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.

scholarly journals Effect of Thrust on the Structural Vibrations of a Nonuniform Slender Rocket

2020 ◽  
Vol 25 (2) ◽  
pp. 29
Author(s):  
Desmond Adair ◽  
Aigul Nagimova ◽  
Martin Jaeger
Keyword(s):  
Natural Frequencies ◽  
Equations Of Motion ◽  
Approximate Solutions ◽  
Mode Shapes ◽  
Algebraic Equations ◽  
Structural Vibrations ◽  
Unknown Parameters ◽  
One Dimensional ◽  
Vibration Problems ◽  
Nonuniform Beam

The vibration characteristics of a nonuniform, flexible and free-flying slender rocket experiencing constant thrust is investigated. The rocket is idealized as a classic nonuniform beam with a constant one-dimensional follower force and with free-free boundary conditions. The equations of motion are derived by applying the extended Hamilton’s principle for non-conservative systems. Natural frequencies and associated mode shapes of the rocket are determined using the relatively efficient and accurate Adomian modified decomposition method (AMDM) with the solutions obtained by solving a set of algebraic equations with only three unknown parameters. The method can easily be extended to obtain approximate solutions to vibration problems for any type of nonuniform beam.

Nonlinear Combination Resonances in Cantilever Composite Plates

1995 ◽  
Author(s):  
Kyoyul Oh ◽  
Ali H. Nayfeh
Keyword(s):  
Natural Frequencies ◽  
Excitation Frequency ◽  
Power Spectra ◽  
Low Frequency ◽  
Composite Plates ◽  
High Amplitude ◽  
Mode Shapes ◽  
Laser Vibrometer ◽  
Combination Resonance ◽  
Response Curves

Abstract We experimentally investigated nonlinear combination resonances in a graphite-epoxy cantilever plate having the configuration (–75/75/75/ – 75/75/ – 75)s. As a first step, we compared the natural frequencies and mode shapes obtained from the finite-element and experimental modal analyses. The largest difference in the obtained frequencies was 2.6%. Then, we transversely excited the plate and obtained force-response and frequency-response curves, which were used to characterize the plate dynamics. We acquired time-domain data for specific input conditions using an A/D card and used them to generate time traces, power spectra, pseudo-state portraits, and Poincaré maps. The data were obtained with an accelerometer monitoring the excitation and a laser vibrometer monitoring the plate response. We observed the external combination resonance Ω≈12(ω2+ω5) and the internal combination resonance Ω≈ω8≈12(ω2+ω13), where the ωi are the natural frequencies of the plate and Ω is the excitation frequency. The results show that a low-amplitude high-frequency excitation can produce a high-amplitude low-frequency motion.

The Use of Interference Diagrams to Avoid Impeller Resonance: An Application to IGV Design

2009 ◽  
Author(s):  
Marco Ferioli
Keyword(s):  
Centrifugal Compressor ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Common Source ◽  
Operating Speed ◽  
Element Analysis ◽  
Exciting Frequency ◽  
Combine Information ◽  
The Impact

Interference diagrams can be used to avoid the potential excitation of a particular mode of vibration for centrifugal compressor impellers, thus reducing the risk of fatigue failures. Such diagrams are an excellent tool to combine information on impeller natural frequencies and mode shapes, excitation sources and operating speed of the machine on the same graph. Once the impeller design has been finalized in terms of aerodynamic performance, structural assessments and therefore geometry, Finite Element Analysis can be used to predict its natural frequencies and mode shapes (i.e. nodal diameters). Results can therefore be shown on a chart, together with the operating speed range of the machine. The need to plot on a single diagram this whole set of data arises from the mathematical evidence to consider the frequency of vibration together with the mode shape and the shape of the exciting force, while analyzing resonances. Typical Campbell diagrams are unable to provide this information at a glance. A common source of excitation for the first impeller of centrifugal compressors is the IGV set. Inlet Guide Vanes produce an exciting frequency that is directly proportional to the number of vanes N, where N represents also the shape of the excitation. The interference diagram can therefore be used: • to design and optimize the IGV for a new machine; • to choose between two different designs; • to evaluate the impact of a new IGV for the impeller of an existing compressor. A case study will be introduced, in order to show the application of interference diagrams to avoid potentially dangerous resonances between an IGV set and the first impeller during the re-design phase for a centrifugal compressor already in operation.

