Not-So-Silent Hazard: Water Hammer Impacts on Fluid Systems

Jens Conzen

Water hammer is a pressure surge that occurs when a fluid quickly stops or moves direction in a pipe. Learn how to manage.

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Have you ever turned off the tap on your kitchen sink, and heard a thud? That’s an example of water hammer, a pressure surge that is a common hazard in fluid systems. Take that scenario and apply it to hydroelectric plants, municipal water or steam systems, chemical plants or fossil fuel power plants and you can start to see how water hammer could have potentially dangerous consequences.

What Causes Water Hammer and What Are the Hazards?

So, what is water hammer? Simply put, water hammer is a pressure surge or wave caused by a fluid quickly stopping or changing direction inside a pipe. It can be caused by a rapid valve closure, pump starts, valves opening or a relief device (rupture disk / relief valve) operating. The pressure surge or wave travels throughout the entire piping network potentially damaging the piping, supports and other pipe network components. The system response is acoustic, sending a shock through the system in a matter of milliseconds.

Water hammer can occur in household piping if no suppressor is installed and a valve is closed too rapidly. A simple example of a water hammer is shown in this video, where a column of accelerating water is rapidly brought to rest which results in water hammer. When water hammer occurs, the impact can overstress pressure gauges, damage the supports of piping structures, and bend internal system mechanisms such as supports and snubbers getting jammed at the end of a stroke. If the water hammer event is large enough, piping systems can rupture.

How to Stop Water Hammer

Many different industries already address water hammer hazards, including the US nuclear industry, where the regulator requires power plants to address potential operational issues related to water hammer events in pipes containing steam (GL 96-06) and non-condensable gas (GL 08-01). Despite this, there are still facilities using fluid systems that don’t properly address this hazard through water hammer protection.

Many facilities don’t have safeguards in place to prevent a water hammer event. Instead, water hammer occurs and prompts facility managers to come up with a plan. From that point, there are a couple steps they can take to reduce the risk of a water hammer event happening again. They can seek out the expertise of engineers and thermal-hydraulics experts, who can analyze the transient fluid and structural response of their system by utilizing information from pipe network drawings and operating procedures. Drawing on these results and operator interviews, the engineers can help identify potential water hammer scenarios. Additionally, they can use software tools to model the system and scenarios susceptible to water hammer events. The water hammer analysis will determine if the system can tolerate the pressure, if modifications to operating sequences or hardware are needed, and design mitigation strategies.

To learn more about our water hammer solutions as well as training opportunities, contact: waterhammer@jensenhughes.com

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