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Flow-Induced Vibration in Safety Relief Valves
Abstract
Flow-induced vibration in safety relief valves (SRV's) in high-energy piping systems such as power plants is identified as the source of many SRV failures. The mechanism is an unstable coupling of vortex shedding at the mouth of the valve with the side branch acoustic resonance. Characteristics of the problem and computerized methods of acquiring data lead to positive identification of flow-induced vibration. Pulsation and vibration data recorded from several valves in power plant steam service are presented for comparison of stable and unstable configurations. Based on this data, a rational design procedure utilizing the relationship among Strouhal number, Mach number, and stub dimensions has been developed to eliminate an existing problem or to prevent one in a new piping system. Proper side branch sizing coupled with flow stabilization techniques provide for the design of a main pipe to safety valve transition piece which has been shown to be successful in several applications.
... open (l/d ≥ 1) cavity flows. The critical difference is illustrated by the vortex-sheddingtrailing-edge impingement, which is the typical characteristic of open cavity flows (or skimming flows) -common in closed side branches in the energy sector, such as stub pipe of high-pressure safety relief valves (SRVs) [188] and small bore connections (SBCs) [189]. in an incompressible liquid piping system. The critical difference is described by the excitation mechanism, where the feedback loop (between Kelvin-Helmholtz vortices and branch acoustic (potential) field) characterises the transverse-mode acoustical oscillation, and mass/momentum exchange (between mainstream and vertically-aligned hydrodynamic (vortical) field -large-scale cavity unsteady recirculations) through Kelvin-Helmholtz instability characterises the hydrodynamic unsteady impulsive pressure loading [190][191][192][193]. ...
... The complex three-dimensional unsteady flowfield in the skimming flows (see Fig. 6.1c) are accompanied by the severing of vortices in the downstream and depthwise direction within the cavity due to the vortex-trailingedge impingement. Skimming flows (see Fig. 6.1c) are common in a wide spectrum of practical applications, ranging from weapon bays [194] in aerospace sector, open-roof cars in automobile sector, deep urban street canyon [195,196] and embankment dams with steep-stepped-spillways [197] in infrastructure construction sector, sheltered zone [198] and aquatic vegetation canopies [199] in riverine environment sector, open-chimney termite mounds ventilation [200,201] and aortic valve [202] in nature system, to trapped vortex combustors (TVC) of heat-exchangers [203] and side-branches of complex piping system [188,189] in the industrial construction sector. Especially in a complex piping system of the energy sector, vortex-shedding-trailing-edge impingement at side branches creates unsteady structural loading due to two potential problems -flow-induced pulsation and flow-induced turbulence. ...
... As a future work, the purpose of this study will be to understand the influence of deep cavity (closed-end side-branch l/d = 4) skimming flow, characterised by mass/momentum exchange between the large-scale vortical structures in mixing layer and branch recirculation region, on the complex hydrodynamic flow field, local branch hydrodynamic surface quantities (skin-friction coefficient and pressure coefficient on the side-walls), and branch structural response (stresses and vibration). This type of flows are encountered in large number of fatigue-sensitive welded closed side-branches present in the industrial complex piping system, such as stub pipe of high-pressure safety relief valves (SRVs) [188], smallbore branch connections (SBCs) [189], which are safety and/or business critical in the energy sector [3]. ...
Various unsteady excitation mechanisms exist in the complex piping systems of the energy sector, e.g., flow turbulence and pressure pulsation. The dominant source is the high-pressure reciprocating pumps that can cause intense energy to be transferred to the piping systems. The energy is then propagated throughout the piping systems via pressure pulsations, which can enhance vibration when coupled with structural modes. The complexities in these piping systems arise due to each pump generating multiple frequencies (i.e., harmonics), types of dynamic pump operations (i.e., steady-state or startup-shutdown), types of pump’s interaction mechanisms (i.e., contrasting driving frequency and phase differences), the presence of long piping networks (i.e., eigenmodes), and the presence of local pipe components (i.e., losses and shaking forces due to fitting pipes, e.g., bends, junctions, and valves). While some attention has been paid to the piping systems connected with multiple pumps, the general influence of their interactions (contrasting phase differences) and dynamic pump operations (startup-shutdown transients) on the network response is scarce. A combination of component-level (3D CFD and empirical models) and system-level (1D CFD-FEM models) computations are used to study three aspects of pulsations in a piping network connected with multiple reciprocating pumps. First, a new acoustic resonance mechanism has been observed in a network driven by multiple pumps. When included in system-level 1D CFD computations, the empirically-derived component-level fitting losses approximately capture the acoustics of BP Shah Deniz’s field measurement. Second, the linear model of pulsating flow in a pipe bend identifies flow acceleration as the predominant source of shaking forces. Third, using numerically-derived component-level (fitting) shaking forces, the system-level 1D CFD-FEM computations identify transient acoustic wave as the dominant mechanisms in pump startup-shutdown events with pulsating flows. The outcomes of this thesis will be a set of engineering tools and recommendations for vibration-induced fatigue in industrial pulsation services.
