Boom Sprayer Nozzle Performance Test
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Boom Sprayer Nozzle Performance Test

   

Boom Sprayer Nozzle Performance Test1

Thomas W. Dean2

This fact sheet describes how to evaluate the performance of a boom sprayer's nozzles.

Introduction

Making sure all nozzle tips on the spray boom function uniformly is the necessary, fundamental, first step of boom sprayer calibration.

The nozzle tips on a spray rig can be affected by many things. Age, lack of maintenance, or type and amount of spray passed through them, can cause nozzle tips to wear or clog. Worn or clogged nozzle tips make a boom sprayer unable to deliver a uniform spray pattern. Using a boom sprayer that has non-uniform nozzle tips will very likely result in misapplication.

This fact sheet discusses and gives examples of:

Getting Ready

Begin by making certain the boom sprayer is empty, mechanically sound, and has clean screens and intact plumbing. While checking the condition of the sprayer's hoses and fittings, make sure all nozzle tips on the boom are the same type and size (for example, all tips are DG8004).

To prepare the sprayer for nozzle tip testing, put at least 15 gallons of clean water in the spray tank.

Note: For nozzle tip testing, knowing the exact amount of water in the spray tank is not important. However, you want enough water in the tank to purge the boom, establish uniform spray pressure, and deliver continuous spray while you collect and measure the spray discharged from each nozzle during a short, but fixed, amount of time. (Typically, the amount of spray caught is less than one quart per nozzle.)

Next, gather together these items:

• clipboard, paper and pencil;

• a timepiece that measures seconds (for example, wristwatch with a second hand, or stopwatch); and

• a hand-held container that can catch and measure the spray discharged from a single nozzle. (For example, TeejetTM makes a handled, pitcher-shaped, plastic container that holds 60 fluid ounces and is marked with both U.S. and metric liquid measurement lines.)

Now, construct a data sheet. Make it complete enough to be a good written record of your nozzle performance test. Include places on the sheet for:

• your name,

• the date,

• the pump pressure used during the test,

• the type and size of nozzle tip being tested,

• the total number of nozzles present on the boom,

• each nozzle's location on the boom (To do this, begin at the left end of the boom and sequentially assign a number to each nozzle until all nozzles have an identifying number such as: noz-1, noz-2, noz-3, etc.),

• the amount of time (in seconds) that each nozzle will be tested(15 seconds is commonly used), and

• the amount of water (in fluid ounces) caught from each nozzle during its test.

With the sprayer parked, walk the length of the boom and record (on your data sheet) a location number for each nozzle present. Then start the engine, engage the PTO, and run the sprayer's pump.

Check all hoses and fittings for leaks and correct any problems found. Now, open the boom shut-off valve. Thereafter, adjust the regulator until it supplies the spray pressure that you plan to use in the field (for example, 35 psi). Record this pump pressure (psi) on the data sheet. Let the boom continue to spray water.

Now you are ready to measure nozzle tip performance.

Measuring Nozzle Tip Performance

Step 1: Take the clipboard, pencil, timepiece, and catch container to nozzle number 1 (left end of the spray boom). Make sure the catch container is empty. (The spray boom is already running -- it's the last thing you did when getting ready.)

Step 2: Put the mouth of the catch container beneath the nozzle tip (as close to the tip as possible) and note the time.

Step 3: Hold the catch container beneath the nozzle tip and catch all spray (water) delivered by the nozzle for exactly 15 seconds.

Step 4: Remove the catch container from the spray stream. Bring the catch container up to eye level and read the the amount of water (in fluid ounces) present in the container. Record this value on the data sheet as the amount of spray delivered by nozzle number 1.

Step 5: Move to the next nozzle on the spray boom and repeat Step 1 through Step 5 until each nozzle tip's spray performance has been measured and recorded.

Step 6: Close the boom shut-off valve, disengage the PTO, and power down the sprayer.

Finding the Bench Mark

A bench mark is a reference point used to standardize measurements. (In olden times, a master craftsman would scribe a reference mark on his workbench to help his workers correctly size and cut new materials.)

The bench mark for boom sprayer nozzle performance is the average nozzle output. This is a calculated value. It is the total amount of spray water caught during nozzle testing divided by the total number of nozzles tested.

To calculate the average nozzle output, use the information recorded on your nozzle test data sheet and do the following:

Step 1: Add together the fluid ounces of spray water caught from each nozzle's 15-second catch test. Record this sum. It is the total amount of spray water (in fluid ounces) caught during nozzle testing.

Step 2: Count the number of individual nozzle test measurements that you added together in Step 1. Record this number. It is the total number of nozzles that you tested. (It's also the total number of nozzles on the boom.)

Step 3: Divide the sum obtained from Step 1 by the count obtained from Step 2. Record this value. It is the average nozzle output that resulted from your nozzle test.

