Pipe Wall Thickness Research Articles

Research on Application of Pulsed Eddy Current Testing in Nuclear Power Plant Pipelines

The condensate pipelines, main water supply pipelines, drain pipelines, and partial extraction pipelines of nuclear power plants are all coated with coatings on the outside of the pipelines to improve heat exchange efficiency. At present, the detection methods of ferromagnetic pipelines are mainly conventional ultrasound and ultrasonic guided waves. It is necessary to remove the insulation layer of the outer wall of the pipeline before the inspection, which leads to a prolonged inspection period and increased labor costs. This paper uses the measured and calculated values of the induced voltage to establish the optimal parameter inversion problem and combines the coupling relationship between the parameters to propose a reliable pulsed eddy current detection method for the relative wall thickness of ferromagnetic pipes. Using the pulsed eddy current detection method for the relative wall thickness of ferromagnetic pipelines proposed in this paper, the scanning detection of nuclear power plant steel pipes is compared with conventional ultrasonic testing. The detection results are reliable and suitable for non-destructive testing and evaluation of nuclear power plant ferromagnetic pipeline wall thickness corrosion thinning.

Discovering the Real Condition of Pipes

Acoustic velocity testing with condition assessment technology improves pipe wall thickness analysis and saves on unnecessary pipe replacement.

Failure Analysis of Multi-Layered Thick-Walled Composite Pipes Subjected to Torsion Loading

In the current study multi-layered thick-walled fibre reinforced composite pipes under torsion loading are considered. To analyse the stress-strain distribution in the pipe the Finite Element model (ABAQUS) has been developed. Using the model the radial, hoop, axial and shear stresses have been calculated for different lay-ups of the fibre reinforced pipes, and modified Tsai-Hill failure coefficients have been computed. The validation of the model was done by comparing the results available in the literature and the semi-analytical three-dimensional elasticity solution. The dependence of the failure coefficient on winding angles and layers’ thickness was investigated and analyzed, and the appropriate design considerations have been suggested for four-layer pipes.

Study on nonuniform microstructure and strength-toughness mechanism of thick-walled hot induction seamless bend

This paper investigated the continuous transformation cooling curve of thick-walled seamless pipe steel, microstructure nonuniformity of thick-walled hot induction seamless bend along wall thickness direction caused by hot induction bending, and their influences on the mechanical properties. The differences in microstructure, dislocation, precipitate characteristic, local misorientation angle, and grain boundary distribution were investigated acocording to scanning electron microscopy, optical microscopy, transmission electron microscopy, x-ray diffraction, and Electron back-scattering diffraction. The tensile tests and low-temperature impact tests were used to determine the strength and impact toughness of thick-walled hot induction seamless bend. The results demonstrate that thick-walled seamless pipe steel can obtain bainite structure in a wide range of cooling rate, which is beneficial to the adjustment of bending process. The nonuniform microstructure is mainly caused by the difference in heating temperature and cooling rate. The structure in the center of wall thickness is dominated by granular bainite, showing the excellent combination of strength and toughness. Among all the samples, dislocation strengthening and fine-grain strengthening are the two most important strengthening mechanisms. However, for the outer surface samples, precipitation strengthening mechanism also plays an significant role, which is attributed to the high heating temperature that causes a large amount of carbonitrides to dissolve and a large amount of precipitation during the subsequent tempering process. The high density dislocations and the large average local misorientation result in dislocation pile-up and strain concentration, which promotes crack initiation and reduces toughness. Large average misorientation and high density high-angle grain boundaries help to consume more energy in crack propagation and improve impact toughness.

