Category: Spray Basics

  • Reading Airblast Nozzle Tables

    Reading Airblast Nozzle Tables

    Airblast operators should know how to read a nozzle table. They are found on dealer and manufacturer websites as well as in their catalogs. Table layout varies with brand, but they all relate a nozzle’s flow rate to operating pressure. The better tables also provide the spray angle and the median droplet size (i.e. spray quality).

    Operators need this information to complete calibration calculations (aka sprayer math) and when deciding how to distribute nozzle rates, angles and spray quality along a boom relative to the target canopy.

    This article focusses on hollow and full cone nozzles, which are commonly found on airblast sprayers. For more information on flat fan nozzle tables (e.g. for banded under-canopy or, vertical booms or broadcast applications from horizontal booms), refer to this article.

    Reading the table

    Let’s use the table below to determine a nozzle’s flow rate for a given pressure. First, find the nozzle colour in the top row. Second, find the operating pressure in the left-most column. Finally, the flow rate is indicated in the cell at the intersection between the row and column. For example, a red ATR hollow cone nozzle operated at 9 bar will emit a flow rate of 1.83 L/min.

    Perhaps you want to determine which nozzle will give a specific flow rate. Find the rate in the body of the table and trace the column and row to determine which nozzle/pressure combination will achieve it. For example, if we want a flow rate of ~1.00 L/min, we can use a Yellow at 10 bar or an Orange at 5 bar. Yellow is the better choice since the Orange would have to be operated at the bottom of its pressure range (more on that later).

    This Albuz nozzle table for 60 and 80 degree molded hollow cones gives flow rates in litres per minute.

    Note: Do not to confuse TeeJet’s ISO-standardized TXA or TXB nozzles with TXVK or ConeJet nozzles. They may be the same colour, but their outputs are very different.

    Higher flow rates or full cone patterns can be achieved using combination disc and core (or disc and whirl) nozzles. Depending on the manufacturer, the disc plate is defined by it’s diameter in 64th’s of an inch. The core or whirl plate might be described by the number of holes (e.g. 2-hole, 3-hole, etc.), or some other manufacturer-specific nomenclature (e.g. 45’s, 25’s etc.).

    Using the table below, we see that a D2 disc and a DC35 core will emit 0.34 gpm at 80 psi. By continuing along the row, we see that the spray angle for this combination will be 47 degrees at that pressure.

    This nozzle Table for TeeJet disc & cores is fairly typical of any manufacturer’s nozzle table. Find the disc & core combination in the two left-hand columns, and follow the row until it intersects your operating pressure to determine the rate in US gallons per minute. Or, if you know your ideal rate already, you can find the best disc & core combination for a given pressure to achieve that rate.
    This TeeJet nozzle table gives the flow rate for a disc (D#) and core (DC#) full cone combination nozzles in US gallons per minute.

    Pressure problems

    Do not choose a nozzle at the extreme of their flow or pressure range. A trailed PTO sprayer will experience pressure changes from driving on hills, or rate controllers will create pressure changes in response to changes in travel speed. In either situation, coverage will be compromised if the nozzle is pushed outside its optimal range.

    Note: Use pressure to achieve small changes in flow, but for more extreme changes, switch nozzles. Remember, it takes 4x the pressure to get 2x the flow. Stated differently, it takes 1/4 the pressure to get 1/2 the flow.

    You may not find a nozzle/pressure combination that emits the rate you are looking for. When your desired rate or pressure falls between the figures listed in the table, you can take the average. When nozzling an entire boom with different nozzle rates, get each position as close as you can to achieve the overall boom rate for a given pressure. It’s always a compromise – don’t stress over it.

    The author looking up nozzle rates during a spring calibration. The operator was running at 190 psi, but the catalogue only listed 180 psi and 200 psi. When span is only 20 psi, it’s fairly safe to approximate the output. When the table only lists in 50 psi increments, it is more difficult to determine the rate without testing the output. This issue usually occurs at pressures above 200 psi, and that’s very high for most horticultural operations. Consider using a lower operating pressure, if possible.
    Looking up nozzle rates during a spring calibration. The operator was running at 190 psi, but the catalogue only listed 180 psi and 200 psi. When the increment is only 20 psi, it’s reasonable to approximate the output. When the span is 50 psi increments, it is more difficult to determine the rate without testing the output (it’s not a linear relationship). This issue usually occurs at pressures above 200 psi, and that’s far too high for cane, bush, vine and high-density orchards. In these situations, consider using a lower operating pressure.

