IDA Universal

July 2016

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I DA U N I V E R S A L J u l y -Au g u s t 2 0 1 6 36 Hoses for All Fluids Hoses transmit any number of industrial fl uids, including motor oils, heavy- duty coolants, and transmis- sion and brake fl uids. Most of these fl uids tend to be petro- leum-based oils, but engineers also work with many obscure fl uids as well, including antifreeze and other glycol- based coolants. e challenge in dealing with such a wide variety of fl uids is fi nding the right hose for a particular fl uid. On top of that, fl uid manufacturers and oil companies regularly update their products, says Nathan Groves, a chemical engineer and project manager with Parker Hannifi n Corp. Fluids are usually changed a er fi ve to 10 years, with a typical update being a change to the additive package, he says. Although the base fl uid remains the same, changing the additives o en aff ects the fl uid's compatibility with the hose's inner elastomer tube. Hose manufacturers are aware of these changes and maintain compatibility databases based on material testing. "If an OEM changes a fl uid's base materials, such as going from a distillate to a synthetic, that can be more of a concern than changing additives because the chemical makeups of the two types of oils diff er and the fl uid may now be more aggressive," Groves says, referring to its eff ects on a hose's tube. Aggressiveness refers to a fl uid's chemical makeup, which is refl ected in the solubility of the polymer in the fl uid. is is one of the key variables engineers must consider when designing hoses for particular applications, Groves says. Some components within a blended fl uid may tend to be absorbed into the hose's rubber compound or extract oils out of the rubber, changing the hose's physical properties. Such changes in physical property can include swelling or contraction. Swelling restricts fl uid fl ow through the hose and so ens the rubber, which can lead to fi ttings leaking at elevated tempera- tures. Extracting oils makes the hose much stiff er at low temperatures, which causes cracking when the hose is stressed or fl exed. "Some end-users actually immerse hoses in fl uids they are trying to transfer, whether by accident or on purpose," Groves says. " is can degrade the properties of the hose cover." e hose cover, usually rubber, primarily acts as a protective barrier against external conditions, such as abrasions and ozone. In most cases, the cover layer should never be exposed to fl uids because it can cause the hose to either crack or lose its abrasion resistance. is could expose the hose's reinforce- ment layers to the environ- ment, weakening the hose. It's up to hose designers to determine the best materials for a particular hose based on the fl uid it will carry and its intended operating environ- ment. Beating the Heat e second most impor- tant variable to consider is the temperature of the fl uid being transmitted. is is especially true with hoses carrying oil in high-temperature applications, says Greg Reardon, business development manager with Parker. If the oil temperature Hydraulic hoses must withstand extreme temperatures to minimize downtime and maintain productivity. Designing Hydraulic Hoses for Extreme Conditions e nylon-fi ber-braid cover of Parker's 293-10 Air Brake hose off ers abrasion resistance with operating temperatures ranging from -58°F to 302F° (-50°C to 150°C). Hose designers determine the best materials for particular hose covers based on the intended operating environment and fl uid it will carry.

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