The answer obtained from Step 3 is your bench mark (your reference point). You can use it to evaluate the performance of the nozzle tips currently installed on your spray boom.

Defining "Good Enough"

Very few things are truly identical. If you closely examine any two cars of the same make and model, you find slight differences. Similarly, even "identical" twins usually have some feature (or behavior) that distinguishes one from the other. The same is true for nozzle tips.

Put plainly, it is not reasonable to expect all nozzle tips of a particular size and type to perform identically. A comparison of any two same-coded nozzle tips (even new ones) will almost always show a difference (sometimes a considerable difference) in spray delivery performance.

Finding difference is so easy that it makes finding an exact match nearly impossible. So, what does this mean to someone trying to evaluate nozzle tip spray performance? It means: you should never expect any given nozzle's spray performance value to exactly match the bench mark value. But, in order for a given nozzle tip to be "good enough," its performance should be similar to the bench mark value.

Thus, the "real world" question (and its answer) is:

Question: How similar should a comparison of the two nozzle tip spray performance values be? (In other words, what's "good enough"?)

Answer: The difference between a test nozzle's spray performance value and the bench mark value should not differ by more than 10% of the bench mark value. Thus, 10% of the bench mark value is the allowable difference, or "tolerance." (So then, "good enough" means "the bench mark value in combination with a tolerance range of ±10%".)

Notice that our definition of "good enough" mentions "plus or minus" and "range". These terms help make sure that "good enough" is focused enough to only apply to nozzle tips that have performance values that both:

For example, let's suppose the bench mark nozzle performance value is 25 fluid ounces. (This is the calculated amount of spray that we expect a nozzle tip to deliver during a 15-second spray test.)

Then, because the tolerance range is ±10% (and 10% of 25 fluid ounces is 2.5 fluid ounces), any nozzle tip that delivers:

is "good enough" to use on the spray boom.

Diagnosing Rejected Nozzle Tips

The previous section shows that the combination of the bench mark value and the ±10% tolerance range separates "good" nozzle tip performance from "bad" nozzle tip performance. But it can also do something else.

It can tell you why each rejected nozzle tip is bad.

Combining the bench mark value and its tolerance range always gives you two calculated nozzle tip performance values. For example, in the previous section we found that combining the bench mark and its tolerance range gave:

These two numbers have three meanings:

1. Any nozzle tip whose catch-test value falls anywhere within the range (from 22.5 fluid ounces to 27.5 fluid ounces) is good enough to use.

2. Any nozzle tip whose catch-test value is more than the upper limit (in other words, puts out more than 27.5 fluid ounces during a spray test) is over-applying.

Remember, before starting the test, we made sure that all tips were of the same size and type. Therefore, any nozzle tip that over-applies during testing must have a worn orifice. (The orifice is the hole in the tip that spray passes through.) A worn nozzle tip cannot be satisfactorily repaired. (It would be very hard to shrink the hole.) Tip replacement is the only good choice.

3. Any nozzle tip whose catch-test value is less than the lower limit (in other words, puts out less than 22.5 fluid ounces during a spray test) is under-applying.

Any nozzle tip that under-applies during testing probably has a clogged orifice. Thus, a clogged orifice is probably why the tip performed badly during the test.

Sometimes a clogged orifice can be cleared. If you attempt to clear one, work carefully. A nozzle tip orifice is easily damaged. Any time you've tried to clear a clogged nozzle tip, be sure to re-test it before returning it to service.

Example: Nozzle Performance Test

The next five sections use "real world" numbers in a step-by-step example that describes the setup, measurement, calculations, and conclusions of a nozzle performance test conducted on a boom sprayer fitted with 6 flat-fan nozzle tips.

Example: Equipment Setup

A sprayer operator loads approximately 20 gallons of clean water into a boom sprayer's clean and empty spray tank.

Beginning from the left end of the boom, the operator assigns a sequence number to denote each nozzle's position on the spray boom. During the numbering procedure, the operator inspects each nozzle body and verifies that each contains a DG8004 flat fan nozzle tip.

With the sprayer's motor adjusted to deliver a steady engine speed of 1500 rpm, the operator engages the sprayer pump and opens the boom shut-off valve. After spray (water) begins discharging from each nozzle tip, the operator adjusts the pressure regulator until the pressure guage steadily indicates 30 psi in the boom.

While the spray boom continues to discharge spray (water), the operator records the following information on a nozzle performance data sheet:

A full-page (printable) data sheet designed specifically for recording nozzle performance testing information is included at the end of this publication and shown here in Figure 1.
Figure 1.

Example: Taking the Measurements

With the sprayer parked and the spray boom operating, the operator begins at nozzle location number 1 (far left end of the boom) and catches the water discharged from that nozzle for exactly 15 seconds. He or she measures the spray caught from that nozzle and records its amount (22 fluid ounces) on the nozzle performance data sheet.