Performance-Based Analysis of Coupled Support Structures and Piping Systems Subject to Seismic Loading

2015 ◽  
Author(s):  
Oreste S. Bursi ◽  
Fabrizio Paolacci ◽  
Md Shahin Reza
Keyword(s):  
Seismic Design ◽  
Seismic Analysis ◽  
Design Method ◽  
Design Guidelines ◽  
Piping System ◽  
Support Structures ◽  
Limit States ◽  
Piping Systems ◽  
Allowable Stress Design

The prevailing lack of proper and uniform seismic design guidelines for piping systems impels designers to follow standards conceived for other structures, such as buildings. The modern performance-based design approach is yet to be widely adopted for piping systems, while the allowable stress design method is still the customary practice. This paper presents a performance-based seismic analysis of petrochemical piping systems coupled with support structures through a case study. We start with a concept of performance-based analysis, followed by establishing a link between limit states and earthquake levels, exemplifying Eurocode and Italian prescriptions. A brief critical review on seismic design criteria of piping, including interactions between piping and support, is offered thereafter. Finally, to illustrate actual applications of the performance-based analysis, non-linear analyses on a realistic petrochemical piping system is performed to assess its seismic performance.

Free Vibration of a Spinning Stepped Timoshenko Beam

2000 ◽  
Vol 67 (4) ◽  
pp. 839-841 ◽  
Author(s):  
S. D. Yu ◽  
W. L. Cleghorn
Keyword(s):  
Free Vibration ◽  
Timoshenko Beam ◽  
Natural Frequencies ◽  
Equation Of Motion ◽  
Mode Shapes ◽  
The Finite Element Method ◽  
Linear Transformations ◽  
Stepped Beam ◽  
Uniform Cross Section ◽  
Vibration Problems

The finite element method is employed in this paper to investigate free-vibration problems of a spinning stepped Timoshenko beam consisting of a series of uniform segments. Each uniform segment is considered a substructure which may be modeled using beam finite elements of uniform cross section. Assembly of global equation of motion of the entire beam is achieved using Lagrange’s multiplier method. The natural frequencies and mode shapes are subsequently reduced with the help of linear transformations to a standard eigenvalue problem for which a set of natural frequencies and mode shapes may be easily obtained. Numerical results for an overhung stepped beam consisting of three uniform segments are obtained and presented as an illustrative example. [S00021-8936(01)00101-5]

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.

Experimental Study of the Dynamic Response of Partially Filled Pipes Focused on Natural Frequencies and Mode Shapes

2017 ◽  
Author(s):  
Oscar de la Torre ◽  
Xavier Escaler ◽  
Jamie Goggins
Keyword(s):  
Natural Frequencies ◽  
Dynamic Properties ◽  
Computational Cost ◽  
Computational Effort ◽  
Mode Shapes ◽  
Significant Drop ◽  
Fluid Structure ◽  
Hydraulic Machinery ◽  
Piping Systems ◽  
Pipe Geometry

The presence of air in piping systems is a major concern in the industry. Problems like flow disruption, reduction of hydraulic machinery efficiencies or a significant drop in pipe capacity are many times related to this fact. The present paper aims to find a simple and non-intrusive experimental method to detect air in piping systems. The method, based on the dynamic properties of fluid-structure systems and underpinned by a novel low computational cost numerical simulation, accurately predicts the volume of water present in a pipe. Good agreement between numerical and experimental solutions has been obtained using much less computational effort than traditional fully coupled Fluid Structure Interaction with CFD analysis. From the numerical and experimental data, two different mathematical expressions relating the system natural frequencies, both vertically and horizontally, and the area occupied by the water have been obtained. These expressions account for the pipe geometry which theoretically would make them suitable for other diameter and wall thickness values. The paper is combined with a preliminary study of the system’s mode shapes for the different volumes of water.

