Category: Speciality Sprayers

Main category for all sprayers that are not horizontal booms

Airblast Nozzles – Nozzle Bodies
Excepting air shear and centrifugal style nozzles, most airblast sprayers employ nozzle bodies designed to except hydraulic nozzles distributed evenly along the booms. Nozzle caps compress the nozzle against the body to force the spray mix through the nozzle orifice. Nozzle bodies are not all created equal.
Double Outlet Roll-Over Nozzle Bodies
Double outlet roll-over bodies (pictured below) allow the operator to quickly switch between two nozzles mounted in each position. This is convenient when alternating from dilute to concentrated applications, or changing the spray distribution from block to block.
A typical brass roll-over style nozzle body with cap and check valve.
The roll-over feature can act as a shut-off and facilitate fine-tuning the orientation +/- 15° from centre. When roll-overs are new there is an audible ‘click’ when they reach 15° to alert the operator that turning them any further will interfere with flow. This feature fails as bodies wear.
Single Nozzle Bodies
Some sprayers employ single nozzle bodies featuring screw or lever-style quarter-turn shut-offs. Some sprayers, like the Turbomist featured below, double the density of the bodies along the boom, arranged in an alternating A-B pattern. The operator shuts off each alternate nozzle, perhaps using the A’s for dilute and the B’s for concentrate applications. The density gives the operator the ability to “double up” in positions along the boom if more spray is required.
Some sprayers do not use double outlet roll-over nozzle bodies. Instead, they double the density of single bodies along the booms for use in an alternating A-B pattern.
Still others may affix the nozzle bodies to the deflectors (like the Air-O-Fan below), permitting the operator to orient the air and nozzles at the same time.
The Air-O-Fan offers double-density by affixing two single nozzle bodies to each air deflector. The operator aims air and nozzles simultaneously and can select flow combinations using quarter-turn shut-offs.
Check Valves
In my opinion, it should be mandatory for nozzle bodies (or at least booms) to have diaphragm check valves. When pressure drops below ~15 psi the valves shut to prevent the boom from draining (see image below).
An older FMC with nozzles bodies that do not have check valves. Once the pressure is off, the booms drain through the lowest nozzle. This is a waste of pesticide and unnecessary environmental contamination.
Booms don’t just drain in the yard. Operators shut off the outside boom when turning at the end of a row. Without check-valves, the boom drains through the bottom nozzle, wasting pesticide and causing repeated and unnecessary point-source contamination. Further, it takes a moment for the boom to refill, meaning the top nozzles may not be spraying at the beginning of each row.
You may be tempted to purchase mesh nozzle strainers with built-in ball valves. They can work as an alternative to integrated nozzle body check valves, but they plug and fail with irritating regularity. The image below shows a creative method for installing check-valves on single nozzle bodies. The nozzles protrude and the check valve seems too close to the shut-off, but reputedly this works.
An example of retrofitting diaphragm check valves on single nozzle bodies.
Thread Types
In North America, you will encounter four inlet thread types: NPT, BSPT, NPS and BSPP.
National, Pipe Tapered (NPT) single-sided, brass roll-over nozzle body with check valve. Note the shallow cap pictured here.
British Standard, Pipe Tapered (BSPT) single-sided, brass roll-over nozzle body with a check valve.
National, Pipe Straight (NPS) single-sided, brass roll-over nozzle body with check valve. Note the deep cap pictured here.
British Standard, Pipe Parallel (BSPP) single-sided, brass roll-over nozzle body with a check valve.
The inlet thread sizes available are 1/4” female, 1/4” male and 3/8” male. 1/4” female is not available on the NPS or BSPP inlet thread types. If you are considering installing new roll-over bodies, know your boom’s thread type. The retrofitted Turbomist below, for example, required bodies with female fittings.
A retrofitted Turbomist with check valves and female double outlet roll-over bodies.
Molded Nozzles
Another reason for installing new bodies is to convert from disc & core combination nozzles to single-piece, molded nozzles. They may not fit existing nozzle bodies. Check the diameter of the body outlet (where the nozzle rests) and the outlet cap (which compresses the nozzle against the body outlet). Your sprayer may currently use an unusual-diameter nozzle, like older FMC disc & whirls or European large-diameter pink ceramic disc & cores. Today’s ISO molded nozzles won’t fit in those bodies, so you’ll need to replace them.
