Modal Analysis of Vibrations in Liquid-Filled Piping Systems

1990 ◽  
Vol 112 (3) ◽  
pp. 311-318 ◽  
Author(s):  
M. W. Lesmez ◽  
D. C. Wiggert ◽  
F. J. Hatfield
Keyword(s):  
Modal Analysis ◽  
Transfer Matrix ◽  
Wave Equations ◽  
Axial Stress ◽  
Fluid Pressure ◽  
Mode Shapes ◽  
Piping System ◽  
Long Wavelength ◽  
Piping Systems ◽  
Single Pipe

The motions of liquid-filled pipe reaches in which long wavelength assumptions are valid can be described by Poisson-coupled axial stress waves in the pipe and in the liquid column, and in the piping structure, by torsional and flexural waves. Based on linearized assumptions, a simultaneous solution of the wave equations is presented. Eigenvalues and mode shapes are derived for the variables fluid pressure and displacements, and pipe forces and displacements. The results are assembled into a transfer matrix, which represents the motion of a single pipe section. Combined with point matrices that describe specified boundary conditions, an overall transfer matrix for a piping system can be assembled. Corresponding state vectors can then be evaluated to predict the piping and liquid motion, and the accompanying forces. The results from two experimental piping systems are compared with the ones obtained by the modal analysis method.

Frequency Domain Analysis of Vibrations in Liquid-Filled Piping Systems

1999 ◽  
Author(s):  
Zongxia Jiao ◽  
Qing Hua ◽  
Kai Yu
Keyword(s):  
Frequency Domain ◽  
Transfer Matrix ◽  
Fluid Structure Interaction ◽  
Viscous Friction ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Piping System ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Piping Systems

Abstract In the analysis of liquid-filled piping systems there are Poisson-coupled axial stress waves in the pipe and liquid column, which are caused by the dilation of the pipe. In some conditions the influence of viscous friction that is usually frequency-dependent should not be omitted, which in fact is another kind of coupled form. It directly influences the amplitude of vibration of piping systems to some degree. The larger the viscosity of the liquid is, the greater the influence will be. Budny (1991) included the viscous friction influence in time domain analysis of fluid-structure interaction, but did not give frequency domain analysis. Lesmez (1990) gave the model analysis liquid-filled piping systems without considering friction. If the friction is not included in frequency domain analysis, the vibration amplitude will be greater than that when friction is included, especially at harmony points, cause large errors in the simulation of fluid pipe network analysis, although it may have little influence on the frequency of harmony points. The present paper will give detail solutions to the transfer matrix that represents the motion of single pipe section, which is the basis of complex fluid-structure interaction analysis. Combined with point matrices that describe specified boundary conditions, overall transfer matrix for a piping system can be assembled. Corresponding state vectors can then be evaluated to predict the piping and liquid motion. At last, a twice-coordinate transformation method is adopted in joint coupling. Consequently, the vibration analysis of spatial liquid-filled piping systems can be carried out. It is proved to be succinct, valid and versatile. This method can be extended to the simulation of the curved spatial pipeline systems.

A Dynamic Investigation of Piping Systems With a Bolted Flange

2002 ◽  
Author(s):  
William H. Semke ◽  
George D. Bibel ◽  
Sukhvarsh Jerath ◽  
Sanjay B. Gurav ◽  
Adam L. Webster
Keyword(s):  
Dynamic Response ◽  
High Strength ◽  
Mode Shapes ◽  
Piping System ◽  
Resonant Frequencies ◽  
Experimental Procedure ◽  
Piping Systems ◽  
Response Output ◽  
Bolted Flange ◽  
Dynamic Investigation

