CPA Application Equipment and Calibration 3 — Questions and Answers
Question 1: What is the purpose of a pressure regulator in a pesticide spray system?
- To increase pump output when tank is low
- To maintain consistent operating pressure regardless of pump fluctuations (Correct answer)
- To filter particles from the spray solution
- To control the direction of nozzle spray patterns
Correct answer: To maintain consistent operating pressure regardless of pump fluctuations
A pressure regulator maintains a steady, pre-set operating pressure by releasing excess pressure back to the tank or bypass line.
Question 2: In the formula GPA = (GPM × 5940) / (MPH × W), what does the value 5940 represent?
- The number of square feet in an acre
- A conversion constant that accounts for minutes and distance units (Correct answer)
- The standard nozzle flow rate in gallons
- The maximum allowable application rate
Correct answer: A conversion constant that accounts for minutes and distance units
The constant 5940 is derived from converting miles per hour and nozzle spacing into a per-acre basis (5280 ft/mile × 60 min/hr / 12 inches per foot × nozzle spacing denominator).
Question 3: Which nozzle type produces the largest droplet size and is therefore most suitable for minimizing drift in windy conditions?
- Flat fan nozzle
- Hollow cone nozzle
- Air induction (venturi) nozzle (Correct answer)
- Full cone nozzle
Correct answer: Air induction (venturi) nozzle
Air induction nozzles mix air into the spray stream, producing large air-filled droplets that are much less prone to drift than conventional nozzles.
Question 4: A granule applicator is set to release 50 lbs of granules per acre. The label requires 60 lbs per acre. To increase output without changing ground speed, the applicator should:
- Use a larger orifice or wider opening on the metering gate (Correct answer)
- Increase the rotational speed of the spreader disc
- Switch to a finer granule formulation
- Increase travel speed to cover more ground
Correct answer: Use a larger orifice or wider opening on the metering gate
Opening the metering gate wider increases the volume of granules released per unit of time, raising the application rate.
Question 5: When calibrating a rotary spreader, the applicator catches material in collection pans placed under the distribution pattern. What is the primary purpose of this step?
- To measure the active ingredient concentration
- To determine the effective swath width and distribution uniformity (Correct answer)
- To test granule size consistency
- To weigh the total tank capacity
Correct answer: To determine the effective swath width and distribution uniformity
Catching granules in collection pans across the spread pattern reveals the effective swath width and whether distribution is uniform from center to edge.
Question 6: A check valve on a sprayer nozzle body serves primarily to:
- Prevent nozzle drip when the boom is shut off (Correct answer)
- Filter debris before it reaches the nozzle tip
- Regulate pressure at each individual nozzle
- Mix two chemicals at the nozzle tip
Correct answer: Prevent nozzle drip when the boom is shut off
Check valves (anti-drip devices) hold the spray tip closed when pressure drops at shutoff, preventing post-application drip onto non-target areas.
Question 7: If a sprayer nozzle's output increases significantly over time without any change in pressure, this most likely indicates:
- The nozzle is clogged with debris
- The nozzle tip is worn and should be replaced (Correct answer)
- Tank agitation is too vigorous
- The strainer is too fine for the formulation
Correct answer: The nozzle tip is worn and should be replaced
Increased flow from a nozzle under the same pressure is a sign of nozzle wear — the orifice has enlarged, delivering more pesticide than intended.
CPA Application Equipment and Calibration 3
What is the purpose of a pressure regulator in a pesticide spray system?