1994-03-01

An Alternative Tubing and Heat Shield Material for Under Hood Application in the Automotive Industry 940313

The future emission requirements for Transitional Low Emission Vehicle (TELV) and Ultra Low Emission Vehicle (ULEV) will force automobile manufacturers to use extraordinary design measures. Compliance is likely to increase the need for heat shielding.
Two system types have been available for some time as design options. These are emission reduction systems such as EGR (Exhaust Gas Recirculation) and A. I. R. (Air Injection Reactor). Both systems create temperature difficulties because of hot exhaust gases. Shielding is needed to insulate other under hood components from high temperature and to retain heat within the emission system.
Heat shielding and air conducting tubes have to be flexible, withstand vibration, resist corrosion from the exhaust gas and endure many cycles of heating over the life of the vehicle. Traditionally stainless steel has been the material of choice. With the increased amount of shielding required for systems in the future a more economical material will provide large cost savings.
A corrugated flexible tube that is a sandwich of fiberglass and stainless steel layers has been developed and tested. The tube is made using an economical, proprietary manufacturing process. Due to flexibility the tubes are formed very easily reducing packaging and assembly effort compared to plain stainless steel.
The durability, heat resistance, shielding capabilities and economics of this new material is discussed. Comparison is made with stainless steel and other materials currently used.

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