Dynamic Load Factor for Surge Load on Pipe Using the Stress Wave Propagation Methodology

2017 ◽  
Author(s):  
Abu Seena
Keyword(s):  
Wave Propagation ◽  
Dynamic Load ◽  
Time History ◽  
Stress Wave Propagation ◽  
Load Factor ◽  
Full Time ◽  
Maximum Value ◽  
Force Time ◽  
Full Force ◽  
Dynamic Load Factor

The full time history method for calculating the pipe stresses and restraint loads due to transient flow event requires high computing memory and long simulation time. Alternately, the static equivalent method has been extensively used in power and process industry where a dynamic load factor is used to account for the dynamic amplification response of suddenly applied surge/hammering loads on pipe. In practice, the DLF is multiplied on the maximum value of dynamic force depending on the time rise of load. Due to the complexity of calculating DLF, the engineers adopt maximum value of DLF = 2.0 irrespective of the load variation. The present paper discusses the uncertainty and inaccuracy involved in performing approximate analysis or static equivalent analysis and shows the significance and need of performing full force time history analysis. A new methodology has been derived for the estimation of approximate DLF from the full force time history profiles. Using the stress wave propagation methodology, the DLF can be estimated for the pipe with axial restraints and guides. The axial line stoppers are precondition to apply present method, which can be easily included during design phase of the pipe routes. The DLF’s are computed for sample force curve with various other parameters and are compared with the FEA results. It has also been shown that the load amplification does not scale with the displacement amplification. With proposed methodology the DLF for can be calculated for each pipe. Then it is recommended to perform the static analysis with the estimated DLF’s based on full time history profiles.

Pressure Surge Load Estimation on Pipes With Dimensional Reduction and Rayleigh Energy Method

2019 ◽  
Author(s):  
Abu Seena ◽  
Juyoul Kim
Keyword(s):  
Dynamic Load ◽  
Time History ◽  
Load Factor ◽  
Load Estimation ◽  
Mass System ◽  
History Analysis ◽  
Pressure Surge ◽  
Force Time ◽  
Full Force ◽  
Dynamic Load Factor

Abstract The pressure surge in pipes due to change in operating conditions exerts an axial load on elbows proportional to the change in momentum of fluid and unbalanced pressure forces. The response of piping structure to such load needs the full time history analysis in three dimensional spaces which is cumbersome process due to high computing memory requirements and long simulation time. In present work it has been shown that using Rayleigh energy balance for each elbow-load configuration, the system can be reduced to equivalent 1D spring mass system and the response can be estimated by solving 1D equation of motion. Then it has been recommended to simulate the response of each elbow which gives good approximation of dynamic amplification of displacement also called as Dynamic Load Factor (DLF). These dynamic load factors for each elbow can be used for the interaction of forces using static equivalent response in 3D space. This approach is pseudo static equivalent analysis where the load amplifications factors DLF are estimated from the dynamic force profile and system response in one-dimensional space. An algorithm is developed for the above explained process. Most of the engineers are using the DLF = 2 for the load estimation due to absence of method to estimate the dynamic load factor. The approach was proposed by Goodling in 1989 and still widely followed in the industry. The present paper discusses uncertainty and inaccuracy involved in performing approximate analysis and shows the significance and need of performing full force time history analysis. The proposed method shows very good agreement with the time consuming 3D full force time history results. There are also limitations for the proposed method. As the spring mass system is simulated with dimensional reduction to single frequency domain, the pipe supports and guides should be properly placed before applying the present approach. It has been shown that with proper support configuration, this simplified approach yields very good approximation of surge load on pipes with reduced time.

scholarly journals Dynamic Load on a Pipe Caused by Acetylene Detonations – Experiments and Theoretical Approaches

1999 ◽  
Vol 6 (1) ◽  
pp. 29-43 ◽  
Author(s):  
Axel Sperber ◽  
Hans-Peter Schildberg ◽  
Steven Schlehlein
Keyword(s):  
Dynamic Load ◽  
Pipe Wall ◽  
Time History ◽  
Load Factor ◽  
Transverse Waves ◽  
Theoretical Approaches ◽  
Pressure Time ◽  
Predicted Values ◽  
Modelling Methods ◽  
Dynamic Load Factor

The load acting on the wall of a pipe by a detonation, which is travelling through, is not yet well characterized. The main reasons are the limited amount of sufficiently accurate pressure time history data and the requirement of considering the dynamics of the system. Laser vibrometry measurements were performed to determine the dynamic response of the pipe wall on a detonation. Different modelling approaches were used to quantify, theoretically, the radial displacements of the pipe wall. There is good agreement between measured and predicted values of vibration frequencies and the propagation velocities of transverse waves. Discrepancies mainly due to wave propagation effects were found in the amplitudes of the radial velocities. They might be overcome by the use of a dynamic load factor or improved modelling methods.

