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A double check valve or double check assembly (DCA) is a backflow prevention device designed to protect water supplies from contamination. [1] It is different from the two-way check valves (sometimes erroneously referred to as double check valves) used in air brake systems on heavy trucks which select from the highest pressure source.
Most automatic irrigation valves are diaphragm valves in which the water above the diaphragm must be discharged for the valve to open. In a hydraulic system, the controller and valves are connected via small plastic tubes approximately 4 mm (¼ in) in diameter. The controller opens the tube connected to the valve, allowing that valve to open.
A satellite image of circular fields characteristic of center pivot irrigation, Kansas Farmland with circular pivot irrigation. Center-pivot irrigation (sometimes called central pivot irrigation), also called water-wheel and circle irrigation, is a method of crop irrigation in which equipment rotates around a pivot and crops are watered with sprinklers.
Surge Irrigation is a variant of furrow irrigation where the water supply is pulsed on and off in planned time periods (e.g. on for 1 hour off for 1½ hour). The wetting and drying cycles reduce infiltration rates resulting in faster advance rates and higher uniformity [ 4 ] than continuous flow.
A one-US-gallon-per-hour (3.8 L) drip flow controller feeding an 82-foot-long (25 m) drip line with check valves comprising 82 drip points along its length so each drip point is putting out about 1 / 82 US gallon (46 mL) per hour. Crimson clover sprouts grown on 1 / 8-inch (0.32 cm) urethane foam mats and flagstone.
This design results in significant increases in servo valve flow capability, stability, and force output. Similarly, three-stage servo valves may use an intermediate stage spool valve to position a larger third stage spool valve. Three-stage servo valves are limited to very high power applications, where significant flows are required.
A further example is shown. If a control valve were used to hold level in a tank, the level controller would compare the equivalent reading of a level sensor to the level setpoint and determine whether more or less valve opening was necessary to keep the level constant. A cascaded flow controller could then calculate the change in the valve ...
Irrigation and conservation districts typically have their own version of mayordomos, usually referred to as "ditch riders" by members of the districts. [ 12 ] Acequias in New Mexico and Colorado have successfully developed and implemented changes in state water laws to accommodate the unique norms, customs, and practices of the acequia systems.