    Different nozzles, same rate

    Different disc core combinations, or molded nozzles at different pressures, can produce similar flow rates. However, their spray quality and spray cone angles can be very different (see last three columns in the TeeJet table above).

    The angle of the spray cone can have a big impact on spray coverage. When the target is far away from the corresponding nozzle (e.g. the tops of nut trees), or the canopy is very, very dense (e.g. citrus canopies), consider tight-angled full cones under high pressure. This is inefficient and can give variable coverage, but it is sometimes the only option in extreme situations.

    Two hollow cone nozzles on top and five full cone nozzles below. Note the lack of spray overlap with the full cones for the first few meters. This would be a concern if the target were closer to the sprayer, such as grape or berry. Also note that the top two nozzles should not be on; their spray will likely not reach the intended target.
    Oops! Two hollow cone nozzles on top and five full cone nozzles below is the exact opposite of how things should be. Note the lack of spray overlap with the full cones for the first few meters. Spray from the top two positions will likely not reach the intended target.

    When the target is very close to the sprayer, full cones do not overlap and create undesirable striping or banded coverage. Creating a full, overlapping spray swath that spans the entire canopy is a function of nozzle spacing, distance-to-target, and sprayer air-settings. It can also be affected by humidity, wind speed and wind direction at the time of spraying.

    Confirm your settings by parking the sprayer in the alley between crops. With the air on, spray clean water while a partner stands a safe distance behind the sprayer to look for gaps in the swath. The partner will see things the operator’s shoulder check will not reveal.

    Shoulder checks may not show you what’s really happening. Have someone stand behind the sprayer while spraying clean water to see the nozzle spray overlaps sufficiently to span the entire canopy.
    Here’s what the operator sees. But, shoulder checks may not show you what’s really happening. Have someone stand a safe distance behind the sprayer while spraying clean water to see the nozzle spray overlaps sufficiently to span the entire canopy.
    Shoulder checks may not show you what’s really happening. Have someone stand behind the sprayer while spraying clean water to see the nozzle spray overlaps sufficiently to span the entire canopy.
    Here’s what the partner standing behind the sprayer sees. Take a picture with a smartphone to show the operator.

    Nozzle tables can be wrong

    Sometimes nozzles do not perform per the nozzle table. We have discovered errors in published tables, worldwide. Here are the big three:

    • Conversion errors. Manufacturers publish catalogs in Metric and in US Imperial, but we have found many errors in the conversions.
    • Spray angle errors. When nozzles are operated at the extremes of their pressure ranges, spray angles deviate from those listed in the tables.
    • Flow rate errors. When tables are not updated to reflect changes in nozzle design, or the manufacturing process, actual flow rates deviate from those listed in the tables.

    Perhaps it’s not the table, but the nozzle itself. Most nozzle manufacturers accept a flow variability up to +/- 2.5% for new nozzles, but we have seen higher. It depends how they are made (machined, stamped, printed) and the material they are made of.

    Validate flow rate and pattern

    When errors are discovered and reported, the manufacturers can be slow to issue corrections and the errors will persist in old tables. Yes, even apps (which are often based on tables) can be wrong. So, predicted flow rates can prove unreliable. This is why it is important to double check by observing nozzle overlap and validating flow rate when you replace nozzles – even when they are brand new.

    Thanks to Dr. David Manktelow (Applied Research and Technologies, Ltd., NZ) for input into this article.

  • The Pressure-Spray-Coverage Relationship

    The Pressure-Spray-Coverage Relationship

    Pressure is integral to nozzle performance. Reducing hydraulic pressure reduces nozzle flow rate, increases median droplet size, and typically reduces spray fan angle. Increasing pressure increases nozzle flow rate, reduces median droplet size and typically increases spray fan angle.

