Control de Ariete Tesis

7/26/2019 Control de Ariete Tesis

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The easiest and least expensive way to control

water hammer in irrigation and drainage network of

Sivand DamReza Gharehkhani, Sayed Abbas Mousavi, Fatemeh Kazemi

Abstract-Water hammer pressure occurs in pipelines of

under pressure and it is based on pressure regulation, flow

velocity and changes of location, time of fluid motion. In some

hydraulic systems under pressure, such as water transmission

lines, oil or water distribution systems and piping leading to the

turbine, water tunnels, gravity flow and pumping systems, water

hammer phenomenon is caused in various risks by creating a

fast and damped transient wave, sometimes destructive power of

these wave pressures are so, which would bring about serious

consequences, burst in pipeline systems and distribution

networks, failures and broken valves, control valves and pumpsare examples of the impact. In this study for simulation of

transmission lines in stable and unstable hydraulic conditions,

we use the two software of Bentley Company with the names of

WaterGems and Hammer. Results from the model indicated that

the phenomenon of water hammer occurs when valves are

closing and for harness of this phenomenon we used the

simplest way with regarding to the parallelism of the two lines

together. Thus, a connection pipe were used that connected with

the two main pipes in several points. In this method, during the

occurrence of water hammer, every line serves as a repository

for other lines.

Keywords-Water hammer effect, Water hammer control,

connection pipe, easiest way

INTRODUCTION

Water hammer is the formation of pressure wave as a

result of sudden change in liquid velocity in a piping

system. The water hammer phenomena usually explained

by considering by ideal reservoir pipe-valve system in

which the steady flow with velocity ! is stopped by an

instantaneous valve closure. In other say it occurs when

the fluid flow start or stop quickly or is forced to make a

rapid change in direction, for example quick closing the

valves and stoppage of a pump can create water

hammer[4,12]

Background of the Investigations

Joukowsky[6] published the basic theory of water

hammer. He achieved acceptable relationship for increase

pressure, fluid density, velocity and wave speed changes.

- Reza Gharekhani : Technical head office in irrigation and drainage

network of Sivand Dam. E-mail: [email protected]

- Sayed Abbas Mousavi: project manager in irrigation and drainagenetwork of Sivand Dam (pars garma company). E-mail:

[email protected]

-Fatemeh Kazemi: Technical Expert in Parese banaye shirazCompany.E-mail: [email protected]

g

VaH

=

H : Increased pressure on the basis of water head(m)

A : wave velocity (m / s)

V : velocity change of liquid in the pipe line (m / s)

G: acceleration of gravity (m / s ^ 2)

Joukowsky also studied and investigated the emission

of waves in the pipeline and their reflections, means the

time it takes a wave to go to the boundaries of reflection

and return[6].

In 1960s and development of computer industry a new

era started in studying and analyzing the phenomenon of

water hammer. Stritter and Whily[9] showed that with the

aim of computer they can solve very difficult and

sophisticate problems and so analyzing of water hammer

that in that era was exclusive to the few number ofexperienced people, proposed for the most of engineers.

Parmakian (1950-1963) stated that the aggregation of

high pressure waves are dangerous and recommended

that for ensuring and having enough safety from danger

of the wave it should prevented from vacuum separation

in system[8].

In the research by Anton [1] water hammer analysis for

control of water in underground mines had been done.

Field measurement are comprised with a computer

simulation analysis of a transient during power failure to

the pump. The result show that the method of

characteristic is an acceptable method for water hammeranalysis of mine pumping systems.

In the research by Don[5], two procedure for solving

the basic transient flow had been comprised . one of them

is based on a numerical procedure using the method of

characteristics (MOC). Another is referred to the wave

characteristics method ( WCM). The results show that the

MOC and WCM are both capable of accurately solving

for transient pressures. The WCM will normally require

fewer calculations and faster execution times. Because of

the difference in calculation requirements and the

comparable accuracy of two techniques, the use of the

WCM will be more suitable for analyzing lang pipe

network.

Advances in Environmental Sciences, Development and Chemistry

ISBN: 978-1-61804-239-2 417
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Cannizzaro [3]discussed on the failure of the water

column in transmission flows and creating a large

pressure rise within the pipeline.

