Issue link: http://read.dmtmag.com/i/703077
I DA U N I V E R S A L J u l y -Au g u s t 2 0 1 6 37 exceeds the hose's threshold temperature, usually between -40°F and 257°F, the heat can bake the inner tube, causing it to harden and crack. is happens when running a system for too long without giving the oil a chance to cool, he says. " is is a common issue with heavy mobile machinery," Reardon notes. "In a perfect world, all mobile equipment would come with oil regulators and coolers to keep oil temper- atures in check. However, this is not always the case due to size or cost restraints. Without cooling, and with the vehicles running for eight to 16 hours at a stretch, the oil heats up and starts baking the hose." Some companies, including Parker, design hoses with inner tubes that handle transfer-fl uid temperatures of up to 302°F. But Reardon still cautions customers to closely monitor the temperature of any transfer fl uid during operation. Ambient heat is also of signifi cant concern, he adds. Hoses in the engine compart- ment of a vehicle, for example, see higher temperatures than those in open areas where there is some natural cooling and the heat has an avenue of escape. Because engine compartments are generally closed off , heat is prevented from escaping. e resulting high temperatures aff ect hoses from the outside in. In addition to oil tempera- ture and ambient heat, nearby operations can expose hoses to dangerously high tempera- tures. Anything from vats of molten metal to stray welding spatter can heat up unpro- tected hoses and increase the possibility of failure. For these situations, Parker and other companies have developed a variety of sleeves to cover and further protect hoses. Sleeve materials range from fabrics to fi re- resistant polymers to steel braid, and some also protect against injuries in the event a hose bursts. All Parker hoses and tubing exhibit their best physical properties at room temperature, 68°F (20°C). As elastomeric materials are exposed to higher tempera- tures, they so en and their physical properties, such as fl exibility, may change. Couplings attached to hoses are held in place in part by the rubber compounds' pliability. If a hose becomes brittle due to excessive operating temperatures, the coupling can break free. To avoid this, conscientious end-users institute preventive maintenance and planned replacements for at-risk components. "When selecting and constructing hoses for customers, we complete a thorough analysis of how the hoses will be used and under what conditions," Groves says. "We ensure all hoses are tested in a controlled, safe environ- ment. Hoses must perform to strict specifi cations, such as SAE or ISO industry standards, under operating conditions dictated by the product's planned operating environment before we deliver them to customers." Fighting the Cold Although temperatures above 257°F are a cause for concern, customers also experience issues with temperatures at the other extreme, -40°F and lower. When exposed to extremely cold temperatures, rubber hoses stiff en and cannot fl ex like they should, causing them to crack. is leads to potential hose failures. Two industries that rely on low-temperature hoses are land-based oil rigs and the logging industry. Hoses can be designed for specifi c operating temperature ranges, and there are versions that operate at temperatures as low as -70°F and with working pressures as high as 6,000 psi. Designing hoses for extreme cold is a matter of getting the Parker's GlobalCore 722TC (ToughCover) works at temperatures ranging from -40°F to 257°F (-40°C to 125°C). Several layers of precisely oriented wire reinforcement create a hydraulic balance, which keeps the hose from moving too much when under pressure. Hoses must be designed to meet strict requirements for each application, including bend radius, fl exibility, and life. Variables, including environment temperature, application pressure, and fl uid being transferred, can all aff ect the hose's ability to meet those requirements. Continued on page 38