Elbow Pipe Research Articles

Seismic fragility evaluation of the base-isolated nuclear power plant piping system using the failure criterion based on stress-strain

Abstract In the design criterion for the nuclear power plant piping system, the limit state of the piping against an earthquake is assumed to be plastic collapse. The failure of a common piping system, however, means the leakage caused by the cracks. Therefore, for the seismic fragility analysis of a nuclear power plant, a method capable of quantitatively expressing the failure of an actual piping system is required. In this study, it was conducted to propose a quantitative failure criterion for piping system, which is required for the seismic fragility analysis of nuclear power plants against critical accidents. The in-plane cyclic loading test was conducted to propose a quantitative failure criterion for steel pipe elbows in the nuclear power plant piping system. Nonlinear analysis was conducted using a finite element model, and the results were compared with the test results to verify the effectiveness of the finite element model. The collapse load point derived from the experiment and analysis results and the damage index based on the stress-strain relationship were defined as failure criteria, and seismic fragility analysis was conducted for the piping system of the BNL (Brookhaven National Laboratory) - NRC (Nuclear Regulatory Commission) benchmark model.

Dynamic fracture response of pre-flawed elbow pipe subjected to internal hydrogen-oxygen detonation

A coupled fluid-structure-fracture approach was presented to study the dynamic fracture of pre-flawed elbow pipes subjected to internal hydrogen-oxygen detonation. The initial flaw is located at the extrados, crown and intrados of the elbow, respectively. The hydrogen-oxygen detonation was modeled by a user-programed burn method based on the CJ theory. The fracture of elbow pipe was simulated by a validated bivariate failure criterion which was deduced based on the adiabatic shear failure mechanism of materials at high strain rates. Results demonstrate that the presented approach can capture the detonation wave propagation and the complex crack extension and branching effectively. It is found the peak pressure at extrados is 2.9 times larger than that at intrados, but the hoop stresses and effective strains at the three initial flaw positions are comparable with each other, even the average amplitude of hoop stress at intrados is higher than those at extrados and crown. The increase of detonation pressure can lead to crack branching and makes more cracks propagate simultaneously. The crack initiating at crown tends to turn and run to the intrados when passing the transition sections of elbow, while the crack initiating at intrados is expected to branch here. The average crack speeds for forward cracks are 100–300 m/s, while the speeds are 70%–90% of the above for backward cracks. The branch crack speeds are generally less than 40% of those before branching. Furthermore, the elbow pipes with initial flaw at intrados generally have the largest total crack length, while elbow pipes with initial flaw at crown have the strongest resistance against crack propagation. It is also suggested that local bucking is an important feature that takes place in dynamic fracture processes of elbow pipes.

Modelling and Simulation of Multiphase Flow Applicable to Processes in Oil and Gas Industry

Abstract Solid particle erosion is a mechanical process of destroying a wall surface material due to the impacts of solid particles entrained with a fluid. It is a frequent phenomenon encountered within various industries such as chemical processes, oil and gas, and hydraulic transportation. Erosion problem has led to enormous consequences such as oil spills caused by equipment failure of oil transmission pipelines, chokes valves, pipe fittings etc; resulting in considerable economic loss as well as safety and environmental concerns. In this study, a 3-D simulations are performed using CFD code ANSYS FLUENT to predict sand erosion rates under different engine-oil viscosity conditions for multiphase liquid, in a 90-degree standard (R/D = 1.5) elbow pipe. The CFD utilizes Eulerian-Lagrangian method to model the multiphase flow oil-water-sand in elbow. The realizable k-ε model is adopted for the fluid turbulence effects. The velocity and pressure distributions are analysed as contours for the fluid flow. In order to understand the dynamics of the erosion process, the motion of the solid particles are also investigated based on Stokes number as well as the effect of secondary flows. The results indicated that erosion rates decrease with the increase in oil viscosity. Additionally, erosion mainly occurs in two locations; at the extrados near the bend exit and also on the side walls of the downstream straight pipe. The unusual distribution of erosion on the side walls occurred as a result of the effect of secondary flows due to centrifugal force. The numerical results are in qualitative good agreement with the experimental data available in the literature for elbows in order to validate the presented modelling approach.

