Crop and Pest Management Guidelines

7.2 Preparing the Airblast Sprayer for Work

7.2.1 Checking the Sprayer

Sprayers must be checked over regularly to ensure that proper maintenance has been carried out and that no repairs need to be done. Faulty sprayers contribute to increased drift and waste money through inefficiency and overuse of chemicals. 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 and used properly.

Maintenance measures such as fitting a new set of nozzles at the beginning of each season also save money. Even when overdosing occurs by as little as 5%, the cost of a new set of nozzles would be recovered in less than a day's work. The cost of replacing a faulty pressure gauge that has been indicating at 15% below the actual pressure is recouped in around two hours' operation.

7.2.2 Fitting the Sprayer to the Tractor

The selected tractor must always be powerful enough to operate the sprayer efficiently and under the working conditions expected. All external services - hydraulic, electrical, and pneumatic - must be clean and in working order. Tractors 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.

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 the tractor seat.

7.2.3 Checking the Operation of the Sprayer

Partially fill the tank with clean water and move the sprayer to an open area. Remove the nozzles. Although you are not using any pesticide at this point, it's a good habit to wear at a minimum a coverall, gloves, and face visor when working with the sprayer. Engage the PTO, gently turn the shaft, and increase the speed slowly to operating revs. Test the on/off and pressure relief valves and check the agitation system. Flush the spray lines, then switch off the tractor. Refit the nozzles and check the liquid system again for leaks.

It is valuable to assess the spray deposits at various points in the canopy, including the upper and lower leaf surfaces of the vines to be sprayed. Dense foliage or vines grown in beds of three or more rows can also affect deposition. Water-sensitive papers, food coloring, 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 deposition.

7.2.4 Pre-season Maintenance

Use the following checklists when preparing the sprayer for the season:

Hoses

• for splits and cracks
• connections to ensure they are water-tight
• for hose chafe, particularly in routing clips

Filters

• for missing filter elements and seals
• for leakage
• for blocked or damaged filters

Tank

• for fractures and any other damage
• that the tank sits firmly in its mount
• that the securing straps are correctly adjusted
• that the agitation is working
• that the tank is clean

Controls

• the control circuitry (electrical, hydraulic, or air) for correct operation
• valves for both internal and external leaks

Pump

• lubrication levels
• for leaks
• that the air pressure in the pulsation chamber (if fitted) is at the recommended level
• that the pump rotates freely without friction or noise. (Do so by rotating manually or starting at low speed, as 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

Always ensure the correct nozzles and operating pressure are selected before use. Have two or three sets of nozzles on hand to meet different spray qualities at different volume rates. Inspect nozzles throughout the season for damage and proper spray patterns. Check:

• that all nozzles are the same
• that all nozzles are in good condition, with no leaks around the body
• that 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)
• that all nozzles deliver to within + or - 5% of the manufacturer's chart value

Calibration

If your sprayer has automatic controllers to monitor the speed of the sprayer and the flow, pressure and area sprayed, check:

• that they are in good condition and properly maintained
• that they are frequently calibrated for accuracy and checked for leaks, blockages, variations in pressure or any minor damage during spraying

Routine maintenance

Lubricate the sprayer at intervals specified by the manufacturer. The following components must be checked daily when a sprayer is in use:

• Pump crankshaft oil level
• Fan drive gearbox oil level
• Fan drive shaft bearings
• Agitator shaft bearings
• PTO shaft bearings
• PTO shaft safety cover
• Wheels, wheel bearings, and tire inflation
• Rotary atomizers (for damage and lubrication)

In addition, 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.
• Tires on trailed machines are sound and correctly inflated; wheel nuts are tight.
• Check the spray liquid system for leaks and signs of damage or wear, making repairs at once.

7.1 Solutions for Safer Spraying – Engineering Controls

7.3 Sprayer Calibration