On the San Xavier Reservation near Tucson, Arizona, the Tohono O’odom Nation grows organic alfalfa for racing horses plus fruits and vegetables. Thanks to Singer Valve, San Xavier is home to a sophisticated flood irrigation system that consists of one 16” (400 mm) globe style and eight 16” angle style valves and five storage tanks each with its own control panel. Controlling flow intake, high pressure and each tank’s water level electronically and simultaneously throughout the entire system, however, was not easy. “Water is piped to the first tank at 120 psi (8.3 bar),” says Dave Buchwald, a fluid dynamics specialist with Pipestone Industrial, a Singer Valve representative based in Denver. “But, it can’t flow more than 10,300 gallons per minute (650 L/sec), which would exceed the water right limit, and, to feed the relatively small storage tank, pressure has to drop to about 5 psi (0.34 bar).” One 16” valve at the first storage tank, which is only 25’ (7.6 m) in diameter and 12’ (3.7 m) tall, was equipped with a flow limiting function and Anti-Cavitation Trim. Each subsequent tank (15’ x 12’ or 4.6 m x 3.7 m) is equipped with 16” valves. Along the pipeline are delivery valves that open to flood the various fields. To flood the fields adequately, however, each of the five tanks must be able to handle up to 10,300 gpm as well as maintain a specified water level. Coordinating both functions at each of the five tanks simultaneously was the ultimate challenge.
Singer Valve built a simulator so it could mimic the behaviour of the San Xavier irrigation system. After testing a standard PID (Proportional Integral Derivative), Singer Valve wrote a custom algorithm for PLC (Programmable Logic Controller) that stabilized water levels within a few minutes compared to the standard PID’s performance of two days.
Thanks to Singer Valve, San Xavier is home to a sophisticated flood irrigation system that consists of one 16” (400 mm) globe style and eight 16” angle style valves and five storage tanks each with its own control panel.