Category: Spray Basics

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:
If collecting in millilitres or grams converting to U.S. Gallons per minute:
If collecting in ounces, converting to litres per minute:
If collecting in millilitres or grams converting to litres per minute:
If collecting in ounces, converting to Imperial gallons per minute:
If collecting in millilitres or grams converting to 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 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.
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.
February 1, 2020
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.
January 15, 2020
Remove and scrub your filters – Even when you use Dawn
This article was co-developed by Mike Cowbrough, OMAFRA Weed Management Specialist in Field Crops
Why scrub filters?
Why do we ask you to manually scrub residue from sprayer filters and housings before changing chemistries? Here are three reasons why rinsing in-place may not be good enough:
- There is potential for biologically-active levels of residue to persist in filters, even after a triple rinse, that could harm the next crop sprayed.
- Persistent residues could cause physical antagonism with the chemistry you use next. This can cost time and/or efficacy should it plug filters and nozzles or reduce spray uniformity.
- Persistent residues could cause chemical antagonism with the chemistry you use next – even several batches later. This could harm crops when the residue carried over from a much earlier application suddenly becomes soluble again thanks to detergents or pH adjusters in subsequent tank mixes.
An experiment
To some, the previous statements may seem excessive. Many sprayer operators claim that scrubbing filters is time consuming, or that they’ve never had a problem before, or that the tiny amount of residue they see in the filters after rinsing couldn’t possibly cause damage. We decided to test the efficacy of rinsing filters without removing them.
We constructed a table-top system that could circulate chemistry through a 50 mesh filter. Think of it as a scaled-down sprayer that returns solution to the tank rather than spray it out. It replicates what the line filters on a larger sprayer might experience during a typical spray day.
Table-top system to circulate spray mix at 1 gallon per minute through a 50 mesh filter.
The method
The tank (i.e. the bucket) would be filled with a tank mix and circulated through the filter to replicate a spray day. The contaminated filter could then be sampled to establish a baseline, and then alternately contaminated and rinsed in place to compare how much residue remained. Specifically, we would drop the filter housing and scrub all surfaces in 500 ml of water to collect any and all residue.
Each sample collected would be poured through a filter for a visual check of residue. A small volume would be reserved to be sprayed on soybean and white bean seedlings as a bio assay of activity.
The process
We used Sencor (metribuzin) mixed at a rate that represented the low end of the label: 250 grams of product per acre at 5 gallons per acre. Not knowing what to expect, we circulated the solution through the filter for 20 minutes pumped at a rate of 1 gallon per minute and peeked into the tank.
After 20 minutes of circulation, Sencor began to foam.
Seeing that we were creating foam, we decided to add defoamer. Then we peeked into the filter housing to see what had accumulated so far.
Very little residue was found on the filter or in the housing after 20 minutes of circulation.
Finding very little in the way of residue, we chose to let the system circulate for an hour. We felt this would represent a single real-world tank’s worth of product. Since we’d added defoamer, we decided it was safe to leave the lab and let the system circulate…
Foam overs: No fun in the field and no fun in the lab.
Despite having added defoamer, we had a mess to clean up. When we opened the bucket we noted all the product clinging to the lid (see below). We collected some of this scum to replicate what might be clinging to parts of the spray tank that are not adequately covered by rinse-down nozzles. We then dropped the filter into 500 ml of water and scrubbed the housing and filter to collect any and all residue.
Collecting residue from the bucket lid to replicate what might remain in a tank that is not sufficiently rinsed.
We then added additional defoamer and checked in regularly as we circulated the mixture for several hours to replicate a full day of spraying. This time when we checked to see how much residue we had collected, found a surprising amount.
Residue following several hours of circulation, prior to triple rinsing with water.
We replaced the filter and performed a triple rinse with water before dropping the filter to collect our residue sample. As shown below, the triple rinse cleared much of the residue, but trace amounts were still visible.
Residue following several hours of circulation and a triple rinse with water.
Dawn Detergent and the 5 Second Squeeze
We refilled the tank with Sencor and defoamer and circulated it for several hours to once again contaminate the filter. This time, however, we added detergent to the second rinse. We did this in response to claims that Dawn dish detergent removed residues from dry products such as Atrazine without having to drop the filters.
