Scaffolds 01 index

(Andrew Landers, Agricultural and Biological Engineering, Ithaca)

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 that 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, food colouring 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 these checklists before you begin spraying:

Hoses

Have you checked…

for splits and cracks

connections to ensure they are water-tight

for hose chafe, particularly in routing clips

Action:

Replace damaged hoses.

Filters

Have you checked…

for missing filter elements and seals

for leakage

for blocked or damaged filters

Action:

Replace any damaged or blocked filters.

Tank

Have you checked…

for fractures and any other damage

the tank sits firmly in its mount

the securing straps are correctly adjusted

the agitation is working

the tank is clean

Action:

See the supplier/manufacturer now about fractures and any other repairs.

Controls

Have you checked…

the control circuitry (electrical, hydraulic or air) for correct operation

valves for both internal and external leaks

Action:

Replace leaky valves, which waste money and are potentially dangerous to operators and the environment.

Pump

Have you checked…

lubrication levels

for leaks

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

Have you checked…

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

Action:

Always ensure the correct nozzles and operating pressure are selected before use. Have two or three sets of nozzles in stock to meet different spray qualities at different volume rates. Inspect nozzles throughout the season to avoid faults which could prove both costly and damaging to the environment if they develop unchecked.

Using water only, set to ‘spray’ at the specified pressure and collect the output from each nozzle in turn for a period of 60 seconds. Record each output and replace those outside the 5% tolerance around 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, have you checked…

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

A recommended calibration technique is summarized as:

•Read the label

•Measure the forward travel speed of the tractor with the booms out and over the field to be sprayed

•Calculate the nozzle output required

•Select the appropriate nozzle set

•Set the appropriate pressure

•Measure the nozzle output against time

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.

Proceed to Diseases 3/26/01