FORMED RUBBER HOSES
For fluid transport and containment, hoses are often essential.
Whether extruded or formed, homogeneous or reinforced, rubber hoses play an integral part in countless products from every sector of industry. Choosing the right hose for a given application requires some knowledge of how hoses are made and what their strengths are. Here's a brief review of hose anatomy and a look at some common hose applications:
Most rubber hoses have three layers. As the innermost layer, the “tube” has two functions: to contain the fluid being conveyed, and to resist being broken down by that fluid. In many instances, the tube is formed when rubber is forced (extruded) through a profile (die) to make it a particular size.
If the fluid to be contained undergoes any sudden increases in pressure, the tube may need to be reinforced by fabric or wire. This “reinforcement” (also called the “carcass”) is the second (or middle) layer of most hoses. Reinforcement helps protect the tube from internal pressure and outside forces. Reinforcing fabric or wire is applied by braiding, knitting, spiraling, wrapping, or weaving.
The third (and outermost) layer is the “cover.” The cover further protects the tube from external damage and environmental deterioration (such as from ozone). The cover can be color-coded to aid identification or improve the look. Though both reinforcement and a cover are commonly used, “homogeneous” hoses with no added layers are available.
Because they are flexible and can absorb vibration, rubber hoses are suited for designs that move and shake. High-pressure hydraulic applications often use hoses to contain water-oil (and water-glycol) mixtures and low viscosity mineral oils.
Automotive air brake systems often include hoses with an oil- and grease-resistant tube made of nitrile (NBR), chloroprene (CR), or a blend of NBR and styrene butadiene (SBR). Reinforcement is typically a synthetic textile yarn with high tensile strength. The cover may be CR, SBR, or chlorosulfonated polyethylene (CSM).
Automotive fuel hoses generally feature oil-resistant tubes of NBR (sometimes compounded with polyvinyl chloride, PVC). As with air brake hoses, reinforcement is often textile yarn made of polyester, polyamide, or rayon. Some fuel hoses don't have a cover; when one is added, it is commonly made of oil-resistant CR or CSM. Because fuel lines can be immersed inside the fuel tank, it may be necessary that the cover be as fuel-resistant as the tube.
Radiator (coolant) hoses can be factory-molded (using mandrels) into curves to fit specific spaces. Ethylene propylene (EPDM) is the typical tube material because of its strong resistance to heat, hot water, and ethylene glycol, the most common antifreeze. In some cases, SBR or NBR may be used instead. Fiber or textile reinforcement may be applied, and the cover may be EPDM, SBR, or CR.
Other uses include liquid propane (L.P.) gas hose, Freon® charging hose, air hose, oxygen hose, acetylene hose, water hose, steam hose, washing machine hose, and gas pump hose.
Freon® is a registered trademark of DuPont.