By Ryan Spooner, Singer Valve
For many years water management systems have used exclusively mechanical components. There is no doubt that these tried and true systems have given useable results, but in recent years there has been a large push to develop better methods for controlling water. The primary focus for solutions has been in the areas of reducing maintenance, saving water, and reducing pipe breakage. With our ever growing population, it has become a necessity to be able to control a large municipality water supply from one central location.
Designing such large, complex systems is no easy task. The design starts at each and every individual chamber, choosing the correct control valve. Even when a valve is deemed right for the application it is usually used for specific situations. For example a pressure reducing chamber may be set based on high capacity flows and pressures of the system. However a large system reducing pressure to the same point at all times of the day can put added excess pressure on the system. Being able to fluctuate the pressure setpoints as the system demands, such as nighttime flow and daytime flow can prevent pipe breakages, reduce water loss, and improve the overall efficiency of the system. The control panel will give the capabilities to have a live system and gain access to the chamber at any time of the day with the capability to change the pressure set point based on the feedback. All this can be done by a local control room instead of traveling throughout the city from chamber to chamber to change mechanical setpoints. Depending on the size of the distribution system and the variable demands, the design can become very, complex.
The first question to ask your self is what are you trying to control? A few of the most common options are:
- Flow control
- Pressure-reducing control
- Pressure-sustaining control
- Valve position control
- Tank level control
- Booster pump control
- Surge anticipation control
Choose one option or choose three; a panel can be designed and programmed with the most efficient algorithm based on your application’s priority sequence, ensuring the system works exactly as you expect it to.
The type of control or the way you would like control a system is often based on what types of feedback elements you plan to use — these may be sensors or switches purchased with your valve, or existing components already connected to your system.
This X156 Positions Senor coupled with dual micro limit switches gives the end user an analog 4–20mA signal for exact position of the valve as well as a digital contact for when the valve is fully closed as well as fully open.
A good control panel can integrate with one or many of these feedback modules and control the system to user set points. One implementation could be as basic as using a control panel to control a single valve for position or pressure management or possibly using that same panel to control two valves in one station for position or pressure management.
A more complex design can use flow rate as a primary feedback element for filling a tank, while simultaneously monitoring pressure as a sustaining feature and tank level control for system alarms. This type of configuration would ensure that the system does not over-draw water upstream of the valve, all while filling and monitoring the level of the tank.
The second question to consider is how will the system be maintained and controlled by the operator. Some control panels have the option to be controlled locally on site or via complete remote control off- site. Depending on the size of the system or site this becomes a key feature to consider in controls. It may be beneficial for onsite staff to adjust a valve parameter based on the changes in site parameters or it may be beneficial for site parameters to change and have them automatically adjust valve parameters remotely.
Here a dual solenoid control valve is used to control the flow of a recirculation line. The flow is measured with a SPI-MV flow meter and a 4–20mA signal is sent to the control panel in the onsite control room.
The control panel then receives the flow signal from the SPI-MV, as well as a remote set point via the onsite SCADA control PLC (left), and controls the valve to the correct set point needed by the system.
A control panel can also be integrated with a SCADA system via 4–20mA signals and dry contacts, or via industrial communication protocols such as Modbus. The panel can receive all necessary set points and I/O controls and retransmit any necessary data needed. Without getting out of your seat at your SCADA control room, you have complete access to your control panel.
Once the communication protocols are set and the control algorithm of the system is decided, the final features to consider are the desired inputs and outputs. A digital input is usually used to remotely control an option on the panel. A digital output of the system is usually configured as an alarm or status indicator to show whether the system is currently idle or running a control sequence.
The final question before design is to determine the installation location and power source. A control panel can be designed for either AC or DC input supply voltages. The environment in which the panel will be installed needs to be taken into account. A control panel can accommodate both indoor and outdoor installations.
Order checklist for choosing your panel:
- Type of control
- Sensor inputs
- SCADA/Remote inputs
- SCADA /Retransmission outputs
- Alarm outputs
- Supply voltage
- Indoor/Outdoor use
When all parts of the checklist are answered, the work on the control panel can begin. A valve manufacturer can supply both the control panel and the control valve it integrates with. With the checklist complete the manufacturer can take the control sequence and turn it into PLC logic to program the panel to all your specifications. Depending on the application, the turnaround time on a small panel can be as quick as four weeks.
If you are new to the electronics world, your best option is to have a valve manufacturer come down to the site and start up and commission the control panel and train the operators.
A good customized control panel can save a municipality many man hours, loss of water, disaster from an unknown situation, and give peace of mind that the system is operating as it should 24 hours a day.