Small-bore Pipe Research Articles

Aeroacoustic analysis of flow induced resonance in a gas pipeline

Flow induced noise and vibration in the pipework of gas production platforms can lead to fatigue failures of attached small-bore pipes, and this can constrain the operating conditions of the platform. Typically such problems comprise a source of turbulence in the flow, an aeroacoustic feedback mechanism due to acoustic resonances inside the pipework, and mechanical resonances which amplify the resulting vibration. The problem described here occurred in the gas metering system of the platform, with the source located in the header which comprised a bifurcation into two metering lines and a number of sharp bends. Because of the cost of rectifying the problem an in-depth study was carried out to analyse the flow and induct acoustic conditions. The predictions will support recommendations for an efficient redesign of the entire system to control the problem at source. Various levels of CFD modelling (RANS and URANS) were carried out using the Openfoam code to predict the exact location and mechanism of the vortex shedding. The acoustic response of the complex ductwork was then modelled using the ACTRAN code to understand the feedback mechanism which led to resonance and high levels of response.

Use of Purgeless Gas Tungsten Arc Welding (GTAW) of Small Bore SS 304L Pipes for Reduction of Oxidation Weld Defect in Nuclear Piping Applications: A Field Deployment Approach

Use of Purgeless Gas Tungsten Arc Welding (GTAW) of Small Bore SS 304L Pipes for Reduction of Oxidation Weld Defect in Nuclear Piping Applications: A Field Deployment Approach

Effect of Pipe Bends on the Low-Frequency Torsional Guided Wave Propagation

Wave motion in pipe bends is much more complicated than that in straight pipes, thereby changing considerably the propagation characteristics of guided waves in pipes with bends. Therefore, a better understanding of how guided waves propagate in pipe bends is essential for inspecting pipelines with bends. The interaction between a pipe bend and the most used non-dispersive torsional mode at low frequency in a small-bore pipe is studied in this paper. Experiments are conducted on a magnetostrictive system, and it is observed that T(0,1) bend reflections and mode conversions from T(0,1) to F(1,1) and F(2,1) occur in the pipe bend. The magnitude of the T(0,1) bend reflections increases with increasing propagation distance and excitation frequency. The amplitude of the mode-converted signals also increases with increasing propagation distance, but it decreases with increasing excitation frequency. Because of their longer bent path, the test signals for a pipe bend with a bending angle of 180X are much more complicated than those for one with a bending angle of 90X. Therefore, it is even more difficult to scan a bent pipe with a large bending angle. The present findings provide some insights into how guided waves behave in pipe bends, and they generalize the application of guided-wave inspection in pipelines.

Actual Stress Analysis of Small-Bore Butt-Welded Pipe by Complementary Use of Synchrotron X-Rays and Neutrons

Residual stresses in astresses in small-bore butt-welded pipe of austenitic stainless steel have never been measured. It is difficult to obtain a detailed residual stress map of the root welded part, because the gauge volume in neutron diffraction is large. The stress evaluation of the welded part by synchrotron X-rays was also difficult due to the dendritic structure. In this study, a double exposure method (DEM) with high-energy synchrotron X-rays was applied to measuring the details of the residual stress of the welded part, and we succeeded in obtaining the detailed axial and radial stress maps of the root welded part of the plate cut from the welded pipe, though the stress map was under the plane stress condition. The hoop stress map of the butt-welded pipe was obtained using the strain scanning method with neutrons under the triaxial stress state. The axial and radialradius stress maps under a triaxial stress state were made up using the complementary use of the synchrotron X-rays and neutrons. As a result, the detailed stress maps of the root welded part of the butt-welded pipe were obtained. The result of the actual stress analysis sufficiently explained the initiation and propagation of SCC.

