9.1 Sprayers, Pumps, Spreaders & Specialized Delivery Systems

Application Equipment: Sprayers, Spreaders, and Delivery Systems

Choose equipment that can place the labeled rate on the target uniformly while controlling drift, runoff, exposure, and damage. Equipment type does not determine legality by itself; the label, license category, site, calibration, and Maine operating rules still apply.

Hydraulic sprayer components

A hydraulic sprayer usually includes a tank, agitation, pump, pressure regulator, gauge, strainers, hoses, valves, shutoffs, boom or handgun, and nozzles. Each part must be compatible with the formulation and operating pressure.

Agitation keeps suspensions uniform. Hydraulic return agitation uses liquid flow; mechanical agitation uses paddles or shafts. Too little agitation allows settling, while excessive agitation can foam products or damage water-soluble packaging.

Strainers protect pumps and nozzles. Mesh must match the pump, nozzle orifice, formulation, and manufacturer design. A suction screen that is too restrictive can starve the pump and cause cavitation, but there is no universal rule that every suction strainer must be 40 or 50 mesh. Use the equipment and nozzle specifications.

Check valves and diaphragm nozzle bodies reduce dripping when pressure falls. They do not replace the main shutoff or permit turning while spraying.

Pump types

Centrifugal pumps use a rotating impeller and generally provide high flow at low-to-moderate pressure. They tolerate many suspensions and bypass flow, but output changes with system resistance and they may require priming depending on installation.

Roller, piston, diaphragm, and other positive-displacement pumps move a more defined volume per cycle. They can provide higher pressure but require suitable pressure relief or bypass. Abrasive products, solvents, maintenance, pulsation, and capacity affect the best choice.

Do not select a pump from a generic pressure range alone. It must provide the required total nozzle flow plus agitation and bypass capacity at the operating pressure.

Boom sprayers

A boom holds nozzles at consistent spacing and height for broadcast or band application. Uniformity depends on matched tips, stable height, proper overlap, pressure, speed, and shutoff timing.

Use section control at headlands and boundaries. Boom suspension and lower travel speed can reduce height variation. Calibrate on representative terrain with the loaded vehicle.

Airblast and orchard sprayers

Airblast equipment carries droplets into plant canopies with high-volume air. Adjust air direction and volume to the canopy and shut off nozzles that spray above or below the target. Excess air can propel droplets through the canopy and off site; insufficient air leaves inner foliage untreated.

Air velocity and pressure vary widely among machines. Do not memorize one 90-to-140-mph range. Use smoke, ribbons, water-sensitive paper, catch devices, or other accepted methods to evaluate airflow and deposition. Follow Chapter 22 weather limits and the label's droplet and drift controls.

Backpack, handgun, and spot equipment

Backpack sprayers and handguns suit small or irregular sites. Operator walking speed, pumping rhythm, nozzle distance, and sweeping motion affect rate. Calibrate the actual person and technique over a measured area.

High-pressure handguns can produce drift and worker exposure. Pressure and long reach are not substitutes for correct access or a label-authorized method.

Granular spreaders

Drop spreaders release particles beneath the hopper and provide a more defined edge than rotary spreaders. Particle bounce, wind, gate lag, steering, and wheel overlap can still move product off target, so “zero drift” is inaccurate.

Rotary spreaders throw particles in a tapered pattern. Effective swath and overlap depend on granule size, density, impeller speed, port position, and equipment. Conduct a catch-tray pattern test and follow the manufacturer's setup rather than assume a universal 30-to-50-percent overlap.

Calibrate by collecting or weighing output over a known area. Confirm that the material flows consistently and that the selected setting remains accurate as granule properties and hopper level change.

Other systems

Injection systems meter concentrate into carrier near the point of delivery and can reduce mixed-product inventory, but both carrier and injection rates require calibration. Chemigation uses irrigation equipment and requires label-authorized equipment, backflow prevention, interlocks, and the applicable license option. Aerial, fumigation, aquatic, seed-treatment, and structural systems have category- and label-specific controls.

Equipment selection checklist

1. Confirm that the label allows the method.
2. Match equipment to site, target, formulation, and required category.
3. Calculate total flow, pressure, agitation, capacity, and refill needs.
4. Select compatible materials and the correct strainers and nozzles.
5. Verify shutoffs, antisiphon protection, guards, and leak-free condition.
6. Calibrate rate and distribution.
7. Evaluate weather, sensitive areas, operator exposure, and cleanup.
8. Record setup and calibration as required.

The best equipment is not the machine with the highest pressure or widest swath. It is the system that can repeatedly deliver the intended distribution while keeping pesticide on target.