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Anyone who has worked on a ship must be aware of the loud thumping noise, apart from the main engine’s sound, that reverberates through out the whole engine room. This scary noise is sometimes so loud that it resembles the sound of breaking of some machinery part. However, ship people know that this is nothing but a sound coming from the labyrinth of steam pipe lines on ship. This thudding sound from the steam lines is known as “water hammering".
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Understanding Water Hammering
Steam lines when shut down have a tendency of accumulating water in them. Accumulation of water in steam lines can be caused due to several reasons, but it is this accumulated water that leads to water hammering. When steam is again allowed to enter these lines already filled with water, it comes in contact with the water and pushes the water down the line. Moreover, as the steam comes in contact with water it condenses to form vacuum, generating a suction force. This suction force pulls the water back with very high velocity. This high velocity water is always looking for a way to escape, and if incase a valve is opened the water strikes it with heavy blows, generating the “hammering" sound.
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Is Water Hammering Dangerous?
Water hammering can be extremely dangerous and sometimes even life threatening if in case the water striking the valve has extremely high pressure. This high pressure might even lead to valve fracture. If the valve fractures, the high temperature water and steam will come out with full force, causing harm to the person standing in front of it or even leading to loss of life.
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How to Prevent Water Hammering?
The first thing that needs to be done for preventing water hammering is to open the steam line drains before passing the steam again through the lines. This process is of utmost importance and should be followed religiously every time before starting the steam. The opening of drains will remove all the water accumulated and clear up the lines.
In case a steam valve is to be opened, it is to be done very slowly (cracked open) so that the line is heated and brought to the working temperature. The slowly opening of the valve facilitates the removal of any accumulated condensate through the drain. The operating of the line drains and the steam valve is a simultaneous process and should be carried out with utmost care. As the temperature of the line rises and the amount of water coming out of the drain reduces, the pressure on the steam line should be increased by opening the steam valve further. After sometime, the drains should be fully closed and the steam valve should be completely opened.
It is a known fact that water hammering cannot be avoided completely; however sufficient steps should be taken to avoid it or else it might lead to disastrous situations. Water hammering has also been the reason behind many fatalities on ship in the past and thus adequate care should be taken to deal with it. In case the hammering doesn’t stop, the passing of steam through the line should be immediately stopped.