Maximum Pressure Head Due to Linear Valve Closure

1991 ◽  
Vol 113 (4) ◽  
pp. 643-647 ◽  
Author(s):  
Chyr Pyng Liou
Keyword(s):  
Flow Characteristic ◽  
Pressure Head ◽  
Head Loss ◽  
Water Hammer ◽  
Point Of View ◽  
Global Perspective ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Subtle Effect ◽  
Dimensionless Variables

The maximum pressure head resulting from one-speed closure of wide open valves is investigated. The dimensionless variables formulated in this study make the subtle effect of the initial valve head loss explicit and separate from that of the pipe frictional head loss. The maximum head is related to initial pipe frictional head loss, the initial valve head loss, the inherent flow characteristic of the valve, and the closure period by plots of dimensionless variables. The trends of the variation of the maximum pressure head are discussed. An example is used to illustrate the usage of the plots, and to show the advantage of having a global perspective of the phenomenon in the selection and sizing of valves from the water hammer point of view.

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.

Charts for water hammer in pipelines resulting from valve closure from full opening only

1985 ◽  
Vol 12 (2) ◽  
pp. 241-264 ◽  
Author(s):  
Bryan W. Karney ◽  
Eugen Ruus
Keyword(s):  
Good Accuracy ◽  
Pipe Wall ◽  
Pressure Head ◽  
Wall Friction ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Closure Time ◽  
Basic Parameters ◽  
Valve Opening ◽  
Open Position

Maximum pressure head rises, which result from total closure of the valve from an initially fully open position, are calculated and plotted for the valve end and for the midpoint of a simple pipeline. Uniform, equal-percentage, optimum, and parabolic closure arrangements are analysed. Basic parameters such as pipeline constant, relative closure time, and pipe wall friction are considered with closures from full valve opening only. The results of this paper can be used to draw the maximum hydraulic grade line along the pipe with good accuracy for the closure arrangements considered. It is found that the equal-percentage closure arrangement yields consistently less pressure head rise than does the parabolic closure arrangement. Further, the optimum closure arrangement yields consistently less head rise than the equal-percentage one. Uniform closure produces pressure head rise that usually lies between those produced by the parabolic and the equal-percentage closure arrangements, except for the range of low pressure head rise combined with low or zero friction, where the rise due to uniform closure approaches that produced by optimum closure.

Understanding Line Packing in Frictional Water Hammer

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Jim C. P. Liou
Keyword(s):  
Numerical Methods ◽  
Wave Front ◽  
Water Hammer ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Governing Equations ◽  
Front Line ◽  
Wave Fronts ◽  
Friction Term

For valve closure transients in pipelines, friction attenuates the amplitude of water hammer wave fronts and causes line packing. The latter is a sustained head increase behind the wave front. Line packing can lead to overpressure. Because of the nonlinearity of the friction term in the governing equations of water hammer, a satisfactory analytical explanation of line packing is not available. Although numerical methods can be used to compute line packing, an analytical explanation is desirable to better understand the phenomenon. This paper explains line packing analytically and presents a formula to compute the line packing that leads to the maximum pressure at the closed valve.

Charts for water hammer in low head pump discharge lines resulting from water column separation and check valve closure

1984 ◽  
Vol 11 (4) ◽  
pp. 717-742 ◽  
Author(s):  
Eugen Ruus ◽  
Bryan Karney ◽  
Farouk A. El-Fitiany
Keyword(s):  
Water Column ◽  
Pressure Rise ◽  
Check Valve ◽  
Pressure Head ◽  
Maximum Pressure ◽  
Valve Closure ◽  
High Point ◽  
Column Separation ◽  
Discharge Line ◽  
Low Head

Maximum pressure head rises resulting from water column separation and check valve closure are calculated and plotted for a simple low head pump discharge line with one well-defined high point. Basic parameters such as pipeline constant, pipe wall friction, complete pump characteristics, pump inertia constant, and the relative location of the high point are accounted for in the analyses. The results of this paper can be used to determine (a) when water column separation is expected, (b) how to avoid water column separation, and (c) the necessary wall thickness in cases where no protection against water column separation is provided. Computer studies indicate that both the vertical and horizontal location of the high point as well as the pipe friction, the pipeline constant, and the pump inertia have a major effect on pressure head rises. Water column separation does not always constitute a danger to the pipeline. Key words: waterhammer, water column separation, check valve closure, pressure rise, pump discharge line, chart.

