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Let's Talk Valves

Katherine Woodford | Valves

Controllers are the brains of an irrigation system, but the heart of the system is the most unglamorous element – the valve.

Generally in the ground, out of site, manufacturers have spent very little in design dollars to change the look of their valves over the last 50 years, choosing instead to concentrate on the longevity that contractors are looking for.

Contractors are very brand loyal when it comes to valves; once they bury a valve, they don’t want to see it again for another 50 years, so if they find a brand that allows them longevity, they seldom vary from it.
“In marketing, you have to remember the ‘concept of switching costs.’ When a customer is loyal to one particular product, you have to overcome that loyalty, and the consumer’s cost to switch, remembering if the risk is too high they simply won’t switch,” explains Jeff Carowitz, vice president of marketing for Hunter Industries.

Originally, valves were made of brass, cast iron, or some kind of metal. Plastic valves arrived in the 1960s, but were not as reliable as they should have been. When plastic is heated, the molecules are aligned, allowing them to flow into each other, creating the solid form of the mold they are poured into. But even then, molecules to molecules are lined up with each other, and it is possible to crack those alignments with enough pressure. It took a while for the contractors to accept plastic valves.

Today, many manufacturers are adding reinforcement filament materials to the plastic to make it stronger and keep it from cracking.

Until plastic came along, brass valves were the valves of choice. Brass valves are still used, though reinforced plastic has taken over as the number-one seller.

Superior Controls and Buckner by Storm have found a niche market selling brass valves. Both companies sell plastic valves as well.

How do automatic valves work? An electric automatic valve is basically a hydraulic valve. There are two basic parts of a hydraulic valve, the upper diaphragm chamber and the lower chamber. The lower chamber is where the flow of the water passes. The upper chamber is used to open or close the valve by way of a diaphragm.

There is an inlet orifice from the inlet side of the valve that supplies fluid pressure to the top of the diaphragm. Since the surface area of the top of the diaphragm has more surface area than the bottom, the pressure from the inlet orifice keeps the diaphragm in the closed position. There is a discharge orifice on the outlet side of the valve; when the electric solenoid is energized, the water exits the discharge orifice and releases the pressure from the top of the diaphragm, allowing the pressure in the lower chamber to push the diaphragm up, thereby opening the valve.

The size of the inlet orifice and the discharge orifice is what controls the opening and closing speed of the valve. The discharge orifice must always be bigger than the inlet orifice, in order to discharge the pressure from the top of the valve, allowing the diaphragm to open.

If the inlet orifice is large, the valve closes more quickly than if the inlet orifice is small, and if the discharge orifice is large the valve opens faster than if the discharge orifice is small. For example, small inlet and discharge orifices will produce slow opening and slow closing valves, but can get plugged with debris, causing a malfunction of the valve.

Large inlet and large outlet orifices will cause fast opening and fast closing. Closing speed is critical in the hydraulic design of a system, so as not to cause hammers and surges. Therefore, a happy medium is needed to cause the valves to open and close at an acceptable speed, keeping in mind the size of the orifices, so as not to plug them with debris from the system.

Basically, there are three things that can go wrong with a valve: the body, the diaphragm, or the solenoid. Manufacturers have fine-tuned servicing of the valves. They do not attach any parts to the body of the valve. When the bonnet or cap is pulled off, the contractor is holding the internal guts in his hand, and hopefully the problem as well.

One problem contractors often face when servicing valves concerns the nuts and bolts. Quite often, when pulling out the bolt, it will drop into muddy water, and is hard to retrieve. Or when bolting the body back together, it may not follow the same thread track, creating a weak point. To simplify this for the contractor, some manufacturers have taken the stud part of the bolt and molded it into the body, so that they are tightening down a nut onto a bolt that is permanently attached to the body.

If a valve won’t close, check to see if the discharge orifice is open somehow, or if no water is being presented through the inlet orifice. If a valve won’t open, then the discharge orifice is not open, or for some reason, more water is entering through the inlet orifice than the discharge orifice can release.

Manufacturers agree that when valves are redesigned to the point that they cannot be interchanged with the older models, the parts should not be changed. You can buy a diaphragm assembly today, and install it in with the same model number you bought 25-30 years ago. Municipalities, in particular, appreciate this.

Although valves may still have the same look as they did fifteen or twenty years ago, they have changed on the inside. Subtle, and not so subtle changes have been made to the valve.

One choice available to the contractor is whether or not they want flow control on their valves. This allows the contractor to control the amount of water going through the valves, similar to the way water flowing through a kitchen faucet is controlled. This can be a helpful feature if the system needs to be balanced. It can also be used to turn the valve off manually if there is any sort of failure.

Earlier valves had manual bleed. A knob on top would allow water to leak out, relieving some of the water in the upper chamber of the valve, causing the diaphragm to rise and the valve to open. The entire time the valve would be on manually, it would be dripping out a small amount of water, eventually filling the valve box, creating a muddy mess.

Today, there is internal manual bleed. The operation is the same as the electronic; the water is relieved internally so there is no leakage into the valve box and no muddy mess in the valve box. Weathermatic valves have a little switch that makes bleeding valves simple, by using just the tip of the finger; no screwdriver is required.

In the early days of valves, the material used to make the diaphragms was a rubber gasket material, similar to that used in automobiles. These diaphragms tore easily because the gasket material eventually wore out. Today’s diaphragms are made of reinforced, tear-resistant rubber that has virtually eliminated valve failure due to torn diaphragms.

Older valves used to have a stem; on the bottom was a rubber seat, on the top was the diaphragm. Today, valves have a fully-molded seat and diaphragm in the same part, thereby eliminating one part.

