Pipeline Defects Research Articles

Ultrasonic guided wave detection of U-shaped pipeline

The guided waves in the elbow was analyzed using semi- analytical finite element method, which was used to calculate the dispersion curves, along with the vibration deformation and energy flow density distribution of the elbow cross-section. The L(0,1) mode guided wave was used to detect different defects in the U-shaped pipeline in experiment. The average experimental velocity of L(0,1) mode in U-shaped pipeline was between the theoretical velocities of the straight pipe and the elbow, due to the different velocities in the two parts. The detection sensitivity difference of L(0,1) mode guided wave to defects in intrados and extrados of the elbow was analyzed, the experimental result showed that the reflected signal amplitude of defect in extrados was significantly larger than the defect in intrados, which was consistent with the energy flow density distribution in elbow cross-section.

DETECTION OF “WALL THINNING” TYPE DEFECTS IN PIPELINES BY THERMAL METHOD

A thermophysical model of a pipe with a local defect of the “wall thinning” type is developed. Calculations of thermal anomalies for pipelines with different parameters of hidden defects are performed, illustrating the possibility of using the thermal method of nondestructive testing. The conditions and methods of thermal control of individual sections of pipelines are specified. Thermal imaging examination of steam pipelines of the main condensate of the nuclear power plant was carried out. External factors that make it difficult to detect hidden defects (the influence of external lighting, cylindrical shape of controlled objects, powerful external heat sources) are analyzed. It was found that cavitation phenomena significantly increase the temperature drop in the locations of local defects. The possibility of using the thermal method of nondestructive testing for rapid detection of hidden defects such as “wall thinning” in the pipelines of the main condensate has been confirmed experimentally

Impact of corrosion product removal to depth of corrosion damage in weldment joint

Abstract Corrosion flaws in pipelines can caused severe financial losses and also can be dangerous for people. One of the most frequently damaged parts are dissimilar pipe welds. We would like to understand how corrosion process reacts on corrosion product removal. Outputs from experiment will be used for production of test specimens. For testing we chose standard dissimilar weldment used in Czech power plants. It is joint with 08Ch18N10T and 22K (GOST) steel. Joint is cut to 24 same specimens. There are exposed to flowing water solution of 5% NaCl. Half of the specimens are regularly mechanically cleaned. The joint is metallographically observed and parts with and without corrosion products are compared. Water salt solution increased pH from 7,25 to 7,86 during 31 days test and conductivity varies around 74 mS cm−1. Metallographic observation indicates that corrosion under corrosion products layer is locally speed up and causes pitting corrosion. Cleaned specimens indicate plane corrosion with lower depth. These results indicate that slag in pipeline could locally speed up corrosion depth penetration. On the other hand, solutions with abrasive particles (which can wipe out the corrosion product) will probably facilitate plane corrosion damage on pipeline walls. This test brings us another knowledge, how to simulate realistic corrosion damage for production of NDT qualification test pieces.

Strain response of API 5L X80 pipeline subjected to indentation

Dent is a common type of defect in offshore pipelines. In this paper, the API 5L X80 unpressurized pipeline subjected to indentation was studied by experimental and numerical methods. Firstly, a full-scale experiment of API 5L X80 pipeline subjected to indentation was completed, and the axial and circumferential strains in the dent area were measured accurately. Then, a finite element model of dented pipeline was established, and the accuracy and reliability of which were verified by comparing with experimental results. Based on the above model, the stress and strain response of dented pipeline were studied in detail. Results obtained from the experiment and FE analyses show that the strain variations at and near the dented region are largely dependent on their location. The influence range of the indenter on the pipe's strain is limited. In most cases, the closer to the center of the dent, the larger the strain amplitude. The strains of longitudinal and hoop direction change dramatically with the increasing indenter displacement, while the strain variation in the 45° direction is small. Tensile-compressive stress transformation occurs at the flank of the dent. The axial stress and strain changes once along the longitudinal direction in "decreasing–increasing–decreasing" which is expressed as the wavy curve. A large amount of plastic deformation is mainly concentrated at the dent center. The dent creates a strong stress concentration, and the location of high-stress zone is dependent on the dent depth, pipe diameter and indenter radius. The plastic collapse strain of the dented pipes was evaluated by twice elastic slope criterion. The plastic collapse strain increased with pipe thickness increasing, pipe diameter and indenter radius decreasing.

