SPRAYER CALIBRATION

 

General maintenance that should be conducted as often as possible


fill the tank half full with water
check the tank, hoses, and fittings for leaks
start the pump and check for recirculating water in the tank
check tank, hoses, and fittings for leaks
turn on the spray boom and check for leaks or other problems
check the spray pattern from each nozzle, make sure that all nozzles are the same style and have the same output
clean the main in-line filter
remove and clean the filters behind each nozzle

Determine speed in miles per hour


generally you want to be between 3-5 mph
to do this measure and mark 200 feet on a flat surface
fill the tank half full with only water
select and record an appropriate RPM and gear to maintain constant speed and pressure
record the time in seconds that is required for the machine to complete the 200 ft
– Make sure the equipment is at speed before starting
do this three times and use an average time

MPH = 200 ft * 60
Time (S) * 88

Example of how to calculate MPH

It takes 45 seconds to travel 200 feet

3 MPH = (200 ft * 60)/(45 * 88)

It takes 27 seconds to travel 200 feet

5 MPH = (200 ft * 60)/(27 * 88)

Determine the output of a nozzle


fill the tank half full with only water
with the equipment stationary, operate the system at the same pressure used to determine MPH
catch the output of a few nozzles for 1 minute
do this a few times to determine an average quantity
remember GPM = Ounces Per Minute/128 oz/gal

To determine output in Gallons per Acre (GPA)

GPA = (5,940 * GPM )/(MPH * width)

Width = the distance between nozzles (2) in inches

Example of how to calculate GPA

You collected 101 ounces in one minute

GPM = (101 OPM)/(128 oz/gal) = 0.79 GPM

Your speed is 3 MPH

GPA = (5,940 * 0.79) /(3 MPH * 18 in)

= 88 GPA

Width = the distance between 2 nozzles is 18 inches

What if you want to change your volume of water to 200 GPA?
you need to know the volume from each nozzle per minute (GPM)
to do this use this formula

GPM = GPA * MPH * width /5,940

GPM = 200 * 3 * 18 /5,940

= 1.82 GPM

 

So how do you adjust your application to a volume of water?

Pressure


– generally it takes a 4 fold increase in pressure to double output

Speed


– you can decrease or increase your speed
– disadvantages can be too slow or too fast


Spacing


– by lowering the boom and decreasing the distance between nozzles you can increase the volume per acre - difficult
Changing nozzle size
– this is the most sensible/easy approach to make large changes in output per acre

So how do you determine if a nozzle is worn out?

All nozzles have a number stamp on them
– the number indicates output (GPM) and the recommended operating pressure which usually 40 PSI
For flat fan nozzles, the number indicates
– the angle of spray
– and output in gallons per minute
– Examples
• 8005 is a nozzle with a 80-degree angle and an output of 0.5 gallon per minute
• 8015 is a nozzle with a 80-degree angle and an output of 1.5 gallons per minute
To determine if the nozzle is worn
– using only water, set the proper PSI, and engage the spray
– collect the output for one minute and determine GPM
– subtract the actual GPM from the GPM on the nozzle to get the difference
– divide the difference in actual by the GPM on the nozzle
– replace if the difference is greater than 10 %
Example
– You collected 0.58 GPM actual from a 8005 nozzle
– 0.58 actual GPM – 0.50 GPM = 0.08 difference
– 0.08 difference / 0.50 GPM on nozzle = 0.16 or 16 %


A thought about nozzles


for turfgrass – usually flat fan nozzles
different materials wear at different rates
– aluminum nozzles and brass nozzles
• wear out quickly
• inexpensive


– Stainless steel nozzles
• wear out slowly
• wear uniformly
• expensive


– nylon nozzles
• wear out slowly
• Can swell when exposed to certain solvents


– Ceramic nozzles
• wear out very slowly
• very expensive
• brittle