Category: Speciality Sprayers

Main category for all sprayers that are not horizontal booms

  • Diluting 20,000-Fold with a 30 Gallon Remaining Volume in a 1,200 Gallon Tank

    Diluting 20,000-Fold with a 30 Gallon Remaining Volume in a 1,200 Gallon Tank

    (This short article is an addendum to this article)

    Our goal in this example is to dilute by a factor of 20,000.

    The maximum amount of dilution possible with a 1,200 gallon tank and a 30 gallon remainder is 1200/30=40.

    The formulae:

    Dilution per Rinse = final dilution ^(1/# of rinses)

    Rinse Volume = (dilution per rinse * remaining volume) – remaining volume

    • One rinse diluting by 20,000 – impossible with a 1,200 gallon tank (max achievable is 40-fold);
    • Two sequential rinses, each diluting by a factor of 20,000^(1/2) = 141. Also impossible with a 1,200 gallon tank;
    • Three sequential rinses, each diluting by a factor of 20,000^(1/3) = 27. A volume of 780 gallons can do this  (27*30)-30=780 gallons. For three rinses, the total volume is 2,340 gallons.
    • Four sequential rinses, each diluting by a factor of 20,000^(1/4) = 12. A volume of 330 gallons can do this, for a total volume of 1,320 gallons;
    • Five sequential rinses, each diluting by a factor of 20,000^(1/5) = 7. A volume of 180 gallons can do this, for a total volume of 900 gallons;
    • Six sequential rinses, each diluting by a factor of 20,000^(1/6) = 5.2. A volume of 126 gallons can do this, for a total volume of 757 gallons.

    Second, let’s assume the operator is prepared to prime the boom where it doesn’t harm soybeans. Now the first new product tank takes care of the last dilution, lowering the cleanout dilution requirement by 1,200/30 = a factor of 40. Now the cleanout dilution requirement is only 20,000/40 = 500.

    • One 1,200 gallon tank rinse can only achieve 40-fold dilution.
    • Two rinses, each diluting by 500^(1/2) = 22. Rinse volumes of 640 gallons are sufficient, for a total of 1,280 gallons.
    • Three sequential rinses, each diluting by a factor of 500^(1/3) = 7.9. A volume of 210 gallons can do this, for a total volume of 630 gallons;
    • Four sequential rinses, each diluting by a factor of 500^(1/4) = 4.7. A volume of 112 gallons can do this, for a total volume of 448 gallons.
  • How Clean is Clean?

    How Clean is Clean?

    One of the more perplexing questions in tank cleanout is knowing when the cleaning process is good enough to prevent harm. This question is especially relevant to producers that grow canola and use Group 2 herbicide products, or grow soybeans and use dicamba on some of their area. In both of these examples, crops can be extremely sensitive to very small residues.

    When does an applicator know that the cleaning job was good enough? In about two weeks! There is no easy way to tell, except to be precautionary.

    A bit of math can help put us in the ballpark. First, we need to know the tolerance of a crop to the herbicide, preferably expressed as a proportion of the tank mix to be cleaned. Let’s use dicamba as an example. It’s been reported that non-dicamba tolerant soybeans can show leaf-cupping symptoms from dicamba at rates as low as 1/20,000 of the label rate.

    Recall that sprayer cleanout is really two separate processes that we’ve written about here, here, and here. The first is dilution of the remaining volume in the system. The second is decontaminating specific sprayer components (filters, boom ends, hoses). We’ll focus on dilution in this article.

    If you’re diluting, the second piece of information you need is how much liquid is left in the sprayer when you start cleaning. All sprayers have a certain amount of liquid left in the tank and associated plumbing after the tank is empty. The sump, the suction line feeding the pump, and the lines returning to the tank via agitation or sparge are most common. Even when the pump no longer draws liquid, those lines retain some volume of product. This volume can’t be pushed out to the boom, most of it goes back to the tank.

    The volume of this “remaining liquid” is likely somewhere between three and thirty US gallons.

    The remainder volume depends on the sprayer, and also how the tank is emptied. Some applicators simply spray until the solution pump pressure drops, others choose to drain the remaining liquid from a sump valve. When draining, product should be captured in pails rather than allowing it on the ground where it will harm the soil and possibly make its way into runoff.

    It’s always preferable to spray the tank empty in a field.

    As we’ll see below, a low remaining volume greatly improves the efficiency of the dilution process. It’s a sprayer feature that should be considered at purchase.

    The table below has some sample calculations. Note that the paired cases (1&2, 3&4, 6&7) all use the same total water volume, but compare a single vs triple rinse of three different remaining volumes.

