Natural Frequencies and Damping of a Full-Scale Pipe Loop in Air and Water

2017 ◽  
Author(s):  
Hugh Goyder
Keyword(s):  
Oil And Gas ◽  
Natural Frequencies ◽  
Damping Ratio ◽  
Full Scale ◽  
Surrounding Water ◽  
Sea Floor ◽  
Dry Conditions ◽  
Vibration Tests ◽  
Complex Manner ◽  
Submerged Conditions

A full scale pipework system, typical of oil and gas installations located on the sea floor, was subjected to vibration tests in both dry and submerged conditions. The frequency range examined covered 10 Hz to 500 Hz. The objective of the tests was to provide experimental data so that computer simulations could be developed and validated. The method used to determine the vibration properties was that of an experimental modal analysis using an impact hammer. The hammer was modified for underwater use. In dry conditions the damping was found to be very small (damping ratio less than 0.0002) despite the construction being typical. When submerged the effect of the surrounding water was significant. The changes in the natural frequencies from the dry case to the wet case occurred in such a complex manner that it was not possible to identify a simple shift between wet and dry vibration modes. It was necessary to include appropriate added mass coefficients in the computer simulation for both the pipe and the support system. The effect of the surrounding water on the damping was measured but found to be insignificant. It was concluded that immersion in water does not add significant damping to oil and gas pipework.

Effect of guy cable constraint on structural damping of open lattice antenna towers

1980 ◽  
Vol 7 (4) ◽  
pp. 614-620
Author(s):  
J. S. Kennedy ◽  
D. J. Wilson ◽  
P. F. Adams ◽  
M. Perlynn
Keyword(s):  
Natural Frequencies ◽  
Damping Ratio ◽  
Field Tests ◽  
Full Scale ◽  
Structural Damping ◽  
Scale Field ◽  
Modes Of Vibration

This paper presents the results of full-scale field tests on two steel guyed latticed towers. The towers were approximately 83 m in height, were guyed at three levels, and were of bolted angle construction. The observed results consist of the natural frequencies of the first two modes of vibration as well as the damping ratio for the first mode. The observed results are compared with analytical predictions and observations made concerning the contributions of structural and cable action to the damping ratio.

An Experimental Investigation of Added Mass and Damping in Submerged Pipework

2015 ◽  
Author(s):  
Hugh Goyder
Keyword(s):  
Experimental Investigation ◽  
Signal Processing ◽  
Oil And Gas ◽  
Natural Frequencies ◽  
Small Diameter ◽  
Added Mass ◽  
Sea Floor ◽  
Damping Effect ◽  
Signal Processing Methods ◽  
Surrounding Fluid

Oil and gas pipework located on the sea floor may sometimes suffer from vibration and possible failure due to fatigue. The vulnerable pipework is usually the small diameter (typically 2 in) pipes in manifold systems. In order to assess this pipework for vibration it is necessary to know the natural frequencies and damping which are significantly influenced by the surrounding fluid. Measurements have been made on an L-shaped pipe to determine how it is affected by the fluid. Interestingly the effect on damping is small. Consequently experiments have also been performed to see the effect of adding vanes to the pipe. This provides a non-linear form of damping. Special signal processing methods have been developed to investigate this damping effect. The paper presents values for damping for pipes with and without vanes. The effect of the vanes is to significantly increase the damping.

Evaluating Vibration Performance of a Subsea Pump Module by Full-Scale Testing and Numerical Modelling

2016 ◽  
Author(s):  
Pieter J. G. van Beek ◽  
Hajo P. Pereboom ◽  
Harmen J. Slot
Keyword(s):  
Evaluation Criteria ◽  
Full Scale ◽  
Operating Conditions ◽  
Piping System ◽  
Vibration Modes ◽  
Surrounding Water ◽  
Pipe System ◽  
Vibration Performance ◽  
Submerged Conditions ◽  
Pipe Vibration

