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Integrating Master Valves Into Your Design

Video Length:  31:51
Presented By:  Dick Greenland
Friday, 11 August 2017
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This webinar will introduce and explain a wide scope of valve concepts that will be relevant for an irrigation designer. You’ll learn about how valves work, what pressure loss and flow considerations you need to keep in mind, and how to select a valve for a variety of design needs. We’ll focus on master valves, including the normally open and normally closed options within the Buckner-Superior line. The webinar will also go over the significance of master valves and techniques to safeguard against excessive water loss, and will emphasize options for low-flow, efficient irrigation design.

 

Webinar Contents:

Note: The following catalog of content covered in this webinar is time stamped to allow you to follow along or skip to sections of the video that are relevant to your questions. You can also search for content on this page using the FIND command in your browser (CTRL + F in Windows, Command + F in Mac OS.)

  • 950 Series Brass Automatic Sprinkler Valves
    • Valve Principles of Operation
  • Master Valves

 

0:00 – 15:59: 950 Series Brass Automatic Sprinkler Valves

This valve series, introduced in the early 1970s, is available in 3/4”, I”, 1 ½”, 2”. 2 ½”, and 3” sizes. It’s known for its interchangeability of parts.

 

How a valve functions (2:00)

 

Valve Principles of Operation (2:30):

 

Manual bleed valve (2:30)

A manual bleed valve is used to relieve pressure in a valve’s diaphragm chamber, allowing the valve to open.

 

Manual bleed valves are available in two possible configurations: internal and external.

 

A manual bleed valve is controlled by a bleed screw. Turning it one way opens the bleed valve; turning it the other way closes the bleed valve.

 

Solenoid (4:05)

A solenoid relieves pressure above the diaphragm.

 

A solenoid stem includes a cylinder with a spring-loaded plunger that can move up and down. When the solenoid is energized, the plunger lifts up, relieving the pressure above the diaphragm and allowing water to escape downstream. As long as the solenoid is energized, water will continue to flow through the valve.

 

When the solenoid is de-energized, the plunger drops down. Water fills the diaphragm chamber and the valve closes.

 

The chamber will only fill, and the valve will only close, if the pressure above the diaphragm exceeds the pressure below the diaphragm as the valve is closing.

 

A valve’s pressure loss will allow for this difference in pressure above and below the diaphragm. The higher flow rate, the greater the pressure loss through the valve. For example, at a flow rate of 18 GPM, the 1” 950 has a pressure loss of 2 PSI. (5:40)

 

Flow control stem (7:30)

The flow control stem is used to adjust the amount of flow through the valve.

 

For an optimum flow rate:

1. Turn the flow control stem to the full open position (counterclockwise).

2. Turn the valve on electrically.

3. Turn the cross-handle a clockwise half turn at a time while observing the water from the sprinkler heads.

4. At the point where the radius of water from the sprinkler heads decreases slightly, turn the cross-handle counterclockwise a half turn. This position, known as the balance point, will provide the optimal flow rate. You should be able to leave the cross-handle as is indefinitely.

 

950 diaphragm assembly (9:00)

This two-piece assembly provides diaphragm protection by removing the diaphragm from the flow path.

 

The self-cleaning metering rod prevents debris from entering the upper diaphragm chamber, allowing only .003” clearance between the metering rod and the wall of the inlet orifice.

 

Model 950DW (11:35)

This model includes all features of the Model 950 with the addition of a self-flushing filter for additional protection against dirty water.

 

Model 950DWIB (12:25)

This model includes all features of the Model 950DW with the addition of a manual internal bleed valve.

 

Model 950PRS (13:30)

This model includes all features of the 950DWIB with the addition of a pressure regulation module.

 

Regulating range is 10 to 125 PSI

 

Downstream pressure remains constant regardless of variations in upstream pressure.

 

Question: How is the 950DW screen cleaned? (15:20)

Answer: It’s self cleaning because it’s in the flow of water through the valve.

