The first offset is achieved by locating the shaft downstream of the centerline of the seat. This allows for a totally unobstructed 360 degree sealing surface.
▪ 2nd offset :
The second offset locates the shafts off-center of the vertical axis of the seat. The combination of these two offsets creates a cam effect as the disc swings into and out of the seat. The disc lifts quickly out of the seat in the first few degrees of travel and does not contact the seat again until it is nearly closed. There are no wear points between the seat and disc, while operating torques are reduced and seat life is extended.
The valve stem is offset behind the seat axis to allow complete sealing contact around the entire seat.
▪ 2nd offset :
The shaft centerline is offset from the pipe and valve which provides interference free opening and closing of the valve.
▪ 3rd offset :
The seat cone axis is offset from the shaft centerline to eliminate friction during closing and opening and to achieve uniform compressive sealing around the entire seat. With this geometry, seat seal interference is completely eliminated ensuring long sealing life. The result is torque seating, process pressure aided frictionless seal. The geometry allows the body seat to be used as the closed limit stop, aiding operator adjustment. The triple offset design is ideally suited to metal seated valves providing bubble-tight performance on high temperature, high pressure and fire safe application.
This offset disc design provides an uninterrupted 360 degree sealing surface. The sealing surface is not interrupted by the valve shaft and does not have any continuous contact points between the body sealing surface and the disc sealing surface. This results in a longer seat life.