Old roll-over bodies without check-valves. These were removed to make way for better bodies.
Older nozzle bodies can seize in the boom, requiring novel approaches to removing them. In this case, the mechanic is heating the fittings using “the blue wrench” to loosen them. If you do this, do not do what this mechanic did. Operate in an open space using gloves and a respirator. Years of residue build-up should be anticipated and respected.
Be aware: that unlike disc and core, molded nozzles protrude and may hit the edge of the sprayer duct when rolled over, preventing them from turning freely
Nozzle Body Caps
Nozzle bodies DO NOT come with the nozzle caps; they are specific to the nozzle type and must be ordered separately. This was an unpleasant surprise the first time I ordered a set of bodies.
The standard caps are threaded brass hex nut-style but there are also nylon wing-style caps that don’t require a wrench. Beware converting to quarter-turn systems for airblast sprayers. It can work, but nozzles may require additional gaskets and O-rings… and even then are known to leak if the cap diameter is too large (see below):
Airblast pressure often exceeds 100 psi and can force the O-ring off the molded nozzle and cause leaks.
Be aware: North American nozzle caps might not fit imported European bodies, and European nozzles might not fit North American cap diameters. The LipCo sprayer is one such example.
Regarding the cap depths, sprayer operators must consider the how much “stuff” is between the nozzle body and cap. Gaskets, spacers, O-rings and strainers take up room that may warrant a deeper cap. Perhaps most critical is the nozzle itself. For example, brass disc-core are quite thin, but ceramic are much thicker. They require different cap depths.
TeeJet’s molded cone nozzles come with an ‘A’ (Thinner) or ‘B’ (Thicker) shoulder. The shoulder is the lip around the nozzle base that is compressed against the nozzle body outlet. The B-shoulder is the ISO standard, and is preferred (see below). Shallow caps may not thread onto a nozzle body using a nozzle with a B-shoulder. Deep caps may bottom-out before compressing a nozzle with an A-shoulder, creating leaks. Be sure to note in the nozzle catalog which caps are recommended for the nozzle.
Molded cone nozzles come in the thin shoulder (A-style) or thick shoulder (B-style) varieties. The B-style is the ISO standard and is preferred.
Nozzle Strainers (aka Filters)
Before we wrap up, here’s one more look-out. As mentioned, the nozzle strainer shoulder takes up some room between nozzle body and cap. It turns out there can be another concern.
A hop grower contacted me. He had installed new nozzle bodies on his sprayer. He’d taken into account the shoulder depth and the cap depth. So why were his nozzles plugged? And why when he loosened the cap to finger-tight did they spray, but leak?
We tried gaskets, O-rings, different cap depths and new nozzles – but no change. That’s when we noticed one side of the roll-over body had a plastic slotted strainer and the other had newer mesh strainer. The mesh strainers were longer and terminated in a disk of solid plastic. When we swapped the two strainers, we had flow! We realized the longer mesh strainers were being compressed against the orifice in the nozzle body, acting like a cork in a wine bottle.
I prefer slotted over mesh because they are a bit more forgiving with dry formulations and hard water residue, but perhaps more critical is that they aren’t long enough to block the flow.
Be aware that some strainers may be long enough to block flow in the nozzle body.
Take Home Tips
If you are considering installing new nozzle bodies:
- Confirm the male or female fitting and thread type of your boom
- Ensure bodies have check valves
- Ensure roll-overs and check valves clear any obstructions with nozzles in place
- Know the nozzle type you intend to use, and ensure cap diameter is appropriate
- Know whether you will use gaskets, o-rings, spacers and strainers, and confirm the cap depth will accommodate everything.
- Be certain the strainer you choose isn’t so long that it interferes with flow.
- Consider buying a single nozzle body to install as a trial before buying an entire set of replacements.
June 18, 2019
Continuous rinsing for airblast sprayers
Why Rinse?
Airblast sprayers are not rinsed as frequently or as diligently as field sprayers. This is primarily because they are not used to spray herbicides, so residue carry-over doesn’t incur an immediately obvious penalty. The typical operator rinses prior to long-term storage or when cross contamination might cause some form of antagonism (e.g. dormant oil followed by Captan or sulfur).