Effect of multi-valve closure on superposed pressure in a tree-type long distance gravitational water supply system

2019 ◽  
Vol 68 (6) ◽  
pp. 420-430
Author(s):  
Xingtao Wang ◽  
Jian Zhang ◽  
Xiaodong Yu ◽  
Sheng Chen ◽  
Wenlong Zhao ◽  
...  
Keyword(s):  
Water Supply ◽  
Pressure Rise ◽  
Water Hammer ◽  
Supply System ◽  
Water Supply System ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Long Distance ◽  
Maximum Water ◽  
Tree Type

Abstract Valves are installed at the end of each branch pipeline in a tree-type long distance gravitational water supply system to regulate flow. However, the sequential closing of all valves may cause a tremendous superposed pressure rise, even larger than the pressure rise under simultaneous valve closure. In this paper, the effects of sequential valve closure on the superposed maximum water hammer pressure rise in a pipeline were investigated. By using the wave superposition principle, a sequential valve closure formula leading to maximum water hammer was proposed and verified using numerical simulation based on a practical project. In addition, the superposed maximum pressure rises in the pipeline were compared under single, simultaneous and sequential valve closure, respectively. The results show that the sequential valve closure formula agrees well with the numerical results and the pressure rise in the pipeline under the sequential closing was the largest. Moreover, compared with the superposed maximum pressure rises at the main pipeline, the effect of sequential valve closure on superposed maximum pressure rise at the branch pipeline is more sensitive.

scholarly journals Optimal closure of system actuators for transient control: an analytical approach

2015 ◽  
Vol 18 (3) ◽  
pp. 393-408 ◽  
Author(s):  
Olya Skulovich ◽  
Lina Sela Perelman ◽  
Avi Ostfeld
Keyword(s):  
Distribution System ◽  
Water Distribution ◽  
Pressure Head ◽  
Optimization Methods ◽  
Optimization Method ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Polynomial Curve ◽  
Curve Change ◽  
Transient Control

The effect of downstream valve closure scheduling was analyzed to find optimal closure parameters that lead to the minimal maximum pressure head in the water distribution system. Several valve closure strategies were explored, combining the known valve performance curve (change in flow as a function of change in valve's opened area) with unknown valve closure curve (change in valve's opened area as a function of time). Second-order polynomial curve, power function curve, and piece-wise linear curve were implemented and compared. Genetic algorithm and quasi-Newton (QN) optimization methods were applied. The methodology was tested for three networks, including looped gravitational and pressurized networks. The results demonstrate that flexible multi-parametric valve closure curve and QN optimization method are more effective in minimizing the maximum pressure head in the system.

Charts for water hammer in high head pump discharge lines resulting from pump failure and check valve closure

1985 ◽  
Vol 12 (1) ◽  
pp. 137-149 ◽  
Author(s):  
Eugen Ruus ◽  
Bryan Karney
Keyword(s):  
Check Valve ◽  
Pressure Head ◽  
Major Effect ◽  
Wall Friction ◽  
Maximum Pressure ◽  
Valve Closure ◽  
Pump Failure ◽  
Basic Parameters ◽  
High Head ◽  
Computer Studies

Maximum pressure head drops and rises resulting from pump failure and subsequent check valve closure are calculated and plotted for a simple pump discharge line at pump end, midpoint, and three-quarter point. Basic parameters such as pipeline constant, pipe wall friction, complete pump characteristics, and pump inertia constant are accounted for in the analyses. Computer studies indicate that pipe friction, pipeline constant, and pump inertia have a major effect on pressure head drops and rises.Studies indicate further that whereas for large pump inertia the pressure head rise or drop at the midpoint is only moderately larger than one-half of the rise or drop at pump end, for small pump inertia this difference is much greater. For very small pump inertia, the pressure head drop or rise at midpoint approaches the values at pump end. This increase in pressure head drop and rise for very small pump inertia is even more pronounced at the three-quarter point.