In another research, [10] results show that water

hammer effect is more in larger and bigger diameter of

pipe line. Water hammer effect in the pvc pipe is greater

than the water hammer effect in steel pipe. The

prevention method of water hammer effect which installthe bypass pipe with non return valve had prove that the

method is successfully to reduce the water hammer effect

in the pipe line. The mean pressure is reducing about

33.33% after installing the prevention method. This

method is useful in the household usage as the non return

valve is not an expensive method.

Consequences from the water hammer phenomenon

low and high pressures

Non-steady flow can be caused high or low pressures.

Excess pressure can damage the pumps, valves and otherpipeline equipment or cause fracture in lines. Low

pressure causes the release of dissolved air of the fluid

and if the pressure reaches the vapor pressure of the fluid

leads to intense evaporation. Low pressure inside the

pipes (plus the pressure due to external loading) can lead

to pipe failure. The vapor cavity-closure can also cause

extreme shock pressure that the system will be impaired.

Vibration

Vibration of non-steady flow in pipelines can cause

significant effects on pipelines. Intense vibration of non-

steady flows results from where that some alternating

currents causes agitation of pipeline equipment in

frequencies close to their natural frequency. In this case,

the stresses and large deformations (with sound) occurs

that may impair the system.

Vacuum induction

Rapid condensation and vaporization causing a vacuum

induction that it is one of the lasting effects of the non-

steady currents. Vapor cavity usually forms when fluid

pressure by dynamic or statistic factors is equal to or less

than vapor pressure. These holes are expanded by low

pressure. When the pressure around these cavities

increases over the vapor pressure, the cavities disappears

and fall down. This creates noise, vibration and possible

damage to the hard surfaces.

Shock waves from collapsing vapor cavities can create

pressure fluctuations and causes vibrations in system.

Such vibrations can cause screws to loosen, Fatigue of

connections, loose or breaking belts and damage to the

pipes. If vapor cavities near the hard borders (such as

plumbing) fall down, erosion is likely and this causes

premature repair or replacement of pipe, valves, pumps,turbines, etc. Vapor induction can reduce system

performance such as increased pump head loss reduction,

reducing power generation in turbines and reducing the

flow through the valves.

Location and causes of water hammer

The possibility of water hammer phenomenon that its

formation mechanism depends on changing in velocity

and pressure of flow exists in fluid transfer systems.

Water hammer occurs in pipes for water transmission,water distribution networks, oil pipelines or fluid

transmission in industries, turbine water flow in pipes or

in open streams such as the failure of a dam failure, the a

huge wave of water downstream along the path and flows

by gravity or pumping flow systems.

The accident occurred due to different causes that the

most important are:

- Reduce or increase the velocity and flow with

maneuver of control valves in water, oil pipelines and

- Reduce or increase the velocity and flow with

opening and closing of control valves in water pipe

turbines.

- Setup or failure of pumps and turbines.

- When switching or increase and decrease in flow and

velocity in gravity flow with using control systems.

- Power failure in pumping systems.

- Existence of changes in flow path, including

increasing and decreasing pipe diameter or existence of

blind pipes.

Calculation of water hammer (Water Hammer)

One of the important factors for the calculation of

water hammer is the calculation of wave velocity. Wave

velocity in the pipe is obtained from the relationship

based on m/s that is called Olivy relationship:

)2

1(*)/(*)/(1

+

=

tDEK

K

a

Where ! is Poisson's ratio (dimensionless), D is

the pipe diameter (mm), t is the thickness of the pipe

wall in terms of (mm), P is the density of water

(kg/m3), E is modulus of elasticity of pipe, K is

modulus of elasticity of water equal to 19/2 GPa. E

values for pipes GRP are 30 to 50 GPa based on the

type of material production.

Water hammer in pipes under gravity pressure

Gravity transmission lines are called networks that

in which fluid flow from a source with a higher level

toward a destination or consumer with lower leveldue to topography condition of pipeline approach is

established by gravity and with the help of gravity.