    You can watch this Exploding Sprayer Myths video to learn how pressure, boom height and nozzle spacing interact. In extreme cases, too low a pressure can collapse the fan angle enough to reduce overlap and compromise coverage, as explained in the video at the end of this article.

    Pressure affects all aspects of spray quality. Using a flat fan nozzle as an example, a lower pressure increases the median droplet diameter, reduces the droplet count, reduces the nozzle rate and typically reduces the spray angle. Alternately, a higher pressure decreases the median droplet diameter, increases the droplet count, increases the nozzle rate and typically increases the spray angle. Always plan to operate a nozzle in the middle of its recommended range so it can handle small changes in pressure during spraying (such as from a rate controller, or changing PTO speeds on hilly terrain).
    Using a flat fan nozzle as an example, a lower pressure increases the median droplet diameter, reduces the droplet count, reduces the nozzle flow rate and typically reduces the spray angle. Alternately, a higher pressure decreases the median droplet diameter, increases the droplet count, increases the nozzle flow rate and typically increases the spray angle.

    Always plan to operate a nozzle in the middle of its recommended range so it can handle small changes in pressure during spraying (such as from a rate controller, or when changing PTO speeds on hilly terrain). Don’t operate an air induction nozzle below 2 bar (30 psi), even if it’s rated lower in the manufacturer’s nozzle table. Most AI nozzles perform best at >4 bar (60 psi).

    Pressure can be used on-the-fly to make minor changes to flow rate while spraying. This is how rate-controllers work to compensate for changes in ground speed and maintain a constant overall rate per planted area.

    However, pressure should not be used to make significant changes to flow rate. It takes a 4x change in pressure for a 2x change in flow rate, so it’s inefficient. Operating pressures at the upper or lower limit of a nozzle’s range can have undesirable impacts on nozzle wear, median droplet size and swath uniformity.

    For a more in-depth discussion of the relationship between spray pressure and nozzle performance, and how rate controllers work, check out this article.

    Note: It is far better to simply switch nozzles when a significant change in flow rate is required.

    In 2015, we ran demonstrations at Ontario’s Southwest Agriculture Crop Diagnostic Days. The 20 minute sessions were designed to explain:

    Although manufacturers of air induction nozzles often rate their performance as low as 15 psi, such a low pressure collapses the spray pattern and the resulting gaps reduce coverage. Additionally, the spray quality at such low pressures is coarser than at higher pressures, reducing the number of droplets available. This further reduces coverage potential.

    This video covers the key speaking points from that demonstration.

  • Airblast Calibration – Clearing up Confusion

    Airblast Calibration – Clearing up Confusion

    “Sprayer calibration is an important part of any crop protection program.” Everyone says so, so it must be important. But what exactly are they asking you to do, and why?

    When delivering presentations I often take the opportunity to ask audiences to define airblast sprayer calibration. Their responses cover a wide range of activities that can be rolled up into three related, but quite different, definitions:

    1. Sprayer maintenance inspection
    2. Adjusting sprayer configuration
    3. Validating sprayer output
    Ask a group of managers, sprayer operators, agrichemical reps, gov’t regulators and equipment manufacturers to define “calibration”. Be prepared for very different answers.

    Traditionally, calibration refers to Number 3: Validating sprayer output, but all three are required to ensure a safe, effective and efficient application. Don’t panic – your workload didn’t just triple.

    There is a time and a place for each of these activities. Some should be performed more often than others, but none of them are difficult. This is easier to accept when you realize that only a portion of the spray-day is actually spent spraying. Filling, travel time, cleaning and calibration-related activities are all essential components.

    Let’s consider each activity.

    Sprayer maintenance inspection

    This is more maintenance than calibration (e.g. is it properly connected, is it worn out, is it plugged, is it leaking?). It should not be confused with spring start-up or winterization. For those lucky readers in temperate regions, “winterization” is preparing the sprayer for long-term storage post season… we just use antifreeze.

    The maintenance inspection is the morning walk-around, no different from what any operator of heavy machinery must do before starting their work day. Learn more about sprayer inspection and download a helpful checklist in this article.

