scholarly journals An Analysis of the Impact of Valve Closure Time on the Course of Water Hammer

2016 ◽  
Vol 63 (1) ◽  
pp. 35-45 ◽  
Author(s):  
Apoloniusz Kodura
Keyword(s):  
Transient Flow ◽  
Pressure Change ◽  
Water Hammer ◽  
Valve Closure ◽  
Calculation Methods ◽  
New Methods ◽  
Closure Time ◽  
Physical Experiments ◽  
Comparison Of The Results ◽  
The Impact

Abstract The knowledge of transient flow in pressure pipelines is very important for the designing and describing of pressure networks. The water hammer is the most common example of transient flow in pressure pipelines. During this phenomenon, the transformation of kinetic energy into pressure energy causes significant changes in pressure, which can lead to serious problems in the management of pressure networks. The phenomenon is very complex, and a large number of different factors influence its course. In the case of a water hammer caused by valve closing, the characteristic of gate closure is one of the most important factors. However, this factor is rarely investigated. In this paper, the results of physical experiments with water hammer in steel and PE pipelines are described and analyzed. For each water hammer, characteristics of pressure change and valve closing were recorded. The measurements were compared with the results of calculations perfomed by common methods used by engineers - Michaud’s equation and Wood and Jones’s method. The comparison revealed very significant differences between the results of calculations and the results of experiments. In addition, it was shown that, the characteristic of butterfly valve closure has a significant influence on water hammer, which should be taken into account in analyzing this phenomenon. Comparison of the results of experiments with the results of calculations? may lead to new, improved calculation methods and to new methods to describe transient flow.

On the Optimum Utilization of Water Hammer

1988 ◽  
Vol 202 (4) ◽  
pp. 249-256 ◽  
Author(s):  
P H Azoury ◽  
M Baasiri ◽  
H Najm
Keyword(s):  
Water Hammer ◽  
Valve Closure ◽  
Pipe Length ◽  
A Value ◽  
Closure Time ◽  
Highly Sensitive ◽  
Pressure Surge ◽  
Comparison Of The Results ◽  
Optimum Water ◽  
Valve Area

The computerized method of characteristics was used to analyse, for a single pipeline discharging into the atmosphere, the effects of valve-closure schedule and pipe length on optimum water-hammer strength. It was found that the criteria of optimum water-hammer utilization are a non-linear inherent valve schedule in which the bulk of the pressure surge occurs near the beginning or towards the end of valve closure, together with as small a value of dimensionless valve-closure time and as high a value of wide-open valve area as is consistent with cavitation-free operation. Also, a comparison of the results with hydraulic ram test data suggests that optimum drive pipe length may be based solely on optimum water-hammer strength, in the light of the relative effects of pipe friction and dimensionless valve-closure time. In general, optimum pipe length is not highly sensitive to inherent valve-closure schedule, water-hammer strength, pipe size or reservoir head.

Comparisons of CFD and Traditional Solutions for Steam Hammer Events

2017 ◽  
Author(s):  
Alex Mayes ◽  
Kshitij P. Gawande ◽  
Dennis K. Williams
Keyword(s):  
Pressure Wave ◽  
Power Plants ◽  
Peak Load ◽  
Critical Length ◽  
Pressure Change ◽  
Piping System ◽  
Valve Closure ◽  
Pipe System ◽  
Closure Time ◽  
Pressure Changes

Sudden pressure changes in the piping system of power plants are inevitable, and thus potential serious damage to large components, piping system, and piping supports is possible. To protect valuable components from such events, abrupt valve closure is employed to restrict the flow and prevent significant incidents and the resulting plant downtime. Unfortunately, when a valve is suddenly closed to prevent damage caused by unexpected events, a pressure wave within the flow is created, which travels upstream and impacts at the pipeline elbows. These events, involving sudden changes in pressure, are known as steam hammer. This steam hammer pressure wave, traveling through the pipe system, is capable of producing significant transient loads and stresses, which can disrupt the piping supports. As such there is a need for further investigation. The pressure wave depends on the characteristics of the flow, valve closure time, the elbow-to-elbow pipe section lengths, and the piping system flexibility. The present study performs a CFD analysis of the fluid experiencing such a sudden pressure change. OpenFOAM is used for this analysis and considers all the flow parameters, valve closure time, and critical length of the straight pipe. The study intends to provide a means of calculating the transient steam hammer loads applied on the pipe elbows, which consequently allows appropriate pipe support selection based upon the resulting peak loads. This computational analysis is compared to analytical methods for peak load determination such as rigid column theory, the Joukowsky method, and the steam hammer method explained by Coccio (1967) and Goodling (1989).

