Pipe Flange Research Articles

An efficient predicting approach for blade frequency line-spectrum noise of marine centrifugal pumps

The paper introduces an innovative and efficient calculation method for the spectral flow noise of the pump system based on the spatial distribution dipole, which predicts the blade frequency radiation noise at the pipe flange of the pump system under different operating conditions. First, the unsteady flow simulation of the centrifugal pump is calculated using computational fluid dynamics (CFD). Then, the pressure on each segmented blade surface is decomposed into lift and drag forces. After that, each segment is decomposed into several dipole point sources based on the blade noise theory. Finally, the simplified dipole point sources are considered sound sources, and the blade frequency line spectrum noise at the pipe flange of the pump system is predicted using acoustic-structure coupling. The results indicate that the simplified method provides high prediction accuracy while significantly improving the computational efficiency of blade frequency line spectrum noise calculation for centrifugal pumps.

A Numerical Comparison of Different Methods for Evaluating Pipe Flanges Under External Loads

Abstract This paper presents a numerical comparison of seven different methods for evaluating external loads on flanged joints in a piping system. The comparison will demonstrate in tabular form the factor of safety of some widely used traditional methods. An explanation of the history and basis of each method will be made. Differences in the results will be discussed, and an attempt will be made to explain the discrepancies between the more rigorous methods.

Material tests of composite rings with recyclates for pipe flange connections

This study aims to determine the material properties of the structural components of the composite ring material for pipe flange connections.

Fabrication of TA2–304 SS laminated metal composite using directed energy deposition-arc: Microstructure, mechanical property, and corrosion resistance

Conventional fabricating methods of TA2–304 SS laminated metal composite (LMC) (e.g., hot rolling, hot stamping, and explosive welding) have difficulty in removing brittle TiFe intermetallic compounds (IMCs) and are not suitable for the preparation of the small size structure components or transition joints. Additive manufacturing of LMCs has the potential to achieve the desired microstructure, properties, and structure. In this study, TA2–304 SS LMC, which has been extensively employed in pipe flanges of nuclear plants and bows of sonar dome, was well fabricated by utilizing directed energy deposition-arc (DED-arc) and copper‑nickel alloy transition interlayers, and the formation of brittle TiFe IMCs was suppressed. The results of this study indicated that the standard deviation of the height of the surface morphology reconstructed by adopting Python VTK technique was evaluated as 0.67. Furthermore, copper‑nickel transition interlayers possessed the capability of isolating Ti from Fe atoms through the formation of laminar-distributed microstructure. Specifically, the Interlayer1 was comprised of (Fe, Cr) grains with different shapes and small-size (Cu) equiaxial grains, Interlayer2 covered large-size (Cu, Ni) dendritic grains and intergranular (Cu), and the TA2 layer comprised α-Ti and Ti2Cu. The result also showed that thermal cycle-induced recovery and recrystallization and diffusion-induced elemental interaction accounted for the different microstructures. Moreover, the interface between the TA2 and Interlayer2 layers contained TiCu4 + (Cu), Ti3Cu4 + TiCu4, Ti2Cu + TiCu, and TiCu + Ti2Cu eutectoid microstructures, which resulted in the highest hardness of 450Hv as well as crack initiation and extension. Furthermore, due to the uniform-distribution of microstructure in the absence of brittle IMCs, the average shear strength was 234.0 MPa, which reached the strength of the conventional method and conformed to the standard requirements. Multiple groups of galvanic reactions between different transition materials can result in reduced corrosion resistance, and the oxidation-reduction reactions can lead to the formation of massive oxides.