A former agrichemical rep explained that the practice likely originated in Western Canada some years ago when several growers suddenly experienced physical incompatibilities with a particular batch of dry product. It was suspected that the problem was due to abnormally cold temperatures during mixing, but the result was that many were left with solids in the tanks that could not be flushed.
Ionic surfactants are found in “cheap and nasty” shampoos, dish detergents and car care products. They can be tough on the skin, but they are of higher surfactantcy than NIS. And so, agrichemical reps bought pallets of Dawn dish detergent (Branded “Fairy” in the UK) from big box stores and found it broke the solids down sufficiently to flush the tanks. From there, it is likely growers started adding it during the rinse to facilitate cleanout. But, is the “Five second squeeze” a myth or does it work?
Results
Adding Dawn detergent to the second rinse reduced visible residue in the filter housing and on the plastic sides of pop bottles that stored the rinsate.
We saw a visible reduction in the filmy residue left behind by Sencor in the filter housing and on the walls of the pop bottles used to store the rinsate. It was easy to see why the 5 second squeeze appeared to improve matters… but was there enough residue to still there to cause trouble?
Rinsate filtered through red cloth for a visual check of residue.
We poured the rinsate from each sample through red cloth. There was little or no visible evidence of Sencor in the sample taken from the lid of the filter following an hour of spraying (left), or our baseline sample of a filter contaminated after an hour of circulation with no rinse (second from left). There was a great deal in the sample from the filter following “a day’s spraying” and a triple rinse (second from right), and less in the triple rinse containing detergent (right). These last two conditions are compared below.
Following several hours of spraying, residue following a triple rinse with water (left) and a triple rinse with detergent in the second rinse (right).
A volume of the rinsate from each sample was reserved for bio assay on soybean seedlings. The filter in the spray booth was cleaned thoroughly between conditions.
The following images show that even when there was little or no visible residue, there was still sufficient activity remaining to injure, or in the case of the triple rinse with water, kill soybean seedlings.
Summary
Bear in mind that this is a single experiment with a single chemistry, but it does support the following observations:
- Always rinse the sprayer as soon as possible and pay attention to dead-end plumbing and filters. Diligence is a function of knowing what was sprayed last, what is coming next, and the sensitivity of the crops being sprayed.
- Cleaners do not decontaminate – they loosen residues to make rinsing more effective. In our experiment, Dawn detergent appeared to reduce residue and that will keep you spraying plug-free for longer. But, the bioassay showed sufficient activity remained to cause carry-over damage.
- A triple rinse with water may be insufficient to remove residue from filters. Even if the residue left behind does not cause damage in the next crop sprayed, it can persist and has the potential to react antagonistically with subsequent sprays.
Bonus: Pro Tips
Not long after publishing this article, we were contacted by a grower who had difficulties with clay-based products plugging up his filters. It took a carry-over incident to convince him he needed to address the problem, so he installed $20 ball valves at the bottom of the filter housings. This isn’t as good as dropping and scrubbing filters, but opening and closing the valve under pressure during rinsing blew the filters clear of visible residue. Others have noted similar modifications on the pump of their tender truck to clear the filter of algae.
Other options include a hydraulic-style ball valve (stronger than plastic). Or, install a gator lock cam after the valve and insert a plug so if it’s accidentally opened it won’t dump the tank. Just keep a hose in the toolbox and insert it when you need to flush. Finally, one grower added a Thompson strainer to the sprayer and removed the screens from the Banjo Y’s. He ran a 1″ hose from the Thompson to a valve by the work station and cracks it open as part of every rinse.
A cheap and effective solution for clearing filters of residue. Not as good as dropping and scrubbing, but a great compromise.
Ball valves tend to protrude below the sprayer, so they may catch high corn. Be careful.
January 10, 2020
Airblast Agitation and Solubags
Agricultural products are formulated to be as emulsifiable as possible, but many do not mix well in water. They contain elements that do not dissolve (e.g. wettable powders), or they may be petroleum distillates (e.g. emulsifiable concentrates). Other products are heavier than water and form precipitates (e.g. fertilizers and powdered metals like copper). Consequently, good agitation is very important.
