Since the ball valve usually uses rubber, nylon and polytetrafluoroethylene as the material of the seat seal, its operating temperature is limited by the material of the seat seal. The cut-off effect of the ball valve is accomplished by pressing the metal ball against the plastic valve seat under the action of the medium (floating ball valve). Under the action of a certain contact pressure, the valve seat sealing ring undergoes elastic-plastic deformation in local areas.
The V-shaped opening ball valve belongs to the fixed ball valve and the single-seat sealed ball valve. The adjustment performance is the best among the ball valves, and other types of ball valves are basically not used for adjustment. The sealing principle is similar to the sealing valve seat after fixing the ball body of the ball valve, but the movable valve seat structure with the preloading force of the plate spring is adopted.
Fixed ball valves are mainly used in high-pressure and large-diameter ball valves. In addition, the transfer of support force and medium force from the valve seat seal to the valve stem, support sleeve or support plate will greatly reduce the torque required to operate the valve. With the correct selection of sealing elements, this form of ball valve also guarantees complete sealing in both directions.
There are two valve seat rings in the valve body of the floating ball valve, and a ball is clamped between them. There is a through hole on the ball. The diameter of the through hole is equal to the inner diameter of the pipe, which is called a full bore ball valve; the diameter of the through hole is smaller than the inner diameter is called a reduced bore ball valve.
The advantages of ball valves are: 1. Has the lowest flow resistance (actually equivalent to only a section of round pipe of the same nominal size). 2. It can be reliably used in corrosive media and low-boiling liquids because it does not get stuck during operation (when there is no lubricant).