WorldWide Drilling Resource®

44 AUGUST 2020 WorldWide Drilling Resource ® Four Keys for Selecting an Irrigation Flow Meter Part 3 Adapted from Information by Katie Englin Agricultural Irrigation Specialist, Seametrics As promised, here is Tip #4 . . . 4. Electromagnetic or mechanical? Also called magnetic meters or magmeters for short, electromagnetic meters operate by Faraday’s law - if a conductive fluid, such as irrigation water, goes through a magnetic field, it creates a small voltage. Motion of a conductive fluid through the field generates a small amount of electricity, just like a generator (more flow = more voltage). Electrical coils placed outside the flow are momentarily energized. A magnetic field crosses the flow at right angles, electrodes measure the changing voltage, and the display unit shows rate and total. In the past 15 years or so, magnetic meter technology has advanced so much that some are now available battery powered, making them great for irrigation use. Most come standard with many features, that are optional on mechanical propeller meters, and the out-of-pocket cost for a magmeter will be lower than a mechanical propeller meter. To ensure you get the best value for your money, consider what you need - add for pulse output, straightening vanes (for tight space installations), high-capacity bearing assembly, digital readout, data logging, and any other options needed on the mechanical propeller meter - then com- pare the price to a battery-powered electromagnetic meter that normally includes all the options as standard features. In the end, magmeters offer higher accuracy over broader flow ranges, no moving parts to replace, durability, no flow obstruction, long battery life, low maintenance, longer warranties, and minimal straight-run requirements for tight space installations. In addition to full-bore, some magmeters are available in saddle insertion style for ease in both new and retrofit/replacement installations of existing saddle propeller meters. Also called propeller meters or prop meters for short, mechanical propeller meters consist of a rotating device, typically a helical-shaped impeller, positioned in the flow stream. The impeller’s rotational velocity is directly proportional to that of the flow. As water flows through the pipe, it spins the propeller. The spinning motion is then carried to the head of the meter, through either gears or a drive cable. The instantaneous flow rate and total volume can be seen on the mechanical or digital meter register. Though they operate under the same principle, these meters are available in a variety of installation configurations to suit installer needs: saddle style, flanged style, threaded ends, grooved ends, etc., which can make installation simpler. Propeller meters offer an economical flow metering solution when all that’s needed is mechanical rate and total volume flowed. They typically work fine in clean water applications, but water carrying debris can damage the moving parts. While mechanical pro- peller meters used to be the most economical choice for irrigation, it’s typically no longer the case. Many times, choosing a mechanical propeller meter is much like ordering your meal from the à la carte menu at a restaurant. If all you want is a taco and glass of water, you will get a low-cost meal; but add rice, beans, guacamole, and sour cream, and you will likely pay more from the à la carte menu than purchasing a combination plate with all of the “options” you want. So, if you need anything other than mechanical rate and total flow, comparing the cost and benefits of electromagnetic before making a purchase, may be wise. We hope you’ve enjoyed this series. WTR Autonomous Drones Explore Historic Mine Adapted from Information by Exyn Technologies Exyn Technologies completed a successful mission in partnership with Canada-based Rupert Resources to produce highly detailed 3D models of a historic gold mine in Central Lapland of Northern Finland, with autonomous drones. By using these drones, Rupert Resources was able to plan for a potential restart of operations by estimating tonnage previously removed from the mine, as well as calculating the remaining ore in heavily restricted areas. Exyn’s fully autonomous aerial robots mapped 30 stopes in three days with a single drone. In addition, Exyn mounted a version of its robot to a car to scan all access drifts which, together with the stope maps, provided a complete mine map in under four days. “Rupert is actively seeking new technologies where we think big gains can be made in terms of safety, productivity, and accuracy,” said Jukka Nieminen, managing director of Rupert Finland. “Exyn achieved accurate assessment of the volume of remaining stopes at Pahtavaara with an unprecedented level of detail, and obviously the use of remote technologies means that this was achieved with a greatly reduced degree of risk. We have no hesitation in recommending this technology.” The industrial-grade autonomous drones provided a safe, efficient way to explore otherwise inaccessible areas for mining operations. External view of data gathered from inside the narrow stope. MIN