Over the years, we've fielded many questions about Valley® PolySpan®, but recently we've seen increasing interest. As you may know, groundwater quality has been changing across the country1, leading many growers to investigate pipeline materials that are more resistant to corrosion than galvanized pipe.
Here at Valley, we've tested numerous corrosion solutions, including aluminum, stainless steel, weathering steel, and a wide variety of paints, linings, and other coatings. From that research, we’re convinced that PolySpan is the best corrosion solution for just about any corrosive water situation.
So what is PolySpan and how can it help you improve your irrigation equipment and increase the efficiency of your operation?
PolySpan consists of a High Density Polyethylene liner and glass-reinforced nylons couplers installed into a hot-dip galvanized pipeline. The entire span and overhang is lined (up to 36’ overhangs), and a 304 stainless steel adapter is used to accommodate the flush-out and mount the booster pump. Optional stainless steel pivot riser pipes and lower elbows are available for a completely corrosion-resistant solution.
PolySpan starts with a steel pipe that is welded and hot-dip galvanized. Then, a poly liner is installed into the pipe. The ends are hot-formed onto the flange and through small retention holes in the flange to create a highly-durable HDPE pipe gasket that locks the liner into the pipe. Finally, self-locking 3/4-inch glass reinforced nylon couplers are installed on the top of the pipe by skilled Valley technicians. These couplers have a wide gasket face that conforms to the inside of the liner for a leak-free seal. Since 2005, PolySpan has been manufactured in Valley, Nebraska, USA, at the same factory where we make the Valley gearbox.
Unlike other so-called corrosion-resistant pipe, PolySpan is an inert material and resists all corrosive elements in irrigation water. There’s no limit on pH, sulfates, chlorides, softness, or saltiness. Also, PolySpan is an excellent choice for growers wanting to take advantage of today’s wide range of chemicals and fertilizers that can be applied through irrigation water. With PolySpan, you don’t have to worry if those chemicals are harming your pipeline. And, because PolySpan is inert, you’ll be able to take advantage of future additives, even if they’re corrosive.
Valley is so confident in PolySpan’s performance that we offer a 20-year, pro-rated corrosion warranty with full replacement for the first 10 years (or 30,000 hours). In fact, the first PolySpan machine was installed in Utah in 1992 and it is still operating. <
Valley PolySpan features special hose drops. These strain-relieving drops isolate the coupler from weight, wind, and crop loads present on the sprinkler package. This ensures the coupler is not damaged and remains leak free. Highly corrosive water can also damage the external structure, and hose drops help minimize this. For extremely corrosive water, Valley offers a powder-coat-over-galvanized Drive Unit for additional protection.
Valley PolySpan is available on center pivots, towables and linears; on both the 7000 and 8000 series; and in span lengths ranging from 115 feet up to the industry-leading 225-foot span. It’s also available in both 6 5/8 inch and 8 5/8 inch pipe to accommodate a range of machine lengths and flow rates. Finally, PolySpan is available on the Valley Precision Corner® and is compatible with the Valley Bender30™, so you can maximize your irrigated acres, even if you have corrosive water!
As you can see, because PolySpan is completely insensitive to water chemistry changes and to a wide range of chemicals and fertilizers, it protects the significant investments you’ve made in irrigation equipment.
1 Lindsey and Rupert. Methods for Evaluating Temporal Groundwater Quality Data and Results of Decadal-Scale Changes in Chloride, Dissolved Solids and Nitrate Concentrations in Groundwater in the United States, 1988-2010
U.S. Geological Survey Scientific Investigations Report 2012-5049