Edge Crack in Longitudinal Butt-Welded Joint in Thick-Wall Cylinder

Thick-wall vessels and pipes cylindrical shape are very typical in power plant, chemical, processing, oil and gas industry. The equipment with cylindrical shape can be either thin or thick wall which depends on the function of that particular equipment. Typically, thick-wall cylinder is used when the equipment is needed to accommodate high pressure contents. Mostly, cracks appear either on the internal or external of a thick-wall cylinder. Primarily, when welding is applied in the fabrication of the thick-wall cylinder, cracks can easily appear due to solidification or hydrogen embrittlement at the welded joint, typically butt-welded joint. Hence, it is critical to examine the stress distribution along the crack and resolve the stress intensity factor of the cracks in both welded and non-welded internally pressurized thick-wall cylinder. Finite element analysis has been conducted using the engineering software, ABAQUS CAE to investigate the stress distribution and to perform the evaluation of stress intensity factor. Besides, weight function method has also been used by other researchers to determine the factor of stress intensity for both welded and non-welded thick-wall cylinder. The results were compared in terms of both of the methods applied. The last, the effect of the butt-welded joint profile in thick-wall cylinder has also been investigated.

Analysis of the screw press mouthpiece parameters for 3D extrusion of peat pieces of tubular type

The results of theoretical and experimental studies on the creation of a screw press composite mouthpiece screw press for 3D-forming of peat pieces of a tubular type in the field for intensifying the process of field drying of material in a complex mechanized pit are presented. The main purpose of the study was to substantiate the geometric and design parameters of the screw press composite mouthpiece of the spread machine for the production of peat-agglomerated products of the tubular type. The parameters of the mouthpiece are selected based on the geometric characteristics of the peat pieces. An increase in moisture loss during drying of peat-agglomerated products is provided by forming a peat piece in the form of a thick-walled pipe made of a peat raw materials composed of low and high decomposition degrees in a ratio of 1:3. Additive production of polymer-fiber peat composites by extrusion allows to produce products with improved mechanical properties in comparison with non-reinforced raw materials. The vertical arrangement of the peat tubular piece on the drying field allows to increase the loading of the field area by 10 %, increase the convective heat supply to the piece and reduce the contact coefficient of the piece with the field by three times in comparison with the peat spreading of the pieces in the form of a horizontal tape. Based on the analysis of the shape and size of the agglomerated products, the design of a screw press composite mouthpiece consisting of two conditional molding zones of various configurations has been developed. The article presents a parametric analysis of the volumetric productivity of a screw press with a composite mouthpiece of a tubular type, the energy intensity of mechanical processing is determined, the degree of mechanical processing of peat raw materials is estimated with the optimization of the screw parameters for the production of agglomerated products of a tubular type.

Applied Systems Theory: Mathematical and Numerical Simulation of Strength of Thick-wall Pipe by Using Static Elastic Problems

In Systems Theory, the Mathematical and numerical simulation of strength of thick-wall pipe by using static elastic problems is an important problem and has attracted the attention of many researches, academicians and practitioners. the The present work studies the change in the strength of a quite long isotropic thick-wall pipe (circular cylinder) for the varying pipe diameter, wall thickness and material. The pipe is in the plane deformed state, i.e. plane deformation is considered. Based on the problems of statics of the theory of elasticity, a mathematical model to calculate the strength of the thick-wall pipe was developed and the problems of statics of the theory of elasticity were set and solved analytically in the polar coordinate system. The analytical solution was obtained by the method of separation of variables, which is presented by two harmonious functions. The dependence of the pipe strength on the thickness and material of the pipe wall, when (a) normal stress is applied to the internal boundary (internal pressure) and external boundary is free from stresses and (b) normal stress is applied to the external boundary (external pressure) and the internal boundary is free from stresses, is studied. In particular, the minimum thicknesses of the walls of homogeneous isotropic circular cylinders of different materials and diameters with a plane deformed mode when the pressures in the cylinders do not exceed the admissible values were identified. Some numerical results are presented as tables, graphs and relevant consideration.

