What is the Water Hammer? What are the causes and how to remedy the Water Hammer phenomenon

Some tragic incidents of victims of death occurred from steam pipeline explosions such as 21 deaths at a Power plant in China or 18 deaths in an explosion in New York, USA. From the above statistics, we can see the risks of pipeline explosion when not given proper attention. And one of the causes of this serious disaster is the water hammer phenomenon. So what is a water hammer? What are its harmful effects and how to avoid this phenomenon? Let’s find out with Khanh Anh through the article below!

What is the Water Hammer phenomenon?

Water hammer is a phenomenon that occurs when the flow of water is suddenly stopped. Specifically, water hammer is a phenomenon in which pressure in a pipeline suddenly increases or decreases, created when a fluid (usually a liquid but sometimes also a gas) is moving but is forced to stop. or change direction unexpectedly.

In factories and production lines, this water hammer phenomenon often occurs when a valve suddenly closes at one end of the pipeline system, and therefore it will create a pressure wave that propagates in that pipeline.

This pressure wave can cause serious problems, from noise and vibrations to pipe damage. And the shock wave created will affect the entire system and the stop valve at the discharge gate, directly affecting the production and business activities of the enterprise.

As for steam systems in factories, water hammer occurs when the steam trap does not operate as designed, for example by not draining condensate or installing it upside down. Water in the pipe moves at high speed in the pipe, easily leading to this water hammer phenomenon. Besides the pressure of water, the pipeline must also bear the high pressure of steam. These things will resonate together, making the risk of steam pipes exploding very high.

Cause of Water Hammer phenomenon

The main causes of water hammer are usually:
– Valve closes or opens too quickly
– The pump starts or stops suddenly
– The steam trap is not working properly

The above reasons will cause the velocity energy in the pipe to be converted into pressure energy. Because the water flow is limited inside the pipe, a shock wave will move back and forth through the water, which, because the water is incompressible in the pipe, will cause a pressure increase at every point in its path.

Specifically, when a pipe is suddenly blocked at the outlet, the water mass in front of the closed outlet is still moving, so the pressure builds up and creates a shock wave. In residential piping systems, this will create a loud bang, similar to a hammer noise, and water hammer can cause the pipe to burst if the pressure is high enough.

On the other hand, when the upstream valve in the pipe closes, the water flow downstream of the valve still tries to continue flowing, creating a vacuum that can cause the pipe to break or burst. . This problem can become especially severe if the pipeline is located on a slope. And to prevent this, air and vacuum relief valves, vents, or steam traps are installed downstream of the valve to let air enter the flow, preventing this vacuum from occurring. .

In addition, there are other causes causing this phenomenon:
– Steam traps that have been damaged for a long time cannot be repaired
– Forgetting to release the valve causes the steam trap to not work
– Loose pipes: If pipes are not properly secured, shock waves in the pipe system can be exacerbated by physical impact to the pipe itself.

Harmful effects of Water Hammer phenomenon

Leaks: Water hammer has the potential to damage joints and fittings, leading to poor sealing and ultimately leaky pipes. In addition, a sudden increase in pressure exceeding the nominal pressure value of the pipeline will also create cracks, leaks, and ruptures. In more severe cases, a system explosion may occur.

Equipment damage: When water hammer occurs in the pipeline system, stop valves are the first affected equipment. When the pressure suddenly increases, it will impact the valve disc causing pressure. In more severe cases, it can deform the valve disc or, most seriously, crack the valve disc or valve.

Property damage: If leaks go undetected, they have the potential to damage surrounding electrical equipment and lead to infrastructure corrosion.

Pipe deformation: Water hammer also causes pressure drop, leading to pipe deformation. This severely affects the operation of other industrial valves in the system.

Financial and health damage: Finally, water hammer can cause financial and health damage to system users. Extreme pressure can cause gaskets to burst and pipes to burst instantly, causing immediate danger to anyone nearby.

How to calculate the peak pressure of Water Hammer

The water hammer pressure spike in a pipeline caused by a closing or opening a valve can be estimated as:

ΔP = 0.070ΔVL / Δt

In there:
ΔP: Increase in pressure – pressure spike (psi)
ΔV: Change in flow velocity (ft/s)
Δt: Valve closing time (s)
L: Pipe length (ft)
1 ft (foot) = 0.3048 m
1 ft/s = 0.3048 m/s
1 psi (lb/in2) = 6894.8 Pa (N/m2)

Example, water hammer generated when closing a solenoid valve, the water hammer pressure spike in a pipeline caused by a closing or opening a valve can be estimated as:
ΔP = 0.070 x ((6 ft/s) – (0 ft/s)) x (100 ft) / (0.1s) = 420 (psi)

With a closing time of 1s (solenoid valve with damper) – the pressure spike (water hammer) can be estimated as:
ΔP = 0.070 x ((6 ft/s) – (0 ft/s)) x (100 ft) / (1s) = 42 (psi)

Measures to mitigate and overcome Water Hammer situation

As mentioned, water hammer has caused serious accidents and even deaths, but usually the damage is limited to broken pipes or auxiliary equipment. Therefore, we need to pay attention to avoid greater risks that may occur by taking specific measures such as:
– Open and close the valve as slowly as possible to avoid sudden pressure differences.
– Use a soft starter before running or stopping the pump.
– Use hydraulic pressure relief valves, anti-water hammer one-way valves, and air release valves for safe operation.
– Use pipes that can withstand high pressure.
– Reduce fluid velocity. To reduce the risk of water hammer, pipe sizing charts for some applications recommend flow velocities of 1.5 m/s (4.9 ft/s) or less.
– Good pipeline control: Engineers and workers must always be properly trained and assess the potential risks of pipeline explosions caused by water hammer. Pipelines transporting hazardous liquids or gases must be given special care in design, construction and operation.

Understanding the importance of controlling pressure in pipelines, at Khanh Anh Company, we are distributing many genuine lines of pressure reducing valves, vacuum valves, and check valves from leading brands in the world such as Inoxpa, Definox, etc. to minimize the negative effects of water hammer phenomenon that can occur. These types of valves have been trusted and chosen by many large manufacturing plants in Vietnam to use in their systems for many years, building trust in the hearts of customers.

Through this article, Khanh Anh Company hopes to bring customers and partners the most useful information about the water hammer phenomenon, its causes and effects to Helps customers better understand the dangers that water hammer brings, thereby applying smart measures to minimize the effects of water hammer.

If Customers – Partners are looking for and choosing the most suitable solutions for their production system, do not hesitate to contact Khanh Anh immediately to receive advice from our Technical team! Best regards.

KHANH ANH COMPANY LIMITED
Address: F10, street 6, Van Gia Phuc block, 295 Tan Ky Tan Quy str., Tan Son Nhi ward, Tan Phu dist., Ho Chi Minh city, Vietnam.
Email: kaco@inoxkaco.vn
Hotline: +84 28 6658 2434 – 6659 2434