    Comparing Case 1 to Case 3 or Case 6, (remaining volumes of 10, 20, and 50, respectively), it’s clear that minimizing the remaining volume is important.

    It’s also striking that the same amount of clean water, subdivided into three smaller repeat batches (Case 2, 4 and 7), is much more powerful than using single batches with the same total clean water amounts.

    Reducing the size of each batch even further and increasing the number of batches (Case 5) approaches what a properly executed continuous rinse can do.

    Is it necessary to dilute to the level that’s safe for the next crop? Not always. The next product in the tank acts to dilute the remainder once again, possibly by a factor of 100, depending on the remaining volume and the tank size (Case 8). The material in the boom, however, won’t be diluted by this additional volume, and therefore may harm the crop unless it is first sprayed out elsewhere, especially when section ends are not drained and rinsed.

    This is where a recirculating boom is valuable, providing an opportunity to charge the boom without spraying. The penalty is that the boom volume is then returned to the tank in the process, increasing the amount that needs to be diluted.

    Let’s return to the dicamba example with a 20,000-fold dilution requirement and a 1,200 gallon tank. We’ll consider two examples. In the first, the operator wants to prime the boom in the soybean field without any harm to the dicamba-susceptible beans. A 20,000-fold dilution is needed.

    We’ve looked at five options that each assume a remaining volume of 10 gallons. Note that our goal is the same – dilute by a factor of 20,000.

    The formulae:

    Dilution per Rinse = final dilution ^(1/# of rinses)

    Rinse Volume = (dilution per rinse * remaining volume) – remaining volume

    The maximum amount of dilution possible with a 1,200 gallon tank and a 10 gallon remainder is 120 (see Row 8, Table above).

    • One rinse diluting by 20,000 – impossible with a 1,200 gallon tank (max achievable is 120-fold);
    • Two sequential rinses each diluting by a factor of 20,000^(1/2) = 141. Also impossible with a 1,200 gallon tank;
    • Three sequential rinses, each diluting by a factor of 20,000^(1/3) = 27. A volume of 260 gallons can do this  (27*10)-10=260 gallons. For three rinses, the total volume is 780 gallons.
    • Four sequential rinses, each diluting by a factor of 20,000^(1/4) = 12. A volume of 110 gallons can do this, for a total volume of 440 gallons;
    • Five sequential rinses, each diluting by a factor of 20,000^(1/5) = 7. A volume of 60 gallons can do this, for a total volume of 300 gallons.

    The first two examples don’t work because the tank isn’t big enough. But the three remaining examples all work equally well, they just consume different amounts of clean water.

    If that doesn’t seem like a lot of work, then repeat this calculation with a 30 gallon remainder volume, common on many sprayers. Short on time? We did it for you here.

    Second, let’s assume the operator is prepared to prime the boom where it doesn’t harm soybeans. Now the first new product tank takes care of the last dilution, lowering the cleanout dilution requirement by 1,200/10 = a factor of 120. Now the cleanout dilution requirement is only 20,000/120 = 166.

    • One 1,200 gallon tank rinse can only achieve 120-fold dilution.
    • Two rinses, each diluting by 166^(1/2) = 13. Rinse volumes of 120 gallons are sufficient, for a total of 240 gallons.
    • Three sequential rinses, each diluting by a factor of 166^(1/3) = 6. A volume of 50 gallons can do this, for a total volume of 150 gallons.

    The math is simple, and can be done using the formula in the first table, or this app:

    The hard part is knowing what the remaining volume is. It would be very useful for a manufacturer to provide this information.

    In the meantime, you can estimate on your own. Add water with surfactant to your tank, and spray it empty. While spraying, turn the agitation on and off to fill and activate the sparge, if equipped. Once the tank is empty and the spray pressure drops, stop and drain the sump into pails. Ensure that the pump suction line and the pressure line up to and including the agitation and sparge lines also drain. Disconnect these if necessary. If there is a filter housing in this circuit, remove it as well.  Avoid collecting liquid from the pressure line beyond where the the agitation or sparge split off, as this will be pushed out to the boom.

    An alternative is to estimate the length of hose in this circuit, using the following table as a guide:

    And remember, diluting the remaining liquid is only one part of a cleaning process.

  • Application Recordkeeping: Focus on Environmental Conditions

    Application Recordkeeping: Focus on Environmental Conditions

    Note: This article was written by Bob Wolf of Wolf Consulting and Research, and first appeared as an NDSU Extension Service publication. Bob has agreed to reproduce the article on our website.