Electrostatic bellow muscle actuators and energy harvesters that stack up

2021 ◽  
Vol 6 (51) ◽  
pp. eaaz5796
Author(s):  
I. D. Sîrbu ◽  
G. Moretti ◽  
G. Bortolotti ◽  
M. Bolignari ◽  
S. Diré ◽  
...  
Keyword(s):  
High Performance ◽  
High Reliability ◽  
Low Cost ◽  
Artificial Muscle ◽  
Pressure Head ◽  
Robotic Systems ◽  
Maximum Pressure ◽  
Term Operation ◽  
Energy Harvesters ◽  
Out Of Plane

Future robotic systems will be pervasive technologies operating autonomously in unknown spaces that are shared with humans. Such complex interactions make it compulsory for them to be lightweight, soft, and efficient in a way to guarantee safety, robustness, and long-term operation. Such a set of qualities can be achieved using soft multipurpose systems that combine, integrate, and commute between conventional electromechanical and fluidic drives, as well as harvest energy during inactive actuation phases for increased energy efficiency. Here, we present an electrostatic actuator made of thin films and liquid dielectrics combined with rigid polymeric stiffening elements to form a circular electrostatic bellow muscle (EBM) unit capable of out-of-plane contraction. These units are easy to manufacture and can be arranged in arrays and stacks, which can be used as a contractile artificial muscle, as a pump for fluid-driven soft robots, or as an energy harvester. As an artificial muscle, EBMs of 20 to 40 millimeters in diameter can exert forces of up to 6 newtons, lift loads over a hundred times their own weight, and reach contractions of over 40% with strain rates over 1200% per second, with a bandwidth over 10 hertz. As a pump driver, these EBMs produce flow rates of up to 0.63 liters per minute and maximum pressure head of 6 kilopascals, whereas as generator, they reach a conversion efficiency close to 20%. The compact shape, low cost, simple assembling procedure, high reliability, and large contractions make the EBM a promising technology for high-performance robotic systems.

scholarly journals Routes of human trafficking in Europe and the position of Serbia on them

Temida ◽  
2008 ◽  
Vol 11 (4) ◽  
pp. 49-68 ◽  
Author(s):  
Sanja Copic
Keyword(s):  
Human Trafficking ◽  
Relevant Literature ◽  
Control Policy ◽  
Point Of View ◽  
Global Perspective ◽  
Human Beings ◽  
Male Victims ◽  
Illegal Migration ◽  
Global Trends ◽  
And Migration

Human trafficking as a form of organized crime is showing its increase today, changing at the same time its structure and characteristics. Some factors that contribute to such a situation are global trends that result in huge social and economic inequalities in the world, but also turbulences and problems that are affecting certain regions (wars, political instability, ethnic conflicts, militarization etc.). Human trafficking, as a complex social phenomenon that encompasses different forms of acting, subjects and aims, can be analyzed within different concepts. One of them refers to the issue of broader migration flows and migration control policy. Namely, from the global perspective, trafficking in human beings can be mostly considered as a form of 'organized illegal migration'. Due to that, it seems important to consider the issue of routes through which this form of migration is realized today. Discovering human trafficking routes, as well as other forms of illegal movement of people and illegal forms of trade are very important from the point of view of implementing adequate measures and relocation of resources in order to suppress these forms of socially unacceptable phenomena. Creating adequate anti-trafficking activities is important on national, regional and international levels. Keeping that in mind, the aim of this paper is to look into the contemporary routes of human trafficking within Europe and find out what is the position of Serbia on these routes, as well to examine possible changes that happened in this field during past several years. This will be done on the basis of the analysis of relevant literature, as well as on some preliminary findings of the survey on male victims of human trafficking in Serbia, which is currently conducted by the Victimology Society of Serbia.

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