The dynamic response of piping systems with a bolted flange is analyzed. Experimental and numerical analyses and results are presented and show excellent correlation. An overhanging piping system at various span lengths with a flange at mid-length is used. The testing configuration consists of a standard 2-in. (51 mm) schedule 40 steel pipe and an ANSI B16.5 class 300-pound flange. The presence of a spiral wound wire gasket and high strength flange bolts is also assessed. Included are multiple resonant frequencies and their respective mode shapes for various span lengths and gasket configurations. The experimental procedure utilizes an accelerometer to gather the dynamic response output of the piping system due to an impulse. The resonant frequencies are then determined using a Fast Fourier Transform (FFT) method. The numerical analysis is conducted using the commercial Finite Element (FE) code ANSYS®. Both methods take into account the complex interaction between the flange and gasket and their impact on the entire piping system. The dynamic effects of a bolted flange and gasket on a piping system are critical in their use and a summary of the results for a variety of configurations is presented.

Computer Piping Analysis, ASME B31.3 Appendix S: Example S3 — Moment Reversal

2007 ◽  
Author(s):  
Don R. Edwards
Keyword(s):  
Stress Analysis ◽  
Petroleum Refinery ◽  
Axial Stress ◽  
Piping System ◽  
Stress Range ◽  
Analysis Software ◽  
Process Piping ◽  
Piping Systems ◽  
Operating Stress ◽  
The Impact

The American Standards Association (ASA) B31.3-1959 Petroleum Refinery Piping Code [1] grew out of an ASA document that addressed all manner of fluid conveying piping systems. ASA B31.3 was created long before widespread engineering use of computer “mainframes” or even before the inception of piping stress analysis software. From its inception until recent times, the B31.3 Process Piping Code [2] (hereafter referred to as the “Code”) has remained ambiguous in several areas. This paper describes some of these subtle concepts that are included in the Code 2006 Edition for Appendix S Example S3. This paper discusses: • the effect of moment reversal in determining the largest Displacement Stress Range, • the impact of the average axial stress caused by displacement strains on the Example S3 piping system and the augmenting of the Code Eq. (17) thereto, • a brief comparison of Example S3 results to that of the operating stress range evaluated in accordance with the 2006 Code Appendix P Alternative Requirements.

System Identification and Reduction of Vibrations of Piping in Different Conditions

2013 ◽  
Author(s):  
Gereon Hinz ◽  
Klaus Kerkhof
Keyword(s):  
System Identification ◽  
Boundary Conditions ◽  
Modal Analysis ◽  
Model Updating ◽  
Steel Structure ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Piping System ◽  
Fe Model ◽  
Model Studies

Safe operation, availability and lifetime assessment of piping are of utmost concern for plant operators. The knowledge on how failures in piping and its support construction are reflected in changes of the dynamic behavior (eigen-frequencies, -modes and damping) is a useful basis for System Identification and Structural Health Monitoring (SHM). Modal analysis of complex piping, the identification of system changes and the use of vibration dampers in piping still constitute challenges. In this study three different piping systems are investigated: 1. In the first piping system at a chemical plant, which is supported by a tall steel structure fixed at the base, piping-elbow forces at the top of the building cause large vibration amplitudes. Tuned mass dampers (TMD) for minimizing vibration amplitudes were first tested in the laboratory of MPA Stuttgart and then designed for the piping system in the plant for preventing failures. 2. Another piping system is reported that is excited at resonance frequency to cause failure due to in-plane bending in an elbow with local wall thinning. 3. Finally, a large piping system at a lignite power plant is investigated under ambient vibration to detect changes in boundary conditions. Experimental Output Only Modal Analysis (OOMA) and Operational Modal Analysis (OMA), FE-model studies and model-updating are performed. Changes in the natural frequencies and corresponding mode shapes due to through-wall cracks or changing boundary conditions were observed.

