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How do I specify hydraulic hose fittings?

- Dec 21, 2017 -

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Hydraulic hose fittings connect hoses to pumps, valves, cylinders and other components used throughout a hydraulic system. These secure connections help contain and direct the flow of hydraulic fluid to where it is needed while preventing leaks and safely maintaining pressure.

Experts say that it pays to differentiate the hose from a completed hose assembly. While selection of the hose is obviously important, selecting the hose without considering the fittings can be a costly mistake. Any hose assembly includes fittings that are specific to the application. An industrial hose assembly must have the hose, fittings, and a way to attach the fittings to the hose. For most hydraulic hoses, the fittings have a barbed end that inserts into the hose ID, and an outer shell or ferrule that attaches to the cover or reinforcement.

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Crimping is the most common method for assembling hoses and fittings. Once the crimp specifications have been checked for a specific hose and fitting, a crimping machine is adjusted to the appropriate crimping diameter setting. The next step is to lubricate the fitting, push it into the end of the hose, and then insert the fitting into the crimper dies. Actuating the crimper closes the dies and compresses the fitting permanently onto the hose.

Many companies offer no-skive options on their hoses. Skiving refers to a process where part of the hose cover or even the inner tube is removed—exposing the reinforcement layers—before a hose end is attached. No-skive hoses do not require this step. Many users prefer no-skive options because it makes hose assembly quicker and reduces the risk of hose damage during crimping.

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Hoses come in many different types made of various rubber compounds, elastomers, plastics, PTFE, composites or even metals. Fittings are made of different materials, too, including steel and stainless steel but also brass, “exotics” like Monel and more. This multitude of materials creates fittings with a wide array of performance capabilities.

Therefore, in addition to the hose, users must choose fittings for chemical compatibility, as well as the security of the connection. Most hydraulic fittings have designated pressure and temperature ratings as well as size and dimension standards set by organizations like SAE International. There is also breakdown by application to consider, such as operating pressure, flow capacity, environmental and temperature extremes, and the operating fluid.

When installing a hose assembly, it’s important to pay attention when identifying the threads of the connections. Often, connections from one standard appear to thread into another standard port but do not have sufficient engagement to be safe. Furthermore, most fittings are brand-specific for certain hoses and may not work with other brands. While fitting dimensions often correspond to the size of the conductor there can still be a variance in fitting options for one size of hose.

That brings up a common question, “Can I use hose and fittings from different manufacturers in the same system?” According to many experts, the short answer is “no.”

Mixing and matching components from different manufacturers is the traditional way of life for many industrial hose distributors and end-users, but this approach to making hose assemblies leaves fabricators and users open to greater liability than ever before.

The “right” components for safe, long-lasting hydraulic assemblies are couplings, hoses, and crimping equipment and accessories that are designed to work together. Tolerances vary from one manufacturer to another and are not interchangeable. Different components from different manufacturers can adversely affect coupling retention. Casual mixing and matching can lead to hoses bursting, couplings leaking and blown-off ends maiming or even killing workers.

In addition to the dangers involved, mixing and matching brand names will void the manufacturer’s warranty and could also exclude manufacturers from liability should someone get injured from a failed hose assembly.

Companies that make their own hose and fittings say their products are combined into finely engineered hose-assembly systems that are specifically designed to work together. However, companies that only make fittings often have their products certified by third-party testing organizations to work with specific types and brands of hoses. For the user, when in doubt, always consult with an expert to guide you through the selection process.



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