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Piping system is the main structure in many industrial applications, especially for large industry relating with processing and transporting fluids, such as oil and gas industries. The fluid-induced vibration is often the cause of structural fatigue in pipes and therefore piping vibration need to be closely monitored. In case of high piping vibration, knowledge of the natural frequency of a pipe section is crucial for an engineer to propose the right troubleshoot action, either for a temporary or even for a long-term solution for the piping vibration. Therefore, prediction of the pipe natural frequency using a simple formulae is thus of interest, without dealing with complex numerical simulation using a commercial software which consumes cost and time. In this paper, the vibration mode shapes of various possible geometries of pipes in practice were simulated in ANSYS and the simulated natural frequency is related to a natural frequency of an Euler-Bernoulli beam using a correction factor for each corresponding piping geometry. This paper extends the previous work by allowing the boundary conditions of the pipe ends to be simply supported, in addition to the clamped edges. In this way, the frequency factor charts are presented in the range of possible correction factor values to accommodate the real conditions of pipe arrangement in practical application. An experiment from a case study to verify the proposed method is also presented.

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Many devastating earthquakes exceeding the design basis levels have occurred in the past. Safety assessment of equipments and piping systems of industrial/nuclear safety related structures subjected to earthquakes beyond design basis levels necessitates consideration of the structural nonlinearity. The In-structure or floor response spectra (FRS) are the input required for qualification of these systems and hence it is essential to generate this input considering structural nonlinearity. This paper addresses the experimental and analytical work on generation of FRS for nonlinear Reinforced Cement Concrete (RCC) structure. Push over and shake table experiments are performed on three storeyed RCC framed structure. A simplified analytical approach is proposed to derive earthquake-induced In-structure response spectra for the structure deforming beyond elastic limits. In this approach, initially, the performance of the structure is evaluated using pushover analysis. Floor spectra of the structure are then obtained considering the degraded stiffness and increased damping evaluated at each performance level iteratively from pushover curve. The floor spectra of the structure generated by the proposed method are validated using experimentally simulated results from shake table tests. [ABSTRACT FROM AUTHOR]

Flow induced vibration problem of an in-service duplex stainless steel piping system was investigated in previous research. The investigation required multiple sets of site measurement results at the offshore gas processing platform which raises the concerns of safety and its practicality. A lab scale of the mentioned piping system is preferable to study the flow induced vibration problem at different operating conditions to better understand the dynamic behaviour of this piping system. In addition, most of the dimensional analyses were performed either solely on structure or fluid system. System with flow induced vibration problem has never been attempted and thus it is important to perform similitude study of the piping system prior to fabrication of the lab scale model. Buckingham Pi theorem was applied and the similitude was verified by computational mechanics both qualitatively and quantitatively. The calculated non-dimensional variables of a scaled piping system in describing the flow characteristics which contribute to the structure deformation give similar scale factor, flow pattern and flow induced dynamic deformation and stress in this fluid-structure interacted piping system indicating that geometric, kinematic and dynamics similarity are achieved. [ABSTRACT FROM AUTHOR]

The axial vibration of liquid-pipes, considering the fluid-structure interaction (FSI), can be described by a four-equation model consisting of two equations for the fluid and the other two for the pipe wall. When distributed friction and damping were neglected, the model could be solved with an exact solution developed from the method of characteristics (MOC). The exact solution with a simple recursion process was presented instead of meshing the distance-time plane, introducing no numerical error, while the only weakness was the high time cost. An improved method based on this exact solution is proposed in this work, using the time-line interpolation rather than the recursive algorithm to speed the calculation. As numerical diffusion and oscillation affect the accuracy a lot, various interpolation techniques are investigated and compared. The mean absolute error (MAE) and the structural similarity index measure (SSIM) are employed to assess the accuracy of proposed methods, and the latter was originally developed for the image quality assessment. A hybrid interpolation scheme, mixing the cubic spline and linear interpolation, is proposed and achieves the highest accuracy and the quadratic-linear interpolation is found to be a good choice considering both accuracy and efficiency. The solution method developed here improves the efficiency significantly while retains an acceptable level of the accuracy, especially suitable for the long duration event. [ABSTRACT FROM AUTHOR]

