Product Overview

The Laux Valve double offset flange butterfly valve is a high-performance butterfly valve designed for applications that exceed the capabilities of standard concentric (rubber-seated) butterfly valves. The double offset (double eccentric) disc design shifts the disc away from the seat during opening, eliminating seat rubbing and extending service life — making it the ideal choice for higher temperatures, higher pressures, and more demanding media.

Classified as API 609 Category B, this valve features flanged connections on both ends (ASME B16.5 Class 150-600), a PTFE or reinforced polymer seat with stainless steel seat retainer, and a ductile iron or carbon steel body. Suitable for bubble-tight shut-off in steam, chemical, thermal oil, and high-temperature water service up to 260°C.

Key Features

• Double Offset (Double Eccentric) Disc Design – The disc rotates off-center in two planes. The first offset moves the disc behind the seat centerline; the second offset shifts the stem axis away from the pipe centerline. This compound motion lifts the disc completely free of the seat within the first 10 degrees of opening, eliminating seat rubbing (cam effect) and reducing wear to virtually zero during cycling.
• PTFE/Reinforced Polymer Seat – The seat is a replaceable PTFE (or reinforced polymer) ring held in place by a stainless steel retainer. PTFE provides near-universal chemical resistance, low friction (reducing operating torque), and a temperature range of -20°C to +200°C (260°C with PEEK).
• Bi-Directional Bubble-Tight Shut-Off – The double offset design and resilient polymer seat achieve zero leakage in both flow directions at full rated pressure, meeting API 598 seat leakage requirements.
• Integral Flange Body Design – Flanged connections on both body ends (short pattern or long pattern per API 609 / EN 558) provide rigid installation, dead-end capability, and simplified valve removal while piping remains in place.
• Extended Service Life – The non-rubbing cam action eliminates seat wear during cycling. In high-cycle applications (50-500 cycles/day), double offset valves last 3-5 times longer than concentric valves before seat replacement is needed.
• Replaceable Seat – The PTFE or polymer seat ring can be replaced in the field. No need to replace the entire valve.
• Fire-Safe Design Available – Optional fire-safe design per API 607 (double seat design with secondary metal seat), suitable for hydrocarbon service in refineries and petrochemical plants.
• Blowout-Proof Stem – One-piece stem with internal thrust bearing and external gland seals. Replaceable stem seals under pressure in most designs.
• ISO 5211 Mounting Pad – Rugged, heavy-section mounting pad for gear, pneumatic, or electric actuator mounting.
• 100% Factory Tested – Shell test at 1.5x rated pressure, seat test at 1.1x rated pressure per API 598.

Double Offset Design – How It Works

Offset 1 – Stem Behind Seat Centerline

The shaft axis is positioned behind the seat sealing plane (toward the downstream side). As the disc begins to open, this offset causes the disc to move away from the seat in the axial direction, breaking the seal with minimal friction.

Offset 2 – Stem Offset from Pipe Centerline

The shaft axis is offset from the pipe centerline (toward one side of the bore). As the disc rotates, this offset causes the disc to move away from the seat in the radial direction, creating clearance between the disc edge and the seat.

Combined Effect – Cam Action

The two offsets work together to create a compound cam motion: in the first 10 degrees of opening, the disc edges lift completely free of the seat before rotating into the flow stream. When closing, the disc re-enters the seat with a wedging action that compresses the polymer seat, achieving a bubble-tight seal. This zero-friction sealing mechanism is the defining advantage of the double offset design.

Concentric vs Double Offset – What to Choose

Technical Specifications

Common Applications

• Chemical Processing – Handling of acids, caustics, solvents, intermediates where the PTFE seat provides chemical resistance that elastomers cannot match.
• Steam Service – Saturated steam up to 200°C for process heating, sterilization, and tracing systems.
• Thermal Oil / Heat Transfer Systems – High-temperature thermal oil systems in chemical plants, plastic/rubber processing, and food processing.
• HVAC High-Temperature Hot Water – District heating, boiler isolation, and high-temperature hot water systems (120-180°C).
• Oil & Gas / Refinery – Fire-safe version (API 607) for hydrocarbon service, fuel oil, and light hydrocarbon products.
• Power Generation – Turbine cooling water, condensate systems, auxiliary steam, and process water in thermal and nuclear power plants.
• Pulp & Paper – Black liquor, green liquor, and high-temperature process streams.

Available Seat Materials

Frequently Asked Questions

What is the difference between single offset, double offset, and triple offset butterfly valves?

Single offset (concentric): No offset – disc rotates on centerline. Seat rubbing throughout rotation. Suitable for low temp, low pressure, general service. API 609 Category A.

Double offset: Two offsets – stem behind seat plane + stem offset from pipe centerline. Disc lifts free of seat during opening via cam action. Zero seat wear. API 609 Category B. This product.

Triple offset: Three offsets – same as double plus a conical seat angle. Disc contacts seat only at the final point of closure. Zero friction throughout full stroke. Metal-to-metal bubble-tight seal at extreme temperatures and pressures. API 609 Category C.

What temperature can a double offset butterfly valve handle?

With PTFE seat: up to 200°C (392°F). With R-PTFE (glass-filled): up to 230°C (446°F). With PEEK seat: up to 260°C (500°F). For applications above 260°C, a metal-seated triple offset (Category C) valve is required.

Is this valve suitable for steam service?

Yes. With PEEK or R-PTFE seat, the double offset butterfly valve is suitable for saturated steam up to 200°C. For superheated steam or higher temperatures, a triple offset metal-seated valve is recommended.

Can the seat be replaced in the field?

Yes. The PTFE/polymer seat is held by a stainless steel seat retainer. The retainer can be unbolted, the old seat removed, and a new seat installed without removing the valve from the pipeline. This is a significant maintenance advantage over bonded-seat designs.

What is the face-to-face standard for this valve?

Standard face-to-face is API 609 Long Pattern / EN 558 Series 14. Short pattern (API 609 Short / EN 558 Series 20) is available on request for retrofit applications.

Is fire-safe design available?

Yes. Our double offset valve can be supplied with API 607 fire-safe certification. The fire-safe design incorporates a secondary metal seat that provides a seal after the primary PTFE seat is destroyed by fire, meeting the requirements of API 607 / ISO 10497 for hydrocarbon service.

Ordering Information

For pricing, dimensional drawings, actuator sizing, or engineering assistance:

Email: james@lauxvalve.com | Tel: +86 18920833829 | Website: lauxvalve.com

Butterfly Valve Manufacturing Process
From Technical Confirmation to Final Delivery



Standardized Quality Control Process

From raw material inspection to final delivery, every butterfly valve undergoes a comprehensive quality inspection to ensure reliable performance and compliance with international standards.

International Certifications

Manufactured to international quality standards and certified for global industrial and potable water applications.