Cracking Failure Analysis of Pipe to Flange Weld Joint

Cracking failures occurred frequently in blowdown pipe to flange weld joint, and the root crack appeared on the blowdown pipe side of the weld joint and extend into the base metal of pipe. To explore the reason why cracking failures occurred on the blowdown pipe side of the weld joint, the weld joint was analyzed via macroscopic and metallographic structure observation, and blowdown pipe was tested by physical and chemical property testing, and corrosion scale was analyzed by SEM, EDS, and XRD. The dent and thinner wall thickness of pipe are found in the internal pipe to flange weld joint. Widmanstatten metallographic structure is found in heat affected zone (HAZ), fusion zone (FZ) and weld metal zone (WZ) of weld joint. Stress concentration form in the weld joint at blowdown pipe side during welding due to the dent and different wall thickness. Under the action of gas vortex in the dent of weld joint, corrosive droplets aggravate the localized corrosion of the weld joint. Stress corrosion cracking (SCC) were initiated in FZ and WZ from the surface of weld joint and propagated into the base metal of pipe under the combined actions of stress resulting from weld process and during operation, and corrosion.

Study on Pipe Wear Based on Large Scale Experiment and Scale Effect for Deep Sea Mining

Abstract For the production of seafloor massive sulfides, the ores are expected to be transported as a slurry up to the sea surface. The pipe wear is caused mainly by the collision of the ores against the pipe wall; thus, the evaluation of pipe wear is required for the operation of the production system. The authors conducted a full-scale experiment for evaluating pipe wear due to slurry flow. As the result, the pipe wear resistance of a SUS304 stainless steel is higher than the ultrahigh molecular weight polyethylene. In addition, the pipe wall thickness was measured before and after the experiment to obtain the distribution of the erosion on the pipe wall. The authors confirmed that the wall thickness reduced uniformly along the circumferential direction for vertical pipe, and the erosion occurred mainly along the bottom surface of the pipe for the horizontal and inclined pipes. Also, the authors investigated the relation between the index of rock abrasivity and erosion and proposed a correlation for pipe wear with the index of rock abrasivity. Finally, the authors predicted the pipe wear on the condition of full-scale experiment based on the data obtained in the reduced-scale experiment conducted previously. Then, the authors compared the predicted pipe wear with that measured in the full-scale experiment.

Purification of granular sediments from wastewater using a novel hydrocyclone

Wastewater is an inevitable product in industry. How to remove fine particles and enhance the impurity removal efficiency of the wastewater purification equipment has always remained a hotspot issue. In this study, a novel hydrocylone with bi-symmetrical involue inlet, thick-wall overflow pipes and conical segment structure was designed and compared with other hydrocyclones including different structures of inlets, i.e., The flow field and separation performance of the novel hydrocylone were investigated via numerical analysis, The simulation results show that the inner flow field in the novel hydrocyclone is more stable, accompanied with significant decline in both short-circuit and circulating flow rates; moreover, using the novel hydrocyclone, the tangential velocity, the axial velocity and the pressure increase significantly, which can make the particle obtain great centrifugal driving force and effectively reduce the number of dislocated particles. The recovery ratio of fine particles with the diameter of 1 μm also shows significant enhancement. Conclusively, using the designed novel hydrocyclone can obtain higher product quality. The present study can provide theoretical foundation for the design of a novel hydrocyclone.

Development of micro soap bubble generator for PIV tracer using home stereolithography 3D printer

A micro soap bubble generator for tracers for PIV measurement was developed using a home stereolithography 3D printer. The nozzle has a coaxial triple pipe structure, and an orifice cap is attached to the nozzle head. The inner diameter of the central pipe is 0.7 mm, and the wall thickness of the central pipe is 0.7 mm. From the comparison of the smoke wire visualization result of the flow around the cylinder placed under the mainstream flow velocity of 3 m/s and the PIV measurement result, it was confirmed that the generated micro soap bubbles have good followability to the flow. Generated bubbles’ particle size was estimated to be Φ0.2 mm at the minimum and Φ6.3 mm at the maximum. The most common was Φ0.9 mm ± 0.1 mm, accounting for more than 50% of the total.

