A similar study conducted in North Dakota indicated that 60 percent of tested sprayers had calibration errors greater than 10 percent. Although inaccurate tank mixing causes some of these errors, a majority of the problems result from improper spray equipment calibration and worn nozzles. Flat-fan nozzles are used for broadcast spraying of most herbicides and some insecticides where a medium droplet size is needed. Flat-fan nozzles are used for banding herbicides. Hollow cone nozzles produce smaller droplets and are used to apply insecticides and contact herbicides that need to penetrate the canopy.
Inaccurate applications can be due to nozzle wear.
Therefore it is important to select the correct nozzle material. Wear-resistant materials such as tungsten, carbide, ceramic and hardened stainless steel help nozzles maintain a constant flow rate after a long period of use. For example, after 50 hours of spraying, a brass nozzle can have an increased flow rate of 10 to 15 percent, whereas a hardened stainless steel nozzle will increase only about 2 percent. The increased flow rates result from an increased nozzle orifice area. The added cost to purchase a more durable nozzle can pay for itself many times over by reducing the over-application that results from nozzle wear.