipeline cracks is a hot research field in the field of nondestructive testing. Firstly, the paper analyzes the crack detection technology by pulse eddy current, and establishes the PECT finite element model with defects by Maxwell simulation software. The influence of lift height on the detection signal and the quantitative evolution law of flux density distribution with crack width and depth under certain lift height are analyzed. The simulation results show that with the increase of lift height, the flux density Z component shows a negative correlation trend; the lift off height is a certain value, and the output signal is negative with the change of crack width and depth, and the minimum crack width recognized by the detector is 0.3mm and the depth is 0.9mm. The conclusion of the study is of great significance to quantitative analysis and cost reduction of crack detection in oil and gas pipelines.

For the analysis of the magnetic flux leakage detection data in pipelines, a single information source data analysis method is used to determine the pipeline characteristics with uncertainty. A multi-source information fusion data analysis technology is proposed. This paper makes full use of the information collected by the multi-source sensors of the magnetic leakage internal detector, and adopts distributed and centralized multi-source information fusion analysis technology. First, pre-analyze and judge the information data of the auxiliary sensors (speed, pressure, temperature) of the internal magnetic flux leakage detector. Then, the data of the main sensor, ID / OD sensor, axial mileage sensor, and circumferential clock sensor of the magnetic flux leakage detector are analyzed separately. Finally, the RBF neural network + least squares support vector machine (LSSVM)fusion analysis technology is adopted to realize the fusion analysis of multi-source information. The results show that this method can effectively improve the quality and reliability of data analysis compared with traditional single information source data analysis.

In order to save land resources for pipeline construction and reduce maintenance costs, a method of parallel laying pipeline has been adopted. The safety spacing was the primary problem to ensure the security of pipeline laying and operating. A numerical simulation method of buried parallel gas pipelines leakage-induced explosion based on TNT equivalent was presented. According to the combustible gas explosion theory, the damage law of shock waves impact on the parallel pipeline was analyzed. The maximum displacement with different parallel space and different thickness were simulated and discussed. Ultimately, the degree of risk of buried pipelines parallel spacing was analyzed and the safety spacing was determined. It provided guidance for the construction and operation of buried parallel gas pipelines.

This study investigated the effect of flowing velocity and impact angle on the fluid-accelerated corrosion (FAC) of X65 pipeline steel in a wet CO2-containing environment by corrosion morphology analysis, electrochemical measurement, and hydromechanical numerical analysis. It has been found that the corrosion behavior was controlled by the ion diffusion rate and shear stress due to the flowing gas. With an increase in the flowing velocity, the pitting corrosion initially decreased and then increased when the flowing velocity exceeded 14 m/s; this increase is caused by the augmentation of shear stress. When the impact angle decreased, the position of serious corrosion gradually moved outwards.

Caliper pigs are widely used for measuring pipeline internal geometry and detecting anomalies, such as dents, wrinkles and flat spots. Due to its excellent transport capacity, caliper pig is more widely used in subsea gas pipelines than smart pig, such as Magnetic Flux Leakage (MFL) pig or Ultrasonic Test (UT) pig. In this article, the bouncing process of detection arm of caliper pig across convex defect is studied. And then, the influence of the collision between the detection arm and deformation defect, as well as the defect shape on the bounce, is discussed. Based on that, a bouncing theoretical model of the detection arm is developed for analyzing the bouncing phenomenon. Furthermore,the bouncing process that the detection arm moves across the convex defect with different velocities and different initial spring forces is studied by experimental method. The bouncing model calculation value is approximately equal with the experimental value, verifying the validity of the bouncing model. The bouncing model has a great significance for caliper pig evaluating the pipeline convex defect.

The corrosion behavior of L80 casing steel was studied in a simulating annulus environment using the electrochemical measurement method, immersion test, and tensile test under a high-temperature and high-pressure H2S/CO2 environment. The partial pressure of CO2 (PCO2), the partial pressure of H2S (PH2S), water content, and preloading stress remarkably affected the corrosion behavior of L80 steel. The influence of PCO2 on stress corrosion cracking (SCC) susceptibility has an inflection point of approximately 1.1 MPa. The SCC susceptibility reaches the maximum when the PCO2 is about 1.1 MPa. The SCC susceptibility has a positive correlation to PH2S and water content. The higher water content of the corrosion medium can increase the electrical conductivity of the corrosion medium and promote the corrosion of L80 steel, which can improve the diffusion of hydrogen into steel and promote the SCC of L80 steel. Preloading stress can promote local corrosion, thereby promoting SCC of steel under stress. The dislocation emergence point caused by preloading stress can accelerate the diffusion of hydrogen into steel and increase SCC susceptibility.

