Defective Pipe Research Articles

Waveguide Acoustic Control of Pipes - Billets of Deep Rod Pumps

Deep rod pumps are expensive maintenance-free equipment for extracting oil from wells. The exclusion of defective billet pipes from the technological cycle of manufacturing elements of such pumps significantly affects both the cost of their production and the cost of production. A waveguide method is proposed for continuous input testing of tube billets of rod pump cylinders. It does not require scanning and is highly sensitive to both internal and surface defects. An experimental assessment of the sensitivity of the method to defects in the form of an influx located on the outer and inner surfaces of a thick-walled pipe with a diameter of 59.3 mm and a wall thickness of 14 mm was carried out. The echo signal from the artificial reflector decreased by 2 dB when the reflector was moved from the outside of the pipe to the inside. The criteria for rejection of the blank pipe are determined by the signal level at the first reflection R1, at the 8th reflection RN and by the attenuation coefficient b. As a result of flaw detection of billet pipes, a pipe with a significant defect was found. An experimental study of the acoustic properties of a batch of pipes with a diameter of 58 mm in the delivery state was carried out. For the billets of the cylinder of the deep rod pump in the delivery state, the lower acceptance limit for the torsional wave velocity of 3255 m/s has been determined. The influence of technological operations of high tempering and straightening on their acoustic properties is estimated. The possibility of quality control when performing the release operation by the guided wave method is shown. It was revealed that during the tempering procedure, the velocity of the torsional wave increases, on average, by 27 m/s per batch.

The influence of fines content on ground collapse due to internal erosion of sand-fines mixtures around defective pipes

Ground collapse caused by defective pipelines has become a global issue with the continuous advancement of urbanization. This study reproduced the internal erosion process of sand-fines mixtures around defective pipes through a series of model tests considering a relatively wide range of fines content and three hydraulic conditions. The erosion characteristics and the evolution of the cavity were analyzed to determine the triggering mechanisms of ground collapse. The results indicate that the formation and evolution of the cavity predominantly depend on fines content under hydraulic loading, which is replaced by ground settlement at lower fines content. Moreover, the scouring of groundwater amplifies the impact of internal erosion, which means the marked ground settlement at lower fines content or the expansion of the cavity even to ground collapse at higher fines content. To prevent sudden ground collapse, it is not recommended to use sand-fines mixtures with a fines content of more than 10% as embedment materials.

A Multi-Strategy Hybrid Sparse Reconstruction Method Based on Spatial-Temporal Sparse Wave Number Analysis for Enhancing Pipe Ultrasonic-Guided Wave Anomaly Imaging.

Ultrasonic-guided waves (UGWs) in defective pipes are subject to severe coherent noise caused by imperfect detection conditions, mode conversion, and intrinsic characteristics (dispersion and multiple modes), inducing the limited performance of anomaly imaging. To achieve the high resolution and accuracy of anomaly imaging, a multi-strategy hybrid sparse reconstruction (MHSR) method based on spatial-temporal sparse wavenumber analysis (ST-SWA) is proposed. MHSR leverages the capability of ST-SWA to extract the wavenumber dispersion curves, thereby providing a more refined and precise search space for MHSR. Furthermore, it mitigates the impact of coherent noise by conducting dispersion compensation on the reconstructed signal. The sparse compensated signals through MHSR are employed for sparse reconstruction imaging. To validate the efficacy of the proposed method, UGW testing is performed on the defective steel pipe, and the results demonstrate the significant enhancement of anomaly imaging in defect resolution and positioning accuracy. The lowest estimated errors for axial and circumferential defect positions are 10 mm and 4 mm, respectively.

A Comparative Analysis on the Optimization of Carbon Fibre Reinforced Polymer and Glass Fiber Reinforced Polymers as Wrapping Structures on Defected Piping System using Computational Simulation Approach

This study examined the application of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) as wrapping structures for defective pipe systems. The structural behavior and performance of the CFRP and GFRP wrapping structures were assessed using computational simulation methodologies. The goal of the study was to determine the best wrapping material for strengthening the integrity and reliability of piping systems with defects by comparing the results of the simulations. The study evaluated the capability of the proposed composite wrapping structure through CAD simulation. The simulations provided preliminary analysis and visually depicted deformations, aiding in the selection of an optimized lamination orientation for the composite wrapping structure in real-world applications. Eventually, this approach could have alleviated two primary failure modes that were common in composite repair: composite overloading due to excessive thickness and composite delamination from the substrate. The results of this study would have helped enhance effective and efficient pipe repair techniques in a variety of industries by offering useful insights into the selection and use of suitable wrapping structures for repairing defective pipes.

