Pipeline Vibration Research Articles

Semi-analytical solution for soil-constrained vibration of subsea free-spanning pipelines

ABSTRACTApart from being induced by internal and external flow, vibration of free-spanning pipelines is also constrained by the soil that supports the span on both ends. A wake oscillator model is chosen to describe the vortex shedding acting on the pipeline, and the soil spring is adopted to describe the pipe–soil interaction at the span shoulders. A semi-analytical solution – the generalised integral transform technique (GITT) – is used to study the dynamic response of free-spanning submarine pipelines. With this method, the coupled fluid-structure system of partial differential equations is transformed into a system of second-order ordinary differential equations in temporal variable. Parametric studies are carried out to analyse the influence of different internal and external flow velocities, and different soil stiffness. GITT is proved to be a fast and accurate approach for analysing the dynamic response of free-spanning submarine pipelines considering the influence of the current and the internal flow, as well as the effect of the soil.

Discussion on Stochastic Analysis of Hydraulic Vibration in Pressurized Water Diversion and Hydropower Systems

Hydraulic vibration exists in various water conveyance projects and has resulted in different operating problems, but its obvious effects on system’s pressure head and stable operation have not been definitively addressed in the issued codes for engineering design, especially considering the uncertainties of hydraulic vibration. After detailed analysis of the randomness in hydraulic vibration and the commonly used stochastic approaches, in the basic equations for hydraulic vibration analysis, the random parameters and the formed stochastic equations were discussed for further probabilistic characteristic analysis of the random variables. Furthermore, preliminary investigation of the stochastic analysis of hydraulic vibration in pressurized pipelines and possible self-excited vibration in pumped-storage systems was presented for further consideration. The detailed discussion indicates that it is necessary to conduct further and systematic stochastic analysis of hydraulic vibration. Further, with the obtained frequencies and amplitudes in the form of a probability statement, the stochastic characteristics of various hydraulic vibrations can be investigated in detail and these solutions will be more reasonable for practical applications. Eventually, the stochastic analysis of hydraulic vibration will provide a basic premise to introduce its effect into the engineering design of water diversion and hydropower systems.

Study on the Effect of Reciprocating Pump Pipeline System Vibration on Oil Transportation Stations

Due to the periodic movement of the piston in the reciprocating pump, the fluid will cause a pressure pulsation, and the resulting pipeline vibration may lead to instrument distortion, pipe failure and equipment damage. Therefore, it is necessary to study the vibration phenomena of reciprocating pump pipelines based on pressure pulsation theory. This paper starts from the reciprocating pump pipe pressure pulsation caused by a fluid, pressure pulsation in the pipeline and the unbalanced exciting force is calculated under the action of the reciprocating pump. Then, the numerical simulation model is established based on the pipe beam model, and the rationality of the numerical simulation method is verified by indoor experiments. Finally, a case study is taken as an example to analyze the vibration law of the pipeline system, and vibration reduction measures are proposed. The following main conclusions are drawn from the analysis: (1) unbalanced exciting forces are produced in the elbows or tee joints, and it can also influence the straight pipe to different levels; (2) in actual engineering, it should be possible to prevent the simultaneous settlement of multiple places; (3) the vibration amplitude increases with the pipe thermal stress, and when the oil temperature is higher than 85 °C, it had a greater influence on the vertical vibration amplitude of the pipe.

Analysis and Procedures for Water Pipeline Leakage Using Three-Axis Accelerometer Sensors: ADXL335 and MMA7361

Previous studies have proposed vibration of the water pipeline using accelerometer sensors as a mechanism to detect leaks. Nevertheless, they only relied on a single x-axis data, no single study investigates all the axes of the sensors. Therefore, this paper aims to investigate a vibration technique to detect leakage on plastic water pipeline using wireless accelerometer sensors, namely, 6DOF accelerometer sensor (i.e., MPU6050) and breakout accelerometer sensors (i.e., ADXL335 and MMA7361) across the x-, y-, and z-axis. A 25-mm diameter of acrylonitrile butadiene styrene (ABS) pipe with a length of approximately 10 m was developed as the water pipeline testbed. All of the accelerometer sensors measured the vibration on the water pipeline across the x-, y-, and z-axis, over ZigBee networks. The vibration signals were then compared between the three sensors and analyzed by extracting the signal features in time and frequency domains. The sensors were examined based on three different cases, which are no pipe leakage, a 1-mm leak, and a 3-mm leak. All three sensors demonstrated a significant difference between no leak and leak conditions when the water pressure is in the range of 0.6– $1.2~kgf/cm^{2}$ for both time and frequency domains. For different leak size cases, ADXL335 can distinguish the 1-mm and 3-mm holes from the three-axis data. On the contrary, MPU6050 can identify similar leak size cases only from the y- and z-axis data. Overall, ADXL335 has the best performance compared with MPU6050 and MMA7361 in detecting water pipeline leakage, which includes the sizes of the leaks. Based on the empirical results, this paper finally proposes a procedure analysis for each sensor on improving the accuracy of water pipeline leakage detection.