The operator then moves to the next nozzle on the boom and repeats the measurement process. The task is complete when all nozzles on the boom have had 15 seconds of spray output measured in fluid ounces and recorded on the data sheet.

In this example, the individual measurements of spray output caught from the six nozzles on the boom were:

Example: Calculating the Bench Mark

Here, the focus is on some simple arithmetic.

We begin by recalling that the bench mark for nozzle performance is average nozzle output. Like any other average, this is a value that must be calculated (it doesn't exist by itself). Once we know a sprayer's average nozzle output, we have a reference point (a bench mark) for evaluating that particular sprayer's nozzles.

So, to calculate average nozzle output, do the following two steps:

1. Add together the six 15-second spray catch values that were obtained by direct measurement and get a total of 125 fluid ounces. This sum is the total fluid ounces of spray caught during nozzle testing. The arithmetic (using the example measurements described earlier) is illustrated in Figure 2.

2. Divide the 125 fluid ounces of spray caught during nozzle testing (calculated in the preceeding step) by the total number of nozzles tested (i.e., 6 nozzles). The result of this calculation is the sprayer's average nozzle output: 20.83 fluid ounces. The arithmetic (involving the example measurements described earlier) is illustrated in Figure 3.

Example: Calculating Tolerance Value and Range

As a general rule, 10% is chosen as the tolerance level for nozzle tip performance. In this example, we follow the rule and choose 10% as the tolerance level.

Now we turn our attention to the 3 different calculations that involve tolerance:

  1. The tolerance value. This is the number of fluid ounces that a given nozzle tip's performance may differ from the sprayer's bench mark nozzle performance value and still be considered "good."

    • To calculate a 10% tolerance value, multiply the bench mark nozzle performance value (20.83 fluid ounces) by 0.10 (the decimal equivalent of 10%). This yields a calculated tolerance value of 2.08 fluid ounces.

    • Figure 4 shows the arithmetic used to calculate a 10% tolerance value.

2. The upper limit of the tolerance range. This is the maximum output allowed for any given nozzle tip currently installed on the spray boom.

  1. The lower limit of the tolerance range. This is the minimum output allowed for any given nozzle tip currently installed on the spray boom.

    • To calculate the lower limit of the tolerance range, subtract the tolerance value (2.08 fluid ounces) from the bench mark performance value (20.83 fluid ounces). This yields a calculated lower limit of 18.75 fluid ounces.

    • Figure 6 shows the arithmetic used to calculate the lower limit of a tolerance range.

Example: Drawing Conclusions

A nozzle performance test gives useful answers to the following questions:

1. Which nozzle tips currently perform satisfactorily?

2. Which nozzle tips currently act like they're clogged?

3. Which nozzle tips currently need replacement because they're too worn?

For the example nozzle performance test, here are the answers to these three questions (and the reasons for them):

1. Nozzles 1,2,3 and 6 give satisfactory performance.

2. Nozzle 4 is under-applying (an indication that its nozzle tip is probably clogged.)

• We conclude this because the amount of spray caught from nozzle 4 during the catch test (18 fluid ounces) is less than the calculated lower limit of tolerance (18.75 fluid ounces).

• In other words, nozzle 4 is putting out less than the minimum spray discharge rate allowed. Since nozzle 4's tip is the same type as all the others (DG8004 flat fan), a partially-clogged tip is the simplest explanation for nozzle 4's performance shortfall.

• As a first action, remove the tip from nozzle 4 and carefully inspect it for clogging. Look for deposits or particles blocking the orifice. If blockage is discovered, use only "soft" tools (nylon brush, wooden toothpick, compressed air) to try and clear the orifice.

• After any attempt to clean a clogged nozzle tip, be certain to repeat its spray-catch test (same pump pressure, same catch time). Compare its new catch-test value with your previously calculated upper and lower limits of tolerance. This is the only good way to see if the tip is serviceable or not.

3. Nozzle 5 is on the verge of over-applying. During its 15-second catch test, nozzle 5 delivered 23 fluid ounces of spray. Because this is more than the upper tolerance limit allows (i.e., more than 22.9 fluid ounces), the best course would be to replace this nozzle's tip. Further use will only make its condition worse. The tip is too worn for us to expect it to give good service with the other nozzles currently on the boom.

Nozzle Performance Data Sheet
Figure 7.

Footnotes

1. This document is PI-23, one of a series of the Pesticide Information Office, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: April, 1998. Revised: March, 2005. Reviewed: March, 2008. For additional information, contact the Pesticide Information Office, University of Florida, P.O. Box 110710, Gainesville, FL 326222-0720. Phone (352) 392-4721. Please visit the EDIS web site at http://edis.ifas.ufl.edu

2. Thomas W. Dean, Ph.D., assistant extension scientist, Pesticide Information Office, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611-0710.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.


Copyright Information

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