Failure evolution and mechanism of ground collapse due to exfiltration of shallowly buried water pipeline

Exfiltration of defective water pipelines is one of the leading causes contributing to the frequent ground collapses in congested urban areas; hence, revealing the failure evolution and mechanism of this hazard is essential to its prevention and mitigation. In this study, comprehensive experimental model tests were conducted first to characterize the evolution of soil erosion and ground collapse due to exfiltration of shallowly buried defective water pipes and examine the effects of six critical parameters, i.e., opening size and location, pipe pressure and buried depth, groundwater level, and exfiltration condition. Three failure behaviors of strata around leaking waterpipe were identified, i.e., minor disturbance (slight), formation and collapse of an erosion cavity (moderate), and soil fluidization (severe). Moreover, the ground loosening zone induced by cavity collapse could be roughly estimated using the modified flow ellipsoid theory; soil fluidization would occur once the ratio of water pressure head inside the pipe to its buried depth was greater than 2. Subsequently, a validated computational-fluid-dynamics and discrete-element-method (CFD–DEM) coupling method was employed to explore the microscopic mechanism of cavity erosion under the exfiltration flow. It was disclosed that the formation and expansion of a temporary cavity resulted from internal soil erosion, including the emigration of massive fine particles and aggregation of coarse particles around the defective pipe. Finally, the numerical simulation results indicated that cavity erosion would be exacerbated by increasing flow velocity and particle size-ratio, reducing soil fines content, and changing the opening from the pipe crown to its invert.

Effects of axial misalignment welding defects on the erosive wear of natural gas piping

When considering solid particles in the pipe and axial misalignment weld defects in natural gas transmission systems, changes in the flow field due to structural differences can lead to various erosion characteristics in the bends. To investigate the erosion process within the bend, the computational fluid dynamics (CFD) - discrete phase model (DPM) method to develop a bend model with axial misalignment weld seam defects was employed. The erosion distributions of a bend with an axial misalignment weld were investigated under various transport parameters, bend orientation, axial misalignment height, and particle incidence angle. The results indicated that the erosion rate of the outermost elbow increases with the increase of the height of the axial misalignment weld on the outside of the bend pipe. When the axial misalignment height ranges from 1 mm to more than 5 mm, the difference in the maximum erosion rate escalates from 7 % to approximately 30 %. When the length of the inlet straight pipe is shorter, an increased incident angle intensifies the erosion effect and vice versa. This research can provide a reference for field construction work involving defective natural gas pipe bends.

Effect of hydrogen embrittlement on the safety assessment of low-strength hydrogen transmission pipeline

Currently, no systematic approach exists for the safety assessment method of hydrogen transmission low-strength pipeline, it is necessary to study the effect of hydrogen embrittlement (HE) on the method of failure assessment diagram (FAD) for the defective pipe. The hydrogen charging experiments of tensile and Charpy impact specimens for the L245 pipe steel were carried out with charging time of 0, 30, 90, and 120 h, and then the tensile and Charpy impact tests were immediately conducted. The HE indexes of tensile and Charpy impact properties were presented to quantitatively analyze the effect of HE under tensile and impact deformation processes. Subsequently, the FAD method coupled with the effect of HE was investigated to analyze the difference in the safety assessment method between hydrogen and non-hydrogen environments. Finally, the fracture morphology of tensile and Charpy impact specimens was observed to analyze the responses of microscopic fracture modes between hydrogen and non-hydrogen environments. The results show that the effect of HE on the tensile properties of the base material is more sensitive than that of the weld joint. The FAC with the effect of HE for safety assessment of defective pipes shrinks by reducing the safe zone. The decrease ratio of safety factors affected by HE presents an increasing tendency as the increase of crack depth while showing a decreasing tendency as the increase of internal pressure.

