Embedded Computer-Controlled Premixing Inline Injection System for Air-Assisted Variable-Rate Sprayers

Abstract

Improvements to reduce chemical waste and environmental pollution for variable-rate sprayers used in orchards and ornamental nurseries require inline injection techniques. A microprocessor controlled premixing inline injection system implementing a ceramic piston chemical metering pump and two small transition tanks was developed for air-assisted variable-rate sprayers. Unlike conventional direct inline injection systems that inject chemical concentrates into the delivery lines, this system first dispensed specific amounts of water and chemical concentrates into an injection chamber and then agitated the mixture in a transition (or premixing) tank. The mixture was then transferred into a second transition (or buffer) tank for discharge from the spray pump. This process was repeated when the buffer tank neared empty. The mixture in the buffer tank was maintained at a constant concentration that allowed the sprayer to discharge a wide dynamic range of variable-rate outputs with a consistent concentration for every nozzle. A touch screen monitor with an embedded computer allowed operators to interface with the injection system. The metering pump accuracy was verified with three simulated pesticides (water, prime oil, and milk). Mixture uniformity consistency was tested with six different viscous simulated pesticides (sucrose solutions) at viscosities ranging from 0.9 to 31.3 mPa-s. Test results confirmed that the metering pump accurately dispensed the simulated pesticides at different pump speeds, and the premixing inline injection system provided consistent concentrations of spray mixtures at the spray pump outlet. The new system avoided lag time, inconsistent spray mixture concentrations and inaccurate metering of chemical concentrates at low flow rates associated with conventional direct inline injection systems, and can further improve spray application efficiencies for variable-rate precision sprayers.