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If you’ve recently purchased a new sprayer, you may still be learning the ins and outs of the equipment. Or if you’re considering the purchase of a new or used tow behind or self-propelled sprayer you may be thinking through the options, features, and accessories you want and need.
Even if you aren’t considering a purchase right now, it’s important that the spraying equipment you use is kept in prime working order to deliver your applications safely and accurately.
This guide will help you learn the basics of owning and operating your own sprayer. It’s designed for farmers who want to learn what the pros know so they can do it themselves. And that starts with equipment expertise.
Since many crop chemicals can be corrosive, it’s also important to select a tank with corrosion resistant material, such as stainless steel, fiberglass or polyethylene plastic. Even when they aren’t in use, it’s important to keep tanks clean and free of dirt, rust and other contaminants that can damage the pump and nozzles.
A tank agitator mixes materials in the tank homogeneously (i.e. with a uniform composition) and keeps chemicals in suspension instead of settling on the bottom of the tank. Different agitators are required for the various types of chemicals being applied. Wettable powders require intense agitation in suspension, so you should use a separate agitator – either a hydraulic or mechanical type.1 An adjustable agitator can minimize foaming that occurs from certain chemicals as the volume in the tank decreases.
The relief valve on a sprayer should always be in the bypass position during start-up. Check your gauges at every start-up. A pressure gauge should have a total range of twice the maximum expected reading. The gauge should indicate spray pressure accurately. If you’re seeing spikes, then the gauge may always read high afterwards and should be replaced. Likewise, an opaque or leaking gauge should be replaced. Measure the discharge rate at a specific pressure on the gauge during calibration and install a gauge protector or damper to prevent damage to your gauges.
A pressure gauge can be used for more than measuring pressure. It also can be a helpful tool in diagnosing other problems – such as pump or plumbing issues – within the sprayer system. Keeping your gauges in good working order will make a big difference in sprayer performance and accuracy.
There are four general types of pumps: centrifugal pumps, roller or rotary pumps, piston pumps, and diaphragm pumps. The nuances of different pump styles are primarily about how much water they displace and how they deliver the volume.
More importantly than the style itself, your pumps should be resistant to corrosion from pesticides, and the materials used in pump housings and seals should be resistant to chemicals, including organic solvents. This shouldn’t be an issue for new equipment, but as your sprayer ages, or if you are considering buying used equipment, take a closer look at the pump.
Undersized hoses and fittings can severely reduce the capacity of any pump. Suction hose diameter should be at least as large as the pump intake opening. Before spraying, all hoses and connections should be examined for cracks or leaks while under pressure. Avoid splices where possible – they offer another opportunity for leaks or failure in your system.
There are three types of strainers commonly used on sprayers: line strainers, tank-filler strainers and nozzle screens. Strainers (and nozzles) should be cleaned after every spray day. It’s best to use a bristle brush, because flushing will not completely clear them.
You already know why you need a properly cleaned sprayer: residue that has been left behind from a previous spray can harm a crop and ruin your next application. The damage might not show up for more than a week, and it usually takes longer to identify that the symptoms and damage patterns are from chemical residue. Once you are able to identify the cause, there isn’t much else you can do except wait for unavoidable yield loss.
So how do you know when your sprayer is really clean enough? It starts with prevention and ends with a complete clean of all parts, while following best practices along the way.
Cleaning a sprayer is a lot like doing the dishes. Using the right detergent, soaking the hard stuff, being thorough, and rinsing properly – they all matter. It all starts, though, with preventing the problem in the first place.
The main culprits that cause sprayer contamination from the mix itself have the following properties:
Dry formulation
Poor water-solubility
Potent in low doses
Poor solubility at low pH
The best advice on preventing a clean out problem is to make sure the product is fully dissolved or suspended – and that takes proper mixing technique and time.
Once properly mixed, you may still encounter problems with nozzle screens or strainers. Dry formulations require a screen mesh of 50 or coarser (according to product labels), but many sprayers contain 80 mesh screens, some 100 mesh.All screens should be inspected before, during and after spraying these products. Screen residues cause longer-term contamination, so cleaning them is an important part of the entire process.
After spraying, the cleaning process relies on three main steps:
STEP 1: Remove as much of the mixture as possible. The best way to remove the remainder is to spray it out in the field you’ve just treated. You can overspray some products again, based on what the product label advises, but it’s never a good idea to drain the tank without thinking through how it will drain off.
STEP 2: Dilute the remainder as much as possible and use it to clean the boom plumbing. Next, dilute the remaining mix, using tank cleaning adjuvants like ammonia (this raises the pH and helps remove those products whose solubility benefits from a higher pH) and detergent (this removes the oily layer formed by EC formulations). You can find commercial cleaners that combine these properties in one jug.Diluting is most effective when done in multiple smaller batches, as long as you can verify you’ve reached the entire surface area of the tank walls. Wash-down nozzles installed in your tank can do this for you.
Here’s an example scenario. Let’s assume your sprayer has a 150-gallon clean water reservoir. It’s tempting to empty the whole thing into the tank, but let’s calculate the diluting power of doing it this way:
If you had a 10 gallon remainder in the tank and added 150 gallons water, the remainder would be diluted by a factor of 16. After spraying this out, you would then have to refill the rinse tank if you wanted to do more.
If you rinsed in two 75-gallon batches (add 75 gallons, agitate via wash-down nozzle, spray out, repeat), you would dilute by a factor of 72.
If you did three rinses of 50 gallons each, your final dilution factor would be 216. That’s the same dilution as adding about 2,150 gallons to the first 10 gallon spray tank remainder. It’s also about 14 times better than dumping the whole 150 gallons in at the beginning.
STEP 3: Ensure anything that came in contact with the spray mix has been cleaned. Lastly, pay attention to the things you can’t see: screens, boom lines, and boom ends. The total inside surface area of black rubber boom hoses on a 100-foot sprayer with seven sections can be as much as 30-50 square feet (or 3-5 square meters) and this surface can bind residues. This job requires detail: scrub screens, soak boom lines, and flush boom ends.
Upgrade to more steel components (tanks and booms). Stainless steel is easier to clean than plastic.
Flush your boom ends. Traditional ball valves do a decent job, but there are some nozzle body end caps that do it automatically. These inexpensive units eliminate the dead space in boom ends, and as a bonus, bleed air from the lines on the go.
Have defoamer handy, since adding a surfactant or a commercial cleaner can generate a lot of foam.
Use a bucket to help collect and clean screens. Drop them right in!
Done well, sprayer cleaning doesn’t have to be unpleasant, difficult, or time consuming. And, it certainly results in a better night’s sleep before your next application.
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