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Factors causes water hammer in the gravity

pipelines

Sudden changes and pressure cause distribution of

wave in pipelines and the occurrence of water

hammer phenomenon. Considering that reservoir

level is almost constant in gravity lines therefore it

can be concluded that the water hammer in lines is

summarized as follows:

A- Sudden closing of taps on pipeline

route

B- Sudden opening of taps on pipeline

route

C- sudden fracture along the pipeline

D- Cut or overload the downstream

consumers that is associated with an increase or

decrease in the current pipeline.

The important point in relation to the gravity

network of transmission lines is that separation of

water column occurs less during water hammerphenomenon, because between upstream reservoir

and nodes or downstream reservoir generally is a line

which causes minimum pressure line become steady

state in gravity system close to slope hydraulic line.

However, where the ground suddenly falls to the

lower elevation there is a possibility of water column

separation phenomenon.

The effect of pipeline profile and taps in gravity

flows on water hammer rate

- Positive pressure due to the maximum height

difference of piezometric attenuation flow thatobtained from curve difference of maximum

difference of piezometric height and profile

evaluation of can provide with choosing the pressure

bearing of the pipe and Characteristics of suitable

work and also, if the pressure is higher than the

nominal pressure can control it by safety valves and

other safety measures.

- Negative pressures that indicate vacuum

induction and water column separation phenomenon

cannot be easily controlled like positive pressures.

The best and safest way is to inhibit negative

pressure is to prevent its occurrence.

- Negative pressures obtain from curve difference

of minimum piezometric height and profile

evaluation of line. So if in normal condition profile

of the line is lower than the curve of minimum

piezometric height, damaging effects of negative

pressure and vacuum generation and separation of

the water column in the line will not create. In design

of gravity transmission pipelines whatever the

pipeline profile has an upward concave cause that the

curve of minimum piezometrc pressure locate above

the profile of pipeline and possibility ofestablishment of negative pressures and destructive

phenomenon of water hammer is reduced. However,

in this case amount of positive pressure on the

pipeline is considerable and only we should select

proper nominal pressure of pipes and valves or can

be controlled by a suitable buffer device.

- In some of the designs that during the creation of

water hammer only enter positive pressures on the

pipeline and negative pressure does not occur due to

the shape of the line profile, can be used a

combination of two types of pipe for the transmissionline.

- In gravity pipelines the main parameters

determining hammer is the time to open and close

TC valves. Therefore for analysis of the equations

you should first select an assumed value of the TC,

then the equation and the output results are

investigated. So the minimum suitable time of

closing that during which no serious danger threaten

the pipeline and transmission system choose as a

closing time of the taps.

Almost in all kinds of taps during closing, amountof creating hammer during closing is about 85 to

90% of low primary tap and the main hammer that

causes damage occurs in about 10-15% of distal

valve closure. For gravity systems of under

pressure15-10% of the final closing of the valve

should occurs in the time more thana

LTr

2= so

water hammer pressure is reduced considerably[11].

- In plans that the route of the pipeline is so long

and the flow discharge capacity is considerable, inorder to reduce the time closing the valve operation

can be carried out in two stages. So that 85 to 90% of

tap sectional area will be operate at first and in a

short time that can be calculated and for closing the

remaining 10-15% should be done in a relative

longer period and so the total time of closing is

reduced.

With using valves with electric or hydraulic

steering (electric actuator) the opening and closing

can be precisely controlled and regulated. In these

taps with changing and reducing the operator the

opening and closing time of the valves increase. Inpilot hydraulic taps we can control and regulate the

opening and closing time by creating local pressure

drop in the power steering line to the diaphragm and

valve components[7].

Existing methods for preventing hammer

In order to avoid sudden shocks in pipes one way

of controlling water hammer is selected according to

the case arises in the design of water supply pipe

networks, pumping stations and turbines.

Basically in prediction of methods of preventingsudden strokes in pipes, pumping stations and water

distribution networks, it is necessary to reduce the

amount of height changing such as the energy


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between tankers and location of taps and pumps,

amount of time during wave movement and also

changes in velocity. For this purpose the following

methods suggested for preventing the hammer:

- Use of safety valves

- The use of check valves (to prevent water from

back)

- The use of buffer tanks

- Flue pipes

- Double orifice air valves

What is important is the fact that basically designing

water pipelines and networks and the choice of the

roughness of the pipe lining and pressure drop should be

done with care so to be able to withstand high pressures.

