The Hidden Cost of Damaged Nozzles

Many factors contribute to a successful spray application: sprayer mechanics, application method, weather conditions, nature of the target, product applied and the aptitude of the operator. All of these factors converge when the spray leaves the nozzle. It is therefore surprising that the most critical part of the sprayer, the nozzles, are so often neglected. Monitoring nozzle performance pays financial dividends because tip damage has a direct impact on product effectiveness and cost (see Table 1).

If the application is seriously compromised, the operator might have to re-spray, which incurs additional labour, time, fuel, and wear-and-tear on equipment. Inevitably, all nozzles wear out so be sure to include regular nozzle maintenance and replacement in every spray program.

Table 1. "The Potential Impact of Damaged Nozzles"

The solution lies in proper maintenance and early detection. Tip orifices have delicate edges, so clean them with a soft-bristled brush or using a can of compressed air. Even a wooden toothpick can distort some plastics, so imagine what a wire does. Better still, carry spares for quick field replacements and clean them later in the workshop where they won't get lost. Be sure to clean nozzle screens with a brush as well because flushing does not dislodge build-up. Nozzle performance should be tested during each calibration (before and mid-way through the season at minimum) or whenever damage is suspected.

Testing is simple, quick and inexpensive:
1. Temporarily install a pressure gauge on the boom behind the nozzle (commercial or home-made);
2. Adjust the regulator to compensate for the pressure change between the pump and nozzle to accurately set nozzle pressure;
3. Use a graduated container or commercial tip-tester to measure the discharge of clean water over a one minute interval;
4. Compare the rate to the manufacturer's rate <OR> compare the flow rate from the used tip to the flow rate of a new tip of the same size and shape.

If the flow rate is 10% (or even 5%) more than the ideal rate, replace ALL nozzles, not just the ones that appear damaged. Replace them once a year or at the first signs of deterioration, whichever is first. The cost of renewing an entire set of nozzles is a fraction of the potential cost of wastage and potential crop damage:

Example:
1. An airblast sprayer with 16 nozzles sprays a product that costs $150/hectare (~$60/acre). Nozzle tips are worn by an average 10%, which sprays an additional $15/hectare ($6/acre).
2. 16 new ceramic hollow cone tips and gaskets cost $80 at $5 each.
3. The nozzles pay for themselves in 5.3 hectares (13.3 acres).

The rate of tip wear depends on spray pressure, product sprayed, and the material of which the nozzle is made. Upgrading to a harder, more durable tip can reduce maintenance costs. Never mix nozzle materials on a boom; from softest to hardest:
Brass < Stainless Steel < Plastics < Hardened Stainless Steel < Ceramic.