A study on the optimization of residual stress distribution in the polyethylene and polyketone double layer pipes

Pipes are generally used in the variety of industries such as water purification, automobiles and air ventilation and so on which is commonly made from various materials like stainless steel, plastic and iron. Recently, plastic and copper pipes were widely used in the water industries due to their higher corrosive resistivity and durability. However, the mechanical defects are the major problem in the usage of the plastic pipes. The plastic pipe wall thickness and stress distribution are key components for the plastic deformation in the pipe. Among them, the residual hoop stress is the mainly affects the life time of the pipe. The present study investigates the effect of the inner and outer wall thickness on the pipe defects is explored by finite element analysis. As a result of observation, a discontinuity of stress is observed at the PK/PE interface of the double-multiple pipe due to the void value, and it is judged that the PK pipe has superior tensile strength due to its high mechanical strength and excellent physical properties such as yield stress and stiffness compared to PE pipe. It is judged that the conditions in the real environment can be analyzed by verifying the peeling phenomenon due to thermal fatigue due to different coefficients of thermal expansion between the heterogeneous resins and observing the peeling phenomenon due to local stress concentration due to the thickness non-uniformity of the bonding interface of the heterogeneous resins. The simulation and experimental results confirmed PK pipe has superior tensile strength due to its high mechanical strength and excellent physical properties such as yield stress and stiffness compared to PE pipe.Capsule: This work investigates the residual stress distribution in the polyethylene and polyketone double layer pipe.

Stress response of a straight hydraulic pipe under random vibration

In this paper, the stress response characteristics of a straight hydraulic pipe subjected to random vibrations were studied. The motion equation of the straight hydraulic pipe subjected to random vibration was established by utilizing the finite element method (FEM), and considering the fluid-structure interaction (FSI). The discrete analysis method was employed to solve the motion equation of the straight hydraulic pipe. The effects of different parameters, including the external excitation, fluid velocity, fluid pressure, and the pipe's structural parameters on the stress response of the straight hydraulic pipe were investigated. The numerical results showed that the maximum mean square values of the pipe stress occurred at the support points of the pipe; the maximum mean square value of the pipe stress increased with an increase in the random acceleration variance, pipe wall thickness, pipe inner diameter, and fluid pressure and decreased with an increase in the pipe length and fluid velocity. The experimental results agreed well with the numerical results, demonstrating the accuracy of the motion equation of the straight hydraulic pipe subjected to random vibration.

Understanding and treatment of brake pipe fracture of metro vehicle bogie

In a railway vehicle air brake system, a brake pipe is used to connect all related elements, for example, the air source system, brake control device, and brake valve. The brake pipe has a significant impact on the safety and reliability of trains. This paper presents a fracture analysis of a brake pipe installed on the bogie of a metro train running on one metro line in China. The analysis was conducted using a brake pipe modal test in a depot, a bogie vibration test, and a brake pipe dynamic stress measurement applied at the field site. The field experiment results indicate that the main cause of a brake pipe fracture is the coupling resonance between the first-order lateral bending eigenmode of the brake pipe (74 Hz) and the eigenmode of the reverse yawing of two side beams of the bogie frame (73 Hz). The wheel out-of-roundness is the main excitation source. To solve the pipe fracture problem, a dynamic stress analysis method that considers the frequency and time domains is presented to assess the possible measures. The measures investigated in this study are the pipe wall thickness, pipe clamp stiffness (elastic modulus), and pipe clamp numbers. The simulation results and on-track tests show that doubling the pipe wall thickness and decreasing the elastic modulus of the pipe clamp by 5.67 fold can reduce the dynamic stress amplitude of the pipe by approximately 60%. If a pipe clamp is added at the middle position between the two pipe clamps on the pipe, the dynamic stress amplitude of the pipe will decrease by 94% compared to the present pipe structure. This is because the additional pipe clamp alters the frequency of the first-order lateral bending eigenmode of the brake pipe to avoid being equal to the eigenfrequency of the reverse yawing of the two side beams of the bogie frame. After the metro corporation added a pipe clamp and applied a regular wheel re-profiling, no brake pipe fracture occurred on the investigated metro line.