    Here are some nasty disc & cores revealed during a calibration workshop. It certainly explained the poor performance the operator was complaining about. Is it time to replace yours? Photo credit – Dr. H. Zhu, Ohio.
    Here are some nasty disc & cores revealed during a calibration workshop. It certainly explained the poor performance the operator was complaining about. Is it time to replace yours? Photo credit – Dr. H. Zhu, Ohio.

    Adjusting sprayer configuration

    This is an ongoing process whereby an operator makes minor sprayer adjustments (e.g. pressure, travel speed, air settings) to reflect environmental conditions, the product’s mode of action and the nature of the target. Would you apply an insecticide to semi-dwarf pears in high wind using the same sprayer settings to apply a fungicide to nursery whips in high humidity? I hope not.

    The process is more intensive at the beginning of the spray season and again around mid-season (e.g. petal fall or whenever the crop changes sufficiently to require a reassessment). It’s described step-by-step in many articles on this website as well as in Airblast101.

    Yes, it requires an investment of time and effort, but the feedback makes subsequent adjustments faster, easier and more intuitive. There are strategies to reduce the number of adjustments required. Large operations can assign sprayers to blocks with similar crop architecture (e.g. one sprayer works large orchards, another sprayer works young or high-density orchards). Smaller operations can change the order in which crops are sprayed.

    Validating sprayer output

    This accounting activity ensures the sprayer is applying the intended rate at the intended speed. “Sprayer math” is really only theoretical; It helps the operator plan for how much pesticide and water must go in the tank and how long the job will require. How the sprayer actually performs may be a different story.

    According to 1992’s “Tools for Agriculture” a horse can deliver 500 watts of power over 10 hours, but the camel can deliver 650 watts over six. Ontario might not employ camels for spraying, but the old adage still applies: “the right tool for the right job”. Photo Credit – R. Derksen, Ohio. Date and location of photograph is unknown.
    According to 1992’s “Tools for Agriculture” a horse can deliver 500 watts of power over 10 hours, but the camel can deliver 650 watts over six. And you thought establishing tractor speed was difficult. Photo Credit – R. Derksen, Ohio. Date and location of photograph is unknown.

    Validating output, or calibrating, confirms that each nozzle delivers the desired rate and that the sprayer travels at the desired speed, so the crop receives the correct dose with no unexpected left-overs or shortages.

    The operator should perform these activities at the beginning of the season and after any significant change to the sprayer set-up. Examples include new nozzles, new tractor tires, using a different tractor or after replacing a pump or any lines/hoses.

    The validation (i.e. calibration) process is explained in our articles on testing airblast sprayer sprayer output and travel speed.

    Conclusion

    Be sure to perform all three calibration-related activities as required. This will keep records up-to-date, improve your spray coverage, and save you from unexpected sprayer malfunctions – almost all of which are preventable.

  • Validate Airblast Output – Nozzle Calibration

    Validate Airblast Output – Nozzle Calibration

    Sprayer math is important. It ensures the operator applies the correct product rate and has enough to complete the job. But, it assumes the airblast sprayer is behaving as expected… and it often doesn’t. After confirming the airblast travel speed, use one of the following methods to assess sprayer output. There are pros and cons to each.

    The area method

    Operators that claim the sprayer empties in the same place every time assume everything’s alright. They are performing a variation on the area method.

    Essentially, you fill the sprayer with enough water to spray one hectare (or acre) and then spray that area. If the tank empties where expected, you know your output rate (i.e. volume / area). But, there are a few problems with this method:

    • Most operators don’t have an accurate test area marked off, and even when they think they know the area, measurements prove otherwise. They’re always amazed when this happens.
    • The area method has poor resolution. It reveals the total output but does not assess individual nozzles. For example, partially-blocked nozzles and worn nozzles average out (we’ve seen it). Rate controllers provide whatever pressure is required to match the desired output, masking individual nozzle problems.

    The dip stick method

    Another method is to fill the sprayer to a known volume using a flow meter, while observing a sight level or a graduated dip stick. Then, while parked, the operator sprays for a given amount of time and determines the difference in the volume remaining in the tank.