Influence of Insulation Stand-Off Membranes and Moisture Drainage on the Corrosion Under Insulation Behavior of Out-of-Service Carbon Steel Piping

Corrosion under insulation (CUI) is reported as being the driver behind the majority of failures in thermally insulated process piping and poses significant maintenance expenditures and service interruptions. Small-bore pipes are more prone to failure from CUI due to their lower wall thickness and lower surface area in comparison to larger diameter pipes. This research work simulates the CUI behavior of small-bore piping over a 12-month period in outdoor settings to mimic the out-of-service conditions in an industrial field setting. For this, two sets of assemblies were made which comprised fibrous stone wool insulations applied over the carbon steel coupons with and without stand-off membranes and low-point drain. Both assemblies were presoaked via submerging in water and tested in outdoor conditions for 12 months followed by insulation removal and detailed characterizations. Corrosion behaviors of steel coupons were studied using weight loss, pit depth measurement, surface profile topography, and scanning electron microscopy, whereas chemical compositions of the corrosion products were investigated using x-ray diffraction. Corrosion rates derived from mass loss data were compared with those calculated using the semi-quantitative risk-based inspection method. The kinetics behind the formation of various corrosion products are also discussed. The stand-off membranes and low-point drain resulted in the reduced time of wetness (i.e., moisture exposure time) that in turn resulted in the domination of lepidocrocite (γ-FeOOH) along with reduced uniform metal loss rate and reduced pit depth in comparison to conventional closed-contact insulation system.

Structure-from-motion based image unwrapping and stitching for small bore pipe inspections

Visual inspection is one of the most ubiquitous forms of non-destructive testing, being widely used in routine pipe inspections. For small bore pipes (centimetre diameter), inspectors often have a restricted field of view limiting overall image and inspection quality. Stitching multiple unwrapped images is a common inspection technique to provide a full view inspection image by combining multiple video frames together. A key challenge of this method is knowing the camera pose of each frame. Consequently, mechanical centralisers are often utilised to ensure the camera is located centrally. For the inspection of small-bore pipes, such mechanical centralisers are often too large to fit. This paper presents a post-processing, Structure-from-Motion (SfM) based approach to unwrap and stitch inspection images, captured by a manually deployed commercial videoscope. It advances state-of-the-art approaches which rely on the projection of a laser pattern into the field of view, thus reducing the equipment size. The process consists of camera pose estimation, preliminary point cloud generation, secondary fitting, images unwrapping and stitching to form an undistorted view of the pipe interior. Two industrial focussed demonstrators verified the successful implementation for small-bore pipe inspections. Whereby the new approach does not rely on image features to create the surface texture and is less sensitive to the image quality, more areas can be retrieved from inspections. The reconstructed area was increased by up to 87% using the new approach versus the conventional 3D model.

On the Suitability of Vibration Acceptance Criteria of Process Pipework

The risk of vibration-induced fatigue in process pipework is usually assessed through vibration measurements. For small-bore pipework, integrity personnel would measure the vibration of the pipework and refer to widely used charts to quantify the risk of vibration-induced fatigue. If the vibration levels are classified as OK, no action is required on behalf of the operators. However, if it is a CONCERN or PROBLEM vibration level, strain measurements are required to adequately quantify the risk through a fatigue life assessment. In this paper, we examine the suitability of a widely used vibration acceptance criteria through finite element models. A total of 4,800 models are used to study the suitability of this vibration acceptance criteria by monitoring both the vibration and dynamic stress. The model comprises a small-bore pipe (2″ SCH 40) that is fitted on a mainline size 5″ SCH 40 using a weldolet; the length of the mainline takes three values resulting in three models. The mainline supporting conditions will be varied using translational and rotational springs. The finite element models will be excited using a point load resembling flow-induced forces (with varying flow velocity and fluid composition). These excitations are obtained from the literature and are based on experimental studies as power spectral density functions. The results show that the studied vibration acceptance criterion is suitable in 99.73% of all the studied models with 68.27% confidence level. For the models with a shorter mainline pipe, the criterial is suitable in 76.5% of the time with 68.27% confidence level.