Charts for water hammer in pipelines resulting from valve closure

1980 ◽  
Vol 7 (2) ◽  
pp. 243-255 ◽  
Author(s):  
Eugen Ruus ◽  
Farouk A. El-Fitiany
Keyword(s):  
Pipe Wall ◽  
Pressure Head ◽  
Water Hammer ◽  
Wall Friction ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Closure Time ◽  
Basic Parameters

Maximum pressure head rises, which result from valve closure according to (a) uniform, (b) equal-percentage, and (c) optimum valve closure arrangements, are calculated and plotted for the valve end and for the midpoint of a simple pipeline. Basic parameters such as the pipeline constant, relative closure time, and pipe wall friction are considered for closures both from partial as well as from full valve openings. The results of this paper can be used to draw the maximum hydraulic grade line along the pipe for these closure arrangements. It is found that the equal-percentage closure arrangement yields consistently less pressure head rise than does the uniform closure arrangement. Further, the optimum closure arrangement yields consistently less head rise than the equal-percentage one. Closures from partial valve openings increase the pressure head rise considerably and must always be considered.

scholarly journals Surge Tank Analysis for Water Hammer Remedy for Long Distance Pipeline

2018 ◽  
Vol 11 (3) ◽  
pp. 47-53
Author(s):  
Nisreen J. Rasheed
Keyword(s):  
Friction Factor ◽  
Method Of Characteristics ◽  
Transient Flow ◽  
Water Hammer ◽  
Pipeline System ◽  
Surge Tank ◽  
Governing Equations ◽  
Long Distance ◽  
Several Variables ◽  
The Impact

Various protection methods can be used for protecting the pipeline system from the impact of water hammer. Which includes the use of special materials for supporting the pipeline and the installation of special devices such as surge tanks, relief valves, and air chambers. In this study, to protect the pipeline system and reduce the effect of water hammer, surge tank has been used. Governing equations of transient flow with and without surge tank is numerically simulated using MATLAB software. Sensitivity analysis was investigated using several variables such as pipe diameter, wave’s velocity and friction factor. Method of characteristics (MOC) was implemented in this study. It was found that the diameter and friction factor of pipe have a significant impact on the results of transient flow and surge tank compared to the effect of wave’s velocity. It has been reached that the capacities of surge tanks at diameter (1m), are (1475m3) at first, second and fourth stages, (1360m3) at third and fifth stages and (570m3) at sixth stage. And at diameter (1.2m), the capacities are (1700m3), (1530m3) and (1475m3) at first, second and third stages respectively. But at diameter (1.4m), the capacities are (1590m3) at first and second stages. For all values of wave’s velocity, the capacities of surge tanks are (1760m3), (1530m3) and (1420m3) at first, second and third stages respectively. But the capacities of surge tanks at friction factor (0.007) are (1810m3), (1585m3) and (1245m3) at first, second and third stages respectively. However, for the capacity of surge tanks at the friction factor (0.008), it was mentioned when the surge tanks capacity of the diameter (1.2m) was mentioned. And when the friction factor is (0.009), the capacities are (1460m3) at first stage, (1415m3) at second and third stages and (570m3) at fourth stage

Assessment and Performance Evaluation of Water Hammer in Hydroelectric Plants With Hydropneumatic Tank and Pressure Regulating Valve

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Bagaragaza Romuald ◽  
Zhang Jian ◽  
Yu Xiao Dong ◽  
Dusabemariya Claire
Keyword(s):  
Transient Flow ◽  
Negative Impact ◽  
Kinetic Characteristic ◽  
Water Hammer ◽  
Electric Power System ◽  
Water Diversion ◽  
Hydropower Plant ◽  
Pipeline System ◽  
Hydraulic Transient ◽  
The Impact

Abstract The simulation approach of pipeline systems, pressure regulating valve (PRV), and hydropneumatic tank (HPT) in hydropower plants (HPP) is performed. The article used suitable protection devices such as hydropneumatic tank and pressure regulating valves to protect the hydro-electric system against water hammer negative effects. The method of characteristics solves hydraulic transient in the HPP system. This article simulates transient phenomena in a hydro-electric power system using FORTRAN language. The aim was to find out and diminish the water hammer at the entrance of the spiral case as well as the pipeline system. The paper has four major philosophies: simulation with no protection, simulation with hydropneumatic tank, simulation with pressure regulating valve, and the combination of hydropneumatic tank with the pressure regulating valve. The results show that a combination of the pressure regulating valve and the hydropneumatic tank is adequate appliances to lessen the effect of water hammer/transient flow in a hydropower plant system. However, in the transient process of the water diversion system, the gas' kinetic characteristic in the hydropneumatic tank has certain complexity when there is high fluctuation in the surge chamber. The study proved that the wicket gate's stepwise could cut down the impact of the water hammer automatically than applying the linear closure law on the network. The automated pressure regulating valve with a high opening stepwise can decrease the negative impact of water hammer significantly. The results from this research paper show that pipeline diameter has crucial factors that influence hydraulic transient in hydropower plant systems.

