Author: Jason Deveau

Sprayer Wheel Maintenance
This article was co-written with Murray Thiessen, Consulting Agricultural Mechanic.
Sprayer wheel assemblies should be cleaned and inspected as part of regular annual maintenance. Wheel bearing maintenance before long-term storage may prevent water from corroding the bearings. The exploded diagram details the parts found in a typical trailed air-assist sprayer wheel assembly.
Exploded diagram of typical airblast sprayer wheel assembly.
The following procedure was performed on a 2012 Durand-Wayland sprayer by Mr. Murray Thiessen, Consulting Agricultural Mechanic and renowned “Sprayer Whisperer”. The steps are applicable to most sprayer makes and models. The entire process should take approximately half-an-hour per wheel.
Step 1
Empty the sprayer and park it in a well-lit, level spot. Un-hitch the tractor and raise one side of the sprayer using a bottle or floor jack to clear the wheel. Secure the sprayer with a jack stand.
Raise with one jack, secure with another.
Step 2
Remove the lug nuts and take the wheel off the hub. Do not remove the wheel and hub together because it is heavy and you might bang the delicate seal on the spindle. Check the wheel rim for signs of corrosion or distortion (often caused by either loose or over-tightened lug nuts). Check the tread for wear or cuts and check the tire pressure.
Remove the lug nuts and take the wheel off the hub.
Step 3
Remove the hub cap and pull out the cotter pin. Then remove the nut and washer that hold the hub on the spindle. Put all the small parts in a plastic container with some de-greaser (e.g. Varsol) to clean the parts and keep them from getting lost.
Remove the nut and washer that hold the hub on the spindle.
Step 4
Knock out the seal and hub bearing and put them in the plastic container. Unless it is damaged, there should be no need to remove the bearing cup (or race) from the hub. The seal is designed to keep dirt out of the assembly, not to keep grease from escaping. Be sure to note which way it is facing. The seal is often ruined during disassembly; have a replacement on hand.
Knock out the seal and hub bearing.
Step 5
Clean the old grease out of the hub. This hub has too much and it has filled much of the air space (or cavity) within the hub. That air space is provided so grease is not forced out as the hub heats up, and so dirt is not pulled in as the hub cools. Note the colour of the grease – if it is black and stains your hands, it has burned because too much grease has caused overheating. Look for evidence of dirt or water in the bearing, which indicates seal failure.
Clean the old grease out of the hub.
Step 6
Wipe dirt from the spindle. Never pressure-wash wheels when they are on the spindles because the spray drives dirt and water past the seal and into the hub. Inspect the sealing surface of the spindle for damage or wear.
Wipe dirt from the spindle.
Step 7
Clean the seal thoroughly. Seals are easily damaged and may need replacement.
Clean the seal thoroughly.
Step 8
Clean the hub bearing. Compressed air is a good way to get all the old grease out, but do not spin the bearing with the air.
Clean the hub bearing.
Step 9
Look for scratching, pitting or blue metal (indicating heat). This scorch mark indicates the bearing was moving on the spindle, and the friction created heat. Agricultural wheel bearings do not fit tight to the spindles. If there is too much clearance, the bearing race will turn on the spindle where it is not supposed to.
Look for scratching, pitting or blue metal (indicating heat).
Step 10
Repack the bearings, reassemble the hub and re-grease the hub. Bearings should only be ~40% full. Too much grease creates heat and does not let the bearing roll properly. Too little increases friction. No matter which grease you choose to use, never combine greases; they may not be chemically compatible.
Re-pack and reassemble.
Step 11
Mount the hub tightly on the spindle. Replace the washer, cotter pin, nut and cap. There is no need to bend the arms of a cotter pin all the way back – it weakens the metal. Just bend one arm to 90° and cut off the excess. Use anti-seize on the wheel pilot to make the rim easier to remove next time.
Mount the hub tightly on the spindle.
Some airblast sprayers (such as this Durand-Wayland) have wheel assemblies that can be rotated to four different positions in the chassis. This will raise or lower the sprayer to better align it with the tractor hitch and PTO shaft.
Step 12
Replace the wheel and rim. Do not grease the lug nuts or they might loosen. Over- or under-torqueing lug nuts can cause damage. Look in the manual for your correct torque and consider using a torque wrench. Tighten the nuts in a star-shaped pattern – not sequentially.
Replace the wheel and rim.
January 10, 2021
Airblast Nozzles – On or Off?
Spray that is not directed at the target is wasted spray. Many pesticide labels specifically require the operator to restrict spray to the target canopy. Spray that escapes above the canopy is a significant source of off-target drift. Foliar applications that extend below the canopy are not efficacious and represent waste and lost productivity.
A spring application or oil and chloropyfiros. Estimate of 50% waste (in red).