Effective agitation requires water to “sweep” the bottom of the tank so that any precipitated material is picked up and re-mixed. Turbulence is often not enough. If there is too little agitation, the pesticide will be applied unevenly and not always at the required rate. If there is too much agitation, the pesticide may foam (which can be controlled using anti-foamers) or cause an invert emulsion (a gel). There are two types of airblast sprayer agitation: Mechanical and Hydraulic (learn about pros and cons here).
Mechanical Agitation
Mechanical Agitation is produced by paddles that are attached to a shaft mounted near the bottom of the spray tank. While effective, this system cannot always sweep the very bottom of the tank, so there is always some material that precipitates out of reach. Are your nozzles and screens plugging frequently, and is there “sludge” left at the bottom of the tank after spraying? You may have an agitation issue.
Note the two paddles set at 90° to one another on the mechanical agitation shaft in this very cool “cutaway” Turbomist sprayer.
Hydraulic Agitation
Hydraulic Agitation is accomplished by returning a portion of the pump output to the tank. Cylindrical and oval tanks are the ideal configuration for the sparging (i.e. rinsing) type of hydraulic return agitation system. This system consists of a tube located longitudinally along the wall of the tank, with volume booster nozzles aimed at the centreline so they sweep across the bottom. Volume booster nozzles take a small amount of water pumped into their venturi chamber and create a vacuum that draws three to four times that volume from the surrounding water and expels it out the end.
For hydraulic agitation to the effective, the agitator nozzle(s) should be fed by a dedicated line from the pressure side of the pump (not the pressure regulator). They should have a valve to throttle the flow or completely shut it off to prevent foaming.
A mixing nozzle in the basket of a Hol sprayer.
With enough pump capacity, a hydraulic return in the tank basket is a great way to agitate as you mix. A return in an older FMC.
Adding Water Soluble Pouches
Adding pesticide to the sprayer may not always be straight-forward. Many airblast operators, for example, place dissolvable pouches in the basket so they can be broken up by the hydraulic return, or the fill water. But fill water often splatters out of the basket, and the bags can burst open, releasing product into the air. This creates unnecessary contamination and both inhalation and dermal exposure concerns.
Photo credit: Mario Lanthier.
Photo credit: Mario Lanthier.
Some elect to temporarily remove the basket and add the pouches to a half-full tank with the agitator on. However, the pump can suck in the partially dissolved bag which then coats the intake screen. This is exacerbated when the fill water is cold. I know of one operator that had to rebuild the pump because the Viton seals burned out. This operator now adds pouches to the basket while standing upwind and away from potential splatter. Or, they mix a pre-slurry.
Mixing a pre-slurry requires the operator cut the bag into a five or 10 gallon bucket filled with water and to incorporate using a paint mixer. However, mixing a pre-slurry increases the chances of dermal exposure, inhalation and point-source contamination. Dissolvable bags were intended as a form of closed transfer, which is a good idea. Mixing a pre-slurry defeats that intent.
And so, for all these reason, I don’t feel dissolvable pouches are a good formulation choice. If possible, select product formulations that do not cause possible filling issues and better match the capabilities of your agitation system. Always choose the safest and most effective filling method for your sprayer design.
January 2, 2020
Exploding Sprayer Myths (ep.12): The Buffer Zone
In this episode of Exploding Sprayer Myths we reduce a complicated best practice to black and white… literally. Watch as Jason and Tom get a creepy lesson in the do’s and do not’s of no-spray areas. Under the watchful eye of Dr. Jim Todd (OMAFRA Industrial Crops Specialist and Rod Serling cos-player), brace yourself as you enter The Buffer Zone.
Learn more about how vegetative filter strips mitigate runoff on this Health Canada webpage.
Thanks to the staff at the Simcoe Resource Station and to RealAgriculture for making this video possible.
And if you’re curious about the kitchen-appliance cameo, you’ll have refer back to earlier episodes.
December 2, 2019