Water present in a steam system moves at a very high velocity driven by the steam pressure. In some cases, the acceleration is even greater than that of steam. When this water at high speed hits a fitting such as valve or a bend, violent impact resulting in noise or a pressure shock which travels through the system is produced. This is called water hammeringMild cases of water hammering can cause noise or vibration. Extremely severe cases can result in fracture of the pipe.
Condensate Hammering is more damaging than water hammering. In condensate hammering, a pocket of steam surrounded by cooler water condenses into water. This causes a rapid reduction in volume. The water surrounding the pocket are thus drawn inwards and a collision occurs. This results in a severe a rapid over pressurization which can easily damage gaskets, valves and other components. The consequences can be very disastrous even fatal.
Hammering can be removed by preventing water from entering the steam lines. Reducing Carryover, ensuring that the steam traps are functioning properly are some of the precautions. The steam velocity in a boiler should not be allowed to exceed limits. Steam velocity has a direct bearing on the intensity of the hammering.
The piping should be as per design. Sagging of the pipeline can cause water hammering. Damaged insulation can cause condensate formation in the pipelines. Insulation should be checked and replaced if damaged.