Study on Mode Repulsion of Ultrasonic-Guided Waves in Pipe Bends

Abstract The wave motion of guided waves in pipe bends is still veiled in some mystery, which hinders the application of guided-wave techniques in the inspection of pipelines with bends. Mode repulsion, which exists in the wavenumber versus frequency dispersion curves of guided waves in pipe bends, is an intriguing phenomenon deserving in depth study. The governing equation of wave motion in pipe bends, deduced by the semi-analytical finite element (SAFE) method, can be regarded as an eigenvalue problem. The eigenvalue derivatives, with respect to the wavenumber, are investigated to determine whether mode repulsion will occur or not. A term in the second derivative of the eigenvalue is identified to determine the mode repulsions. With respect to symmetry, it is found that mode repulsion only occurs between modes of one and the same type, such as symmetric or antisymmetric modes, and does not occur between modes of different type, like between symmetric and antisymmetric modes. A specific case of mode repulsion in a small-bore thin-walled pipe in the low-frequency range, where relatively fewer modes exist, is further studied, and the interactions between these modes are clarified. The evolutions of mode shapes before and after mode repulsion are further illustrated.

Estimation of strength parameters of small-bore metal-polymer pipes

The paper presents results from a set of laboratory studies of strength parameters of small-bore metal-polymer pipes of type TG-5/15. A wave method was used to estimate the provisional modulus of elasticity of the metal-polymer material of the pipes. Longitudinal deformation, transverse deformation and leak-off pressure were determined experimentally, with considerations for mechanical damage and pipe bend.

Research on Ultrasonic Flaw Detection of Steel Weld in Spatial Grid Structure

The welding quality of spatial grid member is an important link in quality control of steel structure. The paper analyzed the reasons that the welding seam of small-bore pipe with thin wall grid structure is difficult to be detected by ultrasonic wave from the theoretical and practical aspects. A series of feasible detection methods was also proposed by improving probe and operation approaches in this paper, and the detection methods were verified by project cases. Over the years, the spatial grid structure is widely used the engineering by virtue of its several outstanding characteristics such as reasonable structure type, standard member, excellent space integrity and quick installation.The wide application of spatial grid structure brings higher requirements on nondestructive test of grid structure. The implementation of new Code for Construction Quality Acceptance of Steel Structure Work GB50205-2001 strengthens the site inspection of steel structure, especially the site inspection of ultrasonic flaw detection in steel weld. The detection for spatial grid member structured by small-bore and thin-walled pipes is difficult due to the irregular influence of sound pressure in near-field region of sound field, sound beam diffusion generated by small bore pipe and reduction of sensitivity. Therefore, it is quite significant to select correct detecting conditions. The spatial grid structure of welding ball and bolt ball is statically determinate structure with high-order axial force which is connected by member bars and joints. It is welded by shrouding or conehead of member bars and of member bar and bolt-node sphere. It is obvious that to ensure the quality of these welding positions is critical to the quality of overall grid structure. However, the complexity of weld structure and limitation of ultrasonic detection method cause many difficulties in detection. No satisfactory results will be obtained by the conventional detection technology, so some special approaches must be used.

Impact of Internal Pipe Grooves on Flow-Accelerated Corrosion of Small-Bore A-106 Carbon Steel Pipes

Segments of welded small-bore A-106 carbon steel from a piping system that experienced severe flow-accelerated corrosion were characterized for surface damage due to flow-accelerated corrosion (FAC). A computational fluid dynamics (CFD) analysis was done to compare findings of CFD model versus observed surface FAC damage inside the pipes. CFD results expressed in terms of turbulence intensity showed good agreement with actual surface damage due to FAC. It was concluded that the presence of internal grooves would cause turbulent flow regime, and therefore, it would cause pipe material damage.

Dynamic strain measurement of hydraulic system pipeline using fibre Bragg grating sensors

Fatigue failure is a serious problem in hydraulic piping systems installed in the machinery and equipment working in harsh operational conditions. To alleviate this problem, health monitoring of pipes can be conducted by measuring and analysing vibration-induced strain. Fibre Bragg grating is considered as a promising sensing approach for dynamic load monitoring. In this article, dynamic strain measurements based on fibre Bragg grating sensors for small-bore metal pipes have been investigated. The quasi-distributed strain sensing of fibre Bragg grating sensors is introduced. Two comparison experiments were carried out under vibration and impact loads among the methods of electrical strain gauge, piezoelectric accelerometer and fibre Bragg grating sensor. Experimental results indicate that fibre Bragg grating sensor possesses an outstanding ability to resist electromagnetic interference compared with strain gauge. The natural frequency measurement results, captured by fibre Bragg grating sensor, agree well with the modal analysis results obtained from finite element analysis. In addition, the attached fibre Bragg grating sensor brings a smaller impact on the dynamic characteristics of the measured pipe than the accelerometer due to its small size and lightweight. Fibre Bragg grating sensors have great potential for the quasi-distributed measurement of dynamic strain for the dynamic characteristic research and health monitoring of hydraulic system pipeline.