Dynamic Amplification Factor for Rigid and Flexible Piping System due to Steam Hammer Transient Load

2015 ◽  
Author(s):  
Anestis Papadopoulos ◽  
Mohamed Ismail ◽  
Ahmed H. Bayoumy
Keyword(s):  
Power Plant ◽  
Dynamic Load ◽  
Time History ◽  
Load Factor ◽  
Piping System ◽  
Pressure Waves ◽  
History Analysis ◽  
Transient Loads ◽  
Dynamic Amplification ◽  
Dynamic Load Factor

Pressure surges and fluid transients, such as steam and water hammer, are events that can occur unexpectedly in operating power plants causing significant damages. The steam hammer normally occurs when one or more valves suddenly close or open. In a power plant, the steam hammer could be an inevitable phenomenon during turbine trip, since valves (e.g., main steam valves) must be closed very quickly to protect the turbine from further damage. When a valve suddenly stops at a very short time, the flow pressure builds up at the valve, starting to create pressure waves along the pipe runs which travel between elbows. Furthermore, these pressure waves may cause large dynamic response on the pipeline and large loads on the pipe restraints. The response and vibrations on the pipeline depend on, one hand, on the pressure waves amplitudes and frequencies of the applied transient loads and on the other hand, on the natural frequencies and dynamic characteristics of the pipeline itself. The piping flexibility or rigidity of the pipeline (piping configuration plus support locations and types), determines how the pipeline will respond to these waves and eventually the magnitude of the loads on the pipe restraints. Consequently, the design of the piping system (pipe configuration and pipe support arrangement) is closely related to the dynamic amplification of applied steam hammer loads. This paper investigates how the pipe support arrangement and the flexibility of the pipeline relate to the dynamic amplification of the piping system due to steam hammer transient loads. The paper examines the correlation that exists, between the applied steam hammer transient spectrum and the pipe frequencies of the pipeline with the dynamic load amplification. Furthermore, it establishes the relation between the dynamic amplification of the pipeline and the pipe support configuration by examining various piping systems from very rigid (many supports) to very flexible (fewer supports). The typical pipe configuration of hot reheat line in a power plant is analyzed for steam hammer due to sudden valve closure (turbine trip) for six cases of closure time (50, 100, 200, 300, 400, 1600 ms). The transient loads on each pipe segment are generated using the PIPENET program and used as an input to CAESAR II stress analysis program to perform a dynamic time history analysis. The dynamic analysis is performed for a range of different pipe support arrangements, from very rigid to a very flexible. The magnitude of the restraint loads from the time history analysis, for each selected pipe support arrangement, is compared with the transient load spectrum associated. The analysis is performed using the PIPENET transient module and CAESAR II pipe stress analysis program, for a range of different pipe support arrangements, from very rigid to a very flexible. The results from the dynamic analysis are compared with the applied transient spectrum, and a dynamic load factor is established for the selected pipe support configuration. The dynamic load factor calculated based on the analysis results is compared with the factor proposed in standard industry practice. The information and the methodology presented in this paper aim to assist the design engineer in the power plant industry to select an optimum support arrangement that will cause the minimum dynamic amplification on the pipeline, thus reducing the steam hammer effects, the size and the cost of pipe supports.

scholarly journals Numerical and experimental study of the dynamic factor of the dynamic load on the urban railway

2020 ◽  
Vol 29 (1) ◽  
pp. 195-202
Author(s):  
Tran Anh Dung ◽  
Mai Van Tham ◽  
Do Xuan Quy ◽  
Tran The Truyen ◽  
Pham Van Ky ◽  
...  
Keyword(s):  
Experimental Study ◽  
Dynamic Load ◽  
Dynamic Measurement ◽  
Experimental Results ◽  
Load Factor ◽  
Dynamic Factor ◽  
Experimental Measurements ◽  
Train Speed ◽  
Dynamic Load Factor

