Disturbances in water distribution systems can be caused by various situations, including changes in pump operations, valve movements, boundary pressures, demand conditions, and transmission conditions. These disturbances can result in variations in flow, pressure, and water quality, which can impact the overall performance and reliability of the system. The following table summarizes the different types of disturbances and their potential effects on the system:
| Disturbance Type | Description | Potential Effects |
|---|---|---|
| Pump Startup/Shutdown | Changes in the operation of pumps in the system | Variations in flow and pressure |
| Valve Opening/Closing | Changes in the flow area caused by the movement of valves | Variations in flow and pressure |
| Boundary Pressure Changes | Changes in the level or pressure of reservoirs, tanks, etc. | Variations in pressure and water quality |
| Rapid Demand Changes | Sudden changes in water usage, such as hydrant flushing | Variations in flow and pressure |
| Transmission Conditions | Changes in the condition of pipes, such as breaks or leaks | Variations in flow and pressure, water quality |
It's important to note that water distribution systems are complex systems and disturbances in one area can have knock-on effects in other parts of the system, so it is important to monitor and control the system to ensure stability and reliability.
Open surge tanks
Closed surge vessels Bladder tanks Hybrid tanks (vented to admit air) Bypass lines Check valves Feed tanks (provide inflow to prevent cavitation) Air release/vacuum valves (2 and 3 stage valves) Pressure relief valves Surge anticipation valves| Type of Tank | Description | Advantages | Disadvantages |
|---|---|---|---|
| Open Surge Tanks | These tanks are open to the atmosphere and allow the excess pressure to be released. | - They are relatively simple and inexpensive to construct. <br> - They can be used to prevent the water hammer effect. | - They are subject to evaporation and contamination. <br> - They are not suitable for use with hazardous materials. |
| Closed Surge Vessels | These tanks are sealed and use a compressible gas (such as air) to absorb the excess pressure. | - They can be used with hazardous materials. <br> - They are less susceptible to evaporation and contamination. | - They are more expensive to construct than open surge tanks. <br> - They require regular maintenance to ensure the compressible gas is at the correct pressure. |
| Bladder Tanks | These tanks use a flexible bladder to separate the water from the compressible gas. | - They are less expensive to construct than closed surge vessels. <br> - They require less maintenance than closed surge vessels. | - They are not suitable for use with hazardous materials. <br> - They have a limited life-span and need to be replaced periodically. |
| Hybrid Tanks (vented to admit air) | These tanks are similar to closed surge vessels but have a vent to admit air. | - They are less expensive to construct than closed surge vessels. <br> - They require less maintenance than closed surge vessels. <br> - They can be used to prevent the water hammer effect. | - They are not suitable for use with hazardous materials. <br> - They are subject to evaporation and contamination. |
| Bypass Lines | These lines allow water to bypass the tank and the pump, reducing the pressure surge. | - They reduce the pressure surge. <br> - They are relatively simple and inexpensive to construct. | - They can increase the system head loss. <br> - They can increase the pump energy consumption. |
| Check Valves | These valves prevent the water from flowing back through the system, reducing the pressure surge. | - They reduce the pressure surge. <br> - They are relatively simple and inexpensive to construct. | - They can increase the system head loss. <br> - They can increase the pump energy consumption. |
| Feed Tanks | These tanks provide inflow to prevent cavitation. | - They prevent cavitation. <br> - They are relatively simple and inexpensive to construct. | - They can increase the system head loss. <br> - They can increase the pump energy consumption. |
| Air Release/Vacuum Valves | These valves release or admit air to the system to prevent or correct negative pressures. They can have 2 or 3 stages. | - They prevent or correct negative pressures. <br> - They are relatively simple and inexpensive to construct. | - They can increase the system head loss. <br> - They can increase the pump energy consumption. |
| Pressure Relief Valves | These valves release the excess pressure to prevent damage to the system. | - They prevent damage to the system. <br> - They are relatively simple and inexpensive to construct. | - They can increase the system head loss. <br> - They can increase the pump energy consumption. |
| Surge Anticipation Valves | These valves are designed to anticipate and absorb pressure surges in a pipeline. | - They anticipate and absorb pressure surges. <br> - They are relatively simple and inexpensive to construct. | - They can increase the system head loss. <br> - They can increase the pump energy consumption. |
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