Water Hammer


In an open space, waves accelerated by high winds can cause severe damage, even when the forces are distributed across a large area. Now think about this scenario taking place in the confines of an enclosed steam system. Waves of accumulated condensate, reacting to naturally occurring shocks in the system, can surge through and block an entire cross section of a pipe. When accelerated through the piping by a shock, these waves can attain significant force. This effect is known as water hammer.

While damage is most often caused by repeated occurrences of water hammer, sometimes damage can be immediate and catastrophic.

The most common types of shock that can cause water hammer in a steam system are:

Hydraulic Shock


You may have experienced this effect in your home when you slam the water faucet closed a little too forcefully and you hear a distinct hammering sound from your pipes. This same effect can occur in a steam system whenever a manual or automatic valve is slammed shut in a flooded line. If the valve suddenly impedes a flow of condensate, a portion of that flow is reversed, causing a pressure wave that reflects off the piping and off equipment until its force is dissipated.

We can prevent hydraulic shock in steam systems by eliminating large condensate accumulations and closing valves slowly or installing a type of automatic valve that always closes slowly. We can prevent hydraulic shock at home by treating our faucets with a little more courtesy.

Thermal Shock


You guessed it. This kind of shock is temperature related. Thermal shock occurs when steam is discharged into a body of cool condensate. A void is instantly created as the steam condenses. Liquid rushes into the void, colliding in the center, causing shock waves through the condensate, and the resulting waves collide with piping and equipment until the energy is depleted.

Reducing condensate accumulations, where possible, can prevent the occurrence of thermal shock. In a process called sparging, a fitting is used to gradually release hot condensate into the cool return line, allowing the temperatures to equalize with less traumatic effect.

Differential Shock


Steam flow over accumulated condensate can create waves that grow as they are pushed downstream. If the steam is moving fast enough and the condensate is sufficiently abundant, the waves will grow until they block the pipe completely, stopping only when something intervenes or they're suddenly diverted by equipment or a bend in the piping.

Differential shock can best be prevented by careful sizing of condensate return lines and by reducing condensate accumulation wherever possible.
To see a synopsis for the video
"Guidelines for the Prevention of Water Hammer,"
click here.

To see a live demonstration from our Steam Energy Seminar, click here.