Sprayers get SMART
Although technological advances — GPS, for example — promise to revolutionize turf spraying in the upcoming years, you don't have to wait to take advantage of innovations. The technology available in turf sprayers today is offering applicators unprecedented control and accuracy in applications.
Not too much, not too little
The need for accurate spray controls stems from the need to apply just the right amount of product. That is, you need to apply the correct rate, which every spray technician knows. “Rate” simply means how much material you apply over a certain area. It is a function of how much material is passing through the spray nozzles, how fast the sprayer is traveling and how wide your application swath is. Thus, a 10-foot boom on a sprayer traveling a thousand feet per minute and pumping 10 gallons per minute is delivering spray at the rate of 1 gallon of spray per 1,000 square feet. Many factors are important with sprayers, but the ability to accurately and consistently achieve the intended rate is one of the most critical.
Calibrating your sprayer is the process of ensuring that you actually are putting down the rate that you think you are. By measuring what comes out of the nozzles, you can check the flow at which the sprayer, with a given set of nozzles at a certain pressure, delivers the spray mix. This allows you to calculate the speed at which the sprayer must travel to deliver the right rate to the turf.
Knowing this, you can see that the rate can be controlled with any of several variables. For example, with a given flow, changing speeds will vary the rate. With a fixed speed, changing flow will vary the rate. Of course, what you want to do when you're spraying is maintain the same rate, not change it. It is to that end that manufacturers direct many of their innovations in sprayer controls.
The objective is to match one parameter (flow, for example) to correspond to another factor (such as speed of travel) in a way that ensures a constant application rate despite variations in that factor. Other parameters, such as pressure, also come into play. As you'll see, manufacturers use a variety of strategies to produce sprayers that deliver the goods.
When you take the approach of varying flow rate to match speed, accurate measurement is key, and there are several ways to do that.
Larry Jones, product manager for Textron Golf and Turf, says that their top-of-the-line controller, available on the Cushman DS300 sprayer, does this with ground-sensing radar. The DS300 uses a Raven controller, and the unit alters flow via flow meter to keep the application rate constant.
Kent Hahn, applications product development manager for Hahn Equipment Co., a Toro subsidiary that manufactures sprayers for Toro, explains that Toro units use speed sensors that operate either off of the transaxle unit (the Multi Pro 1200, 1250 and Workman sprayers) or rear hubs (the Multi Pro 5500).
Chuck Greif, manager of market development for John Deere's Golf and Turf Division, says that Deere, too, makes its controllers to adjust rate by sensing vehicle speed. Deere utilizes an electronic controller that runs based on the speed of the machine and adjusts flow rate accordingly. According to Greif, Deere units such as the 1800 and the ProGator line sense speed off of the transaxle. “You just program the controller to adjust rates [according to speed]. It's really hands-free for the operator.”
As you can see, most major sprayer manufacturers have units that take this approach. Rich Gould, a representative of TeeJet Electronics, basically agrees and states that speed-compensated controllers — that measure speed and adjust output to keep the rate consistent — are not state of the art for sprayers in general, but they are the “popular state of the art” in the turf industry. “Everyone makes a pretty accurate controller. The differences between controllers come down to how you like the features and the approach the manufacturer takes.”
Though varying flow to match speed is a popular approach, it's not the only one. For example, according to Jones, the more basic unit Cushman sprayer, the DS175, uses the Cushman ground-speed governor to maintain a constant speed. The unit may only be equipped with a manual or electronic on/off control, but as Jones explains, “Cushman's ground-speed governor can regulate ground speed very tightly. All you have to do is maintain a constant flow rate.” This is the preferred, traditional setup, according to Jones, and applicators often prefer it because of its simplicity.
For those who desire a more sophisticated control system, Raven controllers are an option on Cushman sprayers. These units monitor ground speed with radar and automatically adjust flow to maintain a consistent application rate. This actually represents an extra layer of control, because these Cushman units still possess the ground-speed govenors.
But there's more than one approach to this. Hahn states that Toro has just come out with a new system and “the industry has never seen one like it before. It is a positive-displacement diaphragm pump used on Toro's Multi Pro 1200 and 1250 units, that is directly tied to the vehicle's speed through the transaxle gearbox. The flow of a positive displacement pump is not affected by pressure. The advantage is that you can increase or decrease the application rate to whatever you want. The speed of the pump is directly tied to the vehicle… you can speed up or slow down and the pump follows exactly, so the rate stays the same… That way you don't have to regulate speed.”