Strategies to anticipate and deal with water hammer in

pipelines, irrigation and drainage network project ofSivand Dam

Before choosing one of the techniques for controlling

the impact of stroking in the transmission line, the

transmission line must be hydraulic modeling and with

calculation of the potential stroke, finally the appropriate

methods should be presented at the end due to the

condition of the project.

Sivand Dam Project of irrigation and drainage network

has been designed and implemented as pipe networks.

For transmission of water to the first part of the network

it has been used from two parallel GRP pipes with adiameter of 1200 mm that receives water from an open

reservoir and shall be transferred to the beginning of the

network in length of 11800 meters. Because of the height

difference between the reservoir and the water outlet area

of agricultural land (about 36 meter) pipes went under

pressure and it was necessary that investigate the hammer

phenomenon and offer a proper method for controlling of

that.

It is necessary to precisely modelling part of hydraulic

system like pipes, tanks and relief, safety and switching

valves for analyzing water transmission line. In this

regard, the pipeline is divided into a number ofcomputational reaches and necessary to be considered the

pressure values at nodes and flow as input data plan in

addition to the physical characteristics. The purpose of

the model is to investigate the impact of hydraulic

transients in pipelines transporting water results from

closing of water taps.

First we stimulate with WaterGems for normal

conditions in steady state and then with Hammer for

unsteady state of pipeline and results are presented as a

graph.

The model boundary conditions

Due to the hydraulic studies conducted, water flow in

the basin divider is designed as a free surface and the

output structure is so that the water level is at a constant

level of 1611 meters.

Hydraulic modeling in stable condition

It is prepared with entering the transmission line route

profile and the placement of nodes and pipes on the

hydraulic model of the transmission line in hydraulic

stability conditions.

Table 1: Names and computational nodes of main line

water transfer project from km 0+000 to 11+800

LabelElevation

(m)

Calculated

Hydraulic

Grade (m)

Pressure

(m

H2O)

J-1-A.V 1,609.00 1,610.30 1

J-2-B.O 1,594.97 1,609.51 15

J-3-A.V 1,596.95 1,609.22 12

J-5-B.O&A.V

1,578.97 1,603.78 25

J-6-

B.V&A.V1,576.68 1,602.47 26

J-7 1,576.57 1,601.61 25

J-8-B.O 1,575.34 1,600.63 25

J-9-A.V 1,575.80 1,599.91 24

J-10-A.V 1,576.20 1,599.38 23

J-12-B.O&A.V

1,573.90 1,596.65 23

J-13 1,573.66 1,595.05 21

J-14 1,573.00 1,594.98 22

Table 2 Names and properties of water transmission

pipe line project from km 0+000 to 11+800

LabelLength

(m)

Pressure

PipeHeadloss

(m)

HeadlossGradient

(m/km)

P-1 147 0.2 1.31

P-2 605 0.8 1.31

P-3 219 0.29 1.31

P-4 2124 2.79 1.31

P-5 2019 2.65 1.31


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LabelLength

(m)

Pressure

Pipe

Headloss

(m)

HeadlossGradient

(m/km)

P-6 999 1.31 1.31

P-7 649 0.85 1.31

P-8 749 0.98 1.31

P-9 549 0.72 1.31

P-10 399 0.53 1.31

P-11 999 1.31 1.31

P-12 1084 1.42 1.31

P-13 1213 1.59 1.31

P-14 53 0.07 1.31

Graph (1) Profiles of main line water transfer project

from zero miles to km 11+800

Figure 1 profiles and hydraulic gradient for water

transmission line projects in stable hydraulic condition .

With viewing the profile of basin divider from the

place of the pipeline to km 11+800, it is observed that

static pressure is up to about 5/36 meters of water.