Life Cycle Assessment of Cold Spray Additive Manufacturing and Conventional Machining of Aluminum Alloy Flange

Cold spray additive manufacturing (CSAM) is generally used to repair worn components and build complex on-demand parts by depositing metal powder layer-wise using compressed air. Previous studies on CSAM were focused on printing parameters, materials properties, and printed part mechanical performance. However, the energy consumption and environmental impacts of CSAM processes have not yet been investigated, which are essential factors for sustainable manufacturing. This study aims to investigate the carbon footprint of the CSAM process and compare it with conventional machining processes and other additive manufacturing. The life cycle assessment methodology was followed to calculate the carbon footprint of a pipe flange, considering rod or tube as a feedstock. Results revealed that the machined flange from the tube had the lowest CO2-eq emissions of 31 kg CO2-eq due to low rough machining energy consumption and scrap production, compared to the machined flange from a rod and a printed flange from powder. Moreover, the life cycle carbon emissions increased by 8% and 19% in case of the printed and machined flanges, with uncertainties of 4% and 9%, respectively, when changing feedstock CO2 emissions. From a regional perspective, the CSAM process was responsible for the lowest CO2-eq emissions in Tasmania and South Australia.

Structural analysis of multi-way block for large-diameter pipeline connector based on ANSYS

This paper introduces a multi-way block for large-diameter pipeline connectors designed based on Hubbed slip-on-welding steel pipe flanges, which solves the problems of complicated processing technology, poor mechanical properties, and short service life of existing welded multi-way pipe joints. The structural analysis and comparison of multi-way blocks and multi-way pipe joints under different working conditions are carried out. This paper adopts certain assumptions to simplify the model, analyzes the multi-way block and multi-way pipe joint in theory, and takes the PN16-150 multi-way block as an example to refine and verify the theoretical analysis results. In this paper, Pro-E is used to establish a three-dimensional model, and ANSYS workbench is used for structural static simulation. The simulation results show that the multi-way block has better mechanical properties than the multi-way pipe joint under the same working conditions, and the multi-way block after reducing the diameter has better mechanical properties than the equal-diameter multi-way block.

The analysis of debonding damage between steel tension wire and epoxy resin in flexible end fitting under cyclic loading

Flexible pipe end fitting is a structure connecting flexible pipe and mental flange, which is a transition between flexible structure and rigid structure. Epoxy resin is used to fix tension steel wire in the end fitting. The bonding interface between epoxy resin and tension steel wire is prone to debonding when flexible pipe end fitting is used under cyclic loading. The damage of bonding interface is mainly due to the cumulative effect of cyclic loading. The damage of epoxy resin can cause temperature changes, which can affect the material properties of the resin and then affect the bonding strength. In this paper, the relationships between cycle numbers of epoxy resin and temperature, temperature and elastic modulus are obtained through fatigue analysis and dynamic mechanical analysis (DMA). The fatigue model is established based on the relationship between the modulus of epoxy resin and temperature. Based on the fatigue model, the bonding damage between steel tension wire and epoxy resin is obtained by finite element analysis (FEA). The results show that it is feasible to characterize the fatigue damage between steel tension wire and epoxy resin by temperature. This work provides a new method for predicting the fatigue of tensile steel wire and epoxy resin in end fitting.

Validation study of in situ sound absorption measurement

An in situ acoustic tube measurement is a non-destructive way to measure the sound absorption coefficient of a material. This method is practical for obtaining sound absorption in cases where it is not straightforward to sample specimens in applications such as automobile interiors, room walls, ceilings, or carpeted floors. However, the in-situ method's limitations lie in measurement errors due to the sound energy leakage through the open boundaries within the materials. In addition, it is not straightforward to provide a general correction factor compared to the standard in-tube method because the errors depend on various factors such as material characteristics, material flow resistance, installation conditions, pipe flange size, etc. The aim here is to provide practical guidelines for reducing in-situ error by analyzing and comparing that procedure with the standard in-tube method. Here, in-tube and in-situ methods were used to measure and they were then analyzed by creating FEM-based acoustic tube and poro-elastic material models. The effect of material flow resistivity and flange thickness were investigated and reported.

