Nelson Irrigation Corp. 848 Airport Rd. Walla Walla, WA 99362-2271 USA Tel: 509.525.7660 Fax: 509.525.7907 E-mail: [email protected] Web site: www.nelsonirrigation.com
Control Valve
Application
Guide
1.0 TYPES OF CONTROLS ON 800 SERIES VALVES
NELSON 800 Series Control Valves
are available in several configurations. Understanding these basic valves puts a
designer in a better position to understand all of the combined types, functions and design requirements. Valves are best
categorized by operating control function.
These are the operating control functions presently available:
Simple ON/OFF Control (manual or automatic) Valves
Pressure Control Valves
(these valves work using a pressure control regulator)
Pressure Reducing
Pressure Sustaining
Pressure Relief
Rate-Of-Flow Control Valves
(used to maintain a desired flow rate)
Combination Valves
More than one control function. EXAMPLE: pressure reducing with automatic on/off.
Special Purpose
Check Valves
Sleeve Exhaust
Special on/off mode or special function.
2.0 SELECTING THE RIGHT VALVE
Selecting the right valve for the job consists of understanding, then selecting the proper control function and proper valve
sizing. The best sequence is 1) Choose the control function to serve the purpose, 2) Select the valve size and pressure rating,
and 3) Verify that the operating range for the selected valve is correct. This document is to be used as a guideline and is
not a complete strategy for design.
2.1 UNDERSTANDING THE CONTROL FUNCTIONS
2.1.1 SIMPLE ON/OFF
MANUAL CONTROL: The MANUAL ON/OFF control is used to open or close the valve. The flow through the valve is controlled
by a rubber sleeve which is actuated by hydraulic pressure. The valve is either in the fully opened or the closed (shut off) position.
The AUTO position on the selector has no effect on valve control but is used when the valve is equipped with automatic controls.
AUTOMATIC CONTROL: If the valve is equipped with an electric solenoid, the on/off function can be automatic by using
an electric controller. When the selector is pointed to the AUTO position then the electric solenoid is used to automatically
open or close the valve. The 3-way electric solenoid must be energized to open the valve and de-energized to close the
valve. Pointing the manual selector handle to OPEN or CLOSE will override the AUTO control.
2.1.2 PRESSURE CONTROL VALVES
Pressure control valves react or respond through a pressure control regulator. The pressure control regulator directs water
flow which positions the sleeve during operation. If the control function is pressure reducing, the sleeve position (or flow
through the valve) is controlled by downstream pressure. If the control function is pressure sustaining or relief, the sleeve
position is controlled by upstream pressure.
2.1.3 RATE-OF-FLOW CONTROL VALVES
The Rate-Of-Flow control valves operate by a flow sensing probe in the pipe. A calibrated adjustment screw is used to set
the desired flow. The flow velocity moves the probe to maintain the desired rate-of-flow.
2.1.4 COMBINATION VALVES
Combining functions of more than one control is possible with the NELSON 800 Series Control Valve. The most common
combination is the automatic on/off combined with a reactive pressure control.
2.1.5 SPECIAL PURPOSE VALVES
The check valve feature is used to prevent flow reversal. The check option is available separately or with most on/off and
reactive control functions.
TYPES OF CONTROLS
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