Experimental studies of a typical sprinkler piping system in hospitals

Based on the issue of life safety and immediate needs of emergency medical services provided by hospitals after strong earthquakes, this paper aims to introduce a research programme on assessment and improvement strategies for a typical configuration of sprinkler piping systems in hospitals. The study involved component tests and subsystem tests. Cyclic loading tests were conducted to investigate the inelastic behaviour of components including concrete anchorages, screwed fittings of small-bore pipes and couplings. Parts of a horizontal piping system of a seismic damaged sprinkler piping system were tested using shaking table tests. Furthermore, horizontal piping subsystems with seismic resistant devices such as braces, flexible pipes and couplings were also tested.
 The test results showed that the main cause of damage was the poor capacity of a screwed fitting of the small-bore tee branch. The optimum improvement strategy to achieve a higher nonstructural performance level for the horizontal piping subsystem is to strengthen the main pipe with braces and decrease moment demands on the tee branch by the use of flexible pipes. The hysteresis loops and failure modes of components were further discussed and will be used to conduct numerical analysis of sprinkler piping systems in future studies.

A New Model of Cuttings Bed Height for Horizontal Small Bore Pipes Without Rotating Drill-Pipe

A New Model of Cuttings Bed Height for Horizontal Small Bore Pipes Without Rotating Drill-Pipe

Localization and evaluation of corrosion in a small-bore piping system using a bobbin-type magnetic camera

This paper presents a nondestructive evaluation algorithm for locating, discriminating, and evaluating inner and outer diameter (ID and OD) corrosion on a small-bore pipe by means of a bobbin-type magnetic camera that uses arrayed solid-state Hall effect sensor elements for measuring alternating magnetic fields. The proposed magnetic camera system is used to experimentally measure artificial ID and OD hole-type cracks on a small-bore copper alloy pipe over a low-frequency range (2-8 kHz). The measured amplitude signal is analyzed to determine both the position and type of crack. The volumes of the cracks are estimated with standard deviation of 0.77 mm 3 to be in the range 1.00-9.01 mm 3 .

Estimation of sizes of cracks on pipes in nuclear power plants using dipole moment and finite element methods

The dipole model method (DMM) for simulating an alternating magnetic field around a hole-type crack in a small-bore pipe as a nondestructive evaluation method is proposed in the present paper. Simulation results were compared with those of the finite element method (FEM) and experimental results obtained using a bobbin-type magnetic camera, and they were found to be in good agreement; thus validating the DMM. The DMM was also found to be faster and easier to implement compared to the FEM. Furthermore, the crack volume could be estimated by linear approximations with a good correlation among the three methods.