Investigation of defect formation in the form of longitudinal folds at the ends of semi-finished pipes during rolling on an automatic TPA mill

The article presents an elimination method aimed at addressing the defects in the form of longitudinal folds at the ends of semi-finished pipes during rolling on automatic mills of a pipe rolling plant (TPA). Currently, this issue is relevant, as it significantly affects the quality of the pipes produced. The developed solution is based on the implementation of a special design that prevents the occurrence of longitudinal folds at the ends of semi-finished pipes. Experimental studies have been conducted to confirm the effectiveness of the proposed technical solution. The obtained results demonstrate a significant reduction in the number of defective pipes and an increase in the overall volume of high-quality production. The developed technical solution represents a significant contribution to the improvement of pipe rolling technology on automatic TPA mills and can be applied in production conditions to enhance outcomes and resource efficiency

Experimental study on the soil erosion through a defective pipe under the cyclic infiltration-exfiltration flow

Ground collapse is becoming a global issue, and it is of significant importance to understand its mechanism and develop models for the prevention and mitigation of this hazard. The cyclic infiltration and exfiltration through defective pipes can lead to soil loss, resulting in ground collapse or sinkholes. This study conducted physical model tests to examine soil erosion through a defective pipe under cyclic infiltration-exfiltration flow, using simplified gap-graded soils made up of bimodal particles composed of two different diameters of glass spheres. Three types of erosion behaviors were identified: clogging, incomplete erosion, and complete erosion. Fines loss can significantly contribute to ground subsidence for bimodal soils, particularly for those with a particle size ratio greater than 2. After introducing a non-dimensional parameter that accounts for particle size, defect size, and fines content, a phase diagram was developed to determine erosion behavior based on the cycle number. When the non-dimensional parameter exceeds 1.75, erosion characteristics may change to complete erosion after applying seven cycles of infiltration and exfiltration. Finally, an analytical model was proposed to predict soil mass loss considering the cyclic number of the exfiltration and infiltration flow for the incomplete erosion.

Effect of soil on leakage rates in water distribution pipes

Abstract This paper describes an experimental and analytical study that examined the effects of soil on leakage rate from defective water pipes. An experimental model was designed and constructed to simulate idealized cracks in defective water pipes discharging into a bed of granular materials. Tests were run on three different materials: LBS-B, LBS-A, and glass ballotini with different characteristics. The results reveal that the presence of bedding material surrounding a leaking pipe causes a significant change in the leakage rate versus free flow conditions. The bedding has a greater impact on larger defect openings. There was a significant drop in the values of the coefficient of discharge (Cd) when the pipe discharged into a soil bed versus free flow conditions; this value was 38% lower for coarse particles and 70% for finer particles. The results also showed that high leakage rates could flow from the defective pipe without fluidization of the bedding materials. An analytical model based on the method of fragments was presented to predict the leakage rate after which the predicted results were compared with values measured experimentally.

Soil Erosion Due to Defective Pipes: A Hidden Hazard Beneath Our Feet

Sinkholes are a significant underground hazard that threatens infrastructure and lives and sometimes results in fatalities. The annual cost of sinkhole damages exceeds $300 million, although this estimate is likely underestimated due to the need for national tracking. Sinkholes can also alter natural drainage patterns, leading to increased flood risk. While natural sinkholes occur, those in urban areas are predominantly manmade, caused by soil erosion from defective pipes, typically due to aging. Climate change, storm surges, and urbanization have accelerated subsidence in urban environments, posing greater risks to critical infrastructure and densely populated areas. Extensive research has focused on soil erosion in dams; however, this knowledge does not necessarily apply to erosion through orifices, where gravity and other factors play significant roles. This paper presents a critical literature review on internal soil erosion due to defective pipes (SEDP). The review highlights that hydraulic loading, backfill type, and pipe conditions (defect shape, size, and depth) influence SEDP. Key findings from experiments and numerical studies are summarized, while mechanisms and knowledge gaps are identified. However, it is concluded that the current understanding in this field remains limited, underscoring the urgent need for further experimental and numerical research to expand the knowledge base on SEDP.

