The disc rotates around the center axis allowing for a potential 360º rotation. Sealing is achieved by the Disc deforming the soft seal resulting in full friction through the full operating cycle.
To allow displacement of the seat the shaft is offset from the centerline of the disc seat and body seal (offset one), and the centerline 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.
The third offset is the geometry design of the sealing components, not the shaft position. The sealing components are each machined into an offset conical profile resulting in a right-angled cone (see Fig 1).
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.
With deformation and friction being such a prevalent issue in the sealing capabilities of concentric and double offset butterfly valves, the life expectancy is substantially minimized after its first operation and can commonly be expected to pass media after time.
Through the introduction of the revolutionary third offset, a solution has been engineered to eliminate deformation and friction leaving the advantages of ‘Triple Offset’ clear to be seen.