Fluid Hammer in Steam Pipes - A Guide to Reducing the Likelihood

The banging of pipes often heard when a faucet is turned off or on is called “water hammer” and is due to the sudden arrest or reversal of direction of the water flow.

Water hammer is a phenomenon seen in many other situations such as the flow of gases, other liquids or even steam, however, and is therefore more correctly called “fluid hammer” or “hydraulic shock”.

Many of us have heard the sound of pipes banging as we turn a faucet on or off. This sound is the water in the pipe being forced to stop or suddenly change direction and is called “water hammer.”

Cause of Fluid Hammer

Fluid hammer is mainly caused by the opening of an isolation valve too quickly. In most steam plants, this valve, called a steam stop, holds back steam under high pressure. If this is opened too quickly, steam rushes into the downstream piping which is at a lower temperature, and there immediately condenses into water. The right type of flow meters would help to detect this and make appropriate corrections.

In the right conditions, this rapidly condensed mass of water is moving at such velocity as to behave like a missile, because of the steam pushing it from behind, which moves ten times as fast as water. It is, to illustrate by a small-scale analogy, like the effect of shooting a water droplet through a straw.

The hydraulic force is such as to enable this bullet of water to break off any object in its path, including gate valves and insertion meters.

How to Reduce Fluid Hammer When Working With Steam

One of our flow energy management experts, Scott, with a vortex flow meter that takes the guess work out of knowing your steam pressure.

Steam fluid hammers can be damaging, but fortunately, they are preventable. Some ways you can avoid fluid hammers in your steam pipes are given below:

• Keep the downstream pipes warm to prevent significant condensation of steam. The majority of steam plants use bypass valves to route steam around the larger stop valves and so allow steam to bleed into the downstream pipes at low levels and warm them up.
• Steam traps should be used to the full to catch any possible condensation in the pipes.
• Regular and careful monitoring of steam parameters such as temperature, velocity and pressure, particularly during startup, is essential, and requires installing apps to remotely monitor and make corrections in the flow meters as required. This will help greatly with preventing water hammer as well as energy mismanagement.

This information has been sourced, reviewed and adapted from materials provided by Sierra Instruments.

For more information on this source, please visit Sierra Instruments.