Performance of externally reinforced CHS X-joints subjected to axial loads

Circular hollow sections (CHS) have evolved as the primary choice for the tubular lattice structures, due to their excellent mechanical properties and aesthetic appearance. However, enhancing the joints capacities in such structures poses as challenge to structural designer. Recent research addressed several external reinforcing schemes that can be utilized for strengthening CHS X-joints. Although each of these schemes was studied thoroughly, no collective study was conducted to compare between their efficiencies in enhancing CHS X-joints strengths and stiffnesses. This study focuses on evaluating the structural performance of these techniques relative to each other. The results showed that CHS X-joints strengthened using outer flanged pipe to confine brace-chord intersection achieved the highest strength and stiffness enhancement among the examined joints. Also, it proved that joints strengthened with single or double outer stiffeners yielded acceptable capacity enhancement with the advantages of easy fabrication and acceptable aesthetically appearance.

Strength and tightness evaluation method for pipe flange connections considering thermal effects

The pipe flange connection is widely applied in chemical, power plants, petrochemical, offshore oil and gas industries, and its strength and tightness are significant for the safe operation. However, there are still no practical and applicable strength and tightness evaluation methods for pipe flange connections working in dramatically varying temperatures. This paper proposed an approach to evaluate the pipeline's strength and sealing performance considering thermal effects in actual operating conditions by combining the experimental measurement and thermostructural analysis. The critical thermodynamic parameters are identified through measured temperature data in operating conditions, and then these parameters are used in the thermostructural analysis to obtain the actual temperature and stress fields. Then, the strength and tightness in complex temperature cases can be evaluated accurately. The pipe flange connection of a liquefied natural gas (LNG) fueling station is analyzed to verify the presented method's effectiveness. This method applies to evaluating the pipeline's strength and tightness and can predict the pipeline's performances under extreme temperatures using the tested data within the measurement range and the corresponding thermostructural analysis. Furthermore, the work in this paper also provides a reference for the design and analysis of pipe flange connections working in complex temperature conditions.

Influence of topology optimization parameters on the mechanical response of an additively manufactured test structure

Topology Optimization (TO) determines a material distribution within a domain under given conditions and design constraints, and generally generates complex geometries as a result. Complementary to TO, Additive Manufacturing (AM) offers the ability to fabricate complex geometries which may be difficult to manufacture using traditional techniques such as milling. AM has been used in multiple industries including the medical devices area. Hence, TO may be used to create patient-matched devices where the mechanical response is catered to a particular patient. However, during a medical device regulatory 510(k) pathway, demonstrating that worst-cases are known and tested is critical to the review process. Using TO and AM to predict worst-case designs for subsequent performance testing may be challenging and does not appear to have been thoroughly explored. Investigating the effects of TO input parameters when AM is employed may be the first step in determining the feasibility of predicting these worst-cases.In this paper, the effect of selected TO parameters on the resulting mechanical response and geometries of an AM pipe flange structure are investigated. Four different input parameters were chosen in the TO formulation: (1) penalty factor, (2) volume fraction, (3) element size, and (4) density threshold. Topology optimized designs were fabricated using PA2200 polyamide and the mechanical responses (reaction force, stress, and strain) were observed through experiments (universal testing machine and 3D Digital Image Correlation) and in silico environments (finite element analysis). In addition, 3D scanning and mass measurement were performed to inspect the geometric fidelity of the AM structures. A sensitivity analysis is performed to examine the effect of each TO parameters. The sensitivity analysis revealed mechanical responses can have non-monotonic and non-linear relationships between each tested parameter.