AbstractThis paper presents simulation calculations and experimental measurements to determine the dynamic load factor (DLF) of train on the urban railway in Vietnam. Simulation calculations are performed by SIMPACK software. Dynamic measurement experiments were conducted on Cat Linh – Ha Dong line. The simulation and experimental results provide the DLF values with the largest difference of 2.46% when the train speed varies from 0 km/h to 80 km/h

Damage Detection in Rods Using Wave Propagation and Regression Analysis

1999 ◽  
Author(s):  
K. T. Feroz ◽  
S. O. Oyadiji
Keyword(s):  
Wave Propagation ◽  
Regression Analysis ◽  
Damage Detection ◽  
Numerical Study ◽  
Time History ◽  
Ball Impact ◽  
Spherical Ball ◽  
Time Histories ◽  
Measured Strain ◽  
Force Time

Abstract The phenomena of wave propagation in rods was studied both numerically and experimentally. The finite element (FE) code ABAQUS was used for the numerical study while PZT (lead zirconium titanate) sensors and a 50 MHz transient recorder were used experimentally to monitor and to capture the propagation of stress pulses. For the study of damage detection in the rods the analyses and the experiments were repeated by introducing slots in a fixed axial location of the rod. A longitudinal wave was induced in the rod via collinear impact which was modelled in the FE analyses using the force-time history computed from the classical Hertz contact theory. In the experimental measurements this was achieved by a spherical ball impact at one plane end of the rods. It is shown that the predicted and measured strain-time histories for the defect-free rod and for the rods with defect correlate quite well. These results also show that defects can be located using the wave propagation phenomena. A regression analysis technique of the predicted and measured strain histories of the defect free rod and of the rod with defect was also performed. The results show that this technique is more efficient for smaller defects. In particular, it is shown that the area enclosed by the regression curve increases as the defect size increases.

Parametric Instability of Tapered Beams by Finite Element Method

1982 ◽  
Vol 24 (4) ◽  
pp. 205-208 ◽  
Author(s):  
P. K. Datta ◽  
S. Chakraborty
Keyword(s):  
Finite Element ◽  
Dynamic Load ◽  
Parametric Instability ◽  
Mathieu Equation ◽  
Stability Diagram ◽  
Load Factor ◽  
Element Analysis ◽  
Load Factors ◽  
Principal Region ◽  
Dynamic Load Factor

The dynamic stability behaviour of a tapered beam has been studied using a finite element analysis. The instability zones of the parametric stability diagram have been discussed for the entire ranges of static and dynamic load factors. It has been observed that at high values of static load and beyond a particular value of the dynamic load factor, the periodic solution of the Mathieu equation does not exist in the principal region. This leads to unstable behaviour due to large displacement of the beam due to increasing values of static and dynamic load factors.

Finite Element Stress Response Analysis of Stepped-Lap Adhesive Joints Subjected to Impact Tensile Load

2000 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Takahiro Ohmori
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Principal Stress ◽  
Impact Load ◽  
Maximum Principal Stress ◽  
Adhesive Joints ◽  
Stress Wave Propagation ◽  
Maximum Value ◽  
Adhesive Thickness ◽  
The Impact

Abstract The stress wave propagation and the stress distribution in stepped-lap adhesive joints of similar adherends subjected to impact tensile loads and elastic deformation are analyzed using three-dimensional finite-element method (FEM). The impact load is applied to the joint by dropping a weight. One end of the upper adherend is fixed, and the other end of the lower adherend is subjected to an impact load. FEM code employed is DYNA3D. The effects of Young’s modulus of the adherends, the number of lapped steps, and the adhesive thickness on the stress wave propagation at the lapped, and fee butted interfaces are examined. It is also found that the maximum value of the maximum principal stress σ1 occurs at the end of the butted interface between the adhesive and the lower adherend to which the impact load is applied. As the number of the lapped steps increases, the maximum value of the maximum principal stress σ1 increases. It is found that the maximum value of the maximum principal stress σ1 increases as the adhesive thickness decreases. The maximum value of σ1 increases as Young’s modulus of the adherends increases. In addition, the experiments were carried out to measure the strain response of stepped-lap adhesive joints subjected to impact tensile loads using strain gauges. A fairly good agreement is seen between the analytical, and the experimental results.

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