Hypalon® Leads in Power Steering Hoses

Power steering continues to increase in popularity, particularly for smaller cars. Automobile manufacturers predict as much as 25 percent growth in demand for the power steering option in A and B class cars over the next five years. At the same time, power steering fluid temperatures have been rising along with ambient under-bonnet conditions. However, traditional hoses with nitrile rubber tube and chloroprene rubber cover rated for periods up to 100°C become embrittled at the 135°C temperature ceilings imposed by new specifications.

To comply, high pressure power steering hose is required to handle fluid at peak temperatures as high as 150°C and pulsed pressures from 0 to 115 bar at 30 to 40 cycles per minute for up to 500,000 cycles without leakage. These auto-industry specifications also demand that such hoses remain leak-free following a 20 cycle cold start test run at -40°C.

Hypalon® is the Most Widely Specified

Power steering hoses with a tube and cover of DuPont Performance Elastomers' Hypalon® chlorosulfonated polyethylene (CSM) fulfill these conditions easily while retaining the required seal force at the end fittings. Hypalon® also offers OEMs the most favorable performance-to-price ratio of all available polymers specified for power steering hoses.

As a result, Hypalon® has been the polymer most often and most widely specified in the power steering hose market for over 10 years. The CSM is used in the construction of more than 80 percent of high pressure output hoses, and over 60 percent of low pressure return hoses fitted to new cars equipped with power steering.

Unique Qualities for this Application

As the proven polymer for tubes and covers, supported by a ready supply base, Hypalon® is now fulfilling growing demand from hose fabricators for hose components in small car power steering systems. In turn, all major hose fabricators, notably ContiTech, Dayco, Gates, Hutchinson and Roulunds use Hypalon® as a power steering hose material of choice. For example, Hutchinson, the leading French automotive hose manufacturer, supplies 9.7mm inner and 19.5mm outer diameter power steering hose based on Hypalon®.

To meet and exceed customer specifications, the hose has been subjected to Dextron and Pentosin hydraulic oils at temperatures up to 135°C and pulsed pressure at 105 bar for more than 500,000 cycles. The hose is rated for use at "Class 135°C," meeting industry demands for tear and blow-out resistance at 500 bar. This provides a high built-in safety margin because normal service pressures reach only 100/120 bar. "Hypalon® offers unique qualities for this application in this temperature class," comments Mr. Yves Ricordeau, Fluid Carrying Systems project manager at Hutchinson's Fluid Transfer Systems plant in Montargis, France.