Deepwater steel lazy-wave riser (SLWR) has won more and more applications in deepwater oil and gas resources development. The dynamic response induced by the wave, ocean current, ship motion, inter...

Many buried oil and gas pipelines are parallel to the high-voltage transmission lines and electrified railways in a long distance. Alternating current (AC) corrosion of these pipelines are very significant in such cases, and might lead to leakage even serious accidents. Laboratory experiment was carried out through weight-loss method in a simulated soil solution at various AC densities from 0 to 200 A/m2 and frequencies from 10 to 200 Hz. The results indicated that the corrosion rate increased with the increasing of AC current density. Furthermore, with the increase of AC interference frequency, the AC current involved in the electrode reaction process is decrescent, which caused a lower corrosion rate of pipeline steel. Morphology and corrosion product investigations explained that a better anti-corrosion behavior of X80 than that for X60 and X70 under AC interference. The investigation results are benefit to provide a new strategy to forecast and evaluate of the AC-induced corrosion, and design of the buried X series oil/gas pipelines.

Oil spill caused by the erosion in elbows is widely encountered in long-distance crude oil transmission pipelines and will lead to a considerable economic loss and potential safety hazards. In order to prevent the equipment failure and evaluate the campaign life of piping systems, there exists an urgent need to identify the positions suffering severe erosion damage and predict the erosion rate in pipelines for multiphase flow. In this study, a mathematical model is established to predict the solid particle erosion in the elbows of petroleum pipelines, in which the particle-fluid interaction is taken into account. The effects of bend orientation and particle properties on the erosion process are investigated in details. In order to understand the erosion mechanism related with the dynamic behavior of flow fluid and entrained particles, the relationship between the secondary flows and the particle trajectories is analyzed emphatically. The results indicate that erosion mainly occurs in the regions near the elbow exit, especially the side walls of the downstream straight pipe and extrados of the bend section. However, erosion on the side walls could not always happen when the effect of the secondary flows is not remarkable. It is also found that the erosion behavior depends upon both the centrifugal effect of pipe flow and the forces acting on particles. Finally, an erosion pattern based on Stokes number is developed to quantify the complex coupled effects of the flow field and particle properties.

An impingement jet system was used to study the corrosion of API X65 steel in a wet CO2-containing environment via electrochemical tests, surface analysis technique and computational fluid dynamics simulation. The corrosion rate decreased in the wet environment compared to that in the bulk solution. When under flow condition, corrosion rate increased with the flowing velocity, especially when above the critical flowing velocity. Continuous electrolyte film was formed and electrochemical reaction started to occur in about 70% RH, and the critical RH appeared at 70–80%, above which pit size and amount remarkably increased with flow velocity.

In order to realize the non-excavation continuous detection of metal loss defects of buried steel pipelines without internal testing conditions, a research was conducted about the the external detection technology for buried steel pipelines based on multi-frequency electromagnetic by the theoretical analysis and the ansys finite element simulation. This paper was mainly about the the influence of pipeline metal loss defects on the multi-frequency alternating current passing through the pipeline and the influence of pipeline metal loss defects on the different frequency magnetic fields around the pipeline, which laid the foundation for the development of multi-frequency electromagnetic-based buried steel pipeline metal loss defect detection equipment and pipeline defect identification. The results showed that the pipeline metal loss defects played a great influence on the direction and magnitude of the flowing current. When the metal loss defect existed in pipeline, the magnetic field signals around the pipeline were abnormal. There was a significant difference between the magnetic field changes caused by the inner wall defect and the outer wall defect. Therefore, it was possible to determine whether the pipeline was defective by analyzing the variation law of the magnetic field around the pipeline and to determine whether the defect was located on the inner wall or the outer wall of the pipeline.