Characteristics, Optimal Design, and Performance Analyses of MRF Damper

Magnetorheological fluid (MRF) damper is one of the most promising semiactive devices for vibration control. In this paper, a shear‐valve mode MRF damper for pipeline vibration control is proposed. The dynamic model and the state equation of the pipeline are established and the linear quadratic regulator (LQR) is used to generate the optimal damping force of MRF damper. The design concept considering the structure and the electromagnetic properties simultaneously is discussed in detail. A mathematical model of the relation between shear stress and control current based on interpolation method is established. Finite element analysis (FEA) software COMSOL is selected to simulate the magnetic field and electromagnetism‐thermal field of the MRF damper. A computational method based on the simulation model is established to calculate the shear stress. In order to reduce the magnetic leakage, a method of adding magnetism‐insulators at both ends of the piston head is presented. The influence of control current, displacement, and velocity on mechanical performance of the proposed MRF damper is experimentally investigated. The test results show that the performance of the MRF damper is basically identical with the theoretical prospective and the simulation conclusions, which proves the correctness and feasibility of this design concept.

Experimental study in reduction of two phase flow induced vibration

Vibration in mechanical devices is one of the major problems in engineering field including power generated industry. In this study we focused on the method and possible equipment design availability in reduction of vibration level. A brief overview of the outcomings of pipeline vibrations is presented, the sources of vibrations are listed and possible solutions for eliminating vibrations are described. Devices for passive quenching of pressure pulsations in pipelines with a two-phase flow are considered. We presented the description of the experimental stand on the investigation of the influence of a two-phase flow on the vibration of sections of a pipeline under different flow patterns of a coolant, as well as the procedure for conducting an experiment to study the properties of developed and manufactured swirl models. An animated model was developed that reflects the relationship of swirl geometry with the reduction of the vibro-displacement of the pipeline as a result of passive action on a two-phase flow.

Numerical study of the vibration of pipelines taking into account the viscoelastic base of the soil

Numerical study of the vibration of pipelines taking into account the viscoelastic base of the soil

Vibration of pipelines under flexural dynamic loads

A SYSTEM OF eight-coupled first-order partial differential equations describing the vibration response of pipelines under external flexural loads is derived. The decoupling of these equations yields a system of eight fourth-order partial differential equations. An analytical solution is achieved with the aid of integral transforms. Vibration analysis of pipelines subjected to impact and harmonic loads is provided.

Вибрация трубопроводов под действием изгибающих динамических нагрузок

Вибрация трубопроводов под действием изгибающих динамических нагрузок

Anti-vibration analysis of vortex probe based on three-axis acceleration measurement

According to the diversity of the pipeline vibration and unicity of vortex signal in direction, a new idea is proposed to distinguish the vortex signal from the vibration interference by the directional character. This idea is applied to improve the anti-vibration performance of vortex flow-meter by a new probe structure based on three-axis accelerometer. Then model analysis is used to optimize the material, and the harmonic response analysis is applied to optimize the shape of probe tip. Finally, experiment is carried out to compare the anti-vibration performance of the traditional piezoelectric vortex probe and the new design. Experimental results show that new probe can accurately distinguish vortex signal from the vibration interference according to the directional character of signal. And its anti-vibration performance is superior to the traditional piezoelectric vortex probe.