This study presents a noncontact measurement method of vibration induced stress (vibration stress) using multiple laser displacement sensors and clarifies its applicability to piping vibration. In the beam structures such as piping, the stress due to bending deformation can be caused by vibration. In the presented method, the vibration displacement in the beam structures induced by the bending deformation is measured at three different locations using laser displacement sensors in a noncontact manner and the vibration stress is estimated by a simple calculation based on the beam theory. First, an applicability validation of the presented method was done by a vibration test using a cantilevered beam plate. This validation was done by comparing measurements by the presented method and the conventional method using strain gauges. Next, an experimental validation was conducted by the vibration test using a pipe specimen, and the applicability to the piping vibration was confirmed. [ABSTRACT FROM AUTHOR]

In this study, two methods to measure bending and torsional vibration stresses of piping systems conveniently and quickly are proposed. The proposed methods are composed of a modeling approach of piping vibration and noncontact measurement techniques. The methods assume the vibration modes as a primary mode within the measuring range without the mode-identification and then estimate the vibration stress by approximating the vibration displacements measured in a noncontact manner as a primary mode. This paper presents the principles and calculation formulas of both methods and shows the measurement techniques for the bending and torsional vibration stresses using laser displacement sensors. Finally the applicability of one method is discussed based on the results of a vibration experiment. [ABSTRACT FROM AUTHOR]

Accurate evaluation of occurrence location and amplitude of pressure pulsations in a piping system can lead to efficient plant maintenance to prevent fatigue failure of piping and components because the pulsations could be main causes of vibration fatigue and acoustic noise in piping. To measure pressure pulsations easily and directly, a method to combine strain measurement on outer surface of pipe with the formula for thick-walled cylinders was proposed. The experimental validation demonstrated the proposed method could measure amplitudes and behavior of pressure pulsations with a practical accuracy. Furthermore, the applicability of the formula for thin-walled cylinders was examined for various shaped pipes.

A dynamic vibration absorber (DVA) can be used as an effective vibration control device. It is essentially a secondary mass, attached to an original system via a spring and damper. The natural frequency of the DVA is tuned such that it coincides with the frequency of unwanted vibration in the original system. This results in absorption of the inertial energy transferred from the primary structure. This work aims at developing an adaptive-passive dynamic vibration absorber with the help of shape memory alloy (SMA) springs in order to attenuate the vibration for a range of excitation frequencies. In this paper, the unique property of SMAs temperature-dependent Young’s modulus has been used to change the stiffness of the spring actively to control the vibration. Experiments were carried out with an SMA-based dynamic vibration absorber to study the effect of reduction in amplitude of vibration of a cantilever structure. A microcontroller-based control system has been developed for timely actuation of SMA and to supply optimum current to the SMA springs connected in parallel. The experimental results show that the SMA-based dynamic vibration absorber is more effective in reducing the amplitude of vibration for a wider frequency range. The developed SMA-based DVA is used to damp out the vibration in piping applications. The effectiveness of adaptive-passive DVA in controlling the vibration for a range of excitation frequencies was proved. [ABSTRACT FROM AUTHOR]

Due to the occurrence of abnormal vibration of reciprocating compressor inlet pipelines during the commissioning of a booster station, the cause of severe vibration problem was investigated, which included modal analysis, calculation of resonant piping length, velocity frequency spectrum analysis, and pressure pulsation measurement. It was found that the inlet pipelines avoided low frequency resonance region, the actual length of the inlet pipelines was in the second resonant piping length, and the pressure pulsation far exceeded API 618 standard. The results indicate that large pressure pulsation and acoustic resonance occurred on the inlet pipelines are the key factors inducing vibration. Vibration elimination treatments included enlarging the buffer volume of gathering manifold, adjusting the inlet piping length to avoid acoustic resonance, and increasing the curvature radius of bend. After remodeling of the inlet pipelines, the test data indicate that the vibration level of the inlet pipelines is reduced to an acceptable level defined by a relevant standard, and the processing capacity of the booster station can be raised at least two times. [ABSTRACT FROM AUTHOR]