    When applying crop protection products, a good steward is one who can identify and record the environmental factors that may negatively impact making an application; particularly, the possibility of spray drift.

    New label language states: “Avoiding spray drift at the application site is the responsibility of the applicator.” A wise sprayer operator must possess the ability to assess the environmental conditions at the field location to determine how best to spray the field, or maybe decide it would be best not to spray that field, or part of that field, at that time. Instruments that assess environmental conditions are available to assist applicators in making good decisions.

    Making the correct measurement is the critical first step. Record the information measured to document the application conditions. Quality records help mitigate against any misapplication allegations, such as a drift complaint. Many of the items listed below are based on past legal experiences with applications involving spray drift litigation.

    The following guidelines should help you measure and accurately record environmental conditions at the application site.

    1- Document any instrument used by recording the manufacturer and model number. Accurate portable weather instruments are recommended. Portable weather instruments are available that log and store data, and aid in auditing and recordkeeping. Some will have Bluetooth/wireless capabilities.

    2- Environmental measurements include wind speed and direction, temperature, and relative humidity.

    3- At a minimum, record data at the start and finish of the job. Consider more often as conditions change or for a job that lasts over a longer period. For example, make observations when tank refilling for larger fields. Time stamp all observations with a.m., p.m., or military time.

    4- Take meteorological readings as close to the application site as possible. Be advised that the weather data received via a smart phone or local weather station may not be accurate for the location being sprayed.

    Note the specific location where the measurement was made, such as GPS coordinates, field entry point, field location, etc. Check the label to see if it requires a specific observation location in relation to the treatment area.

    5- Make all measurements as close as possible to the nozzle release height (boom height) and in an area not protected from the wind by the spray machine or your body. For aerial applications, six feet is suggested when using a hand held instrument.

    6- Record wind speed averaged over a 1 to 2 minute time span. Note the time the observation was recorded. Most instruments give an average over a period of time. Make sure the instrument’s anemometer is facing directly into the wind.

    Do not record winds as variable or with a range i.e. 4 to 8 mph – an average gives a better indication of the transport energy. Light and variable winds, where directions may change several times over a short period, can be more problematic than higher speed winds in a sustained direction. Observe any label restrictions on wind speed.

    Wind direction requires a similar averaged measurement. Record direction in degrees magnetic from a compass (0-360°). The use of alphabetic characters, i.e., N, S, NW, to indicate wind direction is discouraged. The key for determining direction is to have an accurate assessment method: trees moving, dust, smoke, a ribbon on a short stake, etc. Face directly into the wind and record the direction from which the wind is coming. A ribbon on a stake with the ribbon blowing directly at your body is a simple fail safe approach. Movement of smoke, particularly from moving aircraft, or dust may help determine direction.

    7- Record temperature and humidity since they can be helpful in determining temperature inversion potential. It may be advisable to record both temperature and humidity well before and after the application for this purpose. In fact, recording a morning low and an afternoon high would be useful regarding determining the potential for an inversion. Take temperature measurements with the instrument out of direct sunlight. Shade the instrument with your body or spray equipment. This is especially critical if you are trying to assess temperature differentials for determining if an inversion is in place.

    8- Be alert to field level temperature inversion conditions which typically occur from late afternoon, can be sustained through the night, and into the next morning. Beware, inversions can start mid-afternoon. Observe conditions such as the presence of ground fog, smoke layers hanging parallel to the ground, dust hanging over the field/gravel road, heavy dew, frost, or intense odors (i.e., smells from manure or stagnant water from ponds are held close to the surface when inversion conditions exist). Inversions commonly occur with low (less than 3 mph) to no wind speeds. Spraying in calm air is not advised. If a mechanical smoker is used note wind direction and smoke dissipation with a time stamp.

    9- Note any variances due to terrain or vegetation differences, tree lines, buildings, etc.

    10- Initial or sign all recordings to indicate who made the observation(s).

  • Spray Coverage in Carrot, Onion and Potato

    Spray Coverage in Carrot, Onion and Potato

    This research was performed with Dennis Van Dyk (@Dennis_VanDyk), vegetable specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs.

    Prior to 2017, Syngenta introduced the UK to the Defy 3D nozzle, which is a 100° flat fan, designed to run alternating 38° forward or backward along the boom. They prescribed a boom height of 50 to 75 cm, 30-40 psi, and travel speeds of 10 to 14 km/h in cereals and vegetables. Compared to a conventional flat fan, they claimed that the angle and Medium-Coarse droplets promise less drift and improved coverage.