Learn more about the difference between rinsing and cleaning in this article.
Aftermarket Rinsing Systems
Airblast sprayers can be outfitted with rinsing systems that permit operators to rinse quickly, easily, and dispose of dilute rinsate in rotating locations.
A Serial Rinse (SR) system, common on field sprayers, re-purposes the pump to transfer clean water from a saddle tank to the product tank via tank rinse nozzles. The operator introduces a volume of clean water to the remaining volume in the tank, circulates it through the system, and then sprays the rinsate in the crop. Repeating this process three times (i.e. the Triple Rinse) serially dilutes the remainder, resulting in a higher dilution factor than a single high-volume rinse.
A Continuous Rinse (CR) system requires the addition of a dedicated rinse pump. In this case the operator introduces clean water to the tank via tank rinse nozzles while simultaneously spraying. While there is circulation from the bypass (and/or agitation) circuit, the remaining volume is diluted and essentially displaced by clean water.
Objective
Using a fluorescent dye tracer as an analog for pesticide, we wanted to explore the effectiveness and efficiency of both systems. We describe the fluorimetry method in this article. We installed a CR system in a 2,000 L H.S.S. tower sprayer, which unlike most North American airblast sprayers, already features a SR system (150 L clean water tank and two tank rinse nozzles).
Installing a Continuous Rinse System
Installing a CR option required us to address the same three criteria we have already discussed in previous articles on field sprayer installs:
- Identifying a CR pump with sufficient flow to operate the tank rinse nozzles
- Satisfying the electrical or hydraulic requirements of the CR pump
- Matching the supply flow from the CR pump to the demand flow at the booms
The Hol sprayer with an 18-nozzle ducted tower, 150 L clean water tank and two tank rinse nozzles. Inset: Rhodamine WT dye used as a pesticide analog for comparing residue levels.
We mounted two electric Shurflo pumps in parallel to provide flow sufficient to match the typical demand at the booms without excessive electrical load.
Parallel electric Shurflo pumps drew low amperage and provided sufficient flow to the boom.
We found that while the CR flow spun the tank rinse nozzles weakly, the spray didn’t reach all interior surfaces. This was remedied by adding a deflector plate to the bottom of the nozzles to redirect flow.
A brass disc mounted on the tank rinse nozzle deflected spray to all interior surfaces.
We encountered a complication installing CR on an airblast sprayer compared to a field sprayer. Most field sprayers have rate controllers that permit the operator to adjust travel speed or ‘dial in’ a rate to match boom demand to CR pump supply. Unless the airblast sprayer already has this feature, the operator has to calculate in advance how best to match the flows.
The calculation has to be performed for each unique output (e.g. dilute or concentrate nozzle arrangements). The flow from the CR pump is a known constant. The nozzle output is variable according to operating pressure, calculated using a nozzle guide. The operator can adjust pressure (bypass or pressure regulator), PTO-speed (on positive displacement pumps), or even alternate between booms or boom-sections to match the flows.
Matching flow demand to supply using a nozzle catalogue.
In our case, the operator was using 12 blue Albuz hollow cones in their orchard. We knew the CR pump output was 24.25 L/min. So, by setting the pressure to 6.1 bar prior to rinsing, we were spraying about 24.5 L/min. We parked the sprayer and watched to ensure the sump did not fill or drain during CR. Note in the following video how well the two flow rates were balanced (the camera was accidentally turned when we showed the vertical boom).
During trials we noticed that as the sprayer climbed uphill the water level in the tank shifted and the pump drew a little air, causing the nozzles to briefly sputter. This was a welcome sight given reports that introducing a few air bubbles during continuous rinsing can be beneficial.
Field Testing
During testing, we filled the 2,000 L Hol sprayer with 500 L of water and a final concentration of 0.25 ppm rhodamine (0.5 mL dye per 500 L water). The clean water tank was filled to 150 L. We allowed the mix to circulate for two minutes before priming the booms by spraying for a minute. A 50 mL sample was then drawn from the manifold (see below) and later used to represent the starting concentration during the analysis. The sprayer then drove through the orchard, spraying until empty.
Samples were drawn after the tank, before the manifold. Note the telltale Mancozeb coating the sprayer. PPE was worn.