Failure Envelopes for Composite Fiber Reinforced Pipe Elbows Subject to Combined Loading—A Numerical Assessment

Composite pipes are currently being used in a multitude of applications varying from civil to oil and gas applications. Pipes are generally connected together by means of pipe elbows that in turn are subjected to bending moment and pressure loading. This study looks into the effect of combined loading on the first ply and ultimate failure load of pipe elbows. The influence of pressure loading followed by a bending moment versus first applying bending moment followed by subsequent pressure loading, on the ultimate catastrophic failure load, is investigated through numerical models. The combined bending moment and pressure load ramping is also studied. Design by analysis finite element damage mechanics numerical methods are applied to investigate post first ply failure (FPF) and stress redistribution. The study shows that different loading combinations can give rise to different damage mechanisms and ultimately failure loads. A safe design load envelope for different fiber-reinforced pipe elbows based on FPF and ultimate catastrophic load is identified and discussed.

Development of the MRI Flow Phantom System Focused on Low Speed Flows in Fluid Machinery

At present, magnetic resonance imaging (MRI), which is one of the noninvasive diagnostic imaging techniques for medical use, has been applied to industrial product inspection. In this study, a hydraulic model test system, called the “flow phantom system,” which can generate steady flow and oscillating flow for time-resolved MRI, was developed to aid optimum design of fluid machinery. Simple flow phantoms are tested under laminar flow or oscillating flow to evaluate the validity and effectiveness of the proposed system. In this article, the test results of double cylindrical pipe flow, elbow pipe flow, cylindrical valve flow, and jet pump flow, which are often seen in fluid machines, are tested using the 2D time-spatial labeling inversion pulse (Time-SLIP) method, which can track a labeled water mass and visualize it using two-dimensional images. MRI-detected flow patterns were compared with particle image velocimetry (PIV) or numerical simulation.

Numerical Simulation Analysis of Polished Elbow in Solid - Liquid Two Phase Abrasive Flow Machining

As a precision machining technology, abrasive flow polishing technology plays an important role in many precision machining fields. In order to study the effect of abrasive flow polishing on elbow parts, the 90° elbow pipe is taken as the research object to study the numerical simulation of elbow pipe parts polished by solid-liquid two-phase flow. The dynamic pressure and turbulent kinetic energy distribution of the abrasive flow in the elbow channel under different inlet velocities were analyzed. Through the comparative analysis, the effectiveness of the abrasive flow polished elbow parts was explored. The effects of different inlet velocities on the abrasive elbow processing parts were analyzed, which provided theoretical support for the improvement and development of the abrasive flow polishing technology.

Mechanical properties of PE/E-glass commingled yarn wound pipes and pipe elbows

Abstract PE pipes and fittings are used in water, chemicals, as well as gas supply and distribution. In most applications, pressurized piping systems are needed. When pressure grade is increased, p...

Weaving Laser Vision System for Navigation of Mobile Robots in Pipeline Structures

A new laser vision system is proposed for the navigation of mobile robots in pipe environments. This paper mainly focuses on forward recognition of individual T-junctions and elbow pipes to prevent the robots from becoming stuck in pipes. We propose to mount weaving 2-D laser scanners on robots to obtain selective 3-D front-pipe maps. Recognition of T-junctions requires 3-D maps for pipe wall on wheel sides, whereas recognition of elbow pipes requires full-forward 3-D maps. From these selective forward 3-D maps, algorithms for recognition of T-junctions and elbow pipes were developed, utilizing the mathematical approach to describe the pipeline structures. The practicality of the proposed algorithms was validated for several pipe environments, including T-junction, single elbow pipe, and the latter pipe of double elbow pipes.

Texas LPG fire: Domino effects triggered by natural hazards

Abstract On February 2007, a massive fire in a propane de-asphalting unit in an oil refinery in Texas, USA happened due to liquid propane release from a cracked pipe in a control station injuring four people, damaging extensive equipment, causing significant business interruption, and resulting in more than $50 million losses. The accident was triggered by a natural hazard: freezing of piping at a control station caused an inlet pipe elbow to crack, which in turn, led to the release of high-pressure liquid propane which was rapidly ignited. In addition, there were two near-miss events due to potential domino effects. In fact, the accident could reasonably have resulted in much more severe consequences due to the exposure of large butane storage spheres and chlorine containers, increasing the possibility of a catastrophic domino effect. This paper develops a Natech (natural hazard triggering technological disasters) risk assessment methodology that relies upon Bayesian network capabilities and takes into account the potential Natech domino effects. The methodology is implemented in the intended refinery and mathematically graphically represents the dynamic cause–effect relations between units involved in the scenario, and handles uncertainties among the interactions. In addition, the methodology can provide a risk value for the entire scenario that can be used further for risk-based decision making.

