The
triple eccentric butterfly valve, also called
triple offset butterfly valve, has a sealing system similar to the stop valve. The system consists of a fixed valve seat and a rotatable sealing surface, both of which have the same conic section. The
triple offset butterfly valve is closed through rotary motion (instead of axial motion) and the cone whose top is inclined relative to the axis of the pipeline, which makes that butterfly valve a "stop valve with angular travel".
Contact is only made at the final point of closure with a right angle acting as a mechanical stop (like the design of the globe valve), which is the reason why the
triple offset valve can realize frictionless closing. However, unlike globe valves, triple offset valves can be completely closed in both directions, realized by means of its three offsets:
1. The shaft is positioned behind the sealing surface, so that the valve obtains a complete continuous sealing surface.
2. The shaft is arranged on one side of the pipeline/valve centerline to allow the sealing ring to disengage from the valve seat during the opening stroke, effectively reducing torque.
3. The centerline of the seat and sealing ring cone is inclined relative to the pipeline/valve centerline, which completely eliminates friction between the sealing ring and the seat.
During the opening and closing of the triple offset butterfly valve, the contact between the valve seat and the sealing ring is completely eliminated, effectively prolonging the overall service life of the sealing element and the valve. This is combined with the characteristics of the angular travel of the valve, so that the operating torque of the valve is lower and more stable, and the valve is easier to operate. At the same time, the valve can be adjusted at a smaller angle. That feature makes the triple eccentric butterfly valve an ideal valve for various applications requiring emergency shutoff, rapid release or high frequency operation.
As the triple eccentric butterfly valve is an angular travel valve, the sealing element rotates around the axis, which can save the installation space on site and improve the operation performance significantly. In addition, the rotary motion of the angular travel also reduces the adverse effect on the packing, and avoids packing abrasion and external leakage when the stem of the straight strip valve moves up and down. Triple eccentric butterfly valves can be operated manually, electrically, pneumatically and hydraulically. They can be used as cut-off valves or regulating valves.