Prediction of Failure Pressure for Defective Pipelines Reinforced with Composite System, Accounting for Pipe Extremities

The present paper is concerned with the failure analysis of the wall loss defect in pipelines reinforced with a polymer-based composite repair system. The main goal is to propose a methodology that accounts for the pipe extremities (axial stress) in an analysis to predict an accurate failure pressure. The proposed methodology defines a simple expression for a real test specimen condition (closed-cap cylinder), which allows to estimate the failure pressure using the elastic properties of the materials and test specimen geometry. Hydrostatic tests performed in different laboratories are used to validate the proposed methodology. The results show a good agreement between the model prediction and the experimental failure pressure results in all cases. However, a careful selection of the remaining strength factor is needed, as it impacts on the accuracy and conservative level of the failure pressure. In addition to the axial stress, there is a possibility to refine the theoretical prediction of the failure pressure value by accounting for the plastic deformation far from the defect region as well as the radial stress in the failure analysis.

Устранение дефектов трубопроводов с помощью стальных герметизирующих чопов

Устранение дефектов трубопроводов с помощью стальных герметизирующих чопов

Defect Detection of Oil and Gas Pipeline using Remote Field Eddy Current Technology

To solve the problem of wall thickness reduction and defects of oil and gas pipeline caused by corrosion or erosion, a remote field eddy current (RFEC) testing method with coaxial double coil structure is proposed to detect corrosion residual wall thickness of oil and gas gathering pipelines. Based on electromagnetic field theories, RFEC technology is theoretically analyzed. The theoretical model of RFEC detection for coaxial double coil structure is established. The relationship between the voltage phase of detection signal and the wall thickness of pipeline is derived, and an evaluation method of the residual wall thickness of the pipeline based on the phase trough time of the RFEC detection signal is proposed. The parameters of RFEC probe are optimized by Finite Element Method, and the detection system is designed on the basis of it. The practicability and the correctness of the theoretical model of the detection system are verified by experiments. It can be used to detect the residual wall thickness of pipelines in real time under different media conditions.

A calculation method for limit load of the gas pipelines with girth weld surface cracks

In this paper, a finite element model with girth weld defects considering crack tip singularity was established in order to facilitate the accurate and rapid safety assessment on girth weld defects of long distance gas Transmission pipeline. Then the J-integral of girth weld cracks in pipes with different defect sizes was calculated, and the influence of weld matching coefficient and material hardening index on J-integral is analyzed. Furthermore, the influence factors of limit load of pipeline with girth weld defects based on J-integral theory are studied. Based on this, the engineering calculation formula which can calculate J-integral and limit load rapidly in the situations with specific matching coefficient and material hardening index was proposed. And the following research results were obtained. First, the engineering calculation formula based on the fitting of finite element calculation results has high accuracy, which can calculate the J-integral of defects in a large geometric range and the limit load of pipelines with girth weld cracks. Second, the J-integral of cracks in pipes with girth weld defects is closely related to defect size, material properties and weld matching coefficient, and the limit load of pipes with defects decreases as the crack size increases and increases as the material hardening index increases. Third, for the X80 pipes with surface cracks at the centerline of the girth weld, the load carrying capacity of the pipes with low-strength matched weld are lower than that with high-strength or equivalent-matched weld. In conclusion, the research results can be used as reference for the safety evaluation and integrity management of in-service gas pipelines.

Theoretical study on the characteristics of self-magnetic flux leakage signals from pipeline defects

Theoretical study on the characteristics of self-magnetic flux leakage signals from pipeline defects

An Iterative Stacking Method for Pipeline Defect Inversion With Complex MFL Signals

Magnetic flux leakage (MFL) inspection in nondestructive testing (NDT) has been widely used in damaged pipeline defect inversion. The changeable environment and the complexity of MFL signal have brought severe challenges to the accurate estimation of defect sizes in inversion issue. This article proposes a novel pipeline defect inversion method (WT-STACK) based on stacking learning. This method consists of two parts. First, a multi-domain feature extraction with three-axis (axial, radial, and circumferential) signals is constructed. To avoid the feature information loss, signals are analyzed both in time and frequency domains. Second, to study the complex nonlinear relationship between the feature and defect size, an iterative stacking estimation network is developed with dynamic multi-domain features input. An adaptive learning is realized in the network, which enhances the generalization ability for different sample sets of defect inversion issue. Finally, the method is evaluated by experiments using MFL signals collected from experimental platform and simulation signals. Experimental results and comprehensive comparison analysis with other state-of-art methods validate the superiority of this method.

The Design, Construction and Testing of an Intelligent Device for Coating Flaws and Crack Detection in Pipelines

The major pollutant induced by pipeline failure in Oil and Gas industry has been mitigated over the years using non-destructive techniques like liquid penetrant, magnetic particles, radiographic, ultrasound and eddy current testing. The eddy current technique’s advantage over the other testing devices remains the best suitable in the design and construction of the devices due to the nature of the pipeline materials. For this present work, a pre-test-post-test experimental design was used to test devices on a defect free pipe and a pipe with machined defects of known dimensions and different orientation (longitudinal and axial) after construction. The defect detection was done using electromagnetic technique of eddy current by exciting a coil with power supply and placed close to the tested pipe surface, as a micro-controller was used to track the irregularities on the material surface by computer systems. The device set up for the test was a coil with a power supply of a DC battery connected with micro-controller of a quantization level of 4.88mV. For visual display, result obtained indicates no variation in the amplitude of the pulse as demonstrated by a pipe with no defect while variations (deeps) occurred in the pipe with defects as the coil was traversed over the defect. The orientation had no significant effects on the sensitivity and effectiveness of the device. Results validation was done using a non-destructive technique by visual inspection. Thus, device has shown its effectiveness in detecting defects irrespective of the orientation. Similarly, the size of the defects is a determinant in the amplitude variation of the pulse displayed which implies at higher sensitivity, a high frequency is required.