Influence of connection stub parameters and valve closure time on transient measurement accuracy of a pressure transducer

2018 ◽  
Vol 18 (6) ◽  
pp. 1984-1995
Author(s):  
Zhiyong Liu ◽  
Angus R. Simpson
Keyword(s):  
Pressure Transducer ◽  
Measurement Accuracy ◽  
Return Time ◽  
Water Hammer ◽  
Valve Closure ◽  
Measurement Point ◽  
Transient Pressure ◽  
Accurate Representation ◽  
Closure Time ◽  
Transient Measurement

Abstract Consider that a transient pressure measurement occurs at the end of the connection stub attached to a pipeline. The question arises as to whether the pressure being recorded at the end of the stub is an accurate representation of pressure in the pipeline. In this study, the influence of three parameters, including pressure transducer connection stub length, stub diameter and valve closure time, on the measurement accuracy of transient pressure is investigated through numerical simulation on a reservoir-pipe-valve-reservoir system. The results show that the larger the diameter of stub, the larger its influence both on the transient in the pipe and on measurement error; the measurement accuracy increases with an increase of the length of the stub only when the closure time of the end valve is less than the time for the water hammer wave to travel back and forth between the measurement point and the end point of stub. In contrast, when the closure time of the end valve is greater than the water hammer wave return time, the measurement accuracy will decrease with an increase of the stub length; the measurement accuracy is improved as the closure time of the end valve increases. As a result, in practice, diameter and length of connection stub for the pressure-transducer should both be selected to be as small as possible.

scholarly journals Twenty Years of Research in Seabass and Seabream Welfare during Slaughter

Animals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2164
Author(s):  
Ignacio de la Rosa ◽  
Pedro L. Castro ◽  
Rafael Ginés
Keyword(s):  
Carbon Dioxide ◽  
Adverse Reaction ◽  
Loss Of Consciousness ◽  
Stressful Situation ◽  
Clove Oil ◽  
Fish Welfare ◽  
Behavioural Responses ◽  
Welfare Indicators ◽  
New Methods ◽  
The Impact

The behavioural responses of fish to a stressful situation must be considered an adverse reaction caused by the perception of pain. Consequently, the handling prior to stunning and the immediacy of loss consciousness following stunning are the aspects to take into account during the slaughtering process. The most common commercial stunning method in seabream and seabass is based on hypothermia, but other methods such as electrical stunning, carbon dioxide narcosis or anaesthetic with clove oil, are discussed in relation to the time to reach the unconsciousness stage and some welfare indicators. Although seawater plus ice slurry is currently accepted in some guidelines of fish welfare well practices at slaughter, it cannot be considered completely adequate due to the deferred speed at which cause loss of consciousness. New methods of incorporating some kind of anaesthetic in the stunning tank could be a solution to minimize the impact on the welfare of seabass and seabream at slaughtering.

scholarly journals Optimal profile for concave slopes under static and seismic conditions

2016 ◽  
Vol 53 (9) ◽  
pp. 1522-1532 ◽  
Author(s):  
Farshid Vahedifard ◽  
Shahriar Shahrokhabadi ◽  
Dov Leshchinsky
Keyword(s):  
Limit Equilibrium ◽  
Stable Configuration ◽  
Preliminary Evaluation ◽  
Construction Technology ◽  
Stability Of Slopes ◽  
Optimal Profile ◽  
Stabilized Soil ◽  
The Stability ◽  
Comparison Of The Results ◽  
The Impact

This study presents a methodology to determine the stability and optimal profile for slopes with concave cross section under static and seismic conditions. Concave profiles are observed in some natural slopes suggesting that such geometry is a more stable configuration. In this study, the profile of a concave slope was idealized by a circular arc defined by a single variable, the mid-chord offset (MCO). The proposed concave profile formulation was incorporated into a limit equilibrium–based log spiral slope stability method. Stability charts are presented to show the stability number, MCO, and mode of failure for homogeneous slopes corresponding to the most stable configuration under static and pseudostatic conditions. It is shown that concave profiles can significantly improve the stability of slopes. Under seismic conditions, the impact of concavity is most pronounced. Good agreement was demonstrated upon comparison of the results from the proposed method against those attended from a rigorous upper bound limit analysis. The proposed methodology, along with recent advances in construction technology, can be employed to use concave profiles in trenches, open mine excavations, earth retaining systems, and naturally cemented and stabilized soil slopes. The results presented provide a useful tool for preliminary evaluation for adopting such concave profiles in practice.

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