7.2 Application Equipment Types, Maintenance & Chemigation Safety Devices

7.2 Application Equipment Types, Maintenance & Chemigation Safety Devices

Applying pesticides accurately, uniformly, and safely requires well-maintained equipment engineered for the specific target pest, crop canopy, or treatment site. A failure in any single mechanical component—whether a worn nozzle orifice, a clogged suction screen, a fluctuating pressure regulator, or a malfunctioning check valve—can result in severe crop damage, illegal pesticide residues, environmental contamination, or dangerous occupational exposure.

Certified applicators must master the operational principles of hydraulic sprayers, granular spreaders, nozzle tip materials, and legally mandated chemigation safety devices under Utah Administrative Code R68-7 and federal regulations.

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1. Pesticide Application Equipment Types

+-----------------------------------------------------------------------------+
|                     PRIMARY APPLICATION EQUIPMENT TYPES                     |
|                                                                             |
|   1. HYDRAULIC SPRAYERS                                                     |
|      - Boom Sprayers: Low-pressure broadcast on turf, field crops, pastures. |
|      - Air-Blast Sprayers: High-velocity air stream for tree canopies.      |
|      - Backpack / Hand-held: Spot spraying, brush, structural perimeters.   |
|                                                                             |
|   2. GRANULAR APPLICATORS                                                   |
|      - Rotary (Spin) Spreaders: Wide broadcast swath; feathered edges.      |
|      - Drop Spreaders: Precision gravity delivery; sharp, defined borders.  |
|                                                                             |
|   3. CHEMIGATION RIGS                                                       |
|      - Center pivot, lateral move, or drip systems with injection pumps.    |
+-----------------------------------------------------------------------------+

Hydraulic Boom Sprayers

Low-pressure hydraulic boom sprayers are the workhorses of agricultural field crops, pasture management, rights-of-way, and commercial turf management. They operate at pressures between 20 and 50 PSI and utilize a series of nozzles evenly spaced along a horizontal boom (typically 15 to 30 inches apart). They provide uniform broadcast coverage over large flat surfaces.

Air-Assisted (Air-Blast) Orchard Sprayers

Used primarily in Utah fruit orchards (cherries, apples, peaches) and vineyard operations. A high-pressure pump delivers spray solution into a high-velocity air stream generated by a powerful fan. The air blast displaces the calm air inside the tree canopy, turning leaves and depositing fine droplets on both upper and lower leaf surfaces.

• Hazard: High air velocity and fine droplet atomization create severe spray drift risks if applications are made during gusty winds or atmospheric temperature inversions.

Backpack and Hand-Held Sprayers

Manual or battery-powered sprayers used for spot-treating noxious weeds, ornamental beds, structural perimeters, and small turf areas. They typically operate between 15 and 40 PSI with a 1- to 5-gallon tank.

• Calibration Challenge: Walking speed, wand sweeping height, and pumping cadence vary between operators, requiring strict operational discipline to avoid under- or over-application.

Granular Spreaders: Rotary vs. Drop

• Rotary (Spin) Spreaders: Drop dry granules onto a spinning horizontal impeller disc that throws particles in a wide semi-circular arc (8 to 30 feet wide). Swaths feature feathered edges, requiring a 30% to 50% overlap between adjacent passes to achieve uniform distribution. Granule trajectory is heavily influenced by wind, particle mass, and walking speed.
• Drop Spreaders: Meter granules directly out of bottom hopper openings via gravity, dropping particles straight down between the wheels. Produces a crisp, razor-sharp edge with zero throw, making them ideal for fertilizing or applying pre-emergent herbicides along pavement, water features, and ornamental borders without drift.

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2. Sprayer Plumbing & Component Dynamics

A hydraulic sprayer is an integrated fluid circuit practical system consisting of a tank, pump, agitation line, pressure regulator, filtration screens, boom piping, and nozzle assemblies.