Assessment of the stressed-strained state of a reinforced transport pipe under the combined effect of ambient temperature and static loads

The object of this study is a reinforced three-layer transport pipe, which is subjected to the joint action of ambient temperature and static loading of the road subgrade soil. The analytical model for assessing the stressed-strained state of reinforced three-layer pipes, under the combined action of temperature and static loads, has been improved using the theory of elasticity. The stressed-strained state of the reinforced pipe was assessed taking into account the values of the joint action of temperature and loads from vehicles, the physical and mechanical parameters of structural materials, and the geometric parameters of the pipe. As a result of the calculation of the reinforced multilayer pipe, it was found that the maximum movements that occur on the outside of the defective pipe are 0.64 mm, the metal pipe – 0.75 mm, and in the concrete mortar (fine-grained concrete) – 0.69 mm. It was established that under the combined action of ambient temperature and static loads from the road subgrade soil, ring stresses are maximum. They are 151 MPa. Axial stresses are also high – 141 MPa. At the same time, the maximum radial stresses are the smallest – 37.4 MPa. It has been established that a small difference in displacements occurs on the contact of structural materials of the reinforced pipe. However, the magnitude of the stresses is high. The maximum difference in ring stresses was 73 MPa, while the difference in radial and axial stresses was up to 1.0 MPa. It has been established that to restore the bearing capacity of damaged reinforced concrete pipes, it is possible to use the repair technology by the method of "sleeving". It involves pulling a metal pipe into the middle of the layer damaged with concrete mortar remaining between the concrete defective and the new metal pipes.

Numerical analysis of repaired wall loss defect pipelines for optimum composite wrap thickness

The paper presents the numerical analysis of failure pressure of wall loss defect metallic pipelines and validate it with experimental results. An optimization of composite thickness for repair of wall loss defect pipeline is also carried out using numerical analysis. A nonlinear explicit FE code with constitutive models for metallic steel and composite material to failure modelling was used. Three different cases: non-defective pipe, wall loss defective pipe and composite repaired of defective pipe are considered. It was found that the numerical results are in good agreement with the analytical results in all the three cases. The theoretical failure pressure determined by ISO/TS 24817 standard for wall loss defect pipe is highly conservative compared to the numerical failure pressure for the given composite repair thickness. Additionally, the numerical study on optimization of repair thickness revealed that lower composite repair thickness can also sustain the designed failure pressure (composite repair thickness of 8.4 mm can sustain the same designed pressure instead of 16.1 mm thickness), which implies there is scope to further reduce the composite thickness, which ultimately reduce the repair cost.

Physical and analytical modeling of soil loss caused by a defective sewer pipe with different defect locations

Physical and analytical modeling of soil loss caused by a defective sewer pipe with different defect locations

Target Method for the Statistical Processing of the Results of Tensile Testing of Defective Pipes

Target Method for the Statistical Processing of the Results of Tensile Testing of Defective Pipes

Determining patterns of the deformed state of the transport concrete pipe reinforced with a metal clamp under the action of static load

The object of this study is a concrete pipe and a pipe whose integrity was restored using a metal clamp while filling the layer between the existing pipe and the metal clamp with self-expanding concrete mortar. It has been established that the most common types of defects and damage to pipes on the roads are transverse and longitudinal cracks, as well as concrete chipping and spalling. A procedure has been devised to test experimentally a new concrete pipe without reinforcement and a concrete pipe reinforced with a metal clamp under static load. Experimental tests of the concrete pipe without reinforcement and with reinforcement with a metal clamp were carried out in the laboratory. Digital indicators, an analog-to-digital converter, and a personal computer were used to measure pipe deformations. It was found that the maximum value of vertical deformations of a new concrete pipe before cracking was 4.75 mm, and that reinforced by a metal clamp – 4.36 mm. At the same time, the maximum deformation at which the destruction of the new pipe occurred was 6.36 mm, and that of the reinforced pipe with a metal clamp – 10.51 mm. It was established that the reinforcement of the destroyed pipe with a metal clamp in the initial period of loading leads to detachment of the clamp from the concrete of the pipe. Further, when the clamps are included in the work, there is a stable operation of the concrete pipe and the amount of growth of pipe deformations increases smoothly. The results of measuring vertical deformations at the top of the pipe without reinforcement and with it showed different deformation values. It was established that the complete destruction of the pipe with a reinforced metal clamp takes place during deformations 61 % higher than the deformation at which the non-reinforced new concrete pipe is destroyed. It was found that one of the methods of restoring the bearing capacity of damaged and defective pipes in the road industry is the use of metal clamps

Plastic collapse analysis in multiaxially loaded defective pipe specimens at different temperatures

A comprehensive numerical investigation is carried out using a newly developed constitutive model to describe failure at low temperatures in multiaxially loaded cracked pipes made of 316L stainless steel. The kinetic phase transformation and the temperature-dependent fracture criterion are implemented to accurately capture the mechanical response at different temperature levels. Although experimental observations of these simulations were not available, their results were quite consistent with some already published results obtained on similar materials and loading conditions at room temperature. The results indicate that the existing multiaxial plastic collapse failure criterion, including shearing, still provides a fail-safe design margin for low temperature loading conditions, including internal pressure. Moreover, martensite kinetic phase transformation plays an important role, especially during straining at low temperatures.