16:00 end: Master Valves (16:00)

Master valves defined: A master valve is an automatic valve installed in the mainline of an irrigation system to control the flow of water to the zone valves. (16:20)

 

Purpose of a master valve: To safeguard against excessive water loss, erosion, or hazardous conditions caused by a zone valve being stuck in the “on” position, or a rupture in a mainline or lateral line. (16:45)

 

Location of a master valve: A master valve can be installed in the mainline anywhere between the point of connection and the zone valves. Usually, it’s installed downstream of the backflow prevention device.  (17:20)

 

Types of master valves (17:30)

A master valve can be normally closed or normally open. A normally open valve works in the opposite manner of a normally closed valve with electricity required to close the valve rather than open it.

 

Normally Closed Master Valves (17:55)

Normally closed master valves are wired to the MV circuit of the sprinkler controller. They open when the first zone valve opens and remains open until the last zone valve in the cycle is de-energized.

 

Zone valves are normally used as master valves. Superior zone valves that are often used as master valves include the 950 series valves, which are available in ¾” through 3” sizes.

 

Some manufacturers designate certain valves as master valves because of features that are ideal for master valve applications, Superior designates the model 3000 and 3200 as master valves.

 

Model 3000 normally closed master valve (18:42)

This model’s 3-way solenoid allows all water to be exhausted from the top of the diaphragm when energized. This enables the seat disc to lift higher, resulting in increased flow through the valve.

 

Dirty water protection is afforded be a removable screen filter, plus additional protection from non-continuous flow through the solenoid.

 

Available in 1” through 3” sizes.

 

Removable screen filter ensures that only clean water enters the diaphragm chamber.

 

The only time water passes through the filter is when the valve is de-energized at the end of a cycle. At that time, only enough water to fill the diaphragm chamber (about ¼ cup of water) passes through the filter.

 

Model 3200 normally closed master valve (20:26)

Available in ¾” through 3” sizes. Dirty water protection from removable screen filter plus non-continuous flow through the solenoid.

Dual chamber design. No counterforce from under the diaphragm as the valve is closing, so it can close at any flow rate.

 

Enhanced protection (23:10)

The addition of a flow meter and water management controller enables the master valve to close when a flow vault is detected rather than waiting until the end of the watering cycle.

 

The flow meter is wired to the water management controller.

 

Mainline flow limit, station flow limits, and unscheduled flow limit are programmed into the controller.

 

If flow limits are exceeded, the controller will de-energize the normally closed valve so it will close.

 

Normally Open Master Valves (24:47)

Normally open master valves can only be used in conjunction with a flow meter and water management controller.

 

The water management controller must be capable of operating a normally open master calve, Some water management controllers are only able to operate a normally closed master valve.

 

A normally open master valve is energized only when a flow fault occurs or when it is being tested.

 

Because the solenoid of a normally open master valve is not energized on a regular basis, it should be tested periodically.

 

Reasons some designers prefer normally open master valves (26:00):

If quick couplers are installed in the mainline between the master valve and zone valves, water can be accessed from the quick couplers at all times, not just during a watering cycle.

 

Normally closed master valves can hide problems. Watering cycles often run at night. A weeping zone valve would not be detected during the day. However, with a normally open master valve, the weeping zone would be detected and repaired.

 

Normally closed master valves can lead to premature failure of PVC mainlines due to stretching and contracting of the mainline each time the system is pressurized and depressurized.

 

Model 3100 normally open master valve (27:15)

Available in ¾” through 3” sizes

 

Model 3300 normally open valve (27:36)

Available in 1 ½”, 2”, 2 ½”, and 3” sizes. Dirty water protection from removable screen filter, plus non-continuous flow through solenoid.

 

Dual chamber design. No counterforce from under diaphragm as valve is closing, so valve is able to close at any flow rate.

 

Question: Is it preferable to do the pressure regulation at the master valve or at the RCV? (29:20)

Answer: Dick’s preference is to have one pressure regulator either before or after the master valve (although different designers have different preferences and different sites call for different configurations).