+-----------------------------------------------------------------------------+
|                        HYDRAULIC SPRAYER FLUID CIRCUIT                      |
|                                                                             |
|   [SPRAY TANK] ---> [Suction Strainer (40-50M)] ---> [PUMP]                 |
|                                                        |                    |
|                                                        v                    |
|   [Agitation Line] <--- [PRESSURE REGULATOR] <---+--- [Pressure Line]       |
|   (Jet / Bypass)        (Relief Valve & Gauge)   |                          |
|                                                  v                          |
|                                       [Inline Filter (50-100M)]             |
|                                                  |                          |
|                                                  v                          |
|                                           [SPRAY BOOM]                      |
|                                                  |                          |
|                                       [Tip Screen (50-100M)]                |
|                                                  |                          |
|                                            [NOZZLE TIP]                     |
+-----------------------------------------------------------------------------+

Sprayer Pumps

The pump provides the mechanical energy to move liquid from the tank, generate agitation, and force liquid through nozzle orifices under controlled pressure.

Agitation Systems

• Mechanical Agitation: Uses motor- or PTO-driven rotating paddles or propeller shafts positioned near the bottom of the tank. Mandatory for heavy Wettable Powder (WP) and Dry Flowable (WDG) suspensions to prevent settling.
• Hydraulic (Jet/Bypass) Agitation: Diverts a portion of pump output flow back into the tank through a specialized venturi nozzle. Effective for true solutions and emulsifiable concentrates; may be insufficient for high-density wettable powders in large tanks.

Filtration and Strainer Mesh Sizing

Filtration screens protect pumps from abrasive wear and prevent nozzle orifices from clogging. Filters are sized by mesh number, which indicates the number of wire openings per linear inch:

Higher Mesh Number => Smaller Screen Openings (Finer Filtration)

1. Tank Opening Strainer (16–20 Mesh): Coarse basket filter that stops leaves, twigs, and large packaging debris during filling.
2. Suction Line Strainer (40–50 Mesh): Placed between the tank and pump inlet to shield pump impellers/gears from coarse particles.
3. Pressure Line Filter (50–100 Mesh): Located downstream of the pump to catch fine debris before it enters boom lines.
4. Nozzle Tip Strainers (50 or 100 Mesh): Small slotted or wire screens placed directly behind each nozzle tip. Standard practice uses 50-mesh screens for larger nozzle tips (0.2 GPM and higher) and 100-mesh screens for fine nozzle tips (0.15 GPM and lower).

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3. Nozzle Engineering: Spray Patterns & Droplet Spectra

The nozzle tip performs three vital functions: metering liquid flow rate (GPM), atomizing liquid into spray droplets, and distributing droplets into a specific geometric pattern.

+-----------------------------------------------------------------------------+
|                           NOZZLE SPRAY PATTERNS                             |
|                                                                             |
|   [FLAT-FAN (Tapered)]    [EVEN FLAT-FAN (E)]     [FLOOD JET (Wide)]        |
|       / \     / \             |       |               /           \         |
|      /   \   /   \            |       |              /             \        |
|     /_____\_/_____\           |_______|             /_______________\       |
|   (Requires 30-50% Overlap) (Banding Over Row)     (Coarse, Low-Drift Turf) |
|                                                                             |
|   [HOLLOW CONE]           [FULL CONE]             [AIR-INDUCTION (AI)]      |
|       ( O )                   ( @ )                  /  * o *  \            |
|   (Foliar Fungicides/Ins.) (Dense Foliar Canopy)   (Air-Filled Coarse Drops)|
+-----------------------------------------------------------------------------+

Major Nozzle Types

1. Standard Flat-Fan (Tapered Edge): Produces an elliptical fan pattern with tapered edges (lightest output at edges, heaviest in center). Designed to be overlapped by 30% to 50% on a broadcast boom to achieve uniform liquid distribution across the field. Standard fan angles are 80° and 110°.
2. Even Flat-Fan (Designated with an "E", e.g., 8002E): Produces a crisp, uniform rectangular spray pattern across its entire swath with no tapered edges. Strictly designed for band applications over crop rows. Exam Trap: Even flat-fans must NEVER be used on a broadcast boom because overlapping them produces severe double-dosed application stripes.
3. Flood Jet (Flooding) Nozzles: Discharges a wide-angle (110° to 140°), coarse fan spray at low operating pressures (10 to 25 PSI). Produces large droplets with minimal drift; ideal for liquid fertilizers and soil-applied pre-emergent herbicides.
4. Hollow Cone & Full Cone: Cone-shaped spray patterns producing small-to-medium droplets with high target penetration. Primarily used for applying post-emergence contact fungicides and insecticides into dense foliar canopies.
5. Air-Induction (Venturi / AI) Nozzles: Utilizes an internal venturi jet that draws atmospheric air into the nozzle body, mixing it with the spray liquid. Produces large, air-filled, low-drift droplets. Upon impacting plant leaves, the air-filled bubbles shatter into smaller droplets, providing good coverage while virtually eliminating driftable fines (<105 microns).

