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Description / Abstract:
This specification defines fibrous glass materials used as
acoustic-absorbing and thermal insulation media primarily used in
automotive exhaust applications. The specification includes
properties, both chemical and physical, required for moderate-,
intermediate-, and high-temperature applications in exhaust
systems.
Material Description. This specification
describes three (3) types of fibrous glass materials typically used
in silencer components of exhaust systems. The materials are
classified as Type 1 for moderate-temperature applications, Type 2
for high-temperature applications and Type 3 for
intermediate-temperature applications. These materials are utilized
in environments where they will be exposed to hot exhaust gases,
but the primary flow of the exhaust gasses is not normally through
the mass of glass fibers. The fibers provide a mechanism for the
dissipation of acoustic energy as well as providing thermal
insulation around the path of the exhaust gases.
Material Identification
• Type 1, or moderate-temperature applications,
are those applications where the fibrous material itself will
achieve continuous operating temperatures of 730 °C or intermittent
temperatures as high as 825 °C for up to 2 h. Thus, this material
should be suitable for virtually all applications toward the rear
of the exhaust system and many applications near the catalytic
converter, either alone or in combination with a high-temperature
material adjacent to the perforated tube.
•Type 2, or high temperature
applications, are those applications where the fibrous material
itself will achieve continuous operating temperatures of 825 °C or
intermittent temperatures as high as 900 °C for up to 2 h. This
material is suitable for virtually all applications toward the rear
of the exhaust system and near the catalytic converter.
• Type 3, or intermediate-temperature
applications, are those applications where the fibrous material
itself will achieve continuous operating temperatures of 810 °C or
intermittent temperatures as high as 890 °C for up to 2 h. This
material is suitable for virtually all applications toward the rear
of the exhaust system and most applications near the catalytic
converter.
Note: For many silencer applications in
continuous operation, the glass temperature adjacent to the
perforation tube is ≥ 50 °C below the exhaust gas temperature. For
cyclic operations of a few minutes duration, this temperature
differential is larger.
Typical Applications. These materials are
typically used in exhaust systems where thermal insulation and/or
acoustic attenuation are required. The choice of materials is
primarily determined by the maximum operating temperature that the
material will achieve.