Metallurgical Failure Analysis of Closed Water Circuit Containing Molybdate-Based Inhibitor

In this work, two industrial heating/cooling circuits are compared. One of the two systems failed in a short time showing severe corrosion damage and a through thickness crack close to one of the welds. The main difference between the circuits is the presence of a sodium molybdate-based corrosion inhibitor in the damaged one. The addition of these substances is very frequent in such applications, and they generally work very well in preventing serious corrosion attacks. Nevertheless, the technical literature reports other cases in which systems working with fluids containing such inhibitors failed prematurely. The authors performed a failure analysis of the damaged circuit focusing their attention on the regions where fluid leaks were observed because of through thickness cracks. This damage was located close to the pipe–flange weld. These zones were investigated by visual examination, radiographic and scanning electron microscope (SEM) analyses, metallographic observations by light optical microscope (LOM), Vickers micro-hardness tests and optical emission spectroscopy (OES) chemical analysis. The failure was related to the presence of severe pitting and crevice corrosion in the welded areas with the final activation of a further critical corrosion mechanism, i.e., stress corrosion cracking (SCC). In order to explain the shorter working life of the failed system, a physical model of the corrosion mechanisms acting on the two circuits was proposed.

Investigation on leakage cause of 13Cr pipe flange used for a Christmas tree in a high-pressure and high-temperature gas well

The martensitic stainless steel pipe flange used for the 138 MPa Christmas tree failed to leak during ultra-deep high-pressure, high-temperature gas well operations. In order to study the cause of leakage, non-destructive testing, chemical composition analysis, mechanical property analysis, metallographic structure testing, surface characterization, cracking characterization and finite element analysis were performed in the present research. The results show that the leakage failure is related to the crack in the ring groove. The cracks initiated from the edge of the corrosion pits and propagated along the delta ferrite/martensite interfaces. The Cr-rich carbides in the matrix reduced the pitting resistance, while delta ferrite deteriorated the crack resistance, which was the main factor contributing to the failure. In addition, the stress level in the sealing structure of the Type 6BX flange further influenced the crack propagation behavior.

Bending and tensile stressing state features of ductile iron pipe flange connections revealed from tested strain data

The existing theories and methods based on structural ultimate working states with empirical judgment could not estimate the load-bearing capacity of ductile iron pipe flange (DIPF) connections accurately. This paper tries to address the issue applying the novel structural stressing state theory and methods, leading to the revelation of the essential bending and tensile working features of DIPF connections. Firstly, the experimental strain data are transformed into the generalized strain energy density (GSED) values to build the stressing state modes and the characteristic parameters. Then, the Mann-Kendall criterion is adopted to detect the mutation points in the evolution curves of characteristic parameters. Correspondingly, it is verified that the evolutions of stressing state modes also present the mutation features. The mutation features are the embodiment of the natural law from quantitative change to qualitative change of a system, which defines the starting points of DIPF connections’ failure processes. Furthermore, the Mann-Kendall criterion distinguishes the elastoplastic branch (EPB) points in the stressing state evolutions of DIPF connections. Both failure starting points and EPB points provide the new foundation to accurately determine the working capacities of DIPF connections and to improve their design.

Durability improvements of Exhaust pipe joints during operating Condition

Medium and Heavy Commercial Tipper vehicles in India are mainly used for off-road and mining applications where the vehicles are subjected to severe and irregular road load patterns. In such cases it is imperative that quality of weld joints in Exhaust pipes should be capable of withstanding off road duty cycle. The negative impact of any kind of defect will be magnified due to presence of such harsh road & environment conditions. The current paper focus discussion on the various failures and defects found in weld joints of exhaust pipes. Various methodology has been introduced to detect the modes of Weld failure. After detailed study and analysis, a set of recommendations are proposed for welding of Exhaust pipe flange joints to ensure high durability life of weld joints

Safety devices for pipe flanges aid both repairs and scheduled maintenance

Flexitallic UK Ltd has launched a series of safety devices that are installed between pipe flanges and provide flexibility during repairs and scheduled maintenance.

