UPGRADING SYSTEMS I
n today’s increasingly competitive global market, high production efficiency is essential for producers to grow their economic return. Irrigation scheduling, efficiency and uniformity maximize production.
Center pivot and linear move sprinkler systems are capable of attaining efficiencies of 90% to 95%, with uniformity values of 85% generally considered the minimum acceptable level before a system needs maintenance or updating. There are a few simple checks you can perform to ensure you are getting the most out of your existing system. It is also important to stay aware of new technologies that may improve mechanized irrigation performance.
HOW’S YOUR EXISTING SPRINKLER PACKAGE WORKING?
The primary objective in the maintenance of a sprinkler system is to maintain the design flow rate from each sprinkler, which requires that the design pressure and nozzle size at each sprinkler remain unchanged.
Common problems are worn or plugged sprinkler nozzles, plugged or malfunctioning pressure regulators, and improper installation. Malfunction- ing pressure regulators can be difficult to identify visually; however, some emit water through the sides of the regulator when they fail structurally.
A malfunctioning regulator can result in a sprinkler pressure that is too high. A sprinkler emitting a finer spray or with a faster rotation speed relative to adjacent sprinklers may indicate a regulator that is operating above its rating. If operating below its rating, sprinklers will produce larger droplets and
slower rotation speed, as well as reduced wetted diameter.
During the irrigation season, it is important to intermittently observe sprinkler performance. This is best done either early or late in the day when the sun is low, as differences between sprinklers are easier to identify in this light.
Flow rate measurements from randomly selected sprinklers can be used to judge the condition of the sprinkler package. These can be made using a large graduated container and a stopwatch, as when calibrating a sprayer nozzle. Sprinkler flow rate can then be calculated and compared to the sprinkler chart. Flow differences greater than ±10% indicate a problem. The cause should be identified and corrected. Plugging in the nozzle or plugging upstream of the regulator, a “stuck” regulator, or low system operating pressure are common causes of lowered flow. High flows indicate a malfunctioning pressure regulator or worn nozzle.
Pipeline pressure on the machine should be moni- tored throughout the year. Pressure gauges at the pivot point and at the distal end of the system should match the computer-generated sprinkler chart.
A flow meter can also be a valuable tool and can ensure that the flow output of sprinklers, regulators and end guns matches the sprinkler chart. Pressures and flow rates that change during the irrigation season could indicate problems with a sprinkler package.
Yield maps and aerial pictures can also be utilized to identify poor sprinkler performance.
Cutaway of a common pressure regulator
Photo credit: Nelson Irrigation
During the irrigation season, it is important to INTERMITTENTLY OBSERVE sprinkler performance.
A good strategy against wear is to replace the sprinkler package EVERY
FIVE TO 10 YEARS depending on water quality and hours of use. An accepted industry rule of thumb is to consider replacing sprinkler packages at least
EVERY 10,000 HOURS.
irrigationtoday.org Fall 2019 | Irrigation TODAY 21
Photo credit: Reinke
Photo credit: Reinke
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