The first type is called the floating ball valve which refers to the valve with a floating valve body. Under the pressure from the medium, the valve body is forced to press tightly to the sealing face of the exit end, reaching the function of ensuring the tightness. As it has been described, this type of the ball valve is with simple structure and easy operation. But it should be made sure that the sealing face is able to withstand the pressure passed from the medium. Otherwise, all efforts would be in vain. Thus, it is necessary to adopt the suitable material for the sealing face. Commonly, it is widely used in conditions with low or medium pressure.
It is different from the floating ball valve as the valve body of this type is fixed. Instead, the movable part is the valve seat. The received pressure would lead the valve seat to move. Then, the sealing face would be compressed to the valve body, reaching the requirements of the tightness. Generally speaking, it is applicable for conditions with much higher pressure and much bigger diameter resulting from the ball bearings in the shafts of the valve body.
The last type is called elastic ball valve which is applicable for the inside medium with high pressure and temperature. It means that the valve body of this type is elastic. Or it can be said that the sealing can be only reached by the external force. The external force is needed indeed because the pressure from the medium would not be able to ensure the tightness, as the material for the valve body and the sealing face is commonly the metal. The elasticity is gotten by the gap below the inside surface of the valve body. During the working, the valve stem plays an important role. For example, when the channel is closed, the valve stem with the wedge-shaped head compresses the valve body to the valve seat tightly.
Above all, it is obvious to see that the major difference locates in the difference of the valve body. Actually, there are many trials to optimize the operating of each type. Definitely, they are continuing to bring benefits either to the industrial process or to the daily life.