The ball valve is a ball driven by the valve stem as an opening and closing part, and the valve rotates around the axis of the ball valve, which can be used for fluid regulation and control. Ball valves came out in the 1950s and have now become the most widely used valves. 

The structure of the ball valve 

The model of the ball valve is shown in the figure. Its opening and closing part is a sphere located in the center of the valve, which is driven by the valve stem to rotate to realize the opening and closing operation. The ball valve, like the butterfly valve and the plug valve, is a quarter-turn valve, which can be opened and closed quickly. It only needs to be rotated by 90° to fully open and fully closed. 

The ball body and valve body of the ball valve are made of metal materials, such as stainless steel; the valve seat is made of soft elastic materials, such as polytetrafluoroethylene, neoprene, etc. In this way, the sphere can be pressed on the valve seat, so that the valve can be well sealed. 

The connection between the top of the ball valve and the stem is usually rectangular, which allows us to apply a large torque to control the opening and closing of the valve without causing deformation of the ball. 

Advantages of ball valves 

One of the advantages of the ball valve is that when the valve is fully open, the fluid pressure drop through the valve is very small and almost unimpeded. Ball valves can be divided into three types: Venchuri valves, shrinking ball valves and full-diameter ball valves. Among them, the flow size of the full-diameter ball valve is the same as the inner diameter of the pipeline, and the fluid pressure drop through the valve is very small. 

The ball valve has a simple structure, a relatively low price, low maintenance cost and no need for lubrication. 

Another advantage of the ball valve is that the ball seals the valve seat very well, and there is usually no internal leakage. 

Disadvantages of ball valves 

Ball valves are not suitable for throttling. When it is in the half-open position, the fluid through the gap between the ball and the valve seat is very fast, which will cause damage to the ball and the valve seat, causing internal leakage of the valve and making the valve impossible to seal, which is very similar to the plug valve. 

Similarly, the ball valve cannot be used under high-temperature conditions, because the valve seat of the ball valve will be plasticly deformed by heat at high temperature, resulting in a gap between the ball and the valve seat, resulting in internal leakage.