PIVOTAL MOMENT

Published 12:00 am Saturday, May 5, 2007

Oh, an irrigation pivot is a thing of graceful beauty waltzing slowly across brilliant green carpets of mint or barley.

As dazzling as any debutante anticipating her first ball, the glistening new pivot off Highway 237 still awaits its first dance around the field.

The farmer who owns this brand new pivot may, or may not, think my waxing poetic about a practical investment of approximately $130K is silly.

But I think pivots are a perfect blend of beauty and brains, architecture and technology.

I grew up in row crop country we set siphon tubes in muddy brown ditches. So, these high-tech pivots fascinate me.

When I saw the crew from Pendleton Grain Growers building this new one, last week, I just had to check it out.

A center pivot irrigation system functions as the name implies a long line of steel pipe bearing sprinklers and electricity rotate around a center tower that is anchored to the field in concrete. Pivots may be customized to fit the field’s and farmer’s needs. An average pivot will cover approximately one-quarter mile.

In this system, there are 10 spans of 135 feet each connected by 12-foot towers. At the end a swing arm will open into the corners of the field to extend irrigation by another 205 feet.

Each span consists of a large steel pipe that carries the water. Each is fitted with smaller three-quarter steel truss rods and more steel in a framework called a V-jack, which bows the pipe into an arc and holds it in place. A bazillion nuts and bolts holds it together.

Lead-weighted drops with sprinkler heads are attached to the water bearing pipe, and it’s fitted with electrical wire tied into the main computer panel. A three-phase, 480-volt tower box is wired in at one end of each span with two limit switches to signal the span when it is time to move or stop.

At that same end, the crew assembles the 12-foot wheel tower, as a crane carefully lifts the span into the air. Once completed, the span is dollied out to the main system and attached thus the system grows one span at a time across the field.

PGG’s Frank Shaw has been building pivot systems for about 17 years. With Ken Cox, who has been on the job for 14 years, the pair have probably built most of the pivots in the valley. With another one or two men working with them, Shaw says it takes just a few days to put the whole system together. The more experienced the crew is, the faster it goes.

"It’s like a big erector set," Shaw says, grinning. "I like building ’em."

All the pieces parts, including the special lighter weight

4-ply tires made specifically for pivots, were shipped from the Valley Irrigation plant in Nebraska. Shaw has no idea how many parts they have to assemble in the building of this one pivot.

"I never bothered to count ’em, but I suppose by including the nuts and bolts that could put (the number of parts) in the thousands," he estimates.

When finished, the gleaming new pivot will water tomorrow’s food with mathematical precision, via a computer program that can be adjusted for speed, time, water pressure and more. Water application is consistent from one end of the pivot to the other at the touch of a button.

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