If you can't take the pressure…adjust your flow
Altering (or maintaining) pressure and flow are needed for reasons other than matching vehicle speed. Jones explains that “Another technology we have is a pressure-compensating valve bank. If you turn one boom off, the others adjust automatically to maintain same level pressure.” Therefore, the remaining nozzles continue to apply spray properly.
TeeJet also addresses pressure and flow. “We feel we've taken a broader approach… We think about application pressures, not just rate. So we have minimum and maximum limits, or alarms, to regulate pressure,” says Gould. If you have a controller that's constantly trying to match flow to speed, and speed drops below a certain point (such as during turns), pressure can become so low that the nozzles will no longer produce the desired pattern.
Flow meters are the most common device used to measure flow in sprayers. However, because flow and pressure are intrinsically linked, pressure sensors also can be used to sense flow. “Most applicators are more comfortable with flow meters,” says Gould. “But they can be kind of finicky. Our controllers can use either [meters or pressure sensors]. The benefit of a pressure sensor is that it is almost solid state.”
TeeJet's latest controller, the 854, allows you to use both flow meters and pressure sensors. The controller can switch between them so that at very low flows, which are relatively difficult for flow meters to measure, the pressure sensor can take over. The 854 also can switch boom sections on and off at certain speeds.
Cushman also has looked at the issue of dependability. Its sprayers use metered-bypass motorized valves. This is a significant benefit, according to Jones. “It's better than a solenoid valve. It's just a more dependable unit with greater durability.”
Ideas waiting for their time
Several technologies hold great potential for turf sprayers. As is typical, they have been applied in the agricultural industry already, and should eventually filter over to the turf industry. Environmental regulations will be one of the drivers for these technologies, and as they become more well-developed and prices become more affordable, you'll see them emerge in our industry.
One is direct injection (DI). DI systems inject chemicals directly into the plumbing “downstream” of the sprayer's tank, metering the material out in the correct proportion. Thus, the main tank never contacts anything but water. These units can be designed to withdraw chemicals straight from the original container so that the operator never even has to pour the chemical. It reduces the potential for accidental spills associated with loading and mixing, and you don't have to worry about what to do with extra spray mix if you finish the job and have leftover material.
Most people in the spray industry view DI as an idea with merit, and one whose time eventually will come. A few of these units were marketed to the turf industry in the late 1990s, but no turf sprayers currently are so equipped by the original manufacturer. (It is possible to retrofit some turf sprayers with DI controllers).
Greif feels that golf superintendents are ready to embrace DI if manufacturers can improve the technology. However, with current engineering technology, machines that satisfy the “wish list” of superintendents are complex, expensive and relatively difficult to maintain. Nevertheless, Greif still feels DI sprayers will become the industry standard, though not anytime soon.
Terry Stone, of Spraying Devices Inc. (SDI), Visalia, Calif., feels that superintendents “basically don't trust them,” even though the technology is sound and other industries use them successfully. SDI manufactures a DI system that can be adapted to turf sprayers. However, Stone explains that, “Superintendents have been indoctrinated on tank mixing and a proportioning pump is hard to trust. You can't see what's going on…”
A few years ago, a high-profile course using a DI sprayer experienced a particularly costly problem. According to Stone, this incident contributed significantly to the mistrust of these units among superintendents, even though the malfunction wasn't due to any problem inherent in DI.
Stone agrees with Greif that DI units eventually will become the norm, but that may be “down the road a ways.”
Another technology awaiting exploitation in turf sprayers is geographic positioning systems. GPS has the potential to turn sprayers into robotic units that know where to spray and where not to, and can relay application information directly to digital storage for effortless record-keeping. Research and development with GPS is active with several major manufacturers, but it's not clear when the technology will be available and affordable.
As the problems with DI systems showed, a level of discomfort with newer technologies seems to exist among applicators. Most of the manufacturers interviewed for this article seemed aware of this, and felt that this explained, in part, the continuing popularity of units using traditional, simpler technology. However, turf managers looking for the newest, most automated technology to put to work on their turf won't be disappointed, now or in the future.
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