Equipment

Good sprayer hygiene is essential for crop, operator and environmental safety. Matthew Horne explains why cleaning is important and points out some of the areas that can be overlooked or ignored when things start to get a bit busy.

Thorough rinsing and cleaning are vital to prevent contamination to the sprayer, operator and environment, as well as to protect the machine and its components.

The Code of Practice recommends operators: ‘safely clean applicators, inside and out, preferably before leaving the treatment area’, with a safe washings area identified prior to spraying. Note: Spraying out washings on a site, other than crop for which the products are approved, will require a ground water permit.

Rinsing is best done in the field, with the washings sprayed back onto the crop, ensuring the application does not exceed the maximum recommended dose rate. A common technique is to increase the forward speed and half the pressure when spraying out washings.

Good job planning will help cut the number of wash-outs and improve the cleaning efficiency. Correct calibration, and mixing the exact amount for the area, will also minimise the amount of surplus dilute spray solution and save products.

Before filling the sprayer, during routine daily maintenance, look inside the tank to ensure it is clean, there’s no residues and that rinse nozzles are working.

Rinsing routine

Many machines now have auto-rinse systems, which operate all the valves in the correct order. It is important, however, to check the cleanliness to ensure this is working correctly.

Before rinsing the sprayer check the product label for any specific cleaning instructions. Some sulfonylurea (SU) herbicides, for example, require specialist cleaning agents and procedures.

Sprayers without auto-rinse require operators to manually control the process, circulating clean water around the sprayer according to the manufacturer’s cleaning instructions.

During this process it’s important to open all the valves in the right sequence to ensure thorough cleaning. Remember to operate the pressure relief valve and agitation as well as ensuring the water goes through the induction hopper and back to the tank. Take off the end cap on non-recirculating booms because these are dead ends that will trap residue.

Triple rinse

Many operators now use a triple rinse strategy, which provides progressive dilution that is proven to leave the tank eight times cleaner than a single rinse.

First determine the clean water tank capacity e.g. for a 3,000-litre tank this will be 300 litres (Clean water tanks have to hold 10% of the sprayer tank capacity e.g. 300 litres for a 3,000 litre spray tank).

Record how long it takes to transfer the full clean water tank capacity e.g. 90 seconds. Divide this by three: 90 ÷ 3 = 30 seconds. This means the system will transfer 100 litres (a third of the rinse tank capacity) in 30 seconds.

While spraying out the washings check that all nozzles are working. Turn the sections on/off a few times to ensure that any pressure compensation lines are also flushed. Also turn multi-nozzle holders and run liquid through all the nozzles.

Exterior cleaning

It’s also good practice to wash the exterior of the sprayer in the field, which is easier now many machines are equipped with a washer hose and lance. However, ensure this cleaning is done at least 10m away from ditches, streams or boreholes.

Pay particular attention to ‘hotspot areas’, which include the boom, back of the tank and rear wheels.

Although some sprayers are fitted with power washers, the high-water velocity generates splashback and mists that can increase the risk of contamination. Also, certain electrical components can be damaged if the jet is directed at them. Consider moving to using a lower volume washing brush, because these can be more effective and will use less water.

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