According to the technical report of consulting

engineers, shows that the flow rate is about 3.5 cubic

meters per second by PN6 GRP pipes with a diameter of

1200 mm shall be transmitted to the network. Dynamicpressure of the flow path is from zero at the beginning of

the path to about 3 atm.

calculations and modeling results in unstable

hydraulic conditions

inputs to hydraulic hammer model of in HAMMER

software

Coefficients and necessary information relating to the

characteristics of the pipe and fluid inside the pipe are

presented to model the path of unstable modes in TableNo. (3)

Table (3) the physical characteristics of GRP pipes

MaterialYoung's ModulusPoisson's

Ratio (109 lbf/ft2)(GPa)

G.R.P1300.4

fluid properties

Pipe material: GRP

Length of the transmission line: 11800 m

Inner diameter: 1200 mm

Wave velocity in the pipe: minimum 400 and

maximum of 600 meters per second

Partial pressure of water vapor: 10 - Mtrab

Valves: Butterfly valves with a diameter of 1200 mm

and 200 mm diameter air

Water level in the basin divider

Profile Transmission Line

Flow rate for each pipeline 1.75 cubic meter per second

Modeling is done in unstable hydraulic conditions for

slow closing of switching valves at the times of 60, 90,

150, 200 and 300 seconds. In Figure (2) to (9) profiles of

pipelines and minimum and maximum blow pipes are

shown at different times. It is observed with increasing

valve closure time in the last 10% hit rate is decreased but

never reach to zero

Scenario: BaseProfile from R-1-B.V to J-14

Distance along Pipe Walk(m)

(m

)

E

le

va

tio

n

1570.0

1575.0

1580.0

1585.0

1590.0

1595.0

1600.0

1605.0

1610.0

1615.0

0.0 2000.0 4000.0 6000.0 8000.0 10000.0 12000.0


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.

Figure 2: Closing the valve on the wave speed of 600

meters per second for 200 seconds with no impulse

control equipment

. Figure 2 shows unsteady hydraulic condition when

switching valve is closing in about 9+500 km in duration

of 200 seconds. It can be seen that without any water

hammer control equipment, dynamic pressure of pipeline

reaches to about 10 atmospheres before the tap.

Figure 3: Closing valve for 200 seconds at a speed of

400 meters per second without any impulse control

equipment.

Figure (3) shows the increasing pressure result fromclosing of switching valve in around 9+500 km with

wave speed of 400 meters per seconds without any water

hammer control equipment. It is observed that with

decreasing the wave speed from 600 to 400 meter per

seconds, the amount of potential hit rate decrease about 2

atm.

Figure 4: Closing the tap for 90 seconds at a speed of

400 meters per second without any impulse control

equipment.

As can be seen in Figure 4, if the switching valve

closure time reduced from 200 to 90 seconds, pressure

rise due to water hammer occurred slightly than the

previous case (200 seconds) but the frontal of positive

wave moved at about 4 km further upstream side of the

valve.

Figure 5: Closing of the tap in 60 seconds by taking ashort circuit between two pipes (wave velocity of 600

meters per second)


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In figure 5 it is observed in the case of a short circuit

between the two pipelines, since the closure time of the

valve at about 9+500 km has decreased (from 200 to 60

seconds) than the time when it is not a connection

between the two pipes but the increasing pressure of

water hammer is reduced considerably or in other words

the maximum pressure generated during the worst

condition is approximate to working pressure of the pipe

(that will not exceed 6 atm.).

Figure (6): Tap closing in 60 seconds by taking a short

circuit between two pipes.

In Figure 6 it can be seen since the valve closure time

has increased from 60 to 150 seconds, pressure reduction

result from water hammer than the figure 5 is so small.

Figure (7): The use of pressure reducing valve in km

9+500 before switching valve

(Wave velocity of 600 meters per second)

Another way to reduce the impact of pressure is to use

safety valves.

As it is observed in fig.7 pressure reduction of water

hammer in the time of using safety valves is about 1 atm

in comparison with fig.6.

But for observing the effect of slowly closure of

switching valves in the last 10 to 15%, seven case was

modeled, showed that if 90% of the tap close in 200

seconds and the last 10 percent close in 100 seconds

reducing the impact in comparison to the second case

(Figure 3) is about one to one and a half atmosphere.