Prior to subsea installation, a subsea system has to be tested to verify whether it performs in accordance with specifications and component specific performance evaluation criteria. It is important to verify that the assembled components work in accordance with the assumptions and design criteria used in the detailed engineering. These criteria also cover the vibration performance. In the current study, the pump module within the Åsgard subsea compression station has been subjected to such system evaluation test, including its vibration performance. Vibrations may be caused by internal and external flow through a complex process that is affected by numerous factors such as the piping geometry, flow and operating conditions and also the fluid properties. When severe, mechanical vibrations can lead to fatigue failure of the equipment components. One of the major parameters that affects the vibration response of the subsea piping is the surrounding water. It is generally known that surrounding water does participate in some vibration modes by adding mass to the total, dynamic mass participating in the vibration. Therefore, resonant frequencies of a piping system will have different values for non-submerged and submerged cases. In addition, the surrounding water can also lead to higher damping of the vibration modes. In this paper the effect of submerging a pipe system in water is quantified, by analyzing the changes in damping coefficient and the characteristics of measured pipe vibration in-situ. This is achieved by analysis of full-scale frequency response tests performed on a subsea pipe system within the pump module in both non-submerged and submerged conditions. The results are used for validation of numerical techniques that are used to quantify pipe vibration in submerged conditions. Different modeling techniques for the submerged case are investigated. It is shown that the effects from the surrounding water on pipe vibrations are different for small-bore piping than that for main piping. Furthermore the different modeling approaches and general observations and trends in damping coefficients are discussed and compared with the measurements.

scholarly journals Dynamic Property of a New Type of Postearthquake Temporary Prefabricated Lightweight Steel Structure

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
GuoQi Xing ◽  
Qing-hai Li ◽  
JingJie Yu ◽  
Wei Xuan
Keyword(s):  
Finite Element ◽  
Experimental Model ◽  
Dynamic Property ◽  
Natural Frequencies ◽  
Damping Ratio ◽  
Steel Structure ◽  
Full Scale ◽  
Test Method ◽  
Lightweight Steel ◽  
New Type

For a new type of postearthquake temporary prefabricated lightweight steel structure proposed in this paper, mainly composed of steel frame, prefabricated hanger slabs, prefabricated hanger columns, reinforced concrete superposed slabs, etc., parameters of dynamic property for the structure, including natural frequency, vibration mode, damping ratio, etc., are determined by the test method. For prefabricated hanger columns and prefabricated hanger slabs, they are all produced with construction waste in factory and assembled on-site, which can form exterior walls. The united method, based on forced vibration method and ambient random vibration method, can quickly obtain accurate natural frequencies of the full-scale two-story experimental model. In this paper, damping oscillatory method is used to obtain damping ratio which can be determined only by the test method. In order to analyse the modal of the experimental model, a finite element model for the full-scale two-story experimental model is established, where the weight of prefabricated hanger slabs is assumed to be supported by prefabricated hanger columns, and the stiffness of prefabricated hanger columns is also increased. In addition, the connections between lightweight steel frame and prefabricated hanger columns are regarded as flexible connection. Comparing natural frequencies obtained from the finite element method with that obtained from the test method, magnification factor of stiffness for prefabricated hanger column is determined. In the analysis of modal for the full-scale two-story experimental model, the results show that the experimental model satisfies the requirement of design for seismic performance.

Mathematical model of multiphase flow propagation for the case of underwater pipeline damage

2019 ◽  
Vol 14 (2) ◽  
pp. 142-147
Author(s):  
S.R. Kildibaeva ◽  
E.T. Dalinskij ◽  
G.R. Kildibaeva
Keyword(s):  
Oil And Gas ◽  
Control Volume ◽  
Hydrate Formation ◽  
Initial Moment ◽  
Hydrate Shell ◽  
Surrounding Water ◽  
Vertical Coordinate ◽  
Associated Gas ◽  
First Case ◽  
Underwater Pipeline

The paper deals with the case of damage to the underwater pipeline through which oil and associated gas are transported. The process of oil and gas migration is described by the flow of a multiphase submerged jet. At the initial moment, the temperature of the incoming hydrocarbons, their initial velocity, the temperature of the surrounding water, the depth of the pipeline is known. The paper considers two cases of different initial parameters of hydrocarbon outflow from the pipeline. In the first case, the thermobaric environmental conditions correspond to the conditions of hydrate formation and stable existence. Such a case corresponds to the conditions of the hydrocarbons flow in the Gulf of Mexico. In the second case, hydrate is not formed. Such flows correspond to the cases of oil transportation through pipelines in the Baltic sea (for example, Nord stream–2). The process of hydrate formation will be characterized by the following dynamics of the bubble: first, it will be completely gas, then a hydrate shell (composite bubble) will begin to form on its surface, then the bubble will become completely hydrate, which will be the final stage. The integral Lagrangian control volume method will be considered for modeling the dynamics of hydrocarbon jet propagation. According to this method, the jet is considered as a sequence of elementary volumes. When modeling the jet flow, the laws of conservation of mass, momentum and energy for the components included in the control volume are taken into account. The equations are used taking into account the possible formation of hydrate. Thermophysical characteristics of hydrocarbons coming from the damaged pipeline for cases of deep-water and shallow-water pipeline laying are obtained. The trajectories of hydrocarbon migration, the dependence of the jet temperature and density on the vertical coordinate are analyzed.