Flow-pipe-soil coupling mechanisms and predictions for submarine pipeline instability

The stability of a submarine pipeline on the seabed concerns the flow-pipe-soil coupling, with influential factors related to the ocean waves and/or currents, the pipeline and the surrounding soils. A flow-pipe-soil coupling system generally has various instability modes, including the vertical and lateral on-bottom instabilities, the tunnel-erosion of the underlying soil and the subsequent vortex-induced vibrations (VIVs) of free-spanning pipelines. This paper reviews the recent advances of the slip-line field solutions to the bearing capacity, the flow-pipe-soil coupling mechanism and the prediction for the lateral instability, the multi-physical coupling analysis of the tunnel-erosion, and the coupling mechanics between the VIVs and the local scour. It is revealed that the mechanism competition always exists among various instability modes, e.g., the competition between the lateral-instability and the tunnel-erosion. Finally, the prospects and scientific challenges for predicting the instability of a long-distance submarine pipeline are discussed in the context of the deep-water oil and gas exploitations.

Parametric Vibrations of Pipelines with Compensating Inserts

Possible transverse parametric vibrations of pipelines with compensating inserts are described and the basic relationships needed to calculate the amplitude of transverse vibrations are presented.

Failure of industrial pipelines due to low-frequency vibrations

A nonstationary gas flow in the piping of a compressor station at the entrance to a gas pipeline has been considered. Factors that affect the emergence and development of gas flow pulsations that result in hazardous low-frequency pipeline vibrations have been studied. A mathematical model of the process is described. The system of acoustic-approximation equations is used that makes it possible to allow for the tree-type topology of pipeline network in the booster part of a compressor station, with 90-deg pipe turns, the presence of obstacles in the form of shut-off and control valves, and pipeline pitch being disregarded.

Protection of pipeline bridges against vibrations caused by a water hammer

In pipeline systems, bridges are much more exposed to exceptional loadings and related failures than other elements of hydraulic plants. Water hammer, a phenomenon of abrupt change in fluid pressure caused by e.g. the sudden closing or opening of a valve, pump failure or a power cut, is an example of such loading. The reasons for this phenomenon and the possible failure it can cause are discussed in the article. An overview of the currently used protection methods against a water hammer and the possibilities to improve the construction of the devices that are used for such protection are shown. The effectiveness of three selected systems of protecting against a water hammer is discussed in detail. It is underlined that in the case of large-span pipeline bridges, especially suspension bridges, natural frequencies of the bridge can coincide with the frequency of the fluid pressure wave caused by a water hammer. This resonance can cause excitation of pipeline bridge vibrations. The possibilities of eliminating pipeline vibrations by applying vibration absorbers or flexible supports are pointed out. The importance of the need of detailed structural dynamic analysis and the determination of eigenfrequencies with their corresponding eigenforms is highlighted.

Spatial aperiodic vibrations of the pipelines under transient internal pressure

The influence of the average value and amplitude of the transient internal pressure in the pipelines on the spatial vibrations of the latter has been assessed. The graphic dependences of the spatial vibrations, their phase patterns, Fourier spectra, and Poincare maps have been presented. The latter have been analyzed depending on the input parameters and time. Brief conclusions have been formulated.

Vibration and damping analysis of aerospace pipeline conveying fluid with constrained layer damping treatment

The constrained layer damping materials are thoroughly used to control the vibration duo to their high capacity to dissipate vibration energy. Researchers have handled the vibration and damping behavior of the constrained layer damping structures accurately. However, for the constrained layer damping pipeline conveying fluid, there are few works on the investigation of the vibration characteristics. This paper is aimed to investigate the vibration and damping characteristics of the constrained layer damping pipeline conveying fluid under elastic boundary supports. Considering the fluid–structure interaction, the developed finite element method is employed to establish the motion equations of the constrained layer damping pipeline. The influence of the support stiffness, the fluid velocity and pressure, the thickness and the elasticity modulus of viscoelastic, and constraining layer parameters are all considered. The results indicate that an appropriate selection of the boundary support stiffness, the viscoelastic, and constraining layer parameters can obtain desirable modal properties, which can provide an efficient tool in the design and maintenance of aerospace pipeline for passive vibration control.

Free vibrations of thin-walled semi-underground main gas pipelines of large diameter, with the attached ground mass

In this paper, we solve the problem of free bending vibrations of the main thin-walled large-diameter pipeline, corresponding semi-underground laying type. As a result, vibration process involves a pipeline to move the surrounding ground, which significantly affects the frequency free vibrations. The values of the natural frequencies of the pipeline will depend on the characteristics of the ground, and it’s mass. The decision takes into account the impact of the attached ground mass on the free vibration frequency based on the geometrically nonlinear version of semi-momental theory of average bending cylindrical shells.

