Category: Speciality Sprayers

Main category for all sprayers that are not horizontal booms

  • Remove and scrub your filters – Even when you use Dawn

    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.
  • Airblast Agitation and Solubags

    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.
    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.
    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 old FMC.
    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.

  • Exploding Sprayer Myths (ep.4): Speed Spraying

    Exploding Sprayer Myths (ep.4): Speed Spraying

    All set for Star Wars VII
    All set for Star Wars VII

    With due respect to Mickey and Mr. Lucas, and the massive hype surrounding Star Wars Episode VII, we felt we should jump on the bandwagon. Here’s episode IV in our series of short, educational and irreverent videos made with Real Agriculture.

    If there’s a single take-home message in this episode it’s this:

    …may the force be with you – always.

  • Exploding Sprayer Myths (ep.12): The Buffer Zone

    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.

  • Re-imagining of the Axial Airblast Fan

    Re-imagining of the Axial Airblast Fan

    On a trip to Mildura, Victoria I met Matthew McWilliams, Director at Interlink Sprayers. His passion for innovation was exciting. He described Interlink’s history of near-annual design improvements, each of which made the last generation of sprayers look a bit passé. Continual improvement means spending a lot of time educating and upgrading customer’s sprayers, but that level of support is worth it. Their strategy of drawing from leading international designs and improving on them has led to a unique axial fan assembly that boasts impressive benefits for those spraying large canopies.

    A man and his fan housing.

    Matt explained a problem common to any axial fan: they hate back-pressure. When an axial fan blows air against a volute, which redirects the air laterally, the back-pressure acts like an air break. It pushes back against the fan, flexing the blades, reducing output volume and reducing efficiency.

    In an effort to relieve some of this pressure, Interlink cut a hole in the volute (called an “Unloader”). Venting reduced the pressure and increased efficiency significantly. It did something else, too, but we’ll get to that later.

    This success led them to reconsider fan blade design. Classic, rectilinear fan blades are inefficient. They only produce air over the last 1/3 of their length. Using computational fluid dynamics, they modelled an efficient sickle-shape that creates pressure over the entire length. This means it can produce as much volume as a rectilinear blade, but with fewer revolutions.

    The difference between rectilinear and sickle-shaped fan blades.

    When the new blades were combined with the Unloader, they were able to move the fan closer to the volute and make the cowl longer. A less-exposed fan is not only safer, but its proximity to the volute increased efficiency.

    The result was a 2.5x increase in pressure and a concomitant 30% savings in horsepower. In other words, while similarly-sized sprayers were using 25 L (6.5 US gal.) of fuel per hour, they created the same air volume and speed using 17 L (4.5 US gal.) fuel per hour.

    But why stop there?

    Nut orchards in Australia and the US can grow up to 21 meters (~70 feet). A low-profile axial sprayer must produce a great deal of air volume to both penetrate the canopy and reach the top. Increasing fan diameter can help, but perhaps two fans are better? Air-O-Fan has their twin-fan system, where two shaft-driven fans with reversed blade pitches produce high-volume turbulent air. Interlock decided to try it.

    Hydraulics permit the twin-fan head to be raised off the ground.

    When two hydraulically driven fans were placed back-to-back (spinning counter to one another) the Unloaders did something Unexpected. Normally, an axial fan blowing against a volute creates deflection, causing higher speeds on the downward side of the fan. Most sprayers use vanes to correct this, but they cause back-pressure. Serendipitously, when placed back-to-back, the pressure vented through the Unloaders was reclaimed on the upward side of each fan, equalizing airspeed across the outlet.

    The air vented through the Uploader evened-out the airspeed.
    Computational fluid dynamics demonstrate even air-speed and volume on both sides of the sprayer.

    And there’s still more. Since this counter-rotation twin fan design is hydraulically driven, it is not restricted by a shaft. This allows the head to be lifted off the ground. Quite often in large orchards, air and nozzles are aimed too low, wasting spray below the canopy. Lifting the fan and nozzle banks brings everything closer to the top of the canopy; a notoriously difficult target to reach. It also reduces the level of dust and detritus stirred up from the canopy floor. Operators reported that the elevated fan head helped keep fan intakes and radiators (required on Australian airblast sprayers) clear of debris.

    This low-profile axial airblast fan is a refreshing new approach to a design that has seen only marginal improvement over the last 20 years. Given the pace of innovation in Matt’s factory, I’m sure the next set of improvements will be in place by the time this article is published.