With the rapid development of urban underground utility tunnels in China, the leakage of natural gas in urban underground utility tunnels is a major concern in industrial risk assessments. To inspect natural gas pipe leakage and study the diffusion of natural gas diffusion, a computational fluid dynamic (CFD) model combined with realizable k-epsilon turbulence model and component transport equation was performed. The transportation rate of natural gas was accelerated by wind, with the maximum concentration of natural gas decreasing with an increase in wind velocity. The concentration and distance of natural gas spread increased with an increase in temperature. The use of routing inspection robots for the inspection of natural gas pipe leakage and related parameters were proposed. This work had important implications for future codes and standards relating to the inspection robots of gas pipeline leakage inspection in urban underground utility tunnels.

Effect of flow on corrosion of inner wall of metal pipelines is complex, relationship between them has not been fully revealed yet in existing researches. In petrochemical industry, leakage of water pipelines often occurs. Once sewage pipelines leaking, serious pollution may happen. Therefore, valid researches on effect of flow on corrosion could provide a theoretical basis for process designing and inspection planning of water pipelines in petrochemical industry. In this paper, the static and flow induced corrosion were discussed according to the experimental results, the acceleration and influence of the velocity on flow induced corrosion were discussed.

Pipeline transportation is a safe and reliable way for transporting dangerous and flammable substances, such as oil and gas. In the process of transportation, third-party damage, corrosion destruction, design flaws, misuse of factors and other risk factors can also cause leakage or rupture of pipelines, which has a serious influence on social security and environment. In this paper, a comprehensive risk evaluation method based on a fuzzy Petri net (FPN) model for long-distance oil and gas transportation pipelines is proposed. In the process of the fuzzy reasoning, to tackle the impact of subjective factors and objective factors, the related parameters are optimized. In terms of risk factors weights, the combination weighting method is proposed, which combines AHP model and EM model. To reflect the fuzziness and randomness of risk factors, apply the cloud model to calculate the initial degrees of membership of the risk factors under the different risk grades. Furthermore, the risk evaluation values can be modified via the credibility. It is verified that the risk evaluation method based on the FPN model applies for the long-distance oil and gas transportation pipelines and provides some decision support for the risk management of the oil and gas pipelines.

A CFD–DEM-based liquid-particle two-phase flow erosion prediction model occurring over such pipeline connection as elbows, which takes the interaction of liquid–particle, particle–particle and particle–wall into account, is proposed in this study. The standard k − e model is adopted for fluid turbulent flow, the standard wall functions for near-wall zone treatment, and the Hertz–Mindlin (no slip) model for particle–particle and particle–wall contact. Numerical simulations have been performed by combining CFD code ANSYS FLUENT with DEM code EDEM to predict the maximum erosion rate and location in 90°, 60° and 45° elbows with diameter 40 mm. The fluid is water with inlet velocity 3 m/s, and the particles are 150 μm in diameter and 2650 kg/m3 in density. While the maximum erosion rates of the three are found to be quite different, the maximum erosive locations have been indicated to be at or near the exit of the elbows. In addition, the effect of bend-angle on erosion, particle motion and flow field has been discussed.

Oil and gas pipeline deformation detector is of great significance for pipeline deformation detection. In view of the poor throughput of small diameter oil and gas pipelines, this paper presents an internal deformation detection technology based on eddy current effect. Based on the eddy current theory, a mathematical model for eddy current testing of pipeline deformation defects is established. The relationship between probe lift-off value and magnetic field intensity is studied by numerical calculation method. The results show that under the same lift-off value, the composite magnetic field intensity is negatively correlated with the axis distance of the excitation coil, and at the same position, the composite magnetic field intensity is positively correlated with the lift-off value. The research in this paper has certain guiding significance for the internal detection technology of pipeline deformation defect.

Chokes are one of the most important components of downhole flow-control equipment. The particle erosion mathematical model, which considers particle-particle interaction, was established and used to simulate solid particle movement as well as particle erosion characteristics of the solid-liquid two-phase flow in a choke. The corresponding erosion reduction approach by setting ribs on the inner wall of the choke was advanced. This mathematical model includes three parts: the flow field simulation of the continuous carrier fluid by an Eulerian approach, the particle interaction simulation using the discrete particle hard sphere model by a Lagrangian approach and calculation of erosion rate using semiempirical correlations. The results show that particles accumulated in a narrow region from inlet to outlet of the choke and the dominating factor affecting particle motion is the fluid drag force. As a result, the optimization of rib geometrical parameters indicates that good anti-erosion performance can be achieved by four ribs, each of them with a height (H) of 3 mm and a width (B) of 5 mm equaling the interval between ribs (L).

