As the automotive industry continues to keep pace with new emissions regulations, the requirements of exhaust system joints become increasingly demanding. These joints must not only prevent the release of untreated exhaust gas, they must also combat ingestion of oxygen into the exhaust system—which can have adverse effects on the closed-loop emission control system.

To meet these stringent demands, Metex engineers have developed a system approach to joint design, and coupled that with advances in seal and gasket materials, geometry, and construction.

A thin metal jacket fully encapsulates a knitted wire mesh core. This all-metal construction eliminates filler material burn-out and provides far greater resiliency over traditional automotive flange gaskets—even at elevated temperatures. In addition, all component materials can be custom-tailored to achieve further gains in resiliency. The gasket is designed to fit into a groove in the flange, with the groove depth sized to limit ring compression, allowing the gasket to operate in a set portion of the compression/recovery curve.

• Designed for installation between two geometrically identical flanges welded to adjacent system components.
• The slight oval shape of the gasket locks firmly into the flange groove or around the pipe’s OD during assembly.
• The seal is constructed of a stainless steel foil ring with a round, rectangular, or oval cross-section formed around a resilient knitted wire mesh core.
• This durable seal has unique spring-back properties and, due to its all-metal design, is ideal for high-temperature and high-corrosion environments.
• Available with a sheet-metal carrier which fits over the studs that hold the gasket in place in order to seal the joints created when two flat flanges are rigidly bolted to one another. The carrier portion of this gasket is typically 0.2 mm thick and usually matches the shape of their companion flanges.

Metex advances in core material design and construction have led to an improved version of the metal foil ring gasket typically utilized in exhaust system joints. The following tables compare the Metex static flange solution with hollow metal ring and metal ring/graphite core types. Two bolt static flange joints were rigidly fixed 40 mm from the centerline of the joint on the inlet pipe side. A hydraulic actuator was attached to the outlet pipe side of the joint, 115 mm away from the centerline.Test samples were subjected to the following block cycle program: ±335 N at 10 Hz for 50,000 cycles; ±225 N at 20 Hz for 500,000 cycles; and ±180 N at 30 Hz for 1,500,000 cycles. A natural gas burner was used to force hot gas through the exhaust joint.The control temperature was measured by a thermocouple clamped to the pipe 25 mm upstream of the inlet flange.The total test time was approximately 22 hours.

Component		Before Test		After Test
Hollow Metal Ring		<0.1, <0.1, <0.1		0.38, 0.26, 0.31
Metal Ring, Graphite Core		<0.1, <0.1, <0.1		<0.1, <0.1, <0.1
Metal Ring, Metex Mesh Core		<0.1, <0.1, <0.1		<0.1, <0.1, <0.1

Component		Before Test		After Test
Hollow Metal Ring		<0.1, <0.1, <0.1		1.0, 1.2, 1.5
Metal Ring, Graphite Core		<0.1, <0.1, <0.1		<0.91, <0.75, <0.52
Metal Ring, Metex Mesh Core		<0.1, <0.1, <0.1		<0.1, <0.1, <0.1

• Resilient—maintains seal between flanges for leak-free performance
• High Temperature— core maintains resiliency at extreme operating temperatures
• Durable—all stainless steel construction fights corrosion
• Reusable
• Simplified Installation— slight oval shape of gasket locks firmly into flange groove or around pipe OD during assembly. Sheet metal carrier fits over studs, holding gasket in place.