Failures of geothermal system pipes are often caused by limescale buildup on the walls of the pipes. The primary aim of this work is to investigate the influence of the scale formed on the walls of the pipes on the vibration parameters and natural frequencies of pipelines. To this end, the different phases of deposition are artificially simulated in the model experiments. In the different states, vibration tests are preformed to evaluate the status of the pipe section and the rate of deposition by a nondestructive technique. The experimental system is also analyzed by the finite element method (FEM), and the obtained results are compared. [ABSTRACT FROM AUTHOR]

Theeffect of low-frequency vibrations (LFVs) on the thermal performanceof an oscillating heat pipe (OHP) was investigated experimentally.The thermal resistance of the OHP was evaluated under different conditions(e.g., heat rates, filling ratios, and frequencies). Results showthat the LFVs added in the OHP have a significant effect on the heat-transferperformance, which is dependent on the applied frequency. The LFVsremoved the “dry-out” and improved the thermal performanceof the OHP at the lower filling ratio and higher heat transfer rate. [ABSTRACT FROM AUTHOR]

• Applicability of proposed noncontact vibration measurement method was demonstrated. • Influential factors on measurement accuracy were clarified. • Errors due to influential factors were evaluated quantitively. • Measuring accuracy of proposed method was comparable to that of strain gauge method. The purpose of this study is to verify the applicability of the proposed noncontact measurement method of vibration stress using multiple laser displacement sensors. In order to demonstrate its applicability, the factors that influence the measurement accuracy were investigated. Since the proposed method has a simple measurement theory and few restrictions on measurement conditions, it can be applied to vibration measurement of various beam-shaped structures such as pipes. However, in actual vibration measurement, it is expected that an inherent error will occur due to the basic principle of the proposed method. Identification and quantitative evaluation of the influential factors that cause the error are important basic findings for determining the practical application of the proposed method. First, based on the basic principle of the proposed method, the influential factors that can occur due to the use of the laser displacement sensor were clarified. Second, the errors caused by the identified influential factors were quantitatively evaluated. Third, a vibration test was performed to verify the identified influential factors and the errors caused by those factors. Finally, from the obtained results, the applicability of the proposed method was demonstrated, and measures for further improving the accuracy were suggested. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to present a systematic and structured approach to piping vibration assessment and control. Piping vibration assessment is a complex subject, since there are no general analytical methods for dealing with vibration problems. It was noted that most existing vibrating piping systems had poor or degraded support arrangements. This approach therefore focuses mainly on vibration control through assessing and improving the supporting systems. Vibration theory has not been covered in any detail. A simplified procedure is presented for the Integrity custodian to determine when a simple assessment may be carried out and when specialist/consultant services are required. The assessment techniques are based on simplifying assumptions, good rules of thumb and available literature and current practices. A typical case study is used to illustrate the use and the flexibility of the above approach. A standard sheet is proposed to record and document the assessment and recommendations. [Copyright &y& Elsevier]

Previous experimental investigations have shown that when a narrow pipe is inserted into a granular bed and is vibrated vertically but the granular bed is kept still, the grains in the bed can enter the pipe and rise against gravity along the pipe and finally stabilized at a certain height. The growth velocity and final stable height of the grain column inside the pipe can be controlled by varying the vibration conditions. In this paper, we discuss those experimental findings. We establish a mathematic relation between the grain column height (h) and time (t), and by using the relation we discuss the change of the growth velocity (dh/dt) and acceleration (d2h/dt2) with t and h, respectively. We also analyze the mechanism of the rising motion of the grains during vibration. Furthermore, we derive a theoretical expression for describing the final stable height (hst), which shows that the main factors influencing the height are vibration strength (Γ ), bulk density of grains, inner diameter of the pipe, and vibration frequency, and that hst increases nonlinearly in the presence of air and linearly in a vacuum environment with increasing Γ. [ABSTRACT FROM AUTHOR]