Stress Corrosion Crack Propagation Behavior of Elbow Pipe of Nuclear Grade 316LN Stainless Steel in High Temperature High Pressure Water

Stress Corrosion Crack Propagation Behavior of Elbow Pipe of Nuclear Grade 316LN Stainless Steel in High Temperature High Pressure Water

Optimization of Tooling Design for Hot Mandrel Bending of Pipe Elbows

This paper presents the finite element model developed for the simulation of pipe elbow production by the so-called ‘Hamburg process’ in order to improve productivity and resource efficiency. To optimize the tooling design, a sensitivity analysis of the tool parameters that influence the quality of pipe elbows, such as mandrel height and length, is conducted. Different materials data sets including damage models were considered. Using numerical simulations, it is possible to determine an optimized tool geometry for the production of specific pipe elbow dimensions. Furthermore, as a result of the experiments and numerical simulations conducted, it is possible to increase the production velocity of the serial plant. Along with deformation, damage models are included in simulations in order to identify the right process boundaries. Finally, an experimentally validated model is developed for increasing resource efficiency in pipe elbow fabrication.

Effective numerical approach to assess low-cycle fatigue behavior of pipe elbows

Abstract We developed numerical models to efficiently simulate the low-cycle fatigue behavior of a pipe elbow. To verify the model, in-plane cyclic bending tests of pipe elbow specimens were conducted, and a through crack occurred in the vicinity of the crown. Numerical models based on the erosion method and tie-break method are developed, and the numerical results are compared with experimental results. The calculated results of both models are in good agreement with experimental results, and the model using the tie-break method possesses two times faster calculation speed. Therefore, the numerical model based on the tie-break method would be beneficial to evaluate the strength of piping systems under seismic loadings.

Thermal Aging Effect on the Ratcheting Behavior of Pressurized Elbow Pipe

In this study, the ratcheting behaviors of pressurized Z2CN18.10 austenitic stainless steel elbow pipe influenced by the thermal aging process were experimentally investigated in controlled constant internal pressure and reversed in-plane bending after different thermal aging periods (1000 h and 2000 h) at thermal aging temperature of 500 °C. It is shown that the ratcheting behavior of pressured elbow pipe is highly affected by the thermal aging process. The evaluation of ratcheting behavior of pressured elbow pipe was performed using Chen–Jiao–Kim (CJK) kinematic hardening model as a user subroutine of ANSYS. The relationships of yield stress σs and multiaxial parameter χ with thermal aging time were proposed. Ratcheting shakedown boundary of aged elbow pipe was evaluated by CJK model with thermal aging time.

전산유체역학 배관 곡면 침식 모사를 통한 배관 실패 주기 분석

전산유체역학 배관 곡면 침식 모사를 통한 배관 실패 주기 분석

Morphological change in peristaltic crawling motion of a narrow pipe inspection robot inspired by earthworm’s locomotion

Infrastructure pipes require inspection in order to prevent accidents. However, it is difficult to inspect a 1-in-diameter gas pipe because it is long, narrow and complicated. Therefore, an earthworm-type robot was developed to inspect this 1-in pipe. The robot moved by peristaltic crawling with pneumatic artificial muscles and displayed its suitability as a 1-in pipe inspection robot in experiments. However, its speed was extremely slow to be practically utilized. A major cause for this is the small distance covered in a single motion of the robot. Therefore, in this study, we developed an axial extension actuator to increase the moving distance of the robot in a single motion. Furthermore, we installed this new actuator on our robot and made it possible for the robot to change the morphological motion in peristaltic crawling. The experiments with straight and elbow pipes ascertained the importance of morphological change in peristaltic crawling for increasing the speed of the robot. Moreover, in a continuous elbow pipe, the velocity of the proposed robot was 5.5 mm/s, which is 1.3 times faster than that of the conventional robot. Consequently, we confirmed that the speed of the proposed robot was sufficiently fast for inspecting a 1-in pipe.

