Why use control valves?
Water is a scarce resource that we need to protect. We need to secure water for the next generations and a growing population. Control valves can help reduce water losses and contribute to efficient water supply management by maintaining a certain pressure, flow or level, regardless of changes in the supply network.
Implications of water loss
From an environmental perspective, significant amounts of precious water are lost, and the energy used to treat and distribute the water lost is wasted as well.
For water utilities, non-revenue water that has been produced but “lost” before it reaches the customer through leaks, theft or metering inaccuracies is a source of unwanted cost.
Control valves ensure pressure management in the supply network
Automatic control valves are used to obtain efficient pressure and flow management resulting in:
- Reduced water loss through leakages
- Reduced risk of water hammer and pipe bursts
- Less disruption to consumers
- Minimized risk of contamination
- Savings for network operators
What is a pressure sustaining/relief control valve?
A pressure sustaining control valve automatically maintains a minimum preset inlet pressure by relieving excess pressure, regardless of changes in flow rate.
The pressure sustaining pilot reacts to small changes in the inlet pressure, controlling the valve position. If the inlet pressure falls below the set point, the main valve closes or modulates to ensure a minimum inlet pressure. The sustaining valve holds a minimum back pressure on the inlet and normally allows flow. The relief valve normally remains closed and only opens when pressure exceeds a pre-determined set-point.
Example: If the pressure drops when filling a water reservoir, the water flows out of the reservoir. The pressure is maintained by installing a pressure-maintaining control valve.
What is a pressure reducing control valves?
A pressure reducing control valve automatically reduces a higher inlet pressure to a lower outlet pressure regardless of changes in flow rate or inlet pressure.
The pressure reducing pilot senses the outlet pressure through the connection on the valve outlet port. Under flowing conditions, the pressure reducing pilot reacts to small changes in the outlet pressure, controlling the valve position by modulating the pressure in the control chamber. When the outlet pressure changes according to the set-value of the pilot, the pilot modulates to ensure pressure control.
Example: in an area, a pressure of 7-8 bar is suitable for supplying customers in area A with water, but this pressure is too high for the customers in area B. By installing a pressure reducing control valve, it is possible to decrease pressure in area B to 3 bar.
What is a constant flow control valve?
A constant flow control valve automatically monitors the flow and regulates if required, to secure that the flow does not exceed the maximum allowed flow regardless of changes in the supply pressure.
The pressure drop across an orifice plate is sensed by the constant flow pilot. When the flow is low and the pressure drop is below the pilot setpoint, the constant flow pilot and the main valve will be fully open. If the flow is high and the pressure drop becomes higher than the setpoint, the valve starts to regulate the maximum flow according to the setpoint, to secure that the flow does not exceed the maximum allowed flow.