Nozzle Wear and Orifice Materials

Nozzle orifices erode over time due to the abrasive scrubbing of suspended mineral powders, wettable powders, and liquid fertilizers. As an orifice wears, its output (GPM) increases and its spray pattern distorts.

[!CAUTION] Nozzle Cleaning Rule: NEVER clean a clogged nozzle tip with a pocket knife, wire, nail, or sewing needle. Metal tools distort the microscopic dimensions of the orifice, permanently destroying pattern uniformity. Always use a soft-bristled nylon brush or compressed air.

Replacement Threshold: Test nozzle output periodically with a calibration container. Replace any nozzle tip whose flow rate (GPM) deviates by more than ± 10% from the manufacturer's rating for a new tip.

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4. Chemigation Safety Devices & Anti-Siphon Protection

Chemigation is the practice of applying pesticides, agricultural chemicals, or fertilizers through an automated irrigation system (e.g., center pivot, lateral move, solid set sprinklers, or micro-drip systems). While highly efficient, chemigation poses a severe threat to public water supplies and underlying groundwater aquifers if a back-siphonage event occurs.

+-----------------------------------------------------------------------------+
|                   MANDATORY CHEMIGATION SAFETY DEVICES                      |
|                                                                             |
|   [IRRIGATION WATER SOURCE]                                                 |
|          |                                                                  |
|          v                                                                  |
|   [1. Mainline Check Valve]  ---> Heavy-duty spring-loaded check valve      |
|          |                        (Prevents backflow into water supply)     |
|          v                                                                  |
|   [2. Vacuum Relief Valve]   ---> Located on top of pipe upstream of check  |
|          |                        (Breaks vacuum siphon if pump fails)      |
|          v                                                                  |
|   [3. Low-Pressure Drain]    ---> Located on pipe bottom upstream of check  |
|          |                        (Drains any chemical leakage away)        |
|          v                                                                  |
|   ==================== INJECTION POINT ====================                 |
|          ^                                                                  |
|          |                                                                  |
|   [4. Chemical Line Check]   ---> 10+ PSI check valve on chemical hose      |
|          |                        (Prevents water rushing into chem tank)   |
|          v                                                                  |
|   [5. Interlocking Power]    ---> Electrical interlock between pumps        |
|                                   (Stops injection if water pump shuts down)|
+-----------------------------------------------------------------------------+

Under EPA regulations and Utah Administrative Code R68-7, any irrigation system utilized for chemigation must be equipped with five legally mandated safety devices:

1. Mainline Check Valve (Irrigation Line): A heavy-duty, spring-loaded check valve installed on the main irrigation pipeline between the water supply pump and the pesticide injection point. It closes automatically to prevent water-chemical mixtures from flowing backward into the wellhead or canal.
2. Vacuum Relief Valve: Positioned on top of the irrigation pipe between the water pump and the mainline check valve. If the water pump suddenly loses power, the vacuum relief valve opens to admit atmospheric air, breaking any vacuum suction that could siphon contaminated water down the well casing.
3. Automatic Low-Pressure Drain: Located at the lowest point on the bottom of the irrigation pipe upstream of the mainline check valve. It automatically opens and discharges any chemical-laden liquid out of the pipe onto the ground (away from the wellhead) if the mainline check valve leaks under low pressure.
4. Pesticide Injection Line Check Valve: A spring-loaded check valve (with a minimum opening cracking pressure of 10 PSI) installed directly on the chemical injection line. This valve prevents irrigation water from flowing backward through the injection line into the pesticide chemical supply tank if the injector pump stops.
5. Functional Power Interlocking System: An electrical or mechanical interlock connecting the irrigation water pump and the chemical injection pump. If the irrigation water pump shuts down (due to power outage, mechanical failure, or dry well), the chemical injection pump must immediately and automatically shut off, preventing raw, undiluted pesticide from being pumped into stagnant pipes.