Lug-Type Metal-Seated Butterfly Valve

The Lug-Type Metal-Seated Butterfly Valve provides bi-directional zero-leakage shutoff and fluid control under elevated temperatures, high pressures, and severe operating environments. Threaded lug ears designed to match standard line flanges facilitate downstream piping removal for dead-end system maintenance while maintaining line pressure upstream.

Bi-Directional Zero Leakage: Triple-offset geometric arrangement eliminates sliding friction between seat contacts to comply with API 598 and ISO 5208 Rate A seal integrity standards.

Dead-End Capability: Threaded full-lug design enables localized line disassembly under full working pressure without media discharge.

Fire-Safe All-Metal Construction: Metal-to-metal sealing ring system maintains structural integrity during sudden thermal expansion and direct fire exposure.

Blow-Out Proof Shaft: Internally retained stem construction prevents shaft displacement under transient pressure surges.

Direct Actuator Mounting: ISO 5211 top flange interface permits standard mounting of manual, pneumatic, and electric actuators without intermediate brackets.

Triple-Eccentric Kinematics:
• Offset 1: Shaft axis positioned behind the seat contact plane.
• Offset 2: Shaft axis offset laterally from the pipe centerline.
• Offset 3: Conical seat profile inclined from the valve body centerline.

Non-Rubbing Seal Contact: The disc seal contacts the body seat exclusively at the final point of closing, preventing surface mechanical wear.

Resilient Metal Disc Ring: Alternating layers of stainless steel and flexible graphite provide resilient compression during continuous thermal cycling.

Hardfaced Body Seat: Cobalt-base alloy Stellite No. 6 welded directly to the body seat protects against fluid erosion, cavitation, and particulate abrasion.

Movement relies on a triple-offset rotational mechanism. Upon opening, the disc rotates away from the seat instantly without mechanical drag. During closing, the conical seat profile guides the seal ring into a wedge position across the entire seating perimeter. Operational stem torque compresses the laminated seal ring against the hardfaced body seat, establishing a mechanical seal that remains tight against high differential pressure in both flow directions.

Full Lug Body: Threaded bolt holes accommodate standard flange studs, enabling independent securement on either side of the valve body.

Dead-End Service: Retains rated working pressure from either direction when downstream pipe sections are unbolted for maintenance.

Flange Alignment: Precision-machined lug patterns maintain shaft alignment during bolt installation to prevent disc interference.

Hand Lever: Suitable for sizes DN50 to DN150, featuring a 10-position indicator plate and locking mechanism.

Worm Gearbox: Enclosed self-locking gear units for sizes DN200 and above, featuring mechanical travel stops and position indicators.

Pneumatic Actuator: Double-acting or spring-return scotch-yoke and rack-and-pinion actuators fitted directly via ISO 5211 interfaces.

Electric Actuator: Quarter-turn modulating or ON/OFF electric drives suitable for control system integration.

Refining & Petrochemicals: High-temperature fluid isolation, catalytic cracking units, steam header distribution lines.

Chemical Processing: Acid and alkali fluid transfer, hot solvent lines, synthetic monomer handling.

Power Generation: Main steam isolation, boiler feed water control, cooling water circulation lines.

District Energy: Pressurized hot water transmission, district heating distribution grids.

Cryogenic Processing: Low-temperature liquefied natural gas handling lines.
 

Determine Process Conditions: Identify operating temperature, fluid pressure, flow velocity, and chemical composition.

Select Pressure Class: Match working system pressure to ASME Class 150, 300, or 600 ratings.

Choose Body & Trim Metallurgy:
• Carbon steel for saturated steam, water, and non-corrosive hydrocarbons up to 425°C.
• Stainless steel for corrosive chemicals, acids, and low-temperature fluids down to -196°C.
• Duplex stainless steel for high-chloride, seawater, and concentrated organic acids.

Verify Sealing Criteria: Select required leakage rating per API 598 or ISO 5208 Rate A standards.

Calculate Actuator Torque: Calculate required operating torque based on differential pressure across the valve disc.

Shell Pressure Test: Hydrostatic testing performed at 1.5 times the nominal pressure rating per API 598.

High-Pressure Seat Test: Hydrostatic seat test performed at 1.1 times the design rating to verify bi-directional sealing.

Low-Pressure Gas Test: Air test performed at 0.6 MPa to verify zero-bubble shutoff.

Fire Test Verification: Thermal exposure testing according to API 607 standards.

Fugitive Emission Testing: Helium leakage measurement on stem packing seals per ISO 15848-1.

Material Traceability: Full chemical composition analysis and physical test reports provided per EN 10204 3.1.

Extended Shaft Extensions: Custom stem lengths for insulated piping configurations or sub-zero cryogenic service.

Hardfacing Variations: Tungsten carbide or specific cobalt alloys applied to trim components for slurry applications.

Custom Flange Drilling: Non-standard flange bolt pattern machining to match existing plant connections.

Protective Coatings: Multi-layer epoxy systems, high-temperature silicone paint, or specialized fluoropolymer finishes.

Actuator Assembly & Testing: Factory mounting, calibration, and pressure testing of user-specified actuators.