Bolt loading effects on the structural integrity assessment of defects in industrial components

Applied loads in bolted geometries of safety critical components can vary with time and operating conditions. Structural integrity and remaining life assessments of such components in aging industrial plants must consider the resultant changes in damage accumulation rates and acceptable defect sizes. Two case studies are presented that demonstrate the effect of bolt pre-load on creep and fatigue lives as well as on the acceptability assessments of defects. In the first case the sensitivity of creep damage accumulation and crack propagation rates to bolt pre-load in high temperature flanged connections are considered. Predicted results were found to compare well with actual damage quantified on a high pressure turbine loop pipe flange connection. It was shown that decreased pre-loads, in this case, leads to an increase the allowable safe defect size during assembly at room temperature. In contrast to this the second case study of corrosion fatigue cracking in a boiler water circulating pump illustrates that an increase in bolt pre-load leads to an increase in fatigue initiation life, a decrease in fatigue crack propagation rate and an increase in the acceptable defect size. Strain gauge measurements of bolt and casing strain, which correlated well with finite element calculations, indicated the necessity for close control of bolt pre-load during assembly to ensure specified levels are attained. In both cases metallurgical analysis and structural integrity assessments of cracked and excavated geometries were conducted which enabled limited continued operation of the components after which repairs and/or replacements will be implemented.

Bending working law of corroded ductile iron pipe flange connections revealed by structural stressing state theory

Applying structural stressing state theory, this study finds out the bending working law of corroded ductile iron pipe flange (CDIPF) connections from their tested strain data. Firstly, the strain data are transformed into the generalized strain energy density values to build the stressing state mode and the characteristic parameter. Then, the Mann-Kendall criterion is used to detect the mutation points in the evolution curves of the stressing state characteristic parameters with the load increase according to the natural law from quantitative change to qualitative change of a system. Meanwhile, it is verified that the evolutions of the stressing state modes also present the corresponding mutation features. The mutation points define the starting points of the bending CDIPF connections' failure processes. Furthermore, the Mann-Kendall criterion distinguishes the elastoplastic branch (EPB) points in the normal working processes of CDIPF connections. Both the failure starting point and the EPB point lay the new foundation to analyze the working performances of the CDIPF connections and to improve their design.

Monitoring of mechanical changes in a pipe assembly with complex geometry using multi-mode acoustic signals

Guided wave ultrasonic testing has been widely used for nondestructive and long-range evaluation of diverse mechanical structures, such as pipes and plates. In general, a large number of guided wave modes exist even in the simplest geometries, and they exhibit highly dispersive characteristics. Thus, sophisticated excitation methods and elaborate modal analyses need to be implemented to excite, acquire, and process well-defined pure modes as part of such a measurement method. If the interrogated structure has complex geometry, for example, with cross-sectional variations or multiple joints, the utilization of pure modes becomes significantly more difficult. To overcome this difficulty, this paper proposes the use of multi-mode, multi-frequency guided waves for long-range inspection of structures with arbitrarily complex geometries. Using broadband chirp signals and multi-mode time–frequency analysis in a prototypical complex pipe assembly that includes multiple pipe diameters, elbows, and flange connections, we experimentally show sensitive detection of mechanical changes (both material addition and loss). In addition, we demonstrate that the complexity of the structure can be modeled in the digital domain with sufficient detail to allow accurate numerical simulation of the acoustic response using this method.

Load condition analysis of pipe flange connection with gasket flat gasket and loose clamping rings

Purpose: This paper describes the study of the connection with loose fixing composite rings of pipe flanges. The elastic properties of the joint components - gasket, pressure flanges, rings and fixing bolts were determined experimentally. Design/methodology/approach: The criterion of joint tightness was formulated. The constructed model was used to determine the analytical dependence of the joint leakage pressure on the assembly torque of bolts tightening. The correctness of the model was confirmed by the agreement of the analytical results with the experimental results. Findings: Quantitative characteristics were determined for the selected type of joint. Practical implications: The formulated conclusions indicate the possibility of using the model to support the design process and to select the structural parameters of the joint meeting the operational requirements and safety criteria. Originality/value: Produced with recycled materials using.