Air carries spray droplets, so the first step in any adjustment should be to perform a ribbon test to ensure the air outlets are oriented correctly. This is achieved by adjusting deflectors (e.g. low profile axial), the air outlets on a tower, or the entire head on a wrap-around design with individual fan/nozzle combinations.
Spray height should always exceed the canopy height by a small degree. This compensates for the increase in wind speed with elevation, the potential loss of spray height with faster travel speeds, and uneven alleys that cause the sprayer to rock, which changes the spray angle.
Spray angles change as a sprayer rocks on uneven alleys. It is more important that spray is directed at the top of a canopy than at the bottom.
It is less critical that spray align with the lower portion of the canopy. As air energy wanes, or as droplets begin to lose momentum, finer droplets will slowly fall, depositing on random surfaces. Coarser droplets will quickly fall towards the bottom of the canopy, settling primarily on upward-facing surfaces. This secondary deposition can also occur from the cumulative impact of blow-through from upwind rows.
Once the air is aligned, park the sprayer in an alley. Stand behind the sprayer and extrapolate a direct line from each nozzle to target canopy. Nozzles that point at the canopy should be left on. Nozzles that point above or below can be blocked, or turned off via valves or rotating roll-overs. Some roll-over nozzle bodies can be swiveled up or down 15 degrees to fine tune the spray angle. An alternative would be to permanently rotate the nozzle body fitting in the boom line. When aiming nozzles using a roll-over nozzle body, be careful not to swivel them too far or the valve will partially close and compromise the spray pattern.
Use a ladder when adjusting nozzles on a tower sprayer. Some sprayer chassis and tanks are designed to accept a climber, but even so they can be slippery. Please be careful.
When extrapolating, remember that the centre of a nozzle only indicates the centre of the spray pattern. Cone and fan angles can span 60 to 110 degrees, depending on the influence of air. Therefore, even though the centre of the lower-most nozzle intersects the bottom of the target canopy, you may still be able to turn it off because the nozzle above has that portion covered.
Adjust spray distribution across the boom at the beginning and roughly mid-way through the spray season to ensure the sprayer will uniformly cover the target with the optimal volume. These adjustments should account for both canopy growth and fruit set.
For example, as the season progresses in an orchard, fruit may cause limbs to hang lower and warrant a new spray distribution. Turning on the bottom nozzle position will help, but it doesn’t account any increase in density throughout the canopy. You may need more volume distributed across the entire boom. Another example: as grape bunches begin to close, sprayer operators may direct fungicides exclusively at the fruit zone and not the entire canopy.
Remember to always check coverage using water sensitive paper. It’s not worth saving a bit of spray if you’re missing a bit of your target.
December 1, 2020
For Sale: Gently Used 1950s Boom Sprayer
This article isn’t about best practices, or social contracts, or innovative new technologies. It’s just a fascinating bit of history. If it has any moral at all, perhaps it’s to remember where we came from. I wonder where we’ll be tomorrow?
Let’s be clear – the practices described in this article are anachronistic and while I shouldn’t judge from my 2020 high-horse, they’re flat-out terrible. Don’t see them through nostalgic eyes. Instead, be thankful that sprayers and practices have evolved.
Here’s the background. A colleague of mine, a grower and well-respected pesticide safety / sprayer expert, recently held a farm auction in Innerkip, Ontario. He sent me a photo of his family sprayer, used in Oxford county in the 50s and 60s. I fell in love with it.
It was used to control broad leaf weeds in cereal crops. He recollected that thistle was a particularly painful issue. Especially when you had to grab hold of the grain sheaves and stook them. I confess I had to look up the term “stook“. They also sprayed a few cereal acres for neighbours, but never too far from home.
A 1950s barrel sprayer. The frame would be attached to the front of a Massey Harris 44, suspending the 21 foot wet aluminum booms. The drum was supported on the tractor tongue. When you shut down, you picked up the booms and hung them on the fenders. The booms then leaked all over until they were empty.
Fortunately, there was clear guidance for the operator. The speed and rate was written on the distribution head. Still somewhat legible.
A rod would extend from distribution head to the tractor, supported on the steering column. The driver could select the boom: left, right, both or off. The distribution/filter head/pressure gauge (shown here) was supported on front of tractor. On the up side, there was no need for the driver to do a shoulder check. Here the distribution selector is set to ‘off’. The filter, shown here as well, was a metal screen wrapped in a cotton cloth (typically a flour bag).
This is the line from the pressure side of the pump, entering the distribution unit. The butterfly screws made a tight connection… using canning jar rings as gaskets!
Both the cotton bag on the filter and the pressure line were sealed with canning jar rings.
When the broadcast work was done, they would set up a hand boom and spray the fence posts. Bare hands were the order of the day.
Spraying the fence posts was a two-person job, with a driver in the tractor and a kid aiming the boom. Here’s a close-up of a flat fan nozzle on the hand boom.