    In 2017, Hypro and John Deere began distributing the Defy 3D in North America. Our goal was to explore coverage from the 3D in vegetable crops. We compared the nozzle’s performance to common grower practices in onion, potato and carrot in the Holland Marsh area of Ontario.

    Experiment

    We used a technique called fluorimetry. A fluorescent dye (Rhodamine WT) was sprayed at 2 mL / L from a calibrated sprayer based on protocols generously provided by Dr. Tom Wolf.

    Tissue samples from the top, middle and bottom of the canopy were collected from random plants.

    The samples were rinsed with a volume of dH2O and this rinsate was then tested to determine how much dye was recovered.

    The tissues collected were dried and weighed to normalize the samples to µL of dye per gram dry weight to allow for comparison.

    In addition, we used water-sensitive paper as a check in key locations in the canopy to provide laminar and panoramic coverage. Papers were digitized and coverage determined as a percentage of the surface covered.

    In carrot and onion, we compared a hollowcone, an air-induction flatfan, and alternating 03 3D’s at 500 L/ha (~40 cm boom height, ~3 km/h travel speed, ~27ºC, 3-9 km/h crosswind, ~65% RH).

    In potato we compared the alternating 05 3D’s to a hollowcone at 200 L/ha (~55 cm boom height, ~10.5 km/h travel speed, ~22ºC, 6-8 km/h crosswind, ~65% RH).

    Water-sensitive papers were originally intended as a coverage check, and not as a source of analysis, but their use revealed interesting information. The following images are the papers recovered a single pass in each crop.

    Carrot

    Onion

    Potato

    Results

    The following table represents the percent coverage of these paper targets. Papers were digitized using a WordCard Pro business card scanner and analysis made using DepositScan software. This table is small, but you can zoom in for a quick comparison. The following three histograms show the same data graphically for carrot, onion and potato, respectively. Remember, this only represents a single pass, so don’t draw any conclusions about coverage yet.

    Carrot

    Onion

    Potato

    It was interesting to note differences in coverage observed on the papers versus the results of the fluorimetric analysis. It was anticipated that while water-sensitive paper serves for rough approximation of deposition, fluorimetry would be far more accurate. This is because of the droplet spread on the paper, and the evaporation and concentration of a spray droplet en route to the target. Again, here is a small table, and again, the next three histograms show the same data graphically for carrot, onion and potato, respectively.

    Carrot

    Onion

    Potato

    Observations

    While water-sensitive paper is an excellent diagnostic tool for coverage, fluorimetry allows for greater resolution. The high variability in coverage meant little or no statistical significance, however the means suggested the following:

    • In carrot, the 3D deposited more spray at the top of the canopy.
    • In onion, the hollowcone spray had a higher average deposit, and penetrated more deeply into the canopy.
    • In potato, the hollowcone deposited more spray at the top, with little or no difference mid-canopy.

    Each nozzle performed well at the top of the canopy, which is quite easy to hit. Certainly they exceeded any threshold for pest control. With the possible exception of hollowcone in onion, nozzle choice had only minor impact on mid-bottom canopy coverage. And so, if coverage is not a factor for distinguishing between these nozzles, we should consider drift potential. Due to the comparably smaller droplet spray quality, the hollowcone is far more prone to off target movement. This leads us to select the AI flat fan or the 3D as the more drift-conscious alternatives.

    Future analysis would benefit from a larger sample size to reduce variability, and the inclusion of an air-assist boom to better direct spray into the canopy.

    Applitech Canada (Hypro / SHURflo) is gratefully acknowledged for the 3D nozzles. Thanks to Kevin D Vander Kooi (U of G Muck Crops Station) and Paul Lynch (Producer). Assistance from Will Short, Brittany Lacasse and Laura Riches is gratefully acknowledged. Research made possible through funding from Horticultural Crops Ontario.

  • The Agitation over Agitation

    The Agitation over Agitation

    Sprayers101 recently received a couple of seemingly unrelated questions about airblast sprayers:

    What are the advantages and disadvantages of mechanical versus hydraulic agitation? Why would someone want a stainless tank versus the cheaper poly or fiberglass options?

    Recognizing that each manufacturer has their own reasons for the features and materials used in their sprayers, we posed these questions to Mr. Kim Blagborne (formerly of Slimline Manufacturing). The following article was written from Kim’s response, and it turns out these two questions are very much related. Kim writes:

    This is a great debate among customers and manufacturers, and it’s difficult to stay neutral. Let’s consider the following:

    Hydraulic Agitation

    The flow required for hydraulic agitation requires about 30% of the pumps total capacity. This is very important because many sprayers cannot achieve, or maintain, this minimum requirement whilst spraying. This may be why it’s rare for a sales person to demonstrate agitation while the sprayer is spraying; quite often, the agitation slows or even stops. And, of course, because everyone gets wet.