    This method can be defeated if volume is misread. It’s an easy error to make if the sprayer is parked on a grade, or the dipstick shifts in a tank with a rounded bottom. And, of course, it also masks individual nozzle problems.

    Sight levels can be misleading when the sprayer is parked on a grade. They are often opaque and hard to read.

    The timed output method

    The preferred method is to measure the output of each nozzle individually. We performed a review on several timed output methods here. It can be messy and time consuming, but it’s accurate. Appropriate personal protective equipment is required to perform the timed output method – expect to get wet.

    1. Fill the rinsed sprayer half-full with clean water and park it on a level surface.

    2. With the fan(s) off, bring the sprayer up to operating pressure. Start spraying with all nozzles open (closing any will change the pressure).

    3. You will need 1 meter (3 feet) of 2.5 cm (1″) diameter braided hose (have a second, longer hose to reach the top of a tower sprayer). It should be stiff enough that you can slip it over a nozzle body while holding the other end. Use it to guide flow into a collection vessel, held with your other hand. The hose not only reaches the top nozzle on towers, but it lets foam dissipate before it gets to the vessel.

    4. When the flow from the hose is steady, direct it into the collection vessel for 30 seconds (a partner with a stopwatch is very helpful). It is preferable to collect for a minute because it improves the accuracy.

    5. Determine and record the nozzle output per minute. Graduations on plastic collection vessels are unreliable. It’s preferable to weigh the output on a cheap, digital kitchen scale. One milliliter of clean water weighs one gram. Don’t forget to subtract the weight of the vessel (this is called taring) and double the output if you only collected for 30 seconds.

    Interpreting the results

    Once you have recorded all the outputs, you will have to convert the output to U.S. gallons or liters per minute, depending on units in the nozzle manufacturer’s catalogue (see common conversions below).

    Replace any nozzles that are 10% (or preferably 5%) more or less than the rated output. This not only indicates a rate problem, but likely a problem with droplet size as well. If enough nozzles are worn, consider replacing all of them. Nozzles should go on as a set, and come off as a set (unless replacing a broken tip, of course). This can be an expensive proposition for large airblast sprayers, but it is part of operational costs.

    Don’t assume new nozzles are accurate. We’ve found +/- 5% flow variation right off the shelf. Keep your receipts.

    Testing and replacing nozzles is an important part of sprayer operation, no matter how many there are. This Air-O-Fan is nozzled for Australian almonds.

    Helpful conversions

    Anyone that has tried the timed output method in Canada knows the pain of our Metric-esque (Mocktric?) units. We’re an odd hybrid because our label rates are in metric, but our nozzles and many of our sprayers are US Imperial. You can find a complete collection of conversion tables here, but the most common calculations are reproduced below:

    If collecting in ounces, converting to U.S. Gallons per minute:

    us-gallons-per-minute

    If collecting in millilitres or grams converting to U.S. Gallons per minute:

    us-gallons-per-minute

    If collecting in ounces, converting to litres per minute:

    liters-per-minute

    If collecting in millilitres or grams converting to litres per minute:

    liters-per-minute

    If collecting in ounces, converting to Imperial gallons per minute:

    imperial-gallons-per-minute

    If collecting in millilitres or grams converting to Imperial gallons per minute:

    imperial-gallons-per-minute

    A more sophisticated option

    The timed output method is slow and requires math. You can avoid both problems by using electronic calibration vessels like the Innoquest SpotOn SC-4. We’ve tested both, and they are as accurate as weighing the output – but much faster.

    They can, however, be fooled by foam. We’ve had good results using a length of braided hose to direct the flow and dissipate most of the foam. Typically, foaming means the sprayer wasn’t rinsed enough.

    The SpotOn SC-4 calibration vessel is much easier, faster and more accurate than the classic pitcher-and-stopwatch approach to timed output tests.
    The SpotOn calibration vessel is easier, faster and more accurate than the classic pitcher-and-stopwatch approach to timed output tests. The SC-4 (pictured) is for airblast and SC-1 is for field sprayers.

    Another approach is to hose-clamp multiple hoses over nozzle bodies and spray all at once. This is tricky and takes time. Plus, if you suffocate the nozzle’s exit orifice (creating back pressure) or block the air inlets on AI nozzles, you will get a false reading.