The “Smeared” Property Technique for the FE Vibration Analysis of Printed Circuit Cards

1991 ◽  
Vol 113 (3) ◽  
pp. 250-257 ◽  
Author(s):  
J. M. Pitarresi ◽  
D. V. Caletka ◽  
R. Caldwell ◽  
D. E. Smith
Keyword(s):  
Natural Frequencies ◽  
Primary Objective ◽  
Mode Shapes ◽  
Fe Model ◽  
Printed Wiring Board ◽  
Modal Assurance Criterion ◽  
Printed Circuit ◽  
Wiring Board

The primary objective of this paper is to investigate the accuracy of the finite element (FE) smeared properties approach for the determination of the mode shapes and frequencies of a printed wiring board (PWB) populated with electronic modules. Smearing of the material and/or structural properties is a recognized means of reducing a complicated structure to a less complicated approximation. Comparisons of both the natural frequencies and mode shapes are made between the smeared FE model and those obtained from vibration testing. The extent of correlation between the mode shapes is characterized by the modal assurance criterion (MAC). Since the intent of this study is to examine the effectiveness of the smearing technique, free boundary conditions are assumed. It is shown that the smearing technique can produce good correlation of both natural frequencies and mode shapes of PWBs populated with modules. A case study of a PWB with both surface mount technology (SMT) and pin-in-hole (PIH) components is presented.

Vibration Analysis of a Railway Carbody Model as a Non-Circular Cylindrical Shell

2007 ◽  
Author(s):  
Yukinori Kobayashi ◽  
Kotaro Ishiguri ◽  
Takahiro Tomioka ◽  
Yohei Hoshino
Keyword(s):  
Cylindrical Shell ◽  
Natural Frequencies ◽  
Circular Cylindrical Shell ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Elastic Vibration ◽  
Mode Shapes ◽  
Simply Supported ◽  
Vibration Problems ◽  
Good Agreement

Railway carbody is modeled as a non-circular cylindrical shell with simply-supported ends in this paper. The shell model doesn’t have end plates of the carbody and other equipments attached to actual carbody are neglected. We have applied the transfer matrix method (TMM) to the analysis of three-dimensional elastic vibration problems on the carbody. We also made a 1/12 size carbody model for experimental studies to verify the validity of the numerical simulation. The model has end plates and was placed on soft sponge at both ends of the model to emulate the freely-support. The modal analysis was applied to the experimental model, and natural frequencies and mode shapes of vibration were measured. Comparing the results by TMM and the experiment, natural frequencies and mode shapes of vibration for lower modes show good agreement each other in spite of differences of boundary conditions.

Mistuning Analyses of a Bladed Disk: Pole-Zero and Modal Approaches

2008 ◽  
Author(s):  
Alok Sinha
Keyword(s):  
Natural Frequencies ◽  
Peak Amplitude ◽  
Mode Shapes ◽  
Bladed Disk ◽  
Amplitude Maximum ◽  
Excitation Frequencies ◽  
Amplitude Amplification

This paper examines the fundamental aspects of amplitude amplification due to mistuning in a bladed disk. Both pole-zero and modal approaches are used to understand the effects of changes in mode shapes and the natural frequencies on the minimum and maximum values of peak amplitudes among all blades over all excitation frequencies. The nature of variation of this peak amplitude is studied, and algorithms are discussed to determine the statistics of the peak amplitude, maximum and minimum values of the peak amplitude, and corresponding mistuning patterns.

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