CFD-DEM simulation of sand erosion into defective gravity pipes under constant groundwater table

As sewer pipes age, cracks and other forms of structural damage may develop leading to soil infiltration into the pipes that can cause sinkholes and damage the overlying roads and moving vehicles. The fluctuations in the groundwater table following snow melt or heavy rainfall events can exacerbate soil erosion posing risk to the surrounding infrastructure. To understand and adequately characterize erosion in such cases, microscale analysis of both sand and water is needed to resolve the complex interactions around the pipe defects. In this study, a detailed numerical investigation is carried out using a series of coupled Computational Fluid Dynamics-Discrete Element method (CFD-DEM) simulations to evaluate the effects of groundwater table, crack size, defect angle, and the height of sand fill above the pipe on erosion. It is found that raising the groundwater table accelerates erosion only to a certain limit, above which, raising the groundwater level does not have a tangible effect on erosion. This helps explain some of the misunderstandings reported in previous investigations regarding the effect of water level on the rate of erosion. With respect to the location of defects, it was found that, when groundwater is involved, the erosion rate is fastest when the defect is located at the pipe crown. However, inclined defects ultimately resulted in a larger spatial extent of eroded mass. In addition, the thickness of the sand fill above the pipe was found to have little effect on the rate of erosion as a freefall arch regime was dominant in all simulations. Finally, simplified relationships were developed for estimating the total eroded mass for given sand properties, defect geometry, and location of the groundwater table.

Numerical Simulation and Analytical Prediction of Residual Strength for Elbow Pipes with Erosion Defects.

It is well known that the safety and reliability of pipeline transportation are crucial. We are aiming at the problem that the residual life and residual strength of the defective elbow pipes are difficult to predict and usually need to be obtained through experiments. Consequently, a combined method of numerical simulation technology combined with a genetic algorithm to optimize neural network extreme learning machine (GA-ELM) is proposed. Firstly, the erosion characteristics of elbow pipes with different defects under the conditions of different impurity particle flow rates, particle sizes, and mass flow rates are analyzed by numerical simulation. At the same time, the effects of erosion defects of different sizes on the equivalent stress and residual strength of elbow pipes are also studied. Based on numerical simulation data, the extreme learning machine prediction model optimized by a genetic algorithm is used to predict the erosion rate, residual life, and residual strength and compared with the traditional ELM network model. The results show that residual strength of the elbow pipes with the increase of the depth and length of the defect, and increases with the increase of the width of the defect; the GA-ELM model can not only effectively predict the erosion rate, residual life and residual strength of defective elbow pipes, moreover its prediction accuracy is better than the traditional ELM model.

Experimental and numerical study on the ductile fracture response of X65 girth-welded joint made of Inconel 625 alloy

This work presents an experimental/numerical study characterizing the ductile fracture response of a pipeline girth weld of a corrosion-resistant alloy, Inconel 625. The welded joint was prepared with a narrow gap geometry. Thus, a newly designed double-groove bar is used to measure the weld metal’s tensile stress–strain curve. The geometry is extracted directly from the girth weld joint reducing the manufacturing process of tensile weld samples. The tensile result obtained from the bimaterial specimen is used to calibrate the modified Mohr–Coulomb damage model. A critical strain locus is defined for both materials, X65 and Inconel 625, depending on the stress triaxiality and Lode angle. A post-softening law is implemented to model the stable crack extension. The damage model is coded in a VUMAT subroutine in Abaqus software. The post-softening response is calibrated using a fracture toughness test. Then, validations are performed using a bimaterial specimen with a single groove and a bending fracture specimen. Overall, the matching is good between numerical and experimental results. Finally, numerical tests are performed for circumferential defective welded pipes to understand the influences of combined loads and misalignment on the pipe’s strain capacity. For partially undermatched weld joints, a flat double-groove bar is recommend for measuring the tensile mechanical properties of narrow gap welds. The CTOD-R curve measured at the FEM node behind the initial crack tip matches well the experimental CTOD based on the J-integral.