WATER HAMMER: EFFECTS AND SOLUTIONS
Water hammer is a commonly observed phenomenon taking place during a fluid flow. Presence of water hammer can be easily detected by the noise it makes. Noise is not the final effect of water hammer but just an indication of it. Water hammer has multiple adverse effects on steam systems. Water hammer can damage equipments like flow meters which are installed on the steam network. Instances of rupture and disruption of piping on account of water hammer are also quite common. In a few cases, water hammer has resulted into catastrophic hazards. Water hammer is not only a system issue but it is also a safety issue. Water hammer can be defined as follows-
“Water hammer is a pressure surge or wave caused when a fluid (usually a liquid but sometimes also a gas) in motion is forced to stop or change direction suddenly (momentum change)”.
As soon as steam leaves the boiler, it starts losing heat. As a result, steam stats condensing inside the pipe work. The rate of condensate formation is high particularly during the start ups when the system is cold. As a result of the condensation, the droplets of water are formed. These droplets of condensate get built up along the length of steam pipework forming a solid slug. When this slug encounters any obstacle such as a bend, it will be brought to a halt abruptly. All the kinetic energy of the condensate slug will get converted into pressure energy which has to be absorbed by the pipe work. This gives rise to the phenomenon of water hammer.
The Effects of Water Hammer
- Pump and Flow System Damage
Repeated water hammer may also cause significant damage to pumps, existing valves, and instruments, lead to the catastrophic failure of gasketed joints and expansion joints, and affect the integrity of pipe walls and welded joints.
- Leaks
Water hammer can damage fittings, joints, and connections, resulting in leaks. These leaks often start slowly, gradually increasing in intensity over time. Smaller leaks may go unnoticed for quite some time, leaving surrounding equipment susceptible to damage.
- Ruptured Pipes
Ruptured pipelines due to pressure spikes are especially expensive to repair. Rupture results in local pipeline failure and can cause the entire system and other equipment to fail. The ensuing damage can be extensive, often entailing major replacement operations.
- External Property Damage
If left unchecked, water leaks can damage electrical equipment and or lead to the corrosion of equipment or infrastructure.
- Accidents
Pipeline rupture can also endanger the health and safety of employees and maintenance personnel. Depending on the industry and specific facility, unmanaged leaks can also increase the risk of slips, falls, and electrocution.
- Downtime/Maintenance
Property damage can lead to costly repairs or equipment replacements. Additional financial losses may also be incurred due to downtime required for additional maintenance, repairs, or installations.
As you can see, it is essential that immediate action is taken at the initial signs of water hammer. Failing to do so will ultimately result in system wide damage, and may spread beyond the flow system to other equipment or facility infrastructure.
Prevent Water Hammer
The most important way to prevent water hammer is to remove the water from the steam lines before passing the steam again through them. Water is removed from the steam lines using drain connections.
All the water should be drained out to make the lines clear. Once this is done, the steam valve should be opened very slightly (cracked open) to heat the line and to bring it to working temperature. This also ensures that the condensate formed due to inlet of steam is removed through the already opened valve. The drain outlet should be continuously checked to ensure that all water is drained out.
