Corner machine example
Here’s an example. Let’s say you have a square quarter that you want to put a pivot and corner machine on. You contact your local pivot dealer, and he designs a system for you and gives you the bid.
A corner machine is a great option for increasing your number of irrigated acres, but it causes another problem. The corner span is the last span on the machine, which means that it’s the highest flow span. However, the sprinklers on the corner span are not all spraying all the time. As the corner machine moves in and out, the sprinklers turn on and off. This causes the flow and pressure in the pivot to change.
When your pivot dealer designs the machine and determines the flow and pressure necessary to operate the machine, he plans for the highest use scenario, which is when the corner machine is fully extended. This is the time when the system needs the maximum flow. Therefore, the pump is sized to deliver the flow necessary when the corner machine is fully extended.
Right amount, right place
When it comes to irrigation, a grower wants to pump only what’s necessary and make sure it’s applied in the right area. Newer technologies like variable rate irrigation help ensure the water only goes where it’s needed and is applied in the right amount for a given crop and soil type. VRI also ensures that water doesn’t go where it’s not needed or would be wasted like in a waterway or on a pivot road.
VRI presents a challenging scenario for pumping because the pressure and flow are constantly changing. However, any situation that causes a change in flow or pressure in the irrigation system is an opportunity to improve efficiency and save money .
Consider your operation. Do you have a pivot that irrigates on a hill? Do you have a corner machine? Do you have more than one pivot on a given pump? If so, you’re in luck, and you can potentially save operating expense by investing in widely used variable frequency drive technology.
Depending on the overall design, a corner machine can account for 25-40 percent of the total pivot flow. That’s a huge percentage. But here’s the problem: on a square quarter, a corner machine is only fully extended 15-20 percent of the time it’s operating. That means for 80+ percent of the time the pivot is running, the pump is pushing too much water and building up unnecessary pressure in the pivot.
A pump turning faster than necessary results in wasted energy and wasted money. By using a VFD, the grower can save significant operating costs by slowing the pump down and only delivering the flow necessary to meet the needs of the machine based on how far the corner machine is extended.
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