Multi-layer Seated Triple Eccentric Butterfly Valve

Size: 2" - 48" (DN50 - DN1200)

Pressure: Class 150 - 600 (PN 10 - 100)

Standard: API 609, ASME B16.34, API 607 (fire-safe), ISO 15848

Body Materials: A216 WCB, A351 CF8M, A351 CF8, A182 F316

Seat: Multi-layer composite seat—stainless steel or Stellite base ring + flexible graphite sealing layer + optional elastomer cushion layer

Design: Triple eccentric geometry (three-plane shaft offset), cam-action disc rotation

Metal-seated triple eccentric valves handle high temperature beautifully. But at ambient? Microscopic gaps in metal-to-metal contact mean measurable leakage—not terrible, but not zero. Elastomer-seated valves seal bubble-tight at room temperature, every time. Until fire hits. Then the rubber burns away and nothing holds that line.

The multi-layer seat solves both in one component. A stainless steel or Stellite base ring provides structural backbone. On top sits a flexible graphite sealing layer that compresses against the disc edge—bubble-tight at normal temperatures. When fire conditions char the graphite at 800°F+, the metal base ring underneath still holds the disc and maintains seal integrity.

That's why petrochemical specs are shifting toward multi-layer seats. You don't choose between "tight at ambient" and "alive after a fire." This seat delivers both.

Three Offsets Protect the Graphite

Triple eccentric means three offset planes between the shaft centerline and the disc sealing surface. Combined, they produce cam-action rotation—the disc lifts off the seat immediately instead of scraping across it. Less scraping means less wear on the graphite layer. If you've ever replaced a soft seat that looked like it was dragged across sandpaper, you understand why cam-action matters for composite seats. The graphite is durable, but not indestructible. Triple eccentric geometry protects it across thousands of cycles.

Where Engineers Specify This

Refining crude units with temperature swings from 650°F process conditions to ambient during shutdowns. Chemical reactors running hot but isolated at room temperature for maintenance. Offshore platform fire-safe isolation valves that also must meet ISO 15848 emissions compliance. If your spec demands API 607 AND bubble-tight at ambient, this valve checks both boxes without a secondary isolation valve downstream.

Never over-torque flange bolts. The graphite layer compresses under load, but excessive bolt tension crushes it beyond recovery. Follow cross-pattern incremental torque. On 24"+ sizes, check seat compression after initial bolt-up—if air leaks past at ambient pressure test, one more torque pass before the graphite fully seats against the disc edge. Once compressed correctly, it holds.

A: Yes. The flexible graphite layer closes the microscopic gaps that pure metal-to-metal seats leave at ambient. Bubble-tight is achievable and repeatable.

A: The graphite chars. The metal base ring maintains seal contact against the disc. The valve passes fire-safe testing because the metal ring provides the structural sealing surface after the graphite is consumed.

A: Yes. Remove the disc, extract the old seat ring, install the new one, reassemble. On 24"+, plan for two technicians and a clean surface—no debris between the graphite and disc edge during reassembly.

A: Pure metal seats pass fire-safe tests but often allow measurable leakage at ambient. If your spec requires both fire-safe and tight shutoff at normal conditions, pure metal may not satisfy the ambient leakage requirement.