Water Hammer Created by Joshua Toebbe NOHS 2015

Water hammer What is water hammer? Not exactly… Created by Joshua Toebbe NOHS 2015

Water hammer Created by Joshua Toebbe NOHS 2015

Water hammer So as water is flowing it is carrying with it a tremendous amount of energy, and thus the ability to apply a force over a distance. When a valve or gate is closed, the water must suddenly stop moving. According to Newton’s 1 st Law, and object in motion will want to remain in motion. So the kinetic energy of the water must be dissipated some how. This dissipation of energy is known as water hammer, from the characteristic hammer like noise it makes. (also known as fluid shock) Created by Joshua Toebbe NOHS 2015

Water hammer Basically the flowing water pushes against the pipe or vessel and transfers its kinetic energy to the walls of the pipe as a force. Since pipes are generally inflexible, the distance over which the force is applied is relatively small, so the force must be great to dissipate all the kinetic energy. Created by Joshua Toebbe NOHS 2015

Water hammer demo Created by Joshua Toebbe NOHS 2015

Water hammer Created by Joshua Toebbe NOHS 2015

Water hammer solutions That much energy can easily break a valve, which means the dam has to be shut down for maintenance and the energy production goes off-line. So how can this be prevented? (take a second to think about it, and write it down) Created by Joshua Toebbe NOHS 2015

Water hammer solutions Water hammer is the result of rapid dissipation of kinetic energy. So this energy must be dissipated gradually, and not be applied to the valve itself. But how can we dissipate that much kinetic energy? (take a second to think about it, and write it down) Created by Joshua Toebbe NOHS 2015

Water hammer solutions Well where is that energy coming from? In a hydraulic dam, the energy is coming from the height of the falling water. So we can send it back were it came from. Surge drums Created by Joshua Toebbe NOHS 2015

Water hammer solutions When the valve closes the excess energy pushes the water up a surge drum. As the water rises it converts the KE back into PE This prevent the force from being applied to the valve closure. Created by Joshua Toebbe NOHS 2015

Water hammer solutions So what about all the other cases of water hammer, like the loud clunk that happens when the toilet or dishwasher shuts off? How could water hammer be averted on a smaller scale? (take a second to think about it, and write it down) Created by Joshua Toebbe NOHS 2015

Water hammer solutions Its called a water hammer arrestor, and its basically like a tiny surge drum. When the valve shuts the energy carries water into the arrestor or “tiny surge drum”. Why do you think that piston has to be there? Created by Joshua Toebbe NOHS 2015

Water hammer solutions Okay so the water doesn’t push against the valve. What happens to the water on the other side that keeps flowing? Cavitation! But we will look at that tomorrow… Created by Joshua Toebbe NOHS 2015

The End Don’t forget to go with the flow… (I know, I know…) (and turn in your practice problems please) Created by Joshua Toebbe NOHS 2015