Performance Analysis of Thin Shell Bends under High Pressure and Temperature

2015 ◽  
Vol 787 ◽  
pp. 296-300
Author(s):  
P. Govindaraj ◽  
Mouleeswaran Senthilkumar
Keyword(s):  
High Stress ◽  
Fluid Pressure ◽  
Bending Moment ◽  
Piping System ◽  
High Stress Concentration ◽  
Geometrical Imperfection ◽  
Internal Fluid ◽  
Piping Systems ◽  
The Cost ◽  
Work Effect

Around 70% of the cost in piping industry is spent in the pipe manufacturing with optimum design of pipes without defects. Research on design of pipes has gained importance from the last decade. There are numerous methods being developed to improve the efficiency of piping units considering various parameters. The pipe tends to flatten when they are forced to bend, this geometrical changes has a significant role in the acceptability criteria of pipes. It is necessary to bend pipes in order to transmit liquid or gas from one place to other place. In this work special attention is given to pipe bends because of high stress concentration due to various loading conditions. From several kinds of piping systems, process piping systems are chosen for analysis since pipes used here transport important and hazardous materials. Damage to such piping system can cause serious loss to economy and human lives. The geometrical imperfection associated with bending of pipes is ovality. This degree of ovality determines the acceptance of pipes. Thickening and thinning effects cause additional problems like large plastic deformation and loss of flexibility respectively. Hence estimation of the best degree of ovality is required. In this work effect of ovality is estimated by taking the internal fluid pressure and In plane bending moment into account.

Acoustically Induced Structural Fatigue of Piping Systems

1999 ◽  
Vol 121 (4) ◽  
pp. 438-443 ◽  
Author(s):  
F. L. Eisinger ◽  
J. T. Francis
Keyword(s):  
Fluid Pressure ◽  
Acoustic Vibration ◽  
Piping System ◽  
Metal Fatigue ◽  
Hydrocarbon Gases ◽  
Structural Fatigue ◽  
Piping Systems ◽  
Geometry Parameter ◽  
Acoustic Fatigue ◽  
The Relationship

Piping systems handling high-pressure and high-velocity steam and various process and hydrocarbon gases through a pressure-reducing device can produce severe acoustic vibration and metal fatigue in the system. It has been previously shown that the acoustic fatigue of the piping system is governed by the relationship between fluid pressure drop and downstream Mach number, and the dimensionless pipe diameter/wall thickness geometry parameter. In this paper, the devised relationship is extended to cover acoustic fatigue considerations of medium and smaller-diameter piping systems.

scholarly journals Analysis of Symmetrical and Nonsymmetrical Vertical Expansion Loop to Increase Flexibility And Reduce Pipe Stress Based On ASME B31.3

Teknik ◽  
2021 ◽  
Vol 42 (1) ◽  
pp. 63-70
Author(s):  
Pekik Mahardhika ◽  
Adi Wirawan Husodo ◽  
George Endri Kusuma ◽  
Raden Dimas Endro Witjonarko ◽  
Ekky Nur Budiyanto
Keyword(s):  
Fluid Pressure ◽  
Fluid Flows ◽  
Piping System ◽  
Design Code ◽  
Loop Design ◽  
A Value ◽  
Pipe Expansion ◽  
Study Results ◽  
Piping Systems ◽  
Loop 2

Thepiping system is a medium used to convey, distribute, mix, separate, discharge, meter, control or snub fluid flows, and transmit a fluid pressure. The piping system design will have stresses due to thermal and pressure effect. The thermal effect induce pipe expansion. The pipe expansion affect to pipe flexibility, so it is necessary to design an expansion loop. Expansion loop is a method used to increase flexibility in piping systems. This article aims to analyze symmetrical and non-symmetrical in vertical expansion loops whether it can increase flexibility and reduce pipe stress. This article conducts an expansion loop design with 3 trials, namely trial 1 (Vertical Expansion Loop), trial 2 (Nonsymmetrical Vertical Expansion Loop 1), and trial 3 (Nonsymmetrical Vertical Expansion Loop 2). The three trials were compared for flexibility and stress values based on ASME B31.3 requirements. The study results show that all trial 1, trial 2, and trial 3 have good flexibility with a value of 0.00016 because not exceed the requirements of ASME B31.3. The highest design code stress value in trial 1 is 5955 psi (Node A07F), trial 2 is 5906 psi (Node A05F), and trial 3 is 5906 psi (Node A06N). All trials have a code stress not exceeding the allowable stress (20000 psi). So that the symmetrical or nonsymmetrical design of the vertical expansion loop can both increase flexibility and reduce pipe stress.

