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PREPARING THE AIR BLAST SPRAYER FOR WORK
Dr Andrew Landers
Cornell University,
Department of Agricultural and Biological Engineering
Riley Robb Hall, Ithaca, NY14853-5701
Checking the sprayer
Surveys have shown that many farmers are using inaccurate sprayers; faulty sprayers contribute to increased drift levels and waste money through inefficiency and overuse of chemicals.
Sprayers must be regularly checked over to ensure that proper maintenance has been carried out and that no outstanding repairs need to be done. Before attempting any work on a machine make sure that it is fully supported on stands and that all necessary protective clothing is on hand.
The cost of replacing a faulty pressure gauge which has been indicating at 15% below the actual pressure is recouped in around two hours’ operation.
Maintenance measures such as fitting a new set of nozzles at the beginning of each season also save money. Even when there is overdosing by as little as 5%, the cost of a new set of nozzles would be recovered in less than a day’s work.
CAUTION
- Take great care when adjusting a sprayer while the tractor engine is running.
- Always ensure that the fan is stationary before approaching the rear of the sprayer.
- Engage the handbrake when leaving tractor seat.
Fitting the sprayer to the tractor
The selected tractor must always be powerful enough to operate the sprayer efficiently under the working conditions that will be encountered. All its external services — hydraulic, electrical and pneumatic — must be clean and in working order. Tractors fitted with cabs must have efficient air filtration systems. All protective guards must be in place. Trailed sprayers are often close-coupled to the tractor, so it is essential that the drawbar and the PTO shaft are correctly adjusted for turning. PTO shafts must be disengaged when making very tight turns.
Checking the operation of the sprayer
Part fill the tank with clean water and move the sprayer to uncropped waste ground. Remove the nozzles. Although not using any chemical at this point, get into the habit of wearing a coverall, gloves and a face visor when working with the sprayer. Engage the PTO and gently turn the shaft, increasing speed slowly to operating revs. Test the on/off and pressure relief valves, and check the agitation system. Flush through the spray lines, then switch off the tractor. Refit the nozzles and check the liquid system again for leaks.
It is a valuable exercise to assess the spray deposits at various points in the canopy and on upper and lower leaf surfaces of the trees to be sprayed. This is particularly important if the foliage is dense or if the trees are grown in beds of three or more rows. Water-sensitive papers or fluorescent tracers are available for this purpose. An increase in spray volume or adjustment of the nozzles and their locations may be necessary in order to achieve the correct deposits.
Pre-season maintenance
Follow the checklists before you begin spraying
Hoses
check…
- for splits and cracks
- connections to ensure they are water-tight
- for hose chafe, particularly in routing clips
Filters
check…
- for missing filter elements and seals
- for leaks around the joints
- for blocked or damaged filters
Tank
check…
- for splits, cracks and any other damage
- the tank sits firmly in its mount
- the securing straps are correctly adjusted
- the agitation is working properly
- the tank is clean
Controls
check…
- the control circuitry (electrical, hydraulic or air) for correct operation
- valves for both internal and external leaks
Pump
check…
- lubrication levels
- for leakages
- the air pressure in the pulsation chamber (if fitted) is at the recommended level
- the pump rotates freely without friction or noise. Do so by rotating manually or starting at low speed (corrosion may cause seizing up)
Pressure Gauge
The pressure gauge is vital for indicating whether the nozzles are delivering the correct amount of chemical per unit time while spraying.
If you have any doubts about the pressure gauge, replace it or refer the problem to the manufacturer or supplier.
Nozzles
check…
- all nozzles are the same
- all nozzles are in good condition, with no leaks around the body
- all nozzles are clean and free from obstruction (note: clean with a soft brush or airline — don’t damage nozzles by using wires or pins)
- all nozzles deliver to within + or - 5% of the manufacturer’s chart value
Calibration
Where your sprayer has automatic controllers to monitor the speed of the sprayer and the flow, pressure and area sprayed,
check…
- they are in good condition and properly maintained
- they are frequently calibrated for accuracy, with calibration being checked after every 250 acres’ use
- for leaks, blockages, variations in pressure or any minor damage during spraying
Routine maintenance
The following checks should be carried out routinely:
__All hoses are tightly connected and free from sharp bends; cracked or damaged hoses
must be replaced.
__All controls move freely and are fully adjustable.
__Pressure gauge reads zero.
__Pump can be turned over by hand.
__Fan turns freely and is not obstructed; bearings are sound and lubricated.
__Air pressure in pump accumulator (if fitted) is correctly adjusted.
__Drain plugs and clean filters are in position.
__Tyres on trailed machines are sound and correctly inflated; wheel nuts are tight.