Experimental and numerical investigation on slug initiation and initial development behavior in hilly-terrain pipeline at a low superficial liquid velocity

The initiation and initial development behavior of gas–liquid slug flow is experimentally and numerically investigated in a hilly–terrain pipeline at a low superficial liquid velocity. The test section consists of three parts: three sections of horizontal pipe, one ascending pipe, and one descending pipe. The inclined pipes are at an angle of 10°, all sections are connected by elbow pipes, and the inner diameter is 40 mm. Air and water, with a superficial liquid velocity ranging from 0.002 m/s to 0.1 m/s, are used as working fluids, which are operated at ambient temperature and pressure. Differential pressure transmitters and ultrasound Doppler velocimetry are used to measure the pressure drop and liquid film height, and velocity, respectively. Numerical simulation is simultaneously carried out using the coupled level-set and volume of fluid method, and is verified through comparison with experimental data. Slug initiation mechanisms are discussed based on experimental observation and numerical prediction. The characteristics of liquid slug initiation and initial development are also explained using pressure drop fluctuation, liquid holdup, and phase distribution features. The overall qualitative and quantitative analysis can contribute to the improvement of recent theoretical and numerical models.

Numerical Analysis of Solid Particle Erosion in Pipe Elbow

Erosion due to particulate impingement is the key factor responsible for damage of industrial pipeline. A CFD-CFX based simulation study of particle-liquid erosion of pipe elbow that considers the solid-liquid, solid-solid and solid-wall interaction is presented in this work. The simulation work has been performed by using the combination of CFD code ANSYS CFX along standard k-є turbulent model. Erosion rates for particles of different diameters and concentration are investigated at different slurry velocity. The model presented can be employed in industrial flow applications for the forecast of erosion wear caused by solid-liquid slurry flow

Ancestral Caddo Ceramic Vessel Sherds from Sites in the White Oak Creek Basin, Hopkins County, Texas

The ancestral Caddo ceramic vessel sherd assemblages discussed in this article are from five sites in the White Oak Creek basin in the Blackland Prairie of East Texas (Figure 1). They are the E. B. Minter Farm (41HP2), R. H. Taylor Farm (41HP4), Hilman Hathcoat (41HP9), Avery Rasurer (41HP10), and Tom Cannon Farm (41HP11) sites. They were investigated by archaeologists from The University of Texas in 1931 or 1934 who were in search of whole Caddo vessels and burial features, and the collections obtained from the sites (including donated or purchased collections) are held by the Texas Archeological Research Laboratory at The University of Texas at Austin (TARL). The collections include ceramic vessel sherds from each of the sites, elbow pipes from two of the sites, and a few vessels from the E. B. Minter and R. H. Taylor Farm sites.

The Structure Design and Simulation of Ultrasonic Inspection Instrument for Inside Pressurized Pipe Elbows

Elbows in pressure pipes are important parts which may become serious corrosion locations. Ultrasonic detection is a main technique for pipe inner inspection, and the use of traditional ultrasound and phased array technique for in-line inspection are advanced, long-term interesting and known by researchers. Several devices were invented for inside pipeline inspection and suitable to some extent such as detecting long-distance pipelines. However, elbows especially tight elbows are still difficult to implement inner detection or travelling. To obtain good effect in detecting elbows, the inner inspection technique was investigated. Spherical and flat cylindrical probe holder structures were proposed to ensure the ability to pass through elbows, while the spherical holder has many conventional probes in its shell with a uniform distribution. The flat cylindrical probe structures are suitable for phased array ultrasonic technique to form a convex array. CIVA simulation was conducted and the focal effects were analyzed. Comparing with detecting precision and manufacture process, the phased array technique was chosen, and the elbow inspection experiments were carried out. The ultrasonic system was taken by a robot to travel through the elbow, and the experimental data were used to verify the applicability of the ultrasonic inspection technique.

Effect of sand particles on the Erosion-corrosion for a different locations of carbon steel pipe elbow

Erosion combined with corrosion becomes the most problem in the seawater desalination plant due to the fast deterioration of the internal line pipe. Corrosion products were characterized for surface morphology, phase composition and element concentration. In this paper, the prediction of erosion of solid particles in geometry of the elbow is performed by means of a numerical simulation. Fluid Dynamics (CFD) simulations with FLUENT software are performed to study erosion prediction in 3-D, 90∘ elbow for phase (liquid and solid particles), For a range of particle sizes from 2 mm, 0.4mm and 4µm for different valve opening angles in order to obtain the real tool failure reasons of erosion. The obtained conclusion by analyzing the reasons, applies in the middle make downhole tools to control and prevent erosion failure phenomenon.