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Ag equipment manufacturer switches to corrosion-free, worry-free, couplings

Hydraulic connectors survive difficult conditions

Wherever people engage in difficult jobs, machines are hard at work, providing the power to get the job done. Where machines are used, from factory to farm, one of the prerequisites for efficiency and profitability is continuous operation. Industrial machines have to be robust enough to withstand the stresses and strains, as does farm equipment, but the agricultural environment has additional considerations. Tillage implements and planting machines also must be resistant to corrosion from fertilizers, rain, and frost. Good corrosion resistance is necessary for the entire machine, but perhaps nowhere is this more important than on the hydraulic system connectors and fittings. If the components are not compatible with the system requirements or are not assembled correctly, leaks can occur quickly.

Over the last few years, Horsch Maschinen GmbH, Schwandorf, Germany, has noticed an increasing demand for its fertilizer machines. A leading manufacturer of machines and components for soil tillage, seeding, and plant protection, Horsch decided to review the durability of its hydraulic components.

High Quality Standards for Hydraulic Systems

“Corrosion resistance against liquid fertilizer and fertilizer dust is extremely important for our customers,” said Thomas Prüll, a member of Horsch’s R&D department. “They expect operationally safe but also optically flawless machines, even after years of operation.”

For corrosion resistance in machines and components in Germany, the guiding reference is standard 24576 published by the German Association of Machinery and Plant Construction (VDMA). It stipulates resistance to red surface rust after 720 hours in a salt spray test. Common choices in corrosion-resistant couplings are stainless steel, yellow-chromated (A3C), zinc-plated, and zinc-nickel-plated.

Connectors manufactured by Voss Fluid GmbH, which have a zinc-nickel treatment, came to Horsch’s attention. The company’s connectors exhibited corrosion protection after more than 2,000 hours in the salt spray test. The couplers hadn’t gone from the production line to the test, but had been subjected to practical processes: handling, shipment, storage, and installation with standard tools. Despite the mechanical stresses, the couplings fared well.

This was a good start, but it was only a start.

“For us the results from the salt spray test are only of limited significance,” said Prüll. “The actual effects of assembly, fertilizer, temperature, and humidity on corrosion resistance first appear on the fields.”

Accordingly, Horsch conducted its own test. Its staff secured couplings from several manufacturers to a rack and exposed them to natural weathering and sprayed them with liquid fertilizer. Red rust appeared over the entire surface of the zinc-coated, yellow-passivated surfaces and the standard zinc-nickel coating. In contrast, only marginal traces of corrosion were detected on the Voss connectors, even six months into the test (see Figure 1).

The Voss coating is similar to customary zinc-nickel coatings, consisting of a zinc-nickel base coat which is passivated and sealed. However, a distinctive feature is electroplating, according to Voss. The company uses electroplating parameters specific to each product to establish even coating distribution, appearance, and friction coefficients. It also offers training courses for leak-free assembly to improve the likelihood of safe and successful installations. According to Horsch, complaints relating to couplings are a thing of the past.

Figure 1
Horsch’s practical test included spraying the components every workday with a liquid fertilizer solution known for its corrosive effect. The connector from Voss Fluid GmbH showed little corrosion.

About the Author
FMA Communications Inc.

Eric Lundin

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Elgin, IL 60123

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Eric Lundin worked on The Tube & Pipe Journal from 2000 to 2022.