But the eight case was modelled for observing the

effect results from slowly closure of switching valves in

another location of transmission line, showed that if 90

percent of the tap closure (km 3+100) took place in 200

seconds and the other 10 percent took place in 100

seconds, again, there will likely be a hit.

CONCLUSION

Due to the unstable conditions of hydraulic modeling

results and comparison of various methods to control the

impact from the economic view and the condition to

ensure the operation of pipeline the following are

discussed:

1 - Almost in all types of valves during closing, the

amount of water hammer caused by the closure is

approximately 85 to 90 percent of the primary reducing

tap and mainly the water hammer causing damage occurs

in about 15-10% of distal valve closure. For under

pressure gravity systems, 15-10% of the final closing of

the valve should be applied in a time more than

a

LTr

2= , in order to reduce water hammer pressure.

2 - Using a short circuit( connection pipe) between two

pipes that in case of occurrence of strokes, each pipe acts

like a reservoir buffer for the pipe and in addition to cost

reduction compared to control impulse safety valves or

other techniques, the conditions of operation of the

transmission line is easy.

3 - One of the oldest method is to install pressure

before the valve and so the operator should be trained

according to the number of pressure and the maximum

pressure should not be increased to a certain value to

perform the operation of valve closure. Due to the error

of manpower and the possibility of inattention of the

owner this method is not recommended.

4- Using power steering (electric actuator) or hydraulic

valves that it can precisely control and regulate the

opening and closing time. By changing and reducing the

operator rounds, increases the time of opening and

closing of the valve. In hydraulic pilot valves with

creating local pressure drop in direction of hydraulic

steering to the diaphragm and valve components can


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control and regulate the opening and closing time of the

valve.

5 - The modeling results showed that safety valve

control the potential water hammer so good.

6- In total the cost of short circuit(connection pipe)

between two pipes is less than the safety valves and

power steering, also during the operation of this circuit itgives more flexibility to design and it is recommended to

use short circuit between the two pipes in switching valve

basin to control the water hammer phenomenon.

REFRENCES

[1] Anton Bergant., Angus, R. Simpson And Esad Sijahmozic., Water

Hammer Analysis of Pumping Systems For Control of Water in

Underground Mines. 4 th International Mine Water Congress,

Ljubljana, Slovenia, Yugoslavia. September 1991.

[2] Allievi, L., Theory of Water Hammer Ricardo Garoni, Rome,

1925

[3] Cannizzaro, D., Pezzigna.G., 2005. Energy Dissipation in Transient

Gaseous Cavitation Journal of Hydraulic Engineering, ASCE, 131,

724-732.

[4] C.k. su, and c. camara, cavitation luminescence in a water

hammer: up scaling sonoluminescence. Journal of physics of

fluids, vol.15,pp- 1457-1461

[5] Don J. Wood., Water Hammer Analysis Essential And Easy (

and Efficient), Journal of Environmental Engineering, vol. 131,

No.8, August 1.2005.ASCE, ISSN 0733-9372/2005/8-1123-1131

[6] Joukowsky, N., Water Hammer, Proc. Am. Water Works Ass.,

1904, v24,pp 338-424

[7] Magazine NO 517, Vice President of Strategic Planning and

Control: guidelines on the selection and design of control

equipment and water utility of hammer. pp: 260-290, 2006

[8] Parmakian, J., 1963. Water Hammer Analysis. Dover

Publications, inc., New York, NY.

[9] Streeter, V.L. And Wylie, E.B., Water hammer and surge

control.Annual Review of Floud Mechanics, V6, paper 8054, pp57-73, 1974

[10] Tan Wee Choon., Lim Kheng Aik., Lim Eng Aik., Thean Him.,

Investigation of Water Hammer Effect Through Pipe line System

international journal on Advanced Science Engineering

information Technology. Vol. 2( 2012) No. 31SSN: 2088-5334

[11] Taebi, A. And Chamani, M,. Urban Water Distribution Network.

University OF Sfahan, Iran, pp: 330- 340, 2000.

[12] Wood, F.M., History of Water Hammer , Dep. Civ. Eng., Queens

Univ., Kingston, ont., C.E.Res.Rep. n 65.Apr 1970


ISBN: 978-1-61804-239-2 424

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