The ball valve is a ball driven by the stem as the opening and closing part. 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 valve category. 

The structure of the ball valve 

The model of the ball valve is shown in the figure. Its opening and closing part is a ball located in the center of the valve, which is rotated by the valve stem 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. You only need to rotate 90° to open from full to full closed. 

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

Advantages of ball valves 

One of the advantages of the ball valve is that when the valve is fully opened, the fluid pressure drop through the valve is very small and almost unimpeded. The ball valve can be divided into three types: Venturi valve, shrinkage ball valve and full-diameter ball valve. Among them, the flow channel 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 lubrication. 

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

Disadvantages of ball valves 

The ball valve is not suitable for throttling. When it is in a semi-open position, the fluid passing 