Hydraulic Hoses in Extreme Heat

At Power Product Technologies, we understand that your hydraulic hose assemblies are subjected to a variety of challenging environments. One environment that can be detrimental to your hose life is extreme heat. Thermal exposure beyond the maximum rated temperatures rapidly degrades the elastomers in the hose, so choosing the proper hose assembly is critical.

How does extreme heat affect hydraulic hose?

Extreme heat can affect plastics in two ways, both of which are bad. Properties can be degraded by molecular chain growth and crosslinking, which usually decreases elongation and increases tensile strength—resulting in a hard, brittle material. Or high heat causes chain rupture, which results in a weaker, more-pliable plastic or even a resinous mass. When exposed to elevated temperatures, some plastics will even show an initial hardening followed by softening. All aging phenomena are irreversible processes.

Nearly all plastics exhibit some degree of mechanical property degradation as temperatures increase. The same holds for hydraulic hose. Extremely high temperatures can affect a hose’s elastomeric and mechanical properties and cause problems like softening, discoloration, embrittlement or hardening. One visible indication of degradation is thermal-stress cracking, the crazing of some thermoplastic resins resulting from overexposure to elevated temperatures. The cover may show signs of being dried out and charred or even crack when flexed. The assembly may remain “frozen” in its installed shape after it’s removed from a machine.

Hot fluids beyond recommended temperature limits may have a similar, detrimental effect on the inner tube. (Failure to use hydraulic oil with the necessary high-temperature viscosity can also accelerate hose degradation.) And non-petroleum hydraulic fluids like water/oil emulsions and glycol solutions sometimes require lower temperature limits. Regardless, never exceed the recommended maximum operating temperature for a given fluid. If hose maximums for ambient and fluid temperatures differ, the lower limit takes precedence.

Some manufacturers say increasing external temperature by just 18° F (8° C) above maximum rated temperature can cut hose life in half. Actual service life at temperatures approaching the hose’s recommended limit depends on the application and fluid. But simultaneously operating at maximum temperature and maximum working pressure can greatly reduce hose life.
Read more at FluidPowerWorld.com...

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