... Closed side branches exist widely in industry, such as natural gas transmission pipelines [8,9], safety valves of the steam pipeline in nuclear power plant [10][11][12][13][14][15], a vertical-lift system of fighters [16][17][18]. Acoustic resonance in these cases can induce severe vibration and noise, cause fatigue damage to the pipeline, threaten the safe operation of the pipeline, and even cause safety accidents, which need to be avoided or suppressed. ...
... The previous studies focus on the mechanism, characteristics, and suppression methods of the acoustic resonance in closed side branches, in which all the branches are perpendicular to the main pipeline [8][9][10][11][13][14][15][16][17][18][19][20]23,24,26,27]. Some visualization studies of acoustic resonance in square cross-section pipe are to capture the acoustic vortex mode [9,13]. ...
... The main purpose of changing the branch shape is to suppress acoustic resonance. Baldwin et al. [11] proposed that the internal structure of the safety valve should be designed out of the St-range at which acoustic resonance occurs. Jungbauer et al. [30] proposed to increase the diameter of the branch at the connection with the main pipe and use a reducer to connect the original branch pipe to change the St-range of acoustic resonance, thereby suppressing acoustic resonance. ...
Acoustic resonance in closed side branches should be enhanced to improve the efficiency of wind energy harvesting equipment or thermo-acoustic engine. However, in gas pipeline transportation systems, this kind of acoustic resonance should be suppressed to avoid fatigue damage to the pipeline. Realizable k-ε delayed detached eddy simulations (DDES) were conducted to study the effect of different branch pipe shapes on acoustic resonance. At some flow velocities, the pressure amplitude of the simulation results is twice as large as that of the experimental results, but the simulation can accurately capture the flow velocity range where acoustic resonance occurs. The results prove the feasibility of the method of the equivalent diameter of the circular cross-section pipe and the square cross-section pipe to predict acoustic resonance. The pressure pulsation amplitude of acoustic resonance in a square cross-section pipe is significantly increased than that in a circular square cross-section pipe, indicating that the square cross-section branch configuration can be more conducive to improving the efficiency of wind energy harvesting. The influence of the angle between the branch and the main pipe on the acoustic resonance was studied for the first time, which has an obvious influence on the acoustic resonance. It is found that the design of a square wind energy harvester is better than that of a circular one; meanwhile, changing the branch angle can increase or suppress the acoustic resonance, which can improve the utilization efficiency of the acoustic resonance and provide a new method for suppressing the acoustic resonance.
... hard and Jacquelin. (2021) determined a procedure for incorporating the underlying wall pressure fluctuations in a finite element model to determine the fatigue life of a piping system. They studied the manual assessment method based on energy institute Guidelines (2008) and the experimental method to verify and validate the F.E. analysis results. Baldwin and Simmons. (1986) studied flow-induced vibration in safety relief valves (SRVs) in high-energy piping systems. They developed an analytical design procedure based on the Strouhal number, Mach number, and stub dimensions to eliminate the vibration problem in the existing system. Cicero et al. (2016) studied the effect of thermal cutting methods (oxyfuel, ...
The piping system connected with the shipboard equipment may be subjected to excessive vibration due to harmonic base excitation produced by hydrodynamic force imposed on the propeller blades interacting with the hull and by other sources. Vibration design aspects for shipboard pipework are often ignored, which may cause catastrophic fatigue failures and, consequently, leakage and spillage in the sea environment. Without dedicated design codes, the integrity of shipboard equipment against this environment loading can be ensured by testing as per test standard MIL-STD-167-1A (2005). However, in many cases, testing is not feasible and economically viable. Hence, this study develops an FE-based vibration analysis methodology based on MIL-STD-167-1A, which can be a valuable tool to optimize the testing requirement without compromising the integrity of these piping systems. The simulated model dynamic properties are validated with experimental modal testing and Harmonic response analysis result confirm that a mitigating solution option can be verified by a FE based vibration analysis to mitigate the vibration problem.