The research on the critical loading path of thick-walled pipes under external pressure and cyclic bending

The effects of combined external pressure and cyclic bending on the pipe buckling mechanism are investigated by experiments and finite element analysis. Ten experiments are conducted and it is found that the loading paths of external pressure and cyclic bending have a great influence on the buckling pressure of thick-walled pipes. The loading path of pressure followed by cyclic bending (p→ck) is more dangerous than that of cyclic bending followed by pressure (ck→p). The material properties of kinematic hardening, loading application and mesh convergence are taken into consideration in rigorous FE models. The reason of the critical loading path is revealed from the aspects of section ovality and stress-strain accumulation. Sensitivity analysis is conducted on the loading patterns and axial tension. With the application of axial force, the pipe laying process is simulated more precisely which shows that pipe buckling capacity is more sensitive to the bending cycles in the presence of axial force. The comparison between numerical results and present specification shows that the API specification is conservative in predicting the collapse pressure of thick-walled pipes (D/t = 15–21) whose underestimation is about 11%~37% under the effect of cyclic bending.

Experimental-numerical study on the structural failure of concrete sewer pipes

The structural failure of round and egg-shaped sewer pipes is investigated by means of laboratory experiments and finite element method analyses. Two different round pipes are considered, which have an inner diameter of 400 mm and 500 mm, and are respectively referred to as R400 and R500 sewer pipes. The egg-shaped pipe considered in this study has a horizontal inner diameter of 400 mm and a vertical inner diameter of 600 mm, and is labeled as the E400/600 sewer pipe. Sewer pipes with these dimensions are most commonly used in the Netherlands. In full-scale experimental tests the sewer pipe specimens are subjected to biaxial loading, whereby the horizontal pressure loading is set equal to 1/3 times the vertical pressure loading. This loading condition is representative of a sewer pipe embedded in a well-graded sandy gravel and subjected to neutral horizontal earth pressure. Apart from the global load–displacement behaviour, the local strain response is measured at various locations, which indicates how the applied load is distributed across the sewer pipe. The fracture pattern at catastrophic failure is recorded by means of cameras placed at the front side of the pipe specimen. The round pipes fail under the development of 4 distinctive failure cracks, which are located at the top and bottom of the sewer pipe, and halfway the left and right sides. The egg-shaped sewer pipes also fail under the development of 4 failure cracks, which emerge at the top and bottom of the pipe, and at the top-left and top-right sides. The round R500 pipe fails at the lowest ultimate failure load, which is, respectively, a factor of 1.16 and 2.25 smaller than the ultimate failure loads of the round R400 pipe and the egg-shaped E400/600 pipe. The FEM models of the round and egg-shaped pipes accurately predict both the failure response and the fracture pattern measured in the experiments. Accordingly, the FEM model of the round R400 sewer pipe is used to analyse the sensitivity of the overall failure response of the sewer pipe to various parameters, which are the load contact area, the ratio between the applied horizontal and vertical loads, the wall thickness of the sewer pipe, and the tensile strength, mode I toughness and Young’s modulus of the concrete. The variation of these parameters mimics how the load bearing capacity of a sewer pipe decreases under the effects of soil erosion, changes in lateral earth pressure, biochemical degradation, and ageing. The knowledge obtained from the experimental–numerical study may support the decision making process on maintenance and replacement of sewer systems.

Manufacture and investigation on the shape memory polymer composite subsidy pipe

In this paper, a process for restoring damaged pipelines based on shape memory polymer composites (SMPC) was introduced, and the corrosion resistance and mechanical properties of SMPC were evaluated. First and foremost, SMPC was used for repairing damaged oil pipelines. Referring to the wet winding method, the subsidy pipe based on SMPC was fabricated by winding in the axial direction of ±45°. According to the failure theory of composite material, the minimum wall thickness of the subsidy pipe to withstand the pressure was determined. The effects of fiber content and temperature on the structural stiffness of semi-circular hinges with different ratios of carbon fiber were observed. Radial and axial compression tests were carried out on the subsidy pipe to study the effect of compression times and temperature on the stiffness. Radial compression tests are conducted on the subsidy pipes with different wall thicknesses to determine the effect of wall thickness on the stiffness.

