Abstract: An electrically-actuated variable pressure control system for use with flow-controlled liquid application systems. Direct acting solenoid valves are pulsed at varying frequencies and duty cycles to change the resistance to flow encountered by the flow-controlled liquid application system. This pulsing solenoid valve technique preserves a high degree of accuracy and uniformity through a wide range of pressure control. This wide range of pressure control indirectly allows the flow-controlled liquid application system to operate over a wider range of flow control, yielding indirect benefits to performance and productivity. When the solenoid valves are attached to pressure-atomization spray nozzles, control over spray pattern and droplet size is further achieved.

Abstract: The present invention is generally directed to a system and to a process for dispensing a volatile liquid fertilizer and particularly ammonia into a field. The ammonia is placed in a vessel under sufficient pressure to maintain a substantial portion of the ammonia in a liquid form. From the pressurized vessel, the ammonia is fed to a distribution manifold where it is ultimately injected into a soil through a plurality of dispensing tubes. According to the present invention, a constant pressure flow rate control device is placed at each dispensing tube for metering the amount of ammonia fed to the soil. In particular, the flow control devices allow ammonia to be dispensed from the system while maintaining sufficient back pressure within the distribution manifold to maintain the ammonia in a liquid form. By preventing vaporization of the ammonia within the system, uniform and accurately controlled flow rates can be dispensed from the dispensing tubes.