Confirming Nozzle Output for Agricultural Sprayers

From Dr. Jason Deveau, Application Technology Specialist, OMAFRA

You may think your sprayer is set up to deliver a specific output. In fact, the output may be different than expected – even with brand new nozzles. One way to check is to fill the sprayer with enough water to spray one hectare and then go spray the hectare. If the tank is empty, the sprayer is operating correctly. Most operators, however, do not have a test hectare marked off. Furthermore, this may give a false positive if some nozzles are occluded while others are worn.

Alternately, and preferably, the operator can measure the actual output-per-minute of each nozzle. This does not capture travel speed issues, but does double-check nozzle accuracy. Here are the steps for the timed-output test:

–          Clean the sprayer, fill it half-full with clean water and park it on a level surface .

–          Start spraying with all nozzles open. You’re going to get wet so dress appropriately.

–          Place a collection vessel under the nozzle to be tested. Use a short length of braided hose to direct the spray into the vessel, if required. Alternately, use dairy inflations (described later).

–          Collect spray for one minute, or if the output is very high, for thirty seconds. One minute is preferable because it improves the accuracy. Be sure to double the output if only measuring for thirty seconds.

–          Determine the nozzle output either by looking at the graduations on the side of the collection vessel, or preferably, weighing the output on a kitchen scale. If using a scale, one gram of clean water equals one millilitre. Remember to “tare”, which means subtract the weight of the collection vessel.

–          Convert the findings to either U.S. Gallons per minute or Litres per minute; whichever corresponds to the ratings in the nozzle manufacturer’s catalogue.

–          Replace any nozzles that are 10% more or less than the rated output; 5% is preferable, if possible. If two or more are out by 10%, replace all nozzles.

Dr. Heping Zhu, a USDA researcher specializing in horticultural sprayers inOhio, passed on this tip. When you calibrate nozzles it can be tricky to hold a braided hose over a nozzle body while juggling a pitcher or collection vessel. The hose can pop off, you can lose volume and you have a pretty good chance of getting sprayed.

Some use hose clamps, which is a good choice, but tends to drag out the process.

The ‘Inflation’; this is the rubber liner that goes inside milking tubes on dairy farms. For sanitation reasons, they can only be used for so long (six weeks or so) before the dairy farmer has to replace them.

This is good news for growers because the used inflations fit securely over the nozzle cap and can be flexed with one hand to direct the spray into the collection vessel.

This may not be a good fit for all sprayers. On a windy day you may have to flex the inflation to keep out of the spray and over-flexing can cause it to crimp rather than bend.

If you don’t know a dairy farmer to get used inflations, you can go to your local farm supply store and buy a new set of four for less than $30.00.

About Sean Westerveld

Ginseng and Medicinal Herbs Specialist, OMAFRA
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