Main Product Features

Sierra Engineering & Manufacturing delivers high-performance double eccentric butterfly valves engineered for durability, efficiency, and long service life in demanding waterworks applications.

Advanced Double Eccentric Design

The valve incorporates a double eccentric (double offset) disc design, where the disc shaft is intentionally positioned at two offsets from the centerline of the valve seat and the valve body.

The first offset places the shaft slightly behind the centerline of the sealing surface, while the second offset shifts the shaft away from the pipe centerline. This configuration allows the disc to move away from the seat immediately as the valve begins to open.

During the first few degrees of opening, the disc separates quickly from the seat instead of sliding across it. As a result:

• Friction between the rubber seal and the valve seat is significantly minimized.
• Wear on sealing surfaces is reduced.
• Torque required for operation becomes lower.
• The risk of seal damage during operation is minimized.

Because the sealing surfaces experience minimal rubbing contact, the service life of the rubber seal is considerably extended, making the valve suitable for high-cycle industrial applications such as water distribution networks, wastewater systems, and process pipelines.

Welded Stainless Steel Seat
The stainless steel seat is welded and precision-machined directly inside the valve body, ensuring superior alignment and structural integrity. This design provides:

• Reduced coefficient of friction during operation

• High resistance to corrosion

• Enhanced resistance to abrasion and mechanical wear

Pressure-Activated Rubber Sealing System
The one-piece molded rubber seal, is mechanically secured to a robust retainer mechanism. The pressure-activated sealing system ensures reliable performance under varying operating conditions while maintaining long-term sealing integrity.

Bi-Directional Tight Shut-Off
The valve ensures tight closure in both flow directions at rated pressure levels, making it ideal for isolation applications in waterworks, pipelines, and infrastructure projects.

This bidirectional sealing capability ensures that:

• The valve can be installed in pipelines without concern for flow direction.
• Leakage is minimized in both upstream and downstream pressure conditions.
• Operational reliability is maintained in systems where pressure reversals may occur.

This feature makes the valve suitable for applications such as pumping stations, water transmission pipelines, and industrial process lines.

Dry Shaft Mechanism 

The dry shaft mechanism is a design arrangement in which the valve shaft is completely isolated from the process fluid flowing through the valve. The shaft does not pass directly through the wetted flow area of the valve disc or body. Instead, it is protected by bushings, seals, and internal barriers that prevent the process media from reaching the shaft chamber. This design protects the valve body and the disc hub area from internal leakage paths that could occur along the shaft penetration. By preventing fluid from entering the shaft cavity, the design eliminates the possibility of fluid accumulation inside the valve body around the shaft support areas.

Hydrodynamic Disc Design

A hydrodynamic disc design means the butterfly valve does not “fight the water” ,instead, it lets the water flow smoothly, saving
energy (energy efficiency) and protecting the system.
The streamlined disc design minimizes flow resistance, reduces pressure drop, and improves overall system efficiency.

Compact and Space-Saving Construction
The compact valve profile requires minimal installation space, making it suitable for confined pipeline systems and retrofit projects.

In-Line Maintainability
The flexible design allows maintenance and replacement of the disc seal without removing the valve from the pipeline, reducing downtime and operational costs.

T-Shaped Disc Seal

The vertical part of the “T” is divided into two sides: One side fits securely into a machined groove on the valve disc. The other side is locked into the retainer, ensuring firm positioning. The horizontal part of the “T” extends outward and presses tightly against the valve seat, providing reliable sealing.

Worm Gearbox

SIERRA GB-Series worm gear actuators are quarter-turn gearboxes mounted on the valve shaft to provide smooth, controlled opening
and closing of the butterfly valve. Worm gearboxes are available in different versions and sizes to cover different BFV dimensions.

Sierra’s PREMIUM double eccentric butterfly valves combine precision engineering, corrosion resistance, and reliable sealing performance to meet the highest industrial standards.