Butterfly Valves are essential in applications where tight shut off is required. In some applications, tight shut off cannot be achieved using traditional butterfly valves.
In others, harsh chemicals or media with small particles may make shutoff difficult. In such applications, Triple Offset Technology offers superior benefits.
A Triple Offset Butterfly Valve has 3 separate offsets. Two of the offsets apply to the location of the shaft in respect to the centerline of the bore and the centerline of the disc/seat sealing surfaces. The third offset is the design in the axis of the seat cone angle.
Zero Offset (‘Concentric Valve’): The disc rotates around the center axis allowing for a potential 360° rotation. Sealing is achieved by the Disc deforming the soft seal resulting in full friction through the full operating cycle. If automated, this style results in higher actuation costs as high friction forces require more torque found in a larger actuator.
Double Offset (‘High Performance’): To allow displacement of the seat the shaft is offset from the center line of the disc seat and body seal (offset one), and the center line of the bore (offset two). This creates a cam action during operation to lift the seat out of the seal resulting in friction during the first 10 degrees of opening and final 10 degrees of closing.
Triple Offset: In addition to the first and second offsets mentioned above, the third offset is the geometry design of the sealing components. The sealing components are each machined into an offset conical profile resulting in a right-angled cone. This ensures friction free stroking throughout its operating cycle. Contact is only made at the final point of closure with the 90° angle acting as a mechanical stop; resulting in no over-travel of the disc seat.
· Cam-action’ and ‘right angled’ conical sealing design ensures that the metal sealing components are never in contact until its final degree of closing – this results in repeatable sealing and a vastly extended valve life. This also reduces the cost of automation as the valve’s lower rotational torque
· Metal-to-Metal sealing ensures ANSI Class VI shut-off, resulting in zero-leakage performance.
· Suitability to harsh media – construction of the valve features no elastomers or materials typically affected by corrosion.
· Geometric design of sealing components provides friction-free stroking throughout the valve. This extends the valve life and allows a lower torque-actuator to be fitted.
· There are no cavities between sealing components, resulting in no clogging, low maintenance and extended valve life.