Serial Rinse testing: When the sprayer was empty, the operator left the cab to introduce 75 L of clean water to the main tank via the tank wash nozzles. The rinsate was circulated for one minute before the operator returned to the cab and sprayed the orchard until empty. A 50 mL sample was drawn from the manifold to represent the concentration half-way through the rinse. The process was repeated for the remaining 75 L of clean water and a second 50 ml sample was drawn to represent the final concentration. We did this twice. It took about 12 minutes to rinse the sprayer and the operator had to leave the tractor cab twice.
Continuous Rinse testing: When the sprayer was empty, the operator stopped spraying and engaged the continuous rinse pump. After a few seconds, he continued driving and spraying rinsate. When 75 L had passed through the system, we paused to draw a 50 mL sample from the manifold to represent the concentration half-way through the rinse. The operator continued until the remaining 75 L was sprayed and a second 50 ml sample was drawn to represent the final concentration. We did this twice. It took about 5 minutes, 45 seconds to rinse the sprayer and the operator did not leave the tractor cab.
Sample Analysis: A Turner TD 700 fluorometer was calibrated using samples from the tank. Samples were diluted when necessary to ensure they fell in range of the calibration curve (where there is a linear relationship between the concentration of Rhodamine WT and Raw Fluorescence Units (FSU)). This range spanned a maximum of 0.1 ppm and a detection limit of 0.01 ppm active ingredient. Having previously tested recovery accuracy of 95%, data was adjusted accordingly.
Results of rinsate analysis. n=2.
Observations
While both methods diluted the residue significantly, the remainder following both Serial and Continuous Rinse was much higher than anticipated. This may be an artifact given that both concentrations are potentially below our detection limit, per the following:
Assuming 10 L of residual spray volume left in the system once “empty”, 75 L added would give a dilution factor of 9 (according to the ). While the first 75 L of Continuous Rinse seems to remove more residue than a single addition of 75 L, both are higher than anticipated. A subsequent addition of 75 L should result in a dilution factor of 72. In this case, the remainder would be below our fluorometer’s detection limit, and could explain the results.
Nevertheless, there were positive observations:
- Continuous Rinse resulted in a more dilute rinsate with less water than Serial Rinse.
- Continuous Rinse took less time than Serial Rinse.
- The operator did not leave the tractor cab during Continuous Rinse.
- Potentially, any remaining water from the Continuous Rinse system could be used to operate a spray wand to rinse the sprayer exterior before leaving the crop.
- Both systems encourage improved airblast sprayer sanitation and reduce environmental impact from point source contamination.
Thanks to ProvideAgro for performing the installation, Wilmot Orchards in Ontario for supplying the sprayer and running the trials, and OMAFRA summer student Aidan Morgan for assistance with the data analysis.
June 4, 2019
Air Orientation for Wrap-Around Sprayers
One of the pleasures of working in agricultural extension is when you’re able to help a grower solve a problem. This was one of those happy occasions. An orchardist purchased a Lipco multi-row recycling sprayer and wanted help evaluating their spray coverage.
We worked in 3.7 m (12 foot), mature, high-density Royal Gala trees. The sprayer was driving at 5.0 km/h (3.1 mph), operating at 11 bar (160 psi) using orange Albuz 80 degree air-induction flat fans. This resulted in about 350 L/ha (~37 gpa).
This grower wisely invested in the air-assist option, which produces a vertical plane of somewhat laminar air to entrain the spray and carry it into the centre of the target canopy. Whatever spray blows through the tree should impact the opposing shroud and get recycled back to the tank. All in all, how could you miss?
…we managed to.
Water sensitive papers were placed back-to-back facing each alley (in other words, facing the spray booms). Despite our best efforts, each pass resulted in inconsistent coverage. Papers were replaced in the same location and orientation for each pass and no settings were changed. Nevertheless, sometimes a paper got spray and sometimes it didn’t. What was going on? It was as if the two air streams were interfering with one another – almost cancelling each other out.
Air from tangential (cross-flow) fans oriented perpendicular to the canopy in direct opposition will cancel out. This reduces canopy penetration.