    Be careful not to plug air inlets on air induction nozzles – you may get a false reading.

    We prefer nozzle clamps over hose clamps (see the AAMS-Salvarani nozzle clamp pictured below). There are pincers designed to latch behind the nut of the nozzle body, but compatibility can sometimes be an issue (e.g. with Turbomist sprayers).

    Passive flow meters (also pictured below) remove the need for a collection vessel, but they’re a better fit for field sprayers since they have to be held in place manually. They are difficult to source in North America because their accuracy is questionable, but they are fine for comparing relative flow from tip to tip.

    Nozzle clamp or flow meter, avoid suffocating the nozzle exit orifice or AI nozzle air inlets.

    2016_nozzle_flow_meters
    Left: Nozzle body hose clamp. Right: Passive flow meter.

    Some grower groups, or professional consultants, spring for very sophisticated and accurate units, such as AAMS-Salvarani flow measurement system pictured below.

    AAMS-Salvarani flow measurement system. We used these on a pumpkin sprayer in New Hampshire, but they work with airblast too.

    No matter your preferred method, take the time to confirm your sprayer output at the beginning of the season and whenever you make repairs or significant changes to your sprayer.

  • What do European Sprayers Bring to the North American Market?

    What do European Sprayers Bring to the North American Market?

    For many years, European agricultural machinery was considered too small to be relevant for North American conditions. That started to change when Claas and New Holland began introducing large harvesting equipment 20 yrs ago. Larger tractors from the likes of Fendt, and seeding and tillage equipment (e.g. Horsch) followed soon after. Now, European sprayers are knocking on our doors. What do they bring to the party?

    Overall capacity

    The typical large self-propelled European sprayer of 2020 has all the capacity of the largest North American models, and sometimes more. Boom widths of 36 m (120 ft) are common, and wider booms extending to 40 and even 50 m (~131 and 164 ft) are available. Tank sizes of 5,000 and 6,000 L (~1,300 and 1,600 US gal) are not uncommon, and 8,000 to 12,000 L (~2,000 to 3,000 US gallons) are featured on some. On those specs alone, they qualify.

    European sprayers can be significantly larger than their North American counterparts (Dammann DT 3500 H S4).

    Dimensions

    The first thing people notice about European sprayers is their more compact design. In order to comply with the 3 m maximum transport width allowed by law, everything is narrower. That doesn’t prevent the wheel track from widening in the field, of course, where stability is needed or where tramlines need to be matched.

    More efficient use of space in a European sprayer allows a smaller sprayer footprint with equal capacity (Amazone Pantera).

    The more compact design does come at a cost. There’s no room for large ladders with handrails to enter the cab, and catwalks are usually gone, too. Access to service points can be more cramped. But the upside is that most of these sprayers are lighter than their North American siblings, with dry weights between 9,000 to 12,000 kg (20 – 25,000 lbs) not uncommon even for the larger capacities.

    Compact, efficient designs featured in Bateman sprayer, one of UK’s top makes.

    Frame and Cab

    Less space has provided some frame innovations. A central channel frame is sometimes featured, creating room for a sophisticated swingarm suspension, or a walking beam. The cabs typically sit in front of the chassis, with a centrally mounted engine. This offers superior visibility, although it does take some getting used to. Overall, the cabs on these more compact sprayers are every bit as spacious and comfortable as North American types, with better rearward views possible due to the narrow chassis.

    Wishbone swingarm from central tube frame in Fendt Rogator.

    Monitor systems vary, but due to the majority of sprayers being made by smaller firms, third-party controllers will be more likely. Ag Leader, Topcon, and others can be seen in place of the proprietary systems of the larger manufacturers.

    There are no shortcuts with European cabs.

    Tank design

    Again, the compact real-estate requires some unique solutions. The barrel-shaped tank resting on a cradle that we’re used to in North America is replaced by a more complex-shaped tank that needs to utilize every possible available space. Although this is done with steel on many units, molded plastic is once again more common. Access to the tank lid is also more difficult due to the general absence of walking platforms. However, attention is paid to sump design and minimizing the remaining volume, making cleaning easier.