Measurement of Young’s Modulus and Shear Modulus of Some Structures Welded Using Flux Cored Wire by Vibration Tests

2014 ◽  
Vol 216 ◽  
pp. 151-156 ◽  
Author(s):  
Liviu Bereteu ◽  
Mircea Vodǎ ◽  
Gheorghe Drăgănescu
Keyword(s):  
Shear Modulus ◽  
Arc Welding ◽  
Natural Frequencies ◽  
Free Vibrations ◽  
Vibration Modes ◽  
Cored Wire ◽  
Flux Cored Arc Welding ◽  
Longitudinal Elastic Modulus ◽  
Vibration Tests ◽  
Non Destructive

The aim of this work was to determine by vibration tests the longitudinal elastic modulus and shear modulus of welded joints by flux cored arc welding. These two material properties are characteristic elastic constants of tensile stress respectively torsion stress and can be determined by several non-destructive methods. One of the latest non-destructive experimental techniques in this field is based on the analysis of the vibratory signal response from the welded sample. An algorithm based on Pronys series method is used for processing the acquired signal due to sample response of free vibrations. By the means of Finite Element Method (FEM), the natural frequencies and modes shapes of the same specimen of carbon steel were determined. These results help to interpret experimental measurements and the vibration modes identification, and Youngs modulus and shear modulus determination.

scholarly journals Ambient Vibration Tests of an Arch Dam with Different Reservoir Water Levels: Experimental Results and Comparison with Finite Element Modelling

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Sergio Vincenzo Calcina ◽  
Laura Eltrudis ◽  
Luca Piroddi ◽  
Gaetano Ranieri
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Water Levels ◽  
Arch Dam ◽  
Experimental Results ◽  
Ambient Vibration ◽  
Reservoir Water ◽  
Ambient Vibration Tests ◽  
Vibration Properties ◽  
Vibration Tests

This paper deals with the ambient vibration tests performed in an arch dam in two different working conditions in order to assess the effect produced by two different reservoir water levels on the structural vibration properties. The study consists of an experimental part and a numerical part. The experimental tests were carried out in two different periods of the year, at the beginning of autumn (October 2012) and at the end of winter (March 2013), respectively. The measurements were performed using a fast technique based on asynchronous records of microtremor time-series. In-contact single-station measurements were done by means of one single high resolution triaxial tromometer and two low-frequency seismometers, placed in different points of the structure. The Standard Spectral Ratio method has been used to evaluate the natural frequencies of vibration of the structure. A 3D finite element model of the arch dam-reservoir-foundation system has been developed to verify analytically determined vibration properties, such as natural frequencies and mode shapes, and their changes linked to water level with the experimental results.

Response of Liquid in Cylindrical Tank with Rigid Annual Baffle Considering Damping Effect

2011 ◽  
Vol 255-260 ◽  
pp. 3687-3691 ◽  
Author(s):  
Jia Dong Wang ◽  
Ding Zhou ◽  
Wei Qing Liu
Keyword(s):  
Free Surface ◽  
Dynamic Response ◽  
Potential Function ◽  
Natural Frequencies ◽  
Damping Ratio ◽  
Cylindrical Tank ◽  
Generalized Coordinates ◽  
Damping Effect ◽  
Total Potential ◽  
Free Surface Wave

Sloshing response of liquid in a rigid cylindrical tank with a rigid annual baffle under horizontal sinusoidal loads was studied. The effect of the damping was considered in the analysis. Natural frequencies and modes of the system have been calculated by using the Sub-domain method. The total potential function under horizontal loads is assumed to be the sum of the tank potential function and the liquid perturbed function. The expression of the liquid perturbed function is obtained by introducing the generalized coordinates. Substituting potential functions into the free surface wave conditions, the dynamic response equations including the damping effect are established. The damping ratio is calculated by Maleki method. The liquid potential are obtained by solving the dynamic response equations of the system.

Vibration Tests of Full-Scale Earth Dam

1981 ◽  
Vol 107 (3) ◽  
pp. 241-269 ◽  
Author(s):  
Ahmed M. Abdel-Ghaffar ◽  
Ronald F. Scott
Keyword(s):  
Full Scale ◽  
Earth Dam ◽  
Vibration Tests
Sign in / Sign up

Export Citation Format

Share Document