    Let’s say an airblast sprayer has a pump with a manufacturer-listed capacity of 26 gallons per minute (gpm) (Click to download the spec sheet for the pump). The figure in that output chart is determined on a bench at 540 rpm and at 50 psi. However, when an operator uses that pump in the field, they run it at ~150 psi, and that brings the pump capacity down a bit to 25.5 gpm.

    Now we build in the line pressure drop associated with the sprayer’s plumbing. Effectively, another 8-10% of the pump’s output is lost to plumbing (a figure easily measured by collecting the total output capacity of the pump). Let’s say we are now down to a practical capacity of 23 gpm.

    If the operator’s crops are on 14 foot rows, it would be reasonable to spray 200 gpa at a travel speed of 3 mph at 150 psi. With both booms spraying that’s a required flow of 16.8 gpm.

    Remember, our hypothetical 26 gpm pump can only provide 23 gpm in the field. When we subtract the 16.8 gpm required for spraying, we’re left with 6.3 gpm excess capacity for agitation. But, we said we needed 30% of the pump’s 26 gpm capacity, and that comes out to 7.8 gpm. We’re short by 1.5 gpm, or stated differently, we’re about 20% short of what we need.

    Why don’t we see that deficit? Because the flow to the booms is prioritized, and therefore the sprayer output matches the calibration, so everything seems OK. But no one sees the reduced return flow through the regulator, and certainly no one peeks into the tank while spraying to see that the hydraulic agitation is greatly reduced.

    And so, while everything looked great during loading, the spray mix (especially SC and WDG formulations) may not stay suspended correctly during spraying. In extreme cases, that could lead to burning a crop (high concentration) at the start of a spray job, and reduced efficacy (low concentration) at the end. We’re quick to blame the chemical, but no one ever thinks to question hydraulic agitation.

    Let’s consider it from another angle: TeeJet suggests a model number 62905c-5 jet agitator for a sprayer with a 250 US gallon tank. To correctly agitate the contents of this tank, we will need 30 psi and 7.6 gpm (see the chart below).

    Unfortunately, there is no simple way for an operator to measure the agitation pressure or the flow, so it goes unchecked. The only way to determine if the flow demand is satisfied is to apply the generic rule of 30% of pump capacity and make an estimate. That’s pretty loose math since we’ve already established that the listed capacity may not reflect reality.

    Still another angle: Many operators now employ the Gear Up, Throttle Down (GUTD) approach to match their sprayer air settings to the crop canopy. However, when we reduce PTO input speed we also reduce pump capacity. Remember our piston diaphragm pump with the 26 gpm capacity at 540 rpm? We still need 16.8 gpm to spray, but reducing the rpm’s by 100, per GUTD, drops our pump output to only 23.16 gpm.

    23.16 minus 16.8 equals 6.36, and we needed 7.8 gpm to maintain sufficient hydraulic agitation. Oops.

    Mechanical Agitation and Tank Material

    There are definite advantages to mechanical agitation. It is not affected by the PTO speed because it is already excessive at 540 rpm. This means there is no pump capacity issue and it allows the operator to take advantage of GUTD.

    There are also a few disadvantages. Unlike a hydraulic system, mechanical agitation requires maintenance, such as regular (daily?) greasing. The packing where the the system inserts into the spray tank also requires occasional inspection and adjustment to prevent leaks.

    And of course there’s sticker shock. Many European manufacturers offer hydraulic agitation because it is ~$500.00 CAD less expensive. Further, mechanical agitation creates vibrational stress on tanks walls, which fiberglass or plastic tanks can’t handle for long. The solution is stainless tanks, which is a more expensive material. Further, stainless cannot be moulded around pumps and rotating parts, so more steel is required, adding to expense and weight.

    In my opinion, there is sufficient benefit to stainless to easily recover the investment. Beyond permitting mechanical agitation, there’s durability. We have stainless tanks built in 1948 that are still operating today, and we’ve never found a plastic or fiberglass tank that can claim that. There’s also sprayer sanitation. It has long been know that stainless cleans more easily and more reliably that plastic or fiberglass, especially as the tanks begin to age.

    Closing

    The decision to buy a sprayer with hydraulic agitation or mechanical agitation lies, ultimately, with the consumer. But be sure to look past the price tag, and under the hood. Ensure that you have sufficient agitation to properly suspend your tank mix, and give you the flexibility to Gear Up and Throttle Down to improve your spray coverage and efficacy.