Where possible, do not position laminar air outlets in direct opposition. The convergence creates a high-pressure zone that reduces spray penetration. Some sprayers are designed to avoid this by staggering air outlets one ahead of the other. Laminar flows will deflect unpredictably around this pressurized area and carry droplets back out of the canopy. Unless the canopy is particularly narrow and sparse, turbulent air handling systems do not typically create this problem. In both cases, canopy penetration is improved when fans are staggered and/or are angled slightly forward or backward.
Grey arrows indicate direction of travel. The air outlets of wrap-around sprayers should be symmetrical when viewed from behind. A. Tangential fans in direct opposition: Poor coverage. B. Tangential fans angled forward/backward: Possible vortices and good coverage. C. Tangential fans angled backward: Good coverage, but if the angle is too steep, air will not penetrate the canopy. D. Straight-through axial fans in direct opposition: Good coverage in denser canopies. E. Straight-through axial fans angled slightly backward: Good coverage but limit the angle to prevent the trailing edge of the air wash from missing the canopy entirely. F. Straight-through axial fans angled forward: Slight angles are acceptable, but too much in this image. Wind created by travel speed subtracts from air energy. This creates a risk of reduced coverage and increased operator exposure.
We decided to turn the outer boom/shroud/fan assemblies 10˚ backward by loosening the four bolts at the top of the gantry (see below). This minor change in configuration improved spray coverage significantly. Increasing the angle beyond 10° might have caused the air wash to trail along the canopy face and would have made sprayer turns difficult at the row ends.
We loosened the four clamping screws to adjust the fan angle on the outer boom of this Lipco Recycling Tunnel sprayer.
We replaced the water sensitive papers and ran another pass. The operator later told me he could see the leaves and branches rustling in the row where we made the adjustment, but not in the unadjusted row. The result on water-sensitive paper was dramatic.
Since experiencing this in 2013, I have been told that the Lipco instruction manual advises against air in direct opposition. It was a poorly translated and somewhat obscure sentence buried in the manual, but I concede that it was there. Determine whether your sprayer produces more laminar or more turbulent air, and explore how their relative orientation impacts canopy penetration.
Sometimes, you just have to cross the streams!
May 23, 2019
Exploding Sprayer Myths (ep.10): Airblast Coverage
Here in Episode 10 of Exploding Sprayer Myths we’ve coaxed @Nozzle_Guy back into the orchard. This is part two of a two-part mini series on airblast calibration. In Episode 9 we talked about air settings and travel speed, and now we’re tackling nozzling and coverage.
But here’s the twist: Rather than use spray math to determine the required nozzles to achieve ideal coverage, we do it backwards. This process uses ideal coverage to determine nozzles and finishes with sprayer math.
Confused? Watch the video and this surprisingly simple and versatile approach will become clear. See if you catch the subtle visual joke about “coverage” realize that to pull this off, we had to film it backwards.
Special thanks to the @RealAgriculture team, the Simcoe Research Station and Don Murdoch.
March 4, 2019
The Challenges of Spraying by Drone
Spray application by drone is here. It’s common practice in South East Asia, with a very significant proportion of ag areas now treated that way. Estimates from South Korea, for example, suggest about 30% of their ag area being sprayed by drone. It’s in the US, too. The Yamaha RMax and Fazer helicopters, which pioneered drone spraying in Japan dating back to the mid 1990s, have been approved for use in California since 2015. DJI, the world’s largest drone manufacturer, introduced their ag model, the Agras MG-1, to North America in 2016. Many other spray drones are available or in development.
As William Gibson, the author of Johnny Mnemonic, once said, “The future’s here, it’s just not widely distributed yet.”
DJI Agras MG-1 spray drone (Source: DJI.com)
Proponents of drone spraying cite a drone’s ability to access areas where topography is a problem, such as steep slopes, where productivity of manual application is much lower, or low areas where soil moisture prevents ground vehicles. Operator exposure is reduced compared to handheld application.
Opponents talk about productivity and cost factors compared to manned aerial application, spray drift, and rogue use.
Before drone spraying becomes commonplace, two important things need to happen.
1. Federal laws need to be updated to accommodate the unique features of remotely piloted aircraft systems (RPAS), as they’re now called. Current laws make many assumptions unique to manned ships, and the process to correct that will require some patience. A thorough review for US laws, and their shortcomings, can be found here.
2. Federal pesticide labels need to permit the use of drones for application. As of August, 2021, Canadian labels have no such registered use.