Study on Influence of Fluid Parameters on Axial Coupled Vibration of Pipeline Conveying Multiphase Flow

Taking a slurry reservoir-pipeline-valve system as research object, axial dynamic vibrations of pipe system were induced by coupled hydraulic transient due to rapid closure of valve at the end of pipe. The influences of fluid parameters in multiphase flow, including void fraction, density ratio, and elastic modulus ratio between solid phase and liquid phase, on vibration behaviors of pipe system were analyzed. Results of this study show that wave velocities of pressure and stress can be attenuated evidently when void fraction in multiphase fluid is increased appropriately; meanwhile, the amplitudes of pressure fluctuation and pipe vibration are also weakened obviously. With the increase of density ratio between solid phase and liquid phase, the vibrational intension of pipe system becomes stronger and stronger. In this instance, the increments of vibrational energy mainly concentrate in fluid, which leads the pressure energy of fluid to rise up quickly. When elastic modulus ratio between solid phase and liquid phase increases, the total elasticity of fluid decreases gradually. At the same time, both pressure energy of fluid and vibrational intension of pipe are enhanced but the increments are very slight.

CALCULATION-EXPERIMENTAL SUBSTANTIATION OF VIBRATION STRENGTH OF NUCLEAR POWER PLANT PIPELINES BASED ON THE QUASI-STATIC APPROACH

In accordance with NP-096-15 [1], management of equipment and pipelines resources at the stages of design, operation and decommissioning should be based on the evaluation of the technical condition and residual life; identifi cation of the dominant (controlling) mechanisms of aging, degradation and damage of equipment and pipelines of nuclear power plants (NPP); the constant improvement of monitoring processes of aging, degradation and damage of equipment and pipelines of nuclear power plants. Despite the progress in computer development in recent decades, its capabilities are still insuffi cient to solve equations of hydrodynamics when high Re numbers are of practical interest (solution instability: arbitrarily small perturbation radically alters the stability of the solution of the Navier-Stokes equations). Challenges remain in the verifi cation of CFD codes. Due to the complex spatial confi guration of diff erent functional purpose piping systems of NPPs, as well as the specifi cs of the hydro-elastic interaction of the fl ow and tubing, calculation methods to evaluate the dynamic stress-strain state can be selected only based on the results of experimental measurements of vibration parameters of pipelines. The vibration parameters of the pipelines are the vibrational acceleration, velocity and displacement. Vibration of piping from the point of view of resource is classifi ed as high cycle fatigue, which, due to its specifi cs, requires adopting conservative approaches in substantiation of vibration strength of pipelines. As the pipelines are operating within the elastic deformation, the strength test with time-dependent load can in some cases be replaced with a quasistatic calculation. A numerical experiment illustrates the application of the quasistatic approach that gives satisfactory results. Substantiated application of the quasistatic approach is based on the analysis of the spectral density of the pipeline vibration at diff erent points of measurement and can be eff ectively used to assess vibrostresses, fracture toughness and substantiation of vibration strength of NPP pipelines.

基于HHT的航空发动机液压管路系统管路故障诊断研究

针对航空发动机液压管路系统在实际工作中由于振动过大产生的卡箍松脱故障，通过电磁振动台模拟宽频域液压管路基础激励环境，采用光纤光栅分步式监测系统，利用HHT方法可以对航空发动机液压管路系统振动信号中的突变信号进行有效的侦测。HHT分析方法能够反映航空发动机液压管路系统的故障振动响应的不同状态，由此进行航空发动机液压管路系统振动信号的检测具体实施步骤。最后结果表明，采用HHT方法与光纤光栅监测系统能够实现航空发动机液压管路故障的定位和判定。 The objective in this paper is to present HHT method and FBG technology to analyze the aero-engine hydraulic pipeline vibration signal under fault states. Fault diagnosis and location of aero-engine hydraulic pipeline vibration signals based on HHT method and FBG method are ap-plied through HYPERLINK electromagnetic vibration table simulating wide frequency band under clamp loosing and trip state. The results tested in aero-engine hydraulic pipe show that HHT method can clearly reflect the real vibration characteristics of hydraulic pipe under different states. This method overcomes the disadvantage of the traditional Fourier transform (FFT) which cannot obtain the instantaneous frequency of aero-engines, and provides a new idea for the non- stationary vibration information of hydraulic pipe under different states. Fault diagnosis and location of the aero-engine hydraulic pipeline are confirmed by HHT and FBG method.