적외선열화상 카메라를 이용한 원전 소구경 감육배관의 결함 검출

선행 연구에서 적외선열화상기법을 이용하여 원전 배관의 감육 결함을 측정하기 위하여, 4 inch 배관에 인공결함을 가공하여 이에 대한 결함 검출을 도출하였다. 본 논문에서는 선행연구에서 도출된 조건을 이용하여 원전 소구경 배관의 결함 검출 조건에 관한 연구를 수행하였다. 결함의 가공은 감육 길이, 원주방향 각도, 감육 깊이를 변화시켜서 결함 조건을 가공하였다. 사용된 장비는 IR camera와 1 kW용량의 halogen lamp 2개를 사용하였으며, halogen lamp와 대상 배관과의 거리를 1 m, 1.5 m, 2 m 순으로 변화시켜 실험을 수행하였다. 실험 결과의 분석을 위하여 온도분포데이터를 확보하고, 이를 분석하여 결함 길이를 측정하였다. 4 inch 배관의 인공결함은 2 m에서 측정 결과의 신뢰도가 높았으나, 소구경 배관은 1.5 m에서 결함이 명확하게 검출되었다. In the advanced research deducted infrared thermography (IRT) test using 4 inch pipe with artificial wall-thinning defect to measure on the wall-thinned nuclear pipe components. This study conducted for defect detection condition of nuclear small-bore pipe research using deducted condition in the advanced research. Defect process is processed by change for defect length, circumferential direction angle, wall-thinning depth. In the used equipment IR camera and two halogen lamps, whose full power capacitany is 1 kW, halogen lamps and Target pipe experiment performed to the distance of the changed 1 m, 1.5 m, 2 m. To analysis of the experimental results ensure for the temperature distribution data, by this data measure for defect length. artificial defect of 4 inch pipe is high reliability in the 2 m, but small-bore pipe is in the 1.5 m from the defect clearly was detected.

Water-hammer pressure waves interaction at cross-section changes in series in viscoelastic pipes

In view of scarcity of both experimental data and numerical models concerning transient behavior of cross-section area changes in pressurized liquid flow, the paper presents laboratory data and numerical simulation of the interaction of a surge wave with a partial blockage by a valve, a single pipe contraction or expansion and a series of pipe contraction/expansion in close proximity.With regard to a single change of cross-section area, laboratory data point out the completely different behavior with respect to one of the partially closed in-line valves with the same area ratio. In fact, for the former the pressure wave interaction is not regulated by the steady-state local head loss. With regard to partial blockages, transient tests have shown that the smaller the length, the more intense the overlapping of pressure waves due to the expansion and contraction in series.Numerically, the need for taking into account both the viscoelasticity and unsteady friction is demonstrated, since the classical water-hammer theory does not simulate the relevant damping of pressure peaks and gives rise to a time shifting between numerical and laboratory data. The transient behavior of a single local head loss has been checked by considering tests carried out in a system with a partially closed in-line valve. As a result, the reliability of the quasi steady-state approach for local head loss simulation has been demonstrated in viscoelastic pipes. The model parameters obtained on the basis of transients carried out in single pipe systems have then been used to simulate transients in the more complex pipe systems. These numerical experiments show the great importance of the length of the small-bore pipe with respect to one of the large-bore pipes. Precisely, until a gradually flow establishes in the small-bore pipe, the smaller such a length, the better the quality of the numerical simulation.

Experimental and Numerical Evaluation of the Vibration Fatigue of Small Bore Pipe in PWR

The purpose of this paper is to evaluate the vibration of the small bore pipe in nuclear piping under the fatigue loading due to flow fluctuation. The vibration speeds of the pipe-lines were measured to get the effective velocity which is found larger than the allowable value calculated from EDF evaluation method. To perform the piping vibration assessment and construction, the natural shape and the vibration stress at the socket weld position was evaluated by finite element analysis with ABAQUS. From the linear cumulative damage theory, the fatigue life is predicted with the results that lower than the designation level. According to the position of the maximum vibration speed calculated from FEA simulations, the valve is fixed by the rigid support. The natural frequency and the corresponding mode shape are discussed with much lower vibration velocity and vibration stress.

Characterization of oxides on FAC susceptible small-bore carbon steel piping of a power plant

Wall thinning, oxides phase(s) identification, and oxide morphology characterization of nine high-pressure turbine extraction pipes (as-found thickness for pipes A through F) received from Comanche Peak Nuclear Power Plant (CPNPP) located at Glen Rose, Texas, were studied in this investigation. Phase identification performed using Fourier Transform Infrared Spectrophotometry (FTIR) showed that maghemite (γ-Fe 2O 3), magnetite (Fe 3O 4), and trace amounts of Lepidocrocite (γ-FeOOH) were present in the oxide layer on the inside surface of these small-bore carbon steel pipes. Scallop formation and severe pitting were observed. The scallop pattern was observed utilizing an Environmental Scanning Electron Microscope (ESEM) and is attributed to removal of the protective film in a Flow-Accelerated Corrosion (FAC) process. The most severe wall thinning was observed in the vicinity of welds.