Flow control valves are most commonly used to slow-fill pipelines to prevent water hammer, especially at center pivot points on large pipe networks. They can also be used to limit the flow rate of a valve discharging into a pond, canal, or reservoir.
A Nelson Rate-of-Flow pilot uses a velocity-sensing paddle to limit the system flow rate. The paddle and pilot are installed in the pipe upstream of the valve. For slow-fill applications, the pilot should be set to 110-120% of the design flow. When the valve is first opened, the pilot throttles the valve to prevent high flow water hammer. When the pipeline is full and the design flow is reached, the pilot allows the valve to go fully open, or respond to other controls (such as a pressure reducing pilot).
Available for the following pipe sizes and flow rates:
- 3" Pipe: 120-400 gpm
- 4" Pipe: 200-550 gpm
- 6" Pipe: 350-1,000 gpm / 500-2,000 gpm
- 8" Pipe: 500-1,550 gpm / 900-3,800 gpm
Can be combined with other control functions, including solenoid on/off, pressure reducing, and pressure sustaining.
Two additional flow control devices are:
- Shuttle Check: used to prevent flow reversal.
- Sleeve Exhaust: makes the valve fully open below 10 or 30 psi inlet pressure, used in surge anticipating valves and in deep well applications to divert the initial surge of water from causing a pressure spike in the mainline.