In a double-offset or double eccentric butterfly valve, the stem is located behind the disc with an additional offset to one side (Figure 4). This double eccentricity of the stem enables the rotating disc to rub over the seat for only about one to three d
The fluorine-lined ball valve uses a ball with a circular through hole as a starting and closing member, and the ball rotates with the valve stem around the center line of the valve body to open and close the valve.