    Less room on narrow frames requires more complex tank shapes. Will cleanout be as effective?

    Booms

    European sprayers have well-engineered booms with better height control and contour-following capabilities than North American units. Usually triple-fold, they are compact and many offer Norac (Topcon) height sensors. Steel remains the most common material, with aluminum deployed as necessary on outer sections. Wet booms have 25 mm outside diameters and as such are slightly smaller than North American types. However, flow and pressure drop are measured to ensure a quality distribution. If these systems are used at faster travel speeds, flow limitations may become an issue and that will require closer evaluation.

    Large tanks and wide booms are commonplace in Europe (Sands sprayer)

    Plumbing

    An aspect where the European sprayers excel is plumbing design. Most have recirculating booms; some offer continuous rinsing. Both designs minimize waste generation and simplify rinsing and cleaning, saving time. More sophisticated tank level gauge systems that offer cab readouts, better resolution at low volumes and less dependence on having the sprayer resting on a level surface, can also be seen.

    Recirculating booms are common on European sprayers (Bateman sprayers).

    Pumps tend to be diaphragm, with only a few brands offering centrifugal types. The reasons are both technical and traditional. On the one hand, diaphragm pumps can run dry, don’t need to be primed and can be located beside the tank, for example, and can push air into a boom. On the other, they are bulkier and more expensive, noisier, need a pulsation damper and require maintenance. Some manufacturers, notably the Fendt Challenger and the Chafer, ship with centrifugal pumps. These are now equipped with wet seals, and the Challenger has employed an auto-prime system that prevents air-locks.

    Diaphragm pump on Amazone Pantera (top of picture)

    Flow Control

    Whereas all North American manufacturers offer a pulse-width-modulation (PWM) option which now comprises an estimated 30% of new sales, the European sprayers are only beginning to consider this flow management approach. The majority still offer multiple nozzle bodies that permit automatic switching between various sized nozzles to achieve extended travel speed ranges or changes in spray quality. One of the reasons for the delayed adoption of PWM is the European regulatory system, which have yet to approve some aspects of the PWM system.  Low-drift performance, for which most air-induction nozzles have been approved, must still be validated for nozzles that must be used with PWM (recall that air-induced nozzles are not generally recommended for PWM).

    Multiple nozzle bodies are favoured over PWM in Europe, but PWM is gaining acceptance.

    Many UK sprayers also use an interesting means of managing bypass, via a so-called Ramsay Valve. This type of valve uses an air-filled diaphragm to divert flow, and air-pressure change is used to alter the bypass. Such a system was an answer to early butterfly valves which had slow, uneven response, but is bulkier than the modern mechanical bypass valves now available, and may require maintenance.

    Drivetrain

    Like North American sprayers, wheels are driven by hydraulic motors. Hybrid Continuously Variable Transmission (CVT) systems are also available, and these offer superior torque characteristics at slower speeds. Engines are like those offered in North America, supplied by major manufacturers such as John Deere, Deutz, Fiat, etc. We are seeing smaller engines on European sprayers owing to the slower travel speeds. Slower speeds don’t just save cost, weight, and fuel consumption, they also provide the advantage of better boom height control and lower spray drift, as long as productivity can be maintained.

    Wheels

    European sprayers generally use the same wheel sizes as North America, with 46” wheels being common. A unique feature of UK sprayers is their use of 28 to 38” wheels. Although native ground clearance is sacrificed, it is enough for most crops except for corn, for which many sprayers require a lift kit anyway. These smaller wheels allow booms and other components to be cradled lower, improving the centre of gravity and safety.

    Wheel sizes vary, but are sometimes significantly smaller, particularly in the UK.

    Summary

    There is very active competition between European sprayer brands. Many dozens of manufacturers are in the market, and customers have high expectations. Although some of the features on European sprayers will appear strange at first sight, they should be evaluated purely on performance criteria, not aesthetics.  Does the sprayer improve efficiency by reducing downtime?  Does it make drift control easier? Does it waste less product that one would otherwise dump on the ground? Is it more fuel efficient? In this regard, customers will benefit from the competition introduced by other sprayer brands. A rising tide lifts all boats.