A Double Eccentric High Performance Butterfly Valve (also called a Double Offset Butterfly Valve or High Performance Butterfly Valve)

is a quarter-turn valve designed for higher pressure, higher temperature, and more demanding industrial applications than standard resilient-seated butterfly valves.

What Does "Double Eccentric" Mean?

"Double eccentric" refers to the two offsets (eccentricities) in the valve's shaft design:

1. First Offset
   • The shaft is positioned behind the centerline of the sealing surface.
   • This allows the disc to move away from the seat quickly during opening.
2. Second Offset
   • The shaft is offset from the centerline of the pipeline.
   • This creates a cam-like rotation, reducing friction between the disc and seat.

Because of these two offsets, the disc only contacts the seat during the final degrees of closing, greatly reducing wear.

Main Features

• ✔ Low operating torque
• ✔ Minimal seat wear
• ✔ Bubble-tight shutoff
• ✔ Long service life
• ✔ Suitable for high pressure and high temperature
• ✔ Easy maintenance
• ✔ Fire-safe designs available
• ✔ Bidirectional sealing (depending on seat design)

Construction

A typical double eccentric high performance butterfly valve includes:

• Body: Wafer, Lug, or Flanged type
• Disc: Stainless steel, Duplex, Bronze (C95400), etc.
• Stem: Stainless steel
• Seat:
  • PTFE
  • RPTFE
  • PEEK
  • Metal seat (for higher temperatures)
• Bearings and bushings
• Packing and gland

Working Principle

1. Opening
   • The disc immediately lifts away from the seat due to the double-offset design.
   • Friction is very low during rotation.
2. Fully Open
   • The disc is parallel to the flow.
   • Pressure loss is minimal.
3. Closing
   • The disc rotates toward the seat.
   • Sealing contact occurs only at the end of travel, reducing seat abrasion.

Advantages Compared with Resilient-Seated Butterfly Valves

Common Applications

Double eccentric high performance butterfly valves are widely used in:

• Oil & Gas
• Petrochemical plants
• Chemical processing
• Marine and shipbuilding
• LNG terminals
• HVAC systems
• Power generation
• Water treatment
• Desalination plants
• Pulp & Paper
• Food and Beverage (with suitable materials)

Typical Standards

• Design: API 609, EN 593
• Face-to-Face: API 609, ISO 5752, EN 558
• Flange: ANSI B16.5, EN 1092-1
• Pressure Test: API 598, ISO 5208
• Fire Safe: API 607
• Fugitive Emissions: ISO 15848

Typical Materials

Why Choose a Double Eccentric High Performance Butterfly Valve?

Compared with conventional butterfly valves, a double eccentric high performance butterfly valve offers:

• Longer sealing life due to reduced seat friction
• Better sealing performance under high pressure and temperature
• Lower operating torque, making automation easier
• Greater reliability in demanding industrial services
• Lower maintenance costs over the valve's lifetime

For industries such as marine, chemical processing, oil & gas, and power generation, double eccentric high performance butterfly valves are often the

preferred choice because they combine the compact size and low weight of butterfly valves with performance approaching that of more expensive valve types.