There is no doubt that we need to prepare for a future that includes spraying by drones. Features such as topography adjustment for height consistency and autonomous swath control are already essentially standard, and the capabilities that improve control and safety will continue to develop.
And yet I’ve been nervous about the prospect of pesticide application with drones. My primary concern is around – you guessed it – spray drift. Because a drone payload is relatively small (about 5 to 25 L, depending on the model), application volumes will need to be low to have any sort of productivity. How low? For manned aircraft with a 200 to 600 gallon hopper, 2 to 4 US gpa (18 to 36 L/ha) are the lowest commonplace volumes. The lower volumes require a Medium spray quality (among the finer sprays in modern boom spray practice) to achieve the required coverage.
It’s a simple concept: the less water is used, the smaller the droplets need to be to provide the necessary droplet density on the target. Drift control with coarser sprays requires higher volumes, and true droplet-size-based low-drift spraying can’t really happen at volumes less then, say 5 to 7 US gpa.
At 2 to 4 US gpa, a drone would be able to do perhaps 1 acre per load. While OK for spot spraying, it represents a serious productivity constraint for anything larger. There will be a push toward lower volumes, perhaps 0.5 to 1 gpa (5 to 10 L/ha). The only way these will provide sufficient coverage is with finer sprays, ASABE Fine to Very Fine, with expected problematic effects on off-target movement and evaporation. These fine droplets are also more prone to the aerodynamic eccentricities of aircraft.
Vortices from the rotor can create unpredictable droplet movement (Source: kasetforward.com)
The current regulatory models for aerial drift assessment in North America, AgDISP and AgDRIFT, are not yet able to simulate drone application. But by entering finer sprays into these models for their conventional manned rotary wing aircraft, we can see that buffer zones will be higher. Much higher. And that outcome will give pause to regulators. Failure to control the movement of a spray is, and should be, a problem.
Estimated Buffer Zones (calculated by AgDISP) for a reference rotary wing spray aircraft, using three pesticide toxicologies and two spray qualities.
Furthermore, ultra-low volume (ULV) sprays can change the efficacy of some products, and these will require new performance studies. At this time, regulators are seeking information not just on spray drift, but on product efficacy, operator and bystander exposure, and crop residues.
Regulators are currently collecting spray drift and efficacy data from drones. Since the drones available in today’s market do not conform to a common design standard like fixed or rotary winged manned aircraft, each model may have its own characteristics and need its own study. Some will have rotary atomizers, others will use hollow cone hydraulic sprays. Some will have electrostatic charging, others may propose special adjuvants.
Once data are assessed, there will likely be restrictions in flight height, flight speed, wind speed, spray quality, water volume, perhaps air temperature and relative humidity (or Delta T). This is not new to spraying, as current labels already constrain use for both ground and aerial spray application, more so for aerial.
The obvious question is how these proper application practices can possibly be assured. Operators will need more than just regulatory approval to use a drone, they will require proper training, similar to what a commercial aerial applicator now receives prior to operating a business.
Recall that our aerial applicators are governed by national organizations, the NAAA in the US and the CAAA in Canada. These organizations are in regular contact with federal regulators to assure compliance. They also help fund research into application efficacy and safety. They organize conferences in the off-season and calibration clinics in the growing season. At these, flow rates are confirmed and deposited droplet size is measured. Spray pattern uniformity is assessed and corrected as necessary.
Should drone applications be exempt from these controls? I don’t think that would be wise. Are we ready to implement them? Absolutely not.
These requirements would change the drones’ economic model. And despite these precautions, a drone may still leave the control of a pilot due to unforeseen technical or human events.
In the US, Yamaha does not sell their drone helicopters. Instead, they deploy their own teams to make the applications. This way, they have assurance that only trained and experienced pilots use the technology.
As the industry gears up for the first registrations, we see drone service companies take a leading role in testing. Much is being learned via legal applications of liquid micronutrients, for example, or limited use of pesticides under approved research permits. And I’m pleased to see the recognition of drift management in these efforts through the use of low-drift nozzles. We are off to a promising start.
Requests for drone use are in progress at our regulatory agencies. The outcomes of their risk assessments will provide important initial guidance, and food for thought and discussion. In the meantime, the drone development continues at a rapid pace, with new features and greater capacity at each iteration.
February 18, 2019