FLUID POWER HANDBOOK
WWW.HOSEASSEMBLYTIPS.COM
HYDRAULIC
HOSE
HYDRAULIC
hose is a common and important element in countless industrial and mobile machines. It serves as the plumbing that routes hydraulic fluid between tanks, pumps, valves, cylinders and other fluid-power components. Plus, hose is generally straightforward to route and install, and it absorbs vibration and dampens noise. Hose assemblies — hose with couplings attached to the ends — are relatively simple to make. And if specified properly and not overly abused, hose can work trouble-free for hundreds of thousands of pressure cycles. Hydraulic hoses often consist of an inner tube, one or more layers of reinforcement, and an outer cover. Each constituent should be selected with the intended application in mind. Typical operating and performance parameters include the size, temperature, fluid type, pressure-holding capacity and environment, to name a few. Reinforced hose is constructed with some structural element — styles include spiral wire, textile braid, wire braid, wire helix and other designs in many plies or layered configurations. The inner tube contains the fluid and keeps it from leaking to the outside. The cover protects the reinforcement layer. Other construction options for hydraulic hose include coiled, corrugated or convoluted. Coiled hose is designed for flexibility and elasticity. This feature often makes it expandable and easy to store. Corrugated hose contains corrugations, pleats or spiral convolutions to increase flexibility and capacity for compression and elongation. Multi-element hydraulic hoses are constructed of more than one hose formed or adhered together in a flat, ribbon or bundled configuration. Additional features to consider include whether the hose requires integral end connections, anti-static, lay flat, crush-proof and flame-resistance characteristics. In addition, material considerations include the type of fluid being conveyed and its concentration, as well as substances that may attack the hose cover. Hose selection must ensure compatibility if it is to convey special oils or chemicals. The same holds for hose exposed to harsh environments. Substances such as UV light, ozone, saltwater, chemicals and pollutants can cause degradation and premature failure. For in-depth fluid compatibility data, consult the manufacturer.
IMAGE COURTESY OF KURIYAMA
While hydraulic hose is usually constructed of multiple materials, the most commonly used primary materials include elastomers, fluoropolymers and silicone, thermoplastics, metal, and composite or laminated structures. Elastomeric or rubber hydraulic hose are often selected for their flexibility. Fluoropolymer hose offer good flex life, superior chemical and corrosion resistance and can handle high temperatures. Thermoplastic hydraulic hose offers tight minimum bend radii and excellent kink resistance. Metal hoses can handle high temperature flow materials and often can handle higher pressures. They can be either stiff or flexible. Flexible hoses are easier to route and install, compared with rigid tubing and pipe. They lessen vibration and noise, dampen pressure surges and permit movement between parts. In addition, increasing demands for higher productivity, efficiency and environmental compatibility are forcing hose manufacturers to improve product integrity — hoses now withstand higher pressures, extreme heat and cold and accommodate a range of fluids including today’s “green” variants. Most hoses are manufactured to SAE J517, European Norm (EN) or ISO Standards. These standards predominate in the Americas, Europe and Australia, and are also used throughout Asia.
IMA
28
FLUID POWER WORLD
7 • 2020
www.fluidpowerworld.com
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