Section 5.2: Application Equipment, Nozzles, and Maintenance

Application Equipment, Nozzles, and Maintenance

Selecting the right application equipment, maintaining it properly, and choosing the correct nozzle tips are essential responsibilities for any licensed pesticide applicator. Using the wrong equipment or failing to replace worn parts can lead to off-target drift, crop injury, uneven pest control, and financial loss. This section describes the major types of sprayers and dry applicators, nozzle components, the characteristics of different nozzle materials, nozzle wear patterns, flow rate verification, and sprayer maintenance.

Types of Application Equipment

Liquid Sprayers

1. Boom Sprayers: These are low-pressure sprayers equipped with multiple nozzles spaced evenly along a horizontal boom. They are typically used for broadcast applications on turf, field crops, and rights-of-way. Boom sprayers operate at low pressure (15 to 60 psi) to minimize drift while providing uniform coverage.
2. Air-Blast Sprayers: These sprayers use a pump to deliver liquid pesticide to a series of nozzles positioned in a high-velocity airstream generated by a large fan. The air blast breaks the spray droplets into a fine mist and blows them into the canopy of trees, orchards, or dense vine crops. While highly effective for reaching dense foliage, air-blast sprayers present a high risk of spray drift and must not be used in windy conditions.
3. Backpack and Handheld Sprayers: These are small, portable sprayers that utilize manual pumps or small battery-powered pumps to pressurize a tank (typically 1 to 5 gallons). They are designed for spot treatments, structural crack-and-crevice work, and small turf areas. Because they operate at low pressures, they produce minimal drift but require careful walking speed to ensure even application.

Dry Applicators

1. Drop Spreaders: These granular applicators release granules through a series of adjustable openings at the bottom of the hopper. The granules fall by gravity directly beneath the hopper. The application width is exactly equal to the width of the hopper. Exam Tip: Drop spreaders are highly precise, have a low drift risk, and are ideal for applying granules near water or ornamental beds. However, the operator must overlap wheel tracks carefully to avoid untreated strips.
2. Rotary (Centrifugal) Spreaders: These use a spinning disc to sling granules outward in a wide, circular swath. They cover large areas quickly but are less precise than drop spreaders. The distribution is lighter at the outer edges of the pattern, so the operator must overlap swaths (typically by 30% to 50%) to achieve uniform coverage. Rotary spreaders are highly sensitive to wind and granule size.

Nozzle Functions and Components

Nozzles are the most critical component of any sprayer. They perform three primary functions: metering the flow of liquid, atomizing the liquid into droplets, and distributing the droplets in a specific pattern.

Nozzle Components

A standard nozzle assembly consists of four parts:

1. Nozzle Body: The main housing that attaches to the spray boom.
2. Strainer (Filter Screen): Placed inside the body to trap debris and prevent nozzle clogging. Strainer screen size is measured in mesh numbers. A higher mesh number indicates a finer screen with smaller openings (e.g., a 100-mesh screen has smaller openings than a 50-mesh screen). WPs and flowables require a coarse 50-mesh screen, while fine solutions use 100-mesh screens to prevent clogging without blocking the flow of the pesticide.
3. Nozzle Tip: The orifice plate that shapes the spray pattern and determines the flow rate.
4. Cap: Secures the nozzle tip and strainer to the body.

Nozzle Materials and Wear Resistance

Nozzle tips are manufactured from various materials, which differ significantly in their durability and resistance to wear, especially when spraying abrasive formulations like wettable powders.

• Brass: Inexpensive and soft. Brass nozzles wear very rapidly when spraying abrasive materials, leading to frequent calibration changes.
• Aluminum: Inexpensive but wears rapidly and is easily damaged by corrosion.
• Polymer (Plastic): Highly resistant to chemical corrosion and abrasive wear. It is economical and provides a good balance of cost and durability, making it the industry standard for many applications.
• Stainless Steel: Extremely durable and resistant to both abrasion and chemical corrosion. Stainless steel tips maintain their calibration for a long time but are more expensive than polymer or brass.
• Ceramic: The hardest and most wear-resistant material available. Ceramic nozzles are virtually unaffected by abrasive formulations and corrosive chemicals, holding their calibration longer than any other material. Although they have the highest initial cost, they are the most cost-effective over their lifespan.

Nozzle Wear, Verification, and Maintenance

As liquid passes through a nozzle tip, abrasive particles erode the edges of the orifice. This erosion increases the size of the opening, which causes two problems: it increases the flow rate (resulting in over-application) and distorts the spray pattern.

The 10% Rule for Replacement

To check for nozzle wear, an applicator must calibrate the sprayer and measure the output of each nozzle:

1. Run the sprayer at standard operating pressure.
2. Collect the output from each nozzle in a graduated measuring cup for exactly 1 minute.
3. Compare the measured GPM (Gallons Per Minute) of each nozzle to the manufacturer's specification for a new nozzle of that size and pressure, or calculate the average output of all nozzles on the boom.
4. If the output of any nozzle exceeds the manufacturer's specification (or the boom average) by more than 10%, it must be replaced.

Cleaning Clogged Nozzles

If a nozzle becomes clogged, never use a metal pin, wire, pocketknife, or nail to clean the orifice. These hard materials will scratch or gouge the nozzle tip, permanently distorting the spray pattern and increasing the flow rate. Instead, use a soft-bristled brush (like a toothbrush), compressed air, or a wooden toothpick to clear the obstruction.

Equipment Cleaning and Maintenance

Sprayers must be cleaned immediately after use. Leaving pesticides in the system can lead to chemical deposits that clog lines, damage pumps, and corrode tanks. Furthermore, residue from a previous herbicide application can contaminate a subsequent insecticide or fungicide application, causing severe crop damage.

• Triple-Rinsing: Clean sprayers by flushing the system with clean water, then washing with a detergent or commercial tank cleaner, and finishing with a final clean water rinse. Run clean water through the boom and nozzles during each step.
• Winterization: Before winter storage, flush the system, drain all water from the pump and lines to prevent freezing damage, and fill the pump with RV antifreeze (propylene glycol). Store nozzle tips and strainers in a clean, dry container.