Here is the supply drum with opening for suction hose and screen. It served double-duty as pesticide tank and seat for the person holding the hand boom. Pesticide swished out onto the person sitting on the drum. Getting their butt wet as a matter of course. The drum was filled with a 1/2 inch hose right from the well.
When the long season was through, it was over-wintered (with whatever spray liquid remained) in the cellar.
We’ve come a long way.
October 8, 2020
Perspective on Rates, Volumes and Coverage
This short article is a thought exercise designed to give some perspective on chemical rates, carrier volumes and the foliar area we expect them to protect.
Imagine we are spraying the fungicide Captan on highbush blueberry. In Canada, the label rate is to apply 2kg/ha (28.5oz/ac) of planted area. Captan is 80% active ingredient, so a quick unit conversion tells us our objective is to apply 160mg of active ingredient per m² of planted area. Let us suppose we will use 500L of carrier per hectare (53.5 gal/ac), which converts to 50mL/m².
Now let’s say the blueberry patch is mature and well pruned. Each plant has a footprint of 1.2m by 1.2m (4ft by 4ft) and is 1.5m (5ft) high. The Leaf Area Index (LAI) is the one-sided green leaf area per unit ground surface area (LAI = leaf area / ground area) in broadleaf canopies. Assuming a conservative LAI of 2, that’s 2.88m² (65ft²) of leaf surface area per plant. We double that figure since we want to spray both sides of the leaves, and then assuming the bushes are planted on 3m (10ft) alleys we arrive at a total foliar surface area per planted area of 3.25m²/m² (3.25ft²/ft²).
A grower with his mature, well-pruned blueberries. 4′ x 4′ on 10′ alleys.
Let’s take these figures and convert them to something we can picture. An average grain of rice weighs 29mg and there are 15mL in a single tablespoon. What this means is that a sprayer operator’s goal is to dissolve active ingredient with a weight equivalent to 5.5 grains of rice in 3.5 tbsp of water and distribute it evenly over 3.25m² (35ft²) of surface area!
Now that’s perspective.
This photo shows how much foliar surface area exists in a square meter of mature highbush blueberry. In the centre is the typical amount of active ingredient and water that must be distributed over that area. It’s amazing what we ask of an air-assist sprayer.
July 23, 2020
Tipping Sprayers and Spills
This short article is a reminder for sprayer operators to respect the possibility of tipping a sprayer. Every spring I catch wind of someone tipping over. When I can ask the operator questions I start with “Is everyone alright?” and “Was the sprayer full?“. Hopefully the answers are “Yes” and No“, but not always.
The following factors are always involved:
- Driving too fast. Usually entering a field at road speed.
- Entering the field on a downhill slope and/or catching a pothole or soft shoulder.
- Turning in a tight radius, usually 180 degrees. This is made worse when the sprayer is towed.
- Sprayer is not completely full and “slosh” changes the centre of gravity.
- Narrow tires and a narrow base.
Fortunately the sprayer wasn’t damaged and the spill was minor.
A tight turn at high speed coupled with a depression in the entryway and tank slosh was enough to tip the unit. They had it righted and hauled out soon after. No one was hurt.
I’ve heard as many cases involving seasoned operators as new operators. The next few pictures are of a veteran operator’s sprayer carrying 28%/ATS. Just like the images above, a tight turn at high speed sloshed the load just as a deep pot hole caught the outside front wheel. This sent the sprayer into a lane of traffic before it tipped back and over into the field. No one was hurt.
Fortunately for the operator, the spill was contained in their field (not the road or ditches). The 90′ boom had to be cut off before the sprayer could be towed back to the yard to be sold off as parts. While the operator has looked at the bright side (an opportunity to upgrade) it has left them relying on a custom operator for spring spraying and making a hasty in-season equipment purchase.
Lost a tire during the tow back to the yard.
Crumpled boom after having to be cut from the sprayer.
Not the way anyone wants to see their sprayer.
Major Spill
What follows are generic steps for what to do if there is a major spill. Always defer to the process outlined by your regional authority.
1. If you do tip the sprayer, first protect yourself, then others, then animals in that order.
2. Stop any exposure by removing clothing and washing as best you can.
3. Stop people from entering the area.
4. If it is safe to do so, try to prevent the spill from spreading.
5. Contact your local spill centre. In Ontario, the Spills Action Centre will receive calls 24 hours a day at 1-800-268-6060. Consult with your municipality for their spill reporting contact numbers.
Take home
Of course we’d rather avoid this problem altogether. Be sure to slow down before turning into a field. Take the turn as gradually as possible. Remember that soft spring ground and new pot holes can become serious obstacles – consider scouting the entry before the first spray or at minimum getting out of the cab and checking before entering.
May 11, 2020