Won’t PolySpan couplers leak?
No. Valley Irrigation has years of design experience and hundreds of machines in the field. Our wide-gasket, self-locking coupler conforms to the shape of the liner and pipe to ensure a water-tight seal.
Isn’t PolySpan heavier than galvanized pipe?
No. The density of the poly liner is approximately equal to water, so when a poly machine is irrigating it is the same weight as a galvanized span.
What about water seeping between the pipe and liner?
The diameter of the poly liner is temporarily reduced during installation. As the liner returns to normal size, it fills the space between the liner and pipe for a tight fit, virtually eliminating any gaps. Also, full-flow ¾" couplers from Valley are specifically designed to prevent irrigation water from getting between the pipe and liner. Finally, in the highly unlikely event that water was to seep between the liner and pipe, hot-dipped galvanizing protects the steel pipe from corrosion.
What about higher pressure loss caused by the liner inside the pipe?
The differences are insignificant. For a typical quarter-mile pivot, the pressure loss in a 6 5/8” Valley PolySpan machine is only about 1 PSI greater than a 6 5/8" machine with hook-and-eye joints, and only about 2.5 PSI higher than a galvanized Valley pivot.
Are special drops required?
Yes, special hose drops are required on Valley PolySpan. These strain-relieving drops protect the coupler from the weight, wind, and crop loads present on the hose drops. This prevents damage to the coupler and ensures it remains leak free for the life of the machine. In addition, highly corrosive water can damage the external pivot structure. Drops help minimize this. For extremely corrosive water, Valley offers a powder-coat-over-galvanized drive unit for additional protection.
Do humidity and sunlight affect PolySpan?
The extrusion-grade, High Density Polyethylene liner is highly resistant to sunlight and humidity. In addition, the glass-reinforced nylon couplers contain special additives to ensure long life.
Is PolySpan sensitive to wear from sand or sediment?
No. PolySpan is made from durable High Density Polyethylene and glass-reinforced nylon. These materials are not affected by abrasion caused by normal levels of sand or sediment in irrigation water.
How long does PolySpan last?
The first machine was installed in Utah in 1992 and it is still operating. 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).
Doesn’t the liner expand and contract with temperature?
The High Density Polyethylene does expand and contract slightly as temperatures change. That’s why Valley uses an exclusive hot-forming process to lock the liner into retention holes in the flange. In addition, the strong, ¾" glass-reinforced nylon couplers help hold the liner in place, and the wide gasket surface of the couplers conforms to the inside of the liner to ensure a leak-free seal.
What about chemigation or fertigation?
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 the 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.
How is PolySpan made?
Since 2005, PolySpan has been made in Valley, Nebraska, USA, in the same factory where we make the Valley gearbox. After the steel pipe is welded and hot-dip galvanized, 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, couplers are installed by skilled Valley technicians.
How does PolySpan perform?
Unlike other so-called corrosion-resistant pipe, PolySpan resists all corrosive elements in irrigation water. There’s no limit on pH, sulfates, chlorides, softness, saltiness, or farm chemicals. PolySpan is an inert material. Don’t be fooled, PolySpan lasts.
Is my entire span protected?
Yes! The entire span and overhang is lined (up to 36' overhangs). A 304 stainless steel adapter is used between the end of the machine and the overhang to attach the flush-out and mount the booster pump. Optional stainless steel pivot riser pipes and lower elbows are available for a complete corrosion-resistant solution.
But my weathering steel pipe looks just fine.
That’s great! You’ve been fortunate. But, water quality is deteriorating across the country. We’ve seen a number of instances where galvanized, weathering steel, aluminum, and even stainless pipe corrode away in a couple of years due to a change in irrigation water chemistry. And, paint doesn’t always adhere well to weathering steel pipe, especially with poor surface preparation. It’s extremely hard to clean the inside surface of a long irrigation pipe, so how do you know your pipe is completely protected on the inside? PolySpan is completely resistant to these changes and protects the significant investment you’re making in an irrigation machine.
What about other corrosion-resistant pipes such as weathering steel, stainless steel, and aluminum?
Other so-called corrosion resistant pipelines are sensitive to a number of corrosive elements commonly found in irrigation water. More importantly, some combinations of these elements will result in more accelerated corrosion rates.
Weathering steel is only slightly more corrosion resistant in irrigation applications than plain carbon steel. It is also sensitive to humid subtropical climates. In such environments, the protective patina may not stabilize and the pipe will continue to corrode. Painting reduces the corrosion resistance of weathering steel to the same level as conventional carbon steel because the paint prevents a protective patina from forming on the entire surface of the pipe, making it sensitive to corrosion in a localized area, such as at a small paint failure. Even the smallest defect in the paint is an opportunity for corrosion failure.
Stainless steel is sensitive to levels of chlorides above 40 ppm and sulfates greater than 100 ppm. It is also sensitive to highly basic or acidic water (pH greater than 11 or less than 4). It is not recommended for soft water, can be incompatible with certain farm chemicals such as soil remediation products, and it is very expensive.
Aluminum is sensitive to levels of chlorides and sulfates above 50 ppm, pH greater than 8.2 or less than 5.0, crop production chemicals containing high levels of sulfur or copper, fertigation products such as phosphoric acid, and soil remediation products using sulfuric acid. For corrosion resistance, aluminum depends on a thin layer of aluminum oxide on the surface of the pipe. Unprotected, aluminum is highly reactive and corrodes quickly. This frequently happens at moving joints, such as a hook and eye, where the protective layer of aluminum oxide is constantly worn away. Finally, aluminum has about the same strength-to-weight ratio as steel, and has much lower fatigue resistance, so if the aluminum pipe is lighter, it’s also weaker and less durable.
Only PolySpan is resistant to all of these factors, as you can see in the charts below.
Is PolySpan available on all machines?
Valley PolySpan is used on pivots, towables, and linears. It’s available on the 7000 and 8000 series in span lengths ranging from 115' up to the industry-leading 225' span. It is available in both 6 5/8" and 8 5/8" pipe to accommodate a range of machine lengths and flow rates. It is also available on the Valley Precision Corner and Valley VFlex Corner, and is also compatible with the Valley Bender30™, so you can maximize your irrigated acres, even if you have corrosive water!
Can I upgrade my existing machines to PolySpan?
Yes! Valley offers PolySpan re-piping options for older Valley 8000, 7000, and 6000 series machines. And, re-piped machines carry the same 20-year corrosion warranty* as new PolySpan machines.
*Warranty applies to USA and Canada only. Ask your Valley dealer for a copy of the Corrosion Warranty.