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Water Hammer

Water hammer is a pressure surge or wave that occurs when water flowing through a pipe is forced to stop or change velocity suddenly, such as with the rapid closure of a valve. This can cause very high pressure spikes that can damage pipes and equipment. Proper design and use of devices like slow closing valves, surge tanks, and water hammer arrestors can help control water hammer pressures and prevent damage to water systems. While water hammer can be destructive, it is also useful in some applications like hydraulic rams and mine clearing operations where the pressure wave is controlled.

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646 views18 pages

Water Hammer

Water hammer is a pressure surge or wave that occurs when water flowing through a pipe is forced to stop or change velocity suddenly, such as with the rapid closure of a valve. This can cause very high pressure spikes that can damage pipes and equipment. Proper design and use of devices like slow closing valves, surge tanks, and water hammer arrestors can help control water hammer pressures and prevent damage to water systems. While water hammer can be destructive, it is also useful in some applications like hydraulic rams and mine clearing operations where the pressure wave is controlled.

Uploaded by

saishankarl
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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WATER HAMMER

NAVEEN SUDHARSAN
MT14WRE010
What is Water Hammer?

 Water hammer is a pressure surge or wave resulting when a fluid in motion


is forced to stop or change the velocity
 A water hammer commonly occurs when a valve closes suddenly at an
end of a pipeline system, and a pressure wave propagates in the pipe. It is
also called hydraulic shock.
Immature
operation
of valve

Reasons

Sudden
Power
stoppage
outage
of pump
Sudden Closure Of A Valve
Mechanism

Fluid Mechanics with


Engineering
applications by
Joseph B Franzini &
E.John Finnemore
Mechanism
At the Reservoir Sudden Closure of
the valve
•Unbalanced condition
•Due to Negative •Fluid lamina near to the
pressure in the pipe valve compressed
•Flow towards pipe •This compression
starts(4L/a) reaches upstream end
of the pipe(t=L/a)

At the Reservoir
Low pressure
•Unbalanced condition
moves upstream as at the reservoir pressure
waves •Flow from pipe to
•Makes the velocity of reservoir starts as the
wave moves Fluid Mechanics by
flow zero again
downstream Victor L Streeter, E
•But the fluid in the pipe Benjamin Wylie & Keith W
will be expanded(3L/a) •Reservoir pressure Bedford
unchanged(2L/a)
Water Hammer Equations

Joukowsky (1898) eqn


∆𝑃 = 𝜌𝐶𝑝 ∆𝑉
 Where ∆𝑃 is change in pressure
 𝜌 density
 𝐶𝑝 is the velocity of wave (1496 m/s at 25°C in water)

 ∆𝑉 is change in velocity
 This equation can be used only for rapid closure( t < 2L/𝐶𝑝 )
Water hammer equations for all conditions:
 Equation of motion
𝜕𝑉 𝜕𝐻 𝑓𝑉 𝑉
 +𝑔 + =0
𝜕𝑡 𝜕𝑥 2𝐷

 Equation of continuity
𝜕𝐻 𝑎2 𝜕𝑉
 + =0
𝜕𝑡 𝑔 𝜕𝑥

These two pde are solved using method of


characteristics.
 Consider a 500mm dia pipeline, L = 8000 m, 𝐶𝑝 =1000m/s
& v = 2 m/s, a gate valve is closed in 5 seconds.
Calculate the pressure surge. Calculate the force
exerted on the gate.
2𝐿
 𝑇𝑟 = = 16 𝑠 > 5 𝑠
𝐶𝑝

 Joukowsky’s equation may be applied.


 ∆𝑃 = 𝜌𝐶𝑝 ∆𝑉
𝑁
 ∆𝑃 = 20 𝑋 105
𝑚2

 Area = .196 𝑚2 ≈ 0.2 𝑚2


 𝐹𝑜𝑟𝑐𝑒 𝐹 = 𝑃. 𝐴 = 20 𝑋 105 𝑋 0.2 = 400000 𝑁
 F = 400 𝐾𝑁
Applications

Hydraulic Ram
works with the
principal of Water
hammer

The US Navy is
conducting Leaks can
field trials for sometimes be
mine clearing detected using
using water water hammer
hammer.
Effects of Water Hammer

Damage to pipes, fittings, and valves, or any connected


equipment causing leaks and shortening the life of the system

Bursting of pipes can occur if the pressure is high enough

Water hammer can have devastating effects on pump system


Devices for Protection from Water
Hammer
 Soft Starters

 Slow closing valves


 Variable Frequency Devices

 Water Hammer Arrestors


 Surge Tanks

 Pressure Release Valves


Conclusions

Water hammer can cause severe problems in the system if


not designed properly. So at the time of designing of the
system potential water hammer problems should be
considered for thorough analysis. And proper methods or
devices are to be used so as to assure the proper
functioning of the system and to lessen the effect of water
hammer
Water hammer is useful in certain cases as hydraulic ram,
mine clearing etc.
References

 Fluid Mechanics with Engineering Applications by Joseph B Franzini & E


John Finnemore, The McGraw Hill Companies, 1997
 Fluid Mechanics by Victor L Streeter, E Benjamin Wylie and Keith W Bedford,
The McGraw Hill Companies, 2010 reprint
 KSB Know how, Vol 1 Water hammer, KSB Aktiengesellschaft, Johann-Klein-
Straße 9,67227 Frankenthal
 en.wikipedia.org/wiki/Water_hammer

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