... e closed side branch of a natural gas pipeline is a commonly used unit of gas transmission. Flowinduced acoustic resonance occurs as gas flows through the mouth of a closed branch at a certain velocity, causing intensive and continuous gas pressure pulsations that may result severe pipeline vibration and even fatigue damage [3][4][5][6]. ese pulsations are also noisy and intense enough to endanger the physical and mental health of workers. A serious acoustic resonance event occurred in the WKC2 gas transmission station of China in 2012 which fractured a tee connector (Figure 1). ...
Flow-induced acoustic resonance in the closed side branch of a natural gas pipeline can cause intensive vibration which threatens the safe operation of the pipeline. Accurately modeling this excitation process is necessary for a workable understanding of the genetic mechanism to resolve this problem. A realizable k-ε Delayed Detached Eddy Simulation (DDES) model was conducted in this study to numerically simulate the acoustic resonance problem. The model is shown to accurately capture the acoustic resonance phenomenon and self-excited vibration characteristics with low calculation cost. The pressure pulsation component of the acoustic resonance frequency is gradually amplified and transformed into a narrowband dominant frequency in the process of acoustic resonance excitation, forming a so-called “frequency lock-in phenomenon.” The gas is pressed into and out of the branch in sinusoidal mode during excitation. The first-order frequency, single vortex moves at the branch inlet following the same pattern. A quarter wavelength steady standing wave forms in the branch. The mechanism and characteristics presented in this paper may provide guidelines for developing new excitation suppression methods.
... Such a flow can give rise to flow fluctuations and therefore large dynamic forces acting on these valves[91]. This can give rise to valve vibrations, noise and eventual failure of the valve in worst cases.The two major phenomena that originate from the fluid flow within the valve which can cause failure are flow-induced vibration (FIV)[91][92][93][94][95][96][97] and acoustic-induced vibration (AIV)[98]. Although, AIV being a more commonly observed phenomenon in piping systems[99][100][101][102]. ...
This Master’s thesis work is composed of two research categories. The first part seeks to develop a better understanding of the rheological properties of platelet-rich plasma (PRP), a blood-derived product used as a therapy for osteoarthritis and tendon injuries and the second part aims at evaluation of the flow-induced vibration (FIV) within a subsea choke valve. Blood-derived products, particularly PRP, have received increased attention in the past several years due to their great potential as a therapy for osteoarthritis and tendon injuries. Therefore, characterizing the mechanical properties of PRP becomes important to better understand its therapeutic efficacy. Rheological characterization of PRP provides further insight into its mechanism of action. Flow-sweep, Small Amplitude Oscillatory Shear (SAOS), Large Amplitude Oscillatory Shear (LAOS), and thixotropy tests have been performed at room and physiological temperatures to characterize the non-Newtonian properties of PRP samples. Flow-sweep tests reveal shear-thinning behavior (also observed in LAOS experiments), with higher apparent viscosity observed at temperature. Rheological models such as Carreau, Casson, power-law, and Herschel-Bulkley have been fitted to the flow-sweep data with the latter showing the closest agreement. The calculated boundaries of low/high-shear rates in flow-sweep tests as well as minimum-torque, sample-inertia, and instrument-inertia limits in SAOS frequency-sweep experiments are correspondingly provided for accurate interpretation of the results. Although, the window of interpretable SAOS results is found to be narrow. Furthermore, the non-linear and transient viscoelasticity is quantified with the help of the LAOS tests. The thixotropic behavior of PRP solutions is further quantified through the peak-hold test, and further compared against the results of whole blood previously published in the literature. Part two of the thesis investigates a wellhead choke valve, a type of control valve, which is mostly used to control the flow and pressure of fluids from a reservoir in an oil and gas production. A numerical study is performed using STAR-CCM+ software to study and visualize the complex physics of the compressible flow in question. Our study is carried out on a subsea choke valve model obtained from Master Flo Valve (USA) Inc., FIV investigation on dominant frequency modes within the flow has been conducted using fast-Fourier transform (FFT). The dominant frequency is then compared against the experimental natural frequency of vibration of the valve assembly to assess the risk of resonance and mechanical failure. To complement the FFT analysis, the Mach number, pressure, and temperature contours have been presented on three orthogonal planes within the valve.
... In particular, severe acoustic pressure fluctuations have been studied by Mohany (2007), Mohany and Hassan (2013), Okuyama et al. (2012), and Arafa and Mohany (2016) with a focus placed on heat exchanger tube bundles and the flow over side branch cavities. The latter is a geometry which is prevalent in industrial piping, aerospace, and HVAC applications which were studied in a number of works such as those of Shaaban and Mohany (2015), Omer et al. (2016), and Baldwin and Simmons (1986). The focus of the current work is on a specific nuclear application which highlights a common problem faced in industrial piping systems during the operation of reciprocating or rotating turbomachinery. ...
