Double Offset Butterfly Valves

The Double-Offset Butterfly Valve design has evolved through the desire to cope with more extreme process conditions than a low-pressure water system where a rubber-lined butterfly valve would be used.

Suitable applications include water systems, power plants, and HVAC (Heating, ventilation, and air conditioning) systems. Additionally, they are suitable for marine applications due to their corrosion and erosion resistance.

Double-Offset Butterfly Valve designs make use of two offsets of the shaft, one from the centerline of the seal, and one from the centerline of the pipeline bore. The combined effect of these offsets is to generate a cam action which; the cam action assists in pulling the disc out of the seat within a few degrees of the closed position. By pulling the disc out of the seat rather than pulling the disc through the seat, the life of the seat and valve may be extended significantly.

• Ability to be installed in horizontal or vertical lines
• Ability to be installed with the shaft in both horizontal and vertical orientations
• Rapid valve opening and closing
• Compact size making them well-suited for tight spaces
• Low torque operation
• Various seal options available to ensure the seals supplied are suitable for the particular valve application, including those requiring fire-safe designs

The Double-Offset Butterfly Valve delivers several advantages including a relatively smaller size and a lower torque operation than some other valves. This valve type is suitable for both manual and automated (actuated) applications. This range has been designed to deliver longevity and a through-life valve solution by reducing the maintenance and possible repair requirements when it is put into service. The Double-Offset Butterfly Valve range can be used across a range of pressures and temperatures whilst handling liquids, gases, steams, and other substances.

The double-offset range is available with the following body styles and configurations:

• BU01 – Wafer-Type, Raised Face and Flat Face
• BU02 –Lug-Type, Raised Face and Flat Face
• BU03 – Double-Flanged, Raised Face and Flat Face

The benefits of the BU01 Double-Offset Wafer-Type Butterfly Valve include:

• Small form factor (Wafer-Type) – Body is the most cost-effective and suitable for general applications
• Soft seat arrangement provides zero-leakage bi-directional sealing
• The secondary metal seat provides a fire-safe seal in the event of a fire, qualified to API 607/ISO 10497
• The double-offset design ensures cam action reduces seat wear prolonging seat life
• Standard mounting interfaces enable easy actuation

The benefits of the BU02 Double-Offset Lugged Style Butterfly Valve include:

• Lug-type body design provides a cost-effective solution for non-critical services
• Soft seat arrangement provides zero-leakage bi-directional sealing
• The secondary metal seat provides a fire-safe seal in the event of a fire, qualified to AP607/ISO 10497
• The double-offset design ensures cam action reduces seat wear prolonging seat life
• Standard mounting interfaces enable easy actuation

The benefits of the BU03 Double-Offset Double-Flanged Style Butterfly Valve include:

• Double Flange body provides a solution for critical applications requiring high-integrity
• Soft seat arrangement provides zero-leakage bi-directional sealing
• The secondary metal seat provides a fire-safe seal in the event of a fire, qualified to API607/ISO 10497
• The double-offset design ensures cam action reduces seat wear prolonging seat life
• Standard mounting interfaces enable easy actuation

The range supports diverse industries, including:

• Chemical industries and processing
• Energy and power generation
• LNG storage and transportation
• Marine
• Oil and Gas 
• Petrochemical 
• Pulp and paper
• Pharmaceutical
• Refining 
• Water industry and wastewater treatment

Supporting applications such as:

• Carbon capture and storage
• Chemical solvents
• Cooling water systems
• Desalination
• Hot gases
• Hydrocarbon and chemical isolation
• Isolation of reservoirs
• Thermal fluids
• Upstream applications

As a compact, low-maintenance valve the double-offset range is ideal for applications with:

• High-durability requirements
• Require a higher flow capacity
• Repeated cycling needs
• Limited space
• Robust and high durability

This range offers extensive design features that deliver various user benefits including:

Performance and Sealing Properties

High performance across a vast range of user applications

Laminated metal seat arrangements delivering zero leakage bi-directional sealing

Design

• Prolonged valve service longevity with the double-offset design reducing seat wear
• Compact design
• Anti-blowout design as standard – built-in safety mechanism, giving confidence in valve containment even in the event of failure

Certification and accreditation

Firesafe certified to API 607 / ISO 10497

Actuation

• Standard mounting interfaces enable easy actuation