Experimental and Numerical Study on Pressure Pulsations Under Various Acoustic Boundary Conditions in Piping Systems

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Akira Maekawa ◽  
Takashi Tsuji ◽  
Michiyasu Noda ◽  
Tsuneo Takahashi ◽  
Minoru Kato ◽  
...  
Keyword(s):  
Power Plants ◽  
Numerical Study ◽  
Fluid Pressure ◽  
Control Valve ◽  
Acoustic Resonance ◽  
Piping System ◽  
Pressure Pulsations ◽  
Improve Design ◽  
Piping Systems ◽  
Experiment And Simulation

To improve design and troubleshooting techniques of piping systems for operating power plants, it is necessary to investigate, by experiment and simulation, the behavior of fluid inside the piping system in detail. This study was conducted using full-scale piping system under conditions that could seriously threaten the plant operation, by matching pressure pulsations, acoustic resonance, and piping natural frequency. Although piping vibration is reported to influence fluid pressure pulsations, there were no such examples of influence in this experiment. Knowing that the opening ratio of the pressure control valve affects the boundary condition for acoustic resonance, experiment and simulation at different opening ratios were conducted. It has been suggested that the cases in which a valve partially open at 25% or less should not be taken as a closed end. This finding conflicts with such a widespread design assumption.

scholarly journals High Vibration Problem in Compressor Piping Systems: A Case Study

1997 ◽  
Author(s):  
G. Vijaya Kumar ◽  
S. Raghava Chary ◽  
A. Rajamani
Keyword(s):  
Natural Frequencies ◽  
Excitation Frequency ◽  
Mode Shapes ◽  
Piping System ◽  
Mechanical Responses ◽  
Normal Limits ◽  
Piping Systems ◽  
Vibration Problems ◽  
Excitation Frequencies

High vibration problems resulting in damage to supports, instrument stubs etc. have been experienced in many compressor piping systems installed at different fertilizer plants. Investigations aimed at a solution to the problem included vibration measurements on the suction and discharge piping, and mathematical modeling of the piping. The measurements indicated presence of an excitation frequency in the range of 30–35% of the compressor running speed. Dynamic analysis of the piping system showed the presence of natural frequencies coinciding with or very near to the excitation frequencies. This has been further confirmed by impact tests. Analytical mode shapes clearly show that the antinodes match with high vibration zones observed at the site. The mathematical models were used to determine optimum configurations which would separate mechanical responses from excitation frequencies. These modifications have been implemented at site and the piping vibrations are within normal limits.

Effect of Bass Bar Tension on Modal Parameters of a Violin's Top Plate

2015 ◽  
Vol 39 (1) ◽  
pp. 145-149 ◽  
Author(s):  
Ewa B. Skrodzka ◽  
Bogumił B.J. Linde ◽  
Antoni Krupa
Keyword(s):  
Modal Analysis ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Normal Value ◽  
Modal Damping

Abstract Experimental modal analysis of a violin with three different tensions of a bass bar has been performed. The bass bar tension is the only intentionally introduced modification of the instrument. The aim of the study was to find differences and similarities between top plate modal parameters determined by a bass bar perfectly fitting the shape of the top plate, the bass bar with a tension usually applied by luthiers (normal), and the tension higher than the normal value. In the modal analysis four signature modes are taken into account. Bass bar tension does not change the sequence of mode shapes. Changes in modal damping are insignificant. An increase in bass bar tension causes an increase in modal frequencies A0 and B(1+) and does not change the frequencies of modes CBR and B(1-).

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