The structural principle is: when the ball is assembled without preload, it is tangent to point A. The preload makes the ball axis displacement, which is generally between 0.2 and 0.4 (mm). When the ball is under pressure, the ball clings to the sealing surface in the direction of pressure. At this time, the seal ring expands outward, so that the sealing surface and the spherical surface will not stick too tightly, causing torque increase. After pressure relief, The sealing valve seat basically returns to the original installation position. Self sealing is a special sealing form. The valve rod seal of the large caliber pneumatic ball valve produced by the valve adopts this structure. The working principle is to use the medium pressure for self tightening sealing. Its sealing ring is installed outside the inner cone and forms a certain angle with the opposite side of the medium. The medium pressure is transmitted to the inner cone to transmit to the sealing ring. Two components are generated on the conical surface at a certain angle. One is parallel to the centerline of the valve body and the other is pressed to the inner wall of the valve body. The latter force is the self tightening force, The greater the medium pressure, the greater the self tightening force. Considering the sealing at low pressure, a certain pre tightening force must be added on the self tightening seal to ensure its sealing performance.

Pneumatic ball valve is a combination of pneumatic actuator and ball valve. It can replace manual operation, not only save a lot of manpower and material resources, but also control multiple ball valves at the same time. The pneumatic ball valve is relatively simple in structure, convenient in maintenance and high in relative safety. It is made of superior materials and properly used. Its service life can reach 1 million times. Pneumatic ball valve is evolved from plug valve. It has the same 90 degree rotation action, but the difference is that the cock body is a sphere with a circular through hole or channel through its axis. The proportion of the sphere and the passage opening should be such that when the sphere rotates 90 degrees, the inlet and outlet should be all spherical, so as to cut off the flow.