S&W triple offset metal seat butterfly valves provide a bi-directional and bubble-tight shutoff which is attributed to the geometry of triple offset seat. The valve stem is offset by seat (1st offset) and the valve seat surface center line is offs-set against the center line of pipe (2nd offset) and the conical axis is offset by valve center line (3rd offset: inclined cone). The 3rd offset completely eliminates rubbing.The seat surfaces of body and seal ring in triple offset valve contact with the inclined "cone-in- cone" and this design requires excellent sealing and seat part durability by slight wedging effect.In addition, the angle of contact between body and seal ring has a good sealing performance by low torque because the angle travels the initial torque from actuator to seat parts without any loss by jamming. This valve is characteristic of concentric, offset and double offset construction with remarkable sealing performance and seat part durability, and moreover it hardly ever needs repair.