Acoustic pressure pulsations in piping systems can cause detrimental damage and failure of industrial components. Both the acoustic resonance and the traveling wave phenomena are of concern for industrial piping systems and there is a need to study passive damping devices and their implementation into these systems. However, there is a challenge associated with manufacturing and installation of such devices as they may be cumbersome. Therefore, the infinity tube (IT) damping device has been presented here to provide a simplified device geometry which can be easily manufactured and implemented into piping systems. A theoretical equation for the transmission loss spectra of the IT device and the frequencies of resonance have been derived as a tool for designers. Additionally, the experimental investigation has shown a considerable increase in acoustic attenua-tion in comparison to the conventional Herschel-Quincke device due to the significantly shorter length which the IT device can be constructed from. Acoustic pressure and phase angle measurements have elucidated that the fundamental acoustic mode of an open-open pipe can be formed within the IT device. Moreover, a parametric study is presented which has clarified practical considerations required for implementation of the IT device into piping systems for suppressing pressure pulsation.
... When the frequency of shear layer oscillation (acoustic forcing frequency) matches the acoustic quarter wave resonant frequencies of the side branch, high pulsations can occur leading to serious piping vibration, fatigue failures and added maintenance cost. Examples include, pipe branches leading to safety valves when the valve is closed or to any secondary unit such as pump and compressor station when the isolation valve is closed 1 . The configurations are found in a variety of industrial facilities such as pumps and compressor stations, steam generating plants, oil and gas installations, and power plants. ...
The vortex instability at a side branch connection in a piping system may establish an acoustic standing wave in closed branch lines leading to vibration problems. The Energy Institute (EI) screening method for avoiding such resonance works by ensuring that the fundamental acoustic natural frequency of the side branch is larger than the EI calculated excitation frequency. The EI screening method ignores the possibility that the side branch acoustic natural frequency is significantly lower than the main line excitation frequency. Allowing for this possibility, an alternative screening method is proposed based on the fact that side branch resonances occur across a Strouhal Number range of 0.3-0.6. The minimum and maximum permissible length of the side branch is then calculated based on these bounds. The presented case study demonstrated that the new screening method reduced the systems identified at risk and provided sensible solutions based on the overall branch length to avoid resonance. This provides a practical alternative to the restrictive short branch length generated by the EI screening.
Flow‐induced vibration (FIV) is the structural and mechanical vibration of structures immersed in or conveying fluid. Many engineering structures are susceptible to the interaction between the fluid's dynamic forces and the structures' inertial, damping, and elastic forces. Steady fluid flow through a pipe can impose pressures on the pipe walls that deflect the pipe and cause instabilities. Damping of structures, avoidance of resonance, and the streamlining of structures are the primary mechanisms for limiting FIV. Pressure changes in a closed conduit produced by changes in fluid flow are called fluid hammer (or, more generally, water hammer). The simplest method of protecting pipes from water hammer is found to be slowly closing the valve. A water hammer type event called column separation may occur in a pipeline filled with liquid when a vapor cavity forms and suddenly collapses.
Acoustic resonances in internal flows can cause noise, vibration, and even equipment damage. One geometry prone to acoustic resonance is a deadleg at the point where the main flow turns into a side branch. Here we report experimental and CFD studies of flow generated pulsation in such a geometry over a wide range of mean flow velocities. Experimental results of the normalized pulsation pressure amplitudes (P*) vs. Strouhal number characterized the flow-acoustic field for acoustically tuned and detuned systems and for branch to main pipe diameter ratio of 1.0. The unsteady CFD simulations revealed the characteristic volume integral of the cross-product of the vorticity field and the velocity field in the vicinity of the T-junction which helped in quantifying the acoustic source power for different conditions. The pressure amplitude at the closed end of the deadleg reaches maximum when two conditions are met: i) the system overall acoustic resonance frequency matches closely the frequency of the oscillating component of the cross-product characterized by a Strouhal number, and ii) the deadleg length is tuned to an odd number of ¼ wavelength of this frequency such that maximum acoustic velocity is reached at the Tee-junction. Synchronized images generated from the unsteady CFD simulations revealed valuable insight into the velocity and vorticity field in the region of the T-junction in support of Howe's acoustic source power equation.
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