Thick-Wall Elastic Collapse for Casing Design

Summary Elastic collapse is an important piece of the tubular collapse formulation in API TR 5C3 (2008) and ISO/TR 10400 (2007). Elastic collapse is significant because it is independent of the strength of the tubing; for example, K-55 and Q-125 have the same resistance to elastic collapse. Advanced collapse models, such as Klever and Tamano (2006), require a thick-wall collapse result as part of their formulation. What effect would a thick wall have on elastic collapse? There really is no way to tell from the classic formulation. The primary issue is whether the elastic collapse formula overpredicts or underpredicts collapse pressure. The developers of the API collapse equation thought the thin-wall equation overpredicted collapse pressure and put in terms to reduce the predictions. Other studies suggested the opposite effect. What is needed is a formulation that is based on an elastic solution for a thick-wall cylinder, but that can derive the classic solution for a thin wall. The elastic equations for a thick-walled cylinder exist, known as the Kirsch equations (Kirsch 1898). A new set of physically reasonable boundary conditions is proposed for the Kirsch equation, which is then used to determine the collapse resistance for a thick-wall pipe. This result also yields the classic result in the limit as t/D becomes small. The thick-wall elastic collapse formula is then applied to the standard API TR 5C3 (2008) collapse formulation and to the Klever-Tamano formulation (Klever and Tamano 2006).

A New Model for Calculation of Arrest Toughness in the Fracture Process of the Supercritical CO2 Pipeline.

A new model based on a decompression wave prediction model and an improved BTC model has been developed to investigate the arrest toughness in the fracture process of the supercritical CO2 pipeline. The comparison of the decompression wave velocity and the fracture propagation velocity was carried out to identify whether the pipe can prevent fracture propagation relying on its own toughness. If not, the minimum Charpy V-notch energy and the minimum wall thickness of steel pipes required for arrest fracture can be calculated using the improved BTC model. The results show that the working conditions with an initial pressure for the fracture of 11.7 MPa and a temperature of 323.15 K are the most difficult conditions to stop the fracture. The minimum wall thickness calculated only according to the strength design cannot meet the toughness requirements for ductile fracture arrest in the most difficult conditions in some cases. Then, the minimum wall thickness of the supercritical CO2 pipeline required for ductile fracture arrest in these cases will be obtained. For instance, the minimum wall thicknesses of X65, X70, and X80 steel pipes for fracture arrest with a pipe diameter of 610 mm at a design pressure of 13.2 MPa are 17.28, 14.58, and 12.81 mm, respectively, and when the pipe diameter is 1016 mm at a design pressure of 20.4 MPa, the minimum wall thicknesses of X70 and X80 pipes can meet the requirements of arrest toughness. The model established in this study can quickly and accurately calculate the minimum wall thickness and minimum Charpy energy required to stop fracture in the supercritical CO2 pipeline, which is suitable for engineering applications. The findings of this study can help in better understanding of the fracture process of supercritical CO2 pipelines.

Planar Hall sensor for quantitative measurement of pipe wall thickness reduction based on the magnetic flux density method

Quantitatively monitoring the thickness reduction of a pipe by using magnetic flux density method remains a major challenge due to the small and gradual change in magnetic flux density over a long distance along a pipe. This signal change is hindered in the background signal of a detector that has a high temperature dependence and unstable background signal. In this paper, we verify the effectiveness of magnetic flux density method in quantitatively monitoring thickness reduction through simulation and experimental verification. Experimental results show that the proportion of magnetic signal change is 1.4 mT per 10% wall loss. To support this quantitative approach, we optimise an original ultra-high-sensitivity planar Hall sensor with high thermal stability and stable background signal versus time for measurement of the magnetic field over a wide range from 0 to 50 mT. The quantitative measurements were validated on test pipes with varying thickness steps of 0.5 mm.