Impact of hidden defects on the durability and reliability of gas pipelines in cities

The article describes the methods of improving the durability of new gas pipelines, as well as examines the need of rising the level of inspection security. Reliable gas pipelines is an important safety indicator of people’s housing areas and the industrial and commercial organizations work areas. The verification of durability and tightness of gas pipelines is one of the most important inspection, which shows the existence of defects in compliance of the gas pipelines and debt construction technologies and instructions. Detected on time defects influence the number of uncontrolled natural gas leaks in the pipelines. When assessing the impact of hidden defects on the durability and reliability of the gas pipeline, the gas pipeline monitoring process was made, and the defects in the construction of gas pipelines (polyethylene, steel) and fittings were more often detected, the effect of hidden defects of gas pipelines on the safety of pipelines was analyzed. The experiments described in the article were carried out to evaluate the durability and tightness of gas pipelines by simulating the hidden defects on new installed gas pipeline in two sites: Site 1 and Site 2, both places are situated in Latvia. The obtained data was processed and reflected in tables, charts, graphs, and the results were analyzed and summarized in the conclusions, and also proposals are made to improve the problem. In the article is described a calculation methodology, which proves what needs to be improved in order to increase the safety of newly built and reconstructed gas pipelines.

PZT transducer array enabled pipeline defect locating based on time-reversal method and matching pursuit de-noising

In the process of pipeline structural health monitoring, it is necessary to detect pipe defects as well as to locate the defect’s axial and circumferential positions. Axial locating of a pipeline defect can be achieved by identifying the defect reflection packets in the direct detected axial displacement time history signals. In practice, various kinds of noise are involved in the actual detection signal. Using the matching pursuit (MP) algorithm based on a custom over-complete waveform dictionary, the noisy detection signal can be effectively de-noised, and the defect’s axial position can be located. The time-reversal method used in a waveguide leads to temporal and spatial focusing, and this feature is used to locate the defect’s circumferential position in the pipeline. In this paper, a new pipeline defect locating approach based on the time-reversal method and MP de-noising is proposed. The integration of the finite element method (FEM) numerical simulation with experiment is utilized to locate the pipeline defect. The defect axial position Lx is located by the direct detected signal obtained from the actual pipeline defect detection experiment, after MP de-noising. A defect-free FEM reference model is established, and it has the same geometric and material parameters as the actual pipeline. Re-generating the time reversed defect reflection and the converted mode signals in the reference model, the energy will focus on the Lx position. After obtaining the maximum values of the axial displacement time history signals received from the reference model at the Lx position, the polar coordinate map based on these maxima can be plotted. The defect circumferential position is located based on the maximum values on the map. The FEM numerical simulation and experimental results are performed in this research. The defect locating results agree well with the actual pipeline defects, in both the axial and the circumferential directions.

Geomagnetic detection method for pipeline defects based on ceemdan and WEP-TEO

Geomagnetic detection method for pipeline defects based on ceemdan and WEP-TEO

Time-based damage detection of underground ferromagnetic pipelines using complexity pursuit based blind signal separation

The measured sensor data of underground ferromagnetic pipelines consist of hidden damage information that can be explored by developing output data identification models due to the availability of only output signal responses. The current research findings elaborate output-only modal identification method Complexity Pursuit based on blind signal separation. An attempt is made to apply the complexity pursuit algorithms, for time-based damage detection of underground ferromagnetic pipelines which blindly estimates the modal parameters from the measured magnetic field signals for targeting the pipeline defect locations. Numerical simulations for multi-degree of freedom systems show that the proposed tested method could precisely identify the structural parameters. Experiments are conducted primarily under well-equipped controlled laboratory conditions followed by confirmation in the real field on pipeline magnetic field data, recorded through high precision magnetic field sensors. The measured recorded structural responses are given as input to the blind source separation model where the complexity pursuit algorithms blindly extracted the least complex signals from the observed mixtures guaranteed to be source signals. The output power spectral densities calculated from the estimated modal responses unveiled elegant physical interpretation of the underground ferromagnetic pipeline structures.