Field signature method (FSM) is used today by many of the world's major oil companies in a wide range of monitoring applications, with advantages of high degree of reliability and accuracy, non-intrusive, reflecting wall thickness visually. In this paper, the theory of FSM used in inner corrosion monitoring was analyzed and the expression of defects evaluation parameter (F c ) was deduced based on the corresponding relation between wall thickness (T t ) and potential drop (E t ) of plate model. Numerical simulations with a finite element (FE) model were used for current conduction analysis, the models with defect of various depths were simulated, the relation between F c and defects was summarized, and the validity of model formula was verified. The correction formulas was given by data fitting and proved to be effective by examples.

The wear mechanisms of steel by natural rubber (NR) in water medium were investigated. The surface profile, element constitutions and binding energies of the surfaces for both steel and rubber have been analyzed with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. Moreover, the functional groups of natural rubber surfaces were examined with Fourier transform infrared spectrometer (FT-IR). It has been found that the processes of wear of steel by NR involve two stages. Firstly, under the action of frictional forces, some mechanochemical reactions generated among the surfaces of steel and rubber as well as the water medium, which produced a chemical reaction film on the steel surface. Secondly, this film was destroyed and removed by the microcutting action of the debris on the sliding surface, as a result the steel surface wore off. The wear mechanisms might be mainly attributed to the chemistry–mechanics self-catalytic destruction mechanism of steel being rubbed by natural rubber.

The surface physical and chemical effects of abrasive erosion of polyurethane in three different fluids (H2O, polyacrylamide and NaOH) containing quartz particles have been investigated respectively. The surface profiles, elements constitutions, binding energies and functional groups of polyurethane surfaces before and after abrasive eroding have been analyzed with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FT-IR). The surface physical effects of the abrasive erosion process were found to be microcutting, high-cycle fatigue and plastic fracture. The surface chemical effects turned out to be mechanical rupture of macromolecular chains, thermal decomposition of the allophanate groups and the biuret groups, hydrolysis of carbamate groups, and surface oxidative degradation.

A numerical model for predicting the burst failure of corroded pipeline is constructed using the non-linear finite element method, in which the technical points including element mesh, materials model, non-linear solution and failure criterion are recommended. Using this model, the full-size pipe burst experiments in different material, size and defect was analyzed and computed. The proposed FEM model was validated. Based on the calculation result using the model, a new formula predicting failure pressure is proposed, in which depth, length and width of a defect was involved. Comparison of the formula with the other assessment method and experiments show the formula had a satisfactory precision.Copyright © 2008 by ASME

In general, the pipeline external corrosion direct assessment should be synchronously done by two or more inspection tools. Hence, it is very important to know how to develop the high-efficient and accurate combinatorial inspection techniques for engineering application. In this paper, the advantages, disadvantages and adaptabilities of the existing techniques and instruments are reviewed. Considering the technical difficulties in Chinese engineering practices, five different combinatorial inspection techniques were then brought forward. The proper selection of the combinational inspection technique can be determined by the inspection aim, servicing environment and type of the pipeline, soil, and so on. However, it should be noted that each combinatorial inspection technique can be used most of the time with some demerits. Engineering application showed that the proposed techniques can be directly and efficiently used to assess the pipeline external corrosion.Copyright © 2006 by ASME

In general, Rg Value, Y value and holiday density can be used to evaluate the performance of the coating deposited on the buried steel pipelines. However, the evaluation may be misleading when a single parameter is used. A new combination method for assessing the performance of the coating on the steel pipelines is developed in this paper. Using this approach, Rg Value, Y value and holiday density play appropriate role on the assessment. Some new modules are presented in this approach, including current distributary module, holiday module, intelligent critical curve of AC attenuation. Additionally, a computer program is compiled that can finish data processing of AC attenuation automatic, and the result report can be synchronously printed.Copyright © 2006 by ASME