What is Water Hammer/ Steam Hammer?

Have you ever heard a loud 'BANG' or hammer-like sound after quickly turning on or off a water faucet? This is the sound of water hammer in the water piping system. In a factory, a pump starting up operation or shutting down, or an air vent suddenly closing are examples of when this might occur.

In addition to water transport piping systems, water hammer also occurs in steam and condensate recovery (i.e. water circulation) systems. This series of articles will focus on water hammer in these latter two systems. Note that as steam is involved, this type of water hammer is also sometimes referred to as 'steam hammer'.

The Dangers of Water Hammer

When steam is first supplied to steam distribution piping or steam-using equipment, a metallic and repetitive 'bang, bang, bang', or even sometimes a violent 'boom' accompanied by vibration may be heard. Most steam users will probably have experienced one of these at some time.

When water hammer occurs, a momentary abrupt pressure change of over 10 MPa may occur inside the piping.

This impact can severely jar piping, equipment or machinery housing, possibly resulting in damage not only to gaskets in junctions, but also to valve flanges or the valves themselves.

As soon as something like this, such as a valve, becomes damaged, large quantities of steam or hot condensate begin blowing out, which could lead to a serious accident. There have even been reports of deaths occurring as the result of water hammer. In spite of this, there is remarkably little research or literature devoted to its causes and prevention, and many steam users find themselves at a loss with how to cope with the issue.

Places Water Hammer (Steam Hammer) Occurs, by Type

Why Bad Things Happen to Good Steam Equipment

Water Hammer: The Mechanism