Possibility of Piezoelectric Sensor to Monitor Onshore Pipeline in Real Time Monitoring

Transportation oil and gas mostly used pipelines transportation. The condition of a pipeline must be continually monitored to ensure that defects do not cause it to fail and operate optimally. Pipeline has the possibility to experience defects during operations such as general corrosion, fatigue, crack, and others. Defects that occur in the pipeline during operation have serious consequences including loss of property, personal injury, or even loss of lives and serious ecological pollution. Awareness of the importance of conducting pipeline monitoring and safety issues for workers and residents around the pipeline site, emphasizes the importance of developing a technology for conducting pipeline monitoring activities in real time. The new technology for detecting metal defects is by using piezoelectric material. Based on laboratory scale, piezoelectric sensor can be applied to monitor pipeline defect. However, it is necessary challenges to scaling up in real application are following: (1) financial investment, (2) human behavior surrounding pipeline area, (3) receiving signal in long distance, (4) protection of piezoelectric sensor, (5) combination survey for future development.

Failure pressure prediction of corroded pipes under combined internal pressure and axial compressive force

In this work, failure prediction of corroded pipelines under combined loads of internal pressure and axial compressive force is investigated through the Finite Element Method. The study was carried out using the PIPEFLAW program, which was specially developed to automatically generate and analyze corroded pipelines models. Two configurations of idealized defects in pipeline were investigated: with two and three rectangular defects. This work was divided into two stages where, on the first stage, the analysis is performed considering only internal pressure. On the second stage, combined loads are simulated considering internal pressure and axial compressive forces. Results show that failure pressure values decrease with the increase in the axial compressive force, for both Finite Elements models analyzed.

Non-Contact Geomagnetic Detection Using Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise and Teager Energy Operator

During the non-contact geomagnetic detection of pipeline defects, measured signals generally contain noise, which reduces detection efficiency. Complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) has recently emerged as a signal filtering method, but its filtering performance is influenced by two parameters: the amplitude of added noise and the number of ensemble trials. To solve this issue and improve detection accuracy and distinguishability, a detection method based on improved CEEMDAN (ICEEDMAN) and the Teager energy operator (TEO) is proposed. The magnetic detection signal was first decomposed into a series of intrinsic mode functions (IMFs) by CEEMDAN with initial parameters. Signal IMFs were then distinguished using the Hurst exponent to reconstruct the preliminary filtered signal, and its maximum value (except the zero point) of the normalized autocorrelation function was defined as salp swarm algorithm (SSA) fitness. The optimal parameters that maximize fitness were found by SSA iterations, and their corresponding filtered signal was obtained. Finally, the gradient calculation and TEO were carried out to complete non-contact geomagnetic detection. The results of the simulated signal based on magnetic dipole under a noisy environment and field testing prove that ICEEMDAN denoising has better filtering performance than conventional CEEMDAN denoising methods, and ICEEMDAN-TEO has obvious advantages compared to other detection methods in the aspects of location error, peak side-lobe ratio, and integrated side-lobe ratio.

Novel Circuit Implementation Method for Pulse Signal Finite Rate of Innovation Sparse Sampling Based on an Improved Exponential Reproducing Kernel

Finite rate of innovation sampling is a new signal sparse sampling method based on signal information freedom, which can considerably reduce the amount of sampling data. However, the researches on hardware circuit direct implementation of the method are at an initial stage. Therefore, a novel hardware circuit implementation method based on an exponential reproducing kernel (ERK) was developed with an improved ERK sparse sampling theoretical framework, which comprised an analog rational kernel (ARK) and digital rational kernel (DRK). The parameter constraint conditions and selection method for the improved ERK were analyzed. The performance of the ARK hardware circuit and the DRK algorithm were also examined. The designed sparse sampling system was applied to a pipeline flaw ultrasonic inspection by using the sparse sampling data of the ultrasonic signal obtained directly. The experimental results revealed that the proposed method could directly obtain the signal sparse sampling data and accurately reconstruct the initial signal parameters by using a spectrum estimation algorithm. Moreover, the signal sampling rate and the amount of sampling data were reduced considerably.

Review on Computer Aided Sewer Pipeline Defect Detection and Condition Assessment

Physical and operational inspection of sewer pipelines is critical to sustaining an acceptable level of system serviceability. Emerging inspection tools in addition to developments in sensor and lens technologies have facilitated sewer condition assessment and increased the quality and consistency of provided data. Meanwhile, sewer networks are too vast to be adequately investigated manually so the development of innovative computer vision techniques for automation applications has become an interest point of recent studies. This review paper presents the current state of inspection technology practices in sewer pipelines. An overall inspection tool comparison was conducted and the advantages and disadvantages of each method were discussed. This was followed by a comprehensive review of recent studies on visual inspection automation using computer vision and machine learning techniques. Finally, current achievements and limitations of existing automation methods were debated to outline open challenges and future research for both infrastructure management and computer science researchers.