Potato Grower

14 POTATO GROWER | DECEMBER 2019 TOP 4 Questions for Selecting an Irrigation Flow Meter By Katie Englin Agricultural Irrigation Specialist, Seametrics WHAT IS THE APPLICATION? Understanding the fluid media, flow range, temperature, pressure, line size, needed signal outputs and available space for installation are all necessary to ensure proper flow meter selection. • What is the media? Is it groundwater, surface water, water from a pond or lagoon of manure slurries? While a mechanical meter may work fine for a clean water application where the flow range falls within the meter's capabilities, magnetic flow meters offer the highest accuracy and performance in both clean and dirty water applications. • What are the minimum and maximum flow ranges? Propeller meters require a minimum amount of flow to turn the bearing assembly and propeller fast enough to ensure an accurate reading. If the flow rate exceeds the rating of the mechanical meter, the bearing assembly can suffer costly damage and the meter will not function properly. • What is the temperature and pressure? Most flow meters offered for this market are rated up to 150 PSI with an operating temperature of 140 degrees Fahrenheit. Most of these applications fall well within that temperature and pressure range. • What is the line size? This will help determine the style of meter. Both electromagnetic and mechanical meters are available in full bore and insertion- style configurations. • Does the meter need a signal output? Some applications require the meter to send a signal such as pulse, 4-20mA or Modbus. In some cases, the output is used to send a signal to a remote telemetry system, allowing irrigators to collect meter data remotely. Signal outputs are optional on propeller flow meters, and typically require adding the cost of a transmitter or special digital register that can provide outputs. Most electromagnetic flow meters include a pulse signal output as a standard feature, making them "telemetry system- ready." • How much room is available to install a meter? Flow meter straight run pipe requirements are expensive in terms of materials and installation labor. In cases where a new flow meter is added to existing equipment, often there is not enough space to accommodate the straight pipe run necessary for accurate flow measurement. Mechanical propeller meters require more space to install due to the longer straight run requirements to ensure proper and accurate performance. Typically, a standard full- bore electromagnetic flow meter will fit nicely into a tight space and measure flow accurately. HOW IMPORTANT IS ACCURACY? In general, electromagnetic meters are more accurate than mechanical meters. Most electromagnetic meters for irrigation offer +/-1 percent of flow rate over a wide flow range with no head loss. The most common mechanical meters used in irrigation are propeller flow meters. Propeller meters generally offer +/-2 percent accuracy within a specified flow range, and some head loss should be expected. WHAT IS YOUR METER MAINTENANCE SCHEDULE? Just like most farm equipment, all irrigation flow meters will need attention at some point. Mechanical propeller meters have moving parts such as the propeller, bearings and mechanical register that may wear out, causing interruptions in measurement data and resulting in costly repairs. Electromagnetic meters do not have any moving parts to break, and maintenance is usually limited to battery replacement. Many battery- powered magnetic flow meters now Water agencies across the U.S. and abroad continue to require water flow meters for new and existing agricultural irrigation applications to measure and manage surface and groundwater use. There is a growing need to conserve resources and balance the water needs of agriculture with other industries. With the continuing growing population, residential use is driving water conservation as never before. Good irrigation scheduling practices include knowing how much water is applied to each field. A properly selected and installed flow meter accurately measures the amount of water volume applied. An accurate flow meter is an essential tool to practicing good irrigation scheduling. The two most common types of flow meters for irrigation are electromagnetic and propeller. Propeller meters are mechanical flow meters that have been around in irrigation since as early as 1919, and therefore make up a large portion of installed base of irrigation water meters in the U.S. Fifteen years ago, many considered propeller meters the best meter choice for irrigation; that's not the case today. Costly propeller meter repairs caused many meter users to look for other flow measurement options. With technology advancements, electromagnetic flow meters are now available as battery-powered for remote irrigation locations. Magnetic flow meters are quickly gaining popularity in irrigation. Consider the following four questions to help with proper flow meter selection.

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