Filling Up your Tank
With the coming of spring and the muggy days of summer to follow, you are no doubt hoping for little or no turf disease this year. This is a nice concept, but is it realistic? Your best bet is to put up a good defense against disease. It's time to be thinking about your turf sprayer. It may be time to replace your sprayer or perhaps you're thinking of purchasing one for the first time. Whichever the case, when you go to select spraying equipment for use on turfgrass there are several factors you will need to consider.
It's important to know the total acreage you will be spraying and if there is any chance you may be responsible for spraying larger areas in the future. This will have a bearing on the size of tank you need to purchase. Other factors you need to consider are the type of material the tank is made out of and what type of agitation is available. You will need to determine if the sprayer will be tractor-drawn, truck-mounted or mounted on a turf utility vehicle. You will also choose the type of spray boom and nozzles for the sprayer. Finally, you should evaluate the type of accessories manufactures offer to help make your spaying job more efficient.
Common tank sizes for turfgrass sprayers can range from 100 to 300 gallons. If you need a 300-gallon sprayer (or even larger), the tank may require a couple of baffles for sprayer safety and to cut down on the bouncing. Sprayer tanks should be easy to fill, clean, service and be resistant to corrosion. The tanks used for turf spraying are usually made out of two types of material. If you are looking to keep the weight down, there are tanks made of polyethylene that are lightweight, impact resistant and offer UV inhibitors that protect the poly from drying out and cracking. The other material that is used on turf sprayers is fiberglass. This material is durable and is normally used when mechanical agitation is part of your standard procedure. You will find that any of these tanks can be mounted on single or tandem axles, turf utility vehicles or used as dedicated turf sprayers.
PUMPS: THE HEART OF THE SPRAYER
The pump is by far one of the most important factors to consider when you are looking to purchase spraying equipment. The pump is the heart of the sprayer. There are two types of pumps widely used in turf applications: diaphragm and centrifugal pumps.
Pumps can be divided into two general categories: positive displacement and non-positive displacement pumps. Diaphragm pumps are in the positive displacement category. With positive displacement pumps, the flow from the pump is directly proportional to the pump speed. This positive flow is why all positive-displacement-pump hook-ups include a relief valve and a bypass line between the pump outlet and the nozzle shut-off valve. The pump must be capable of delivering the volume of material required by the nozzles, plus the volume required by the tank agitators, plus an additional capacity of 10 to 20 percent.
Because of their design, diaphragm pumps are positive displacement and provide improved handling of abrasive and corrosive materials. Their design may involve two to six pumping cylinders that are separated from the piston chambers by a synthetic diaphragm. This keeps the spray material from contacting and corroding the internal pump components. Diaphragm pumps are compact, self-priming and are low-volume, high-pressure units. A diaphragm pump will produce 10 to 14 gpm. The pressure output of a diaphragm pump can be as high as 800 to 1,000 psi. The PTO on your vehicle or a gasoline engine mounted to the sprayer frame can also power these pumps.
Falling in the non-positive displacement category are centrifugal pumps. These pumps have a rotating impeller that creates a centrifugal force that, in turn, feeds the liquid through the system (instead of capturing and discharging a fixed volume of material as diaphragms would do). Therefore, if the outlet is closed, the impeller will simply continue to rotate harmlessly. This is why there are no special relief valves required in centrifugal pumps. Traditionally thought of as high-volume, low-pressure pumps, centrifugals are compact and can be powered by a PTO on the vehicle, hydraulics or by a gasoline engine mounted to the sprayer frame. A centrifugal pump can generate 60 to 100 gpm at a pressure of 70 to 100 psi. The spray material travels directly through the pump to make contact with a rotating impeller. Centrifugal pumps are not self-priming, so they must be situated below the tank and also be positioned low on the machine.
Agitation of most spray solutions is necessary. Any separation of material will vary the spray concentration. Jet, venturi and mechanical agitation are designed to keep chemicals in suspension and prohibit them from settling on the bottom of the tank. For a jet agitator, a flow of 6 gpm for every 100 gallons of tank capacity is usually adequate. Venturi-type agitation ensures full coverage across the bottom of the tank and to the corners. If you use venturi-type attachments, they will reduce the agitator flow from the pump 2 to 3 gpm for every 100 gallons of tank capacity. Mechanical agitation incorporates a shaft that passes along the lower part of the tank and has paddles attached to it. The shaft is powered by a pulley and belt that is driven by the sprayer's power source. Mechanical agitation is used with diaphragm-type pumps because of the low volume that it produces.
Depending on your needs, you can select from booms that you can mount with your sprayer or a walking boom. The boom may be a “wet boom” or a “dry boom.” The “wet boom” actually carries the spray material through a pipe to the nozzles and is made of stainless steel. The “dry boom” carries material through poly tubes to the nozzles and is attached to steel framing to give it the ridgity it needs. Depending on your situation, choose from mounted booms that are 15 or 20 feet in length and adjustable. They come in three sections, with each section having its own independent control for on/off that you can fold up for maneuverability and transport. This offers you the flexibility to spray in tight areas and also helps you to control your chemical cost. There are walking spray booms that can be up to 80 inches in length with three sections that can also be folded up. You can use these booms where turf compaction is a factor, such as on greens and tees. You can control the spray material to the boom and at the boom with the use of electric solenoids, manual screw-type closure valves or electronic systems. Manufacturers will use one or all of these types of closures, depending on the particular sprayer model.
There are nozzles for practically every kind of spray application, but only a few are commonly used for applying chemicals that are labeled for turf. The different types of nozzles available can provide different flow rates, spray angles, droplet sizes and patterns. Nozzle types commonly used in turf and agricultural sprayers include flat fan, flood, raindrop, hollow-cone and full-cone. Often, you will base nozzle selection on droplet size. The droplet size from a nozzle becomes important when the efficacy of a particular chemical is dependent on coverage, or the prevention of spray leaving the target area is a priority.
The majority of the nozzles used in turf and agriculture can be classified as producing either fine, medium or coarse droplets. Nozzles that produce fine droplets are usually recommended for post-emergence applications that require excellent coverage on leaf surfaces. The most common nozzles used are those producing medium-sized droplets. You can use nozzles producing medium-sized droplets for contact and systemic herbicides, pre-emergence surface-applied herbicides, insecticides and fungicides.
An important point to remember when choosing a spray nozzle that produces a droplet size in one of the three categories is that one nozzle can produce different droplet-size classifications at different pressures. A nozzle might produce medium droplets at low pressures while producing fine droplets as you increase pressure. Higher pressure not only increases the flow rate through a nozzle, but it also influences the droplet size and the rate of orifice wear. As pressure increases, the droplet size decreases and the rate of orifice wear increases.
Once you have determined the other features of your sprayer, you need to consider accessories. All these extras can help you build the sprayer you want and need. Available accessories include electronic controllers, personal wash tank, rinse tank, foam marker system, hose reels, outer-wheel kits, electric boom lifts and kits for controlling drift. Sprayer controllers can provide you with three-boom section control, programmable application rates, readouts for your speed, total volume of material applied, total field area, volume left in the tank and the distance traveled. From a safety standpoint you can include a personal wash tank that provides a clean water source in case of an emergency. A foam marker kit will help you to increase the accuracy of chemical applications. Foam markers can pay for themselves just by decreasing the amount of chemical you use and additional savings can come from preventing skips or overkill. Electronic boom lifts are also good time savers when you're working in tight areas. If you're trying to decide between two similar sprayers, accessories can often be your final deciding factor.
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