Until five years ago, the contractor chose from globe, angle or anti-siphon valves. HIT Products added another choice with its patented line of valves which has a spherical diaphragm that allows a straight through path of water flow, eliminating the four 90 degree angles normally required to get the water through the valves. This valve also operates at any flow, from one gallon per hour to fifty gallons per minute.
On an average, solenoids are probably changed out every seven to ten years. These are easy to get to in the valve: turn the water to the valve off, cut the two wires, unscrew them, screw the new one on, then reconnect the wires. Solenoids need to be replaced more often if the system is in an area of high lightning incidence.

Pressure rating is a very important feature when choosing a valve for a job. Choices range all the way up to 220psi in plastic valves. This is directly related to the strength of the body, the bonnet, and the diaphragm.

Pressure regulation is another feature introduced in the last few years. A modular can be installed on the valve that measures the amount of pressure on the inside of the valve. The contractor sets the dial to the amount of pressure he wants to come out of the valve.

Hunter Industries has a unit called Accu-Set, which operates similar to a wall thermostat. Rain Bird has a unit called the PRS Dial that also features easy visual pressure settings. Other units may require a screwdriver or gauge to be accurately set. These modules will give constant downstream pressure, offering optimum system operation, regardless of what pressure is operating the system.

Buckner offers two different pressure-regulating valves. One can be set for two different pressures. The other can be set for two different pressures, plus full flow.

Another application for pressure regulation modules is with a system that has both drip irrigation running at 20psi and large rotors running at 70psi. The contractor can now keep the 70psi in the main line, and still regulate down to 20psi in the line for the drip irrigation without causing problems.
“One of the biggest mistakes you see being made is the old plumbers rule that if you have a 2-inch line, you need a 2-inch valve”, explained Gary Bailey, vice president of sales and marketing at Storm Irrigation and Buckner. “That is not necessarily true. Most valves will accommodate more water through them than the pipe will handle. It is quite conceivable to have a 2-inch line and 1-inch valve. When you are talking about valves, you are talking about metering devices. That’s all you are doing, you’re metering the amount of water that goes through them, so you size a valve based on the application, not based on the pipe size.”

Installing traditional valves in clean water is no problem. But clean water is not always what these valves will be sucking in. Depending on what the situation is, there are several solutions available.

For the pond or lake, where algae or scum is a problem, there are valves that have scrubbers that literally scrape the inside of the valve as it is operating, so that the algae cannot build up there, gumming up the works. In Florida, this could be water from a pond or channel; in Idaho, this could be water from an irrigation ditch, which is not cleaned or filtered and has algae.

Additionally, manufacturers are making valves for reclaimed or recycled water. Superior Controls has one that has the traditional purple top, with all the rubber parts made from the special rubber compound, EPDM, which is impervious to the destructive properties of chloramines found in recycled water.

Weathermatic recently introduced the “Albino Rhino” diaphragm, blending modern technology and the EPDM rubber; they are offering a 10-year warranty on this diaphragm for use in systems using treated gray water, or potable water. It will not deteriorate when exposed to water treatment chemicals, such as chloramine compounds.

A unique feature from Hunter Industries has been to make the top of its valve non-tool specific. The tops of the valves will come off with any of three tools: a Phillips screwdriver, a slot screwdriver, or a nut driver – a feature for the contractor who never seems to have the right tool on the right job.

Superior Controls entered the irrigation business in the 1950s with its Actuator, used to convert valves from manual to automatic. This product is still a strong seller today, according to Richard Greenland, vice president of marketing. Contractors use it in conjunction with manual valves for an inexpensive, above-ground installation.

Weathermatic has recently introduced a new 1-inch “Nitro Series” valve. With a 150psi rating, it features a PVC body with the combination no-specific-tool-required bonnet.

A new valve with the highest pressure rating for a plastic valve in the industry, 220psi, is available from Toro. The P220 also has all the venting and porting for the pressure regulation inside the valve, so there is no external tubing of any sort exposed.

Sturman BG has introduced the toggle valve, a revolutionary concept designed to reduce cost and labor by eliminating solenoids and wires. It also facilitates one pipeline instead of a manifold of many lines. These have been in testing for two years, and were introduced on the market six months ago.

The toggle valve is a direct replacement for any standard , 1- or 2-inch valve already in the field. Turning the main on and off activates the valve. The first time the main comes on, the first toggle valve will come on. The main is shut down and the first valve turns off. The main is turned back on and the next toggle valve in line activates. It does this all down a single line; it does not need multiple lines to manifold and can do this indefinitely, as long as there is 20psi.Toggle valves do not have to be buried in a valve box; they can be buried at any angle.

“The most important feature of any valve is that it must be reliable. It must turn on, and it must turn off,” stated Ron Wolfarth, marketing manager, commercial division for Rain Bird. “If the valve fails in the open position, you have a huge loss of water, and potential liability for property damage. There have been cases of loss of life from flooded streets, car accidents, hillsides failing, and literally, flooding houses while people slept. To replace a valve is very time consuming, very labor intensive. It requires that the contractor dig a giant hole, and literally cut the valve out. So, if the valve body fails in any way, that is a major failure in an irrigation system.”

“If the valve doesn’t work properly the whole system doesn’t work,” Carowitz added. “And so, as a manufacturer, we spend a lot of time working on valves, even though they are very simple devices. The consequences of a failure in a valve are the most severe of any problem in an irrigation system. If the valve fails in the open position, you can flood something, kill plants, wash the landscape away, and worse. If the valve fails closed, and you don’t find it in time, everything dies in the area that is controlled by that valve. Valve reliability is also very important, because the most difficult component to change or work on in a system is a valve,” emphasizes Carowitz. “It’s the equivalent to a major engine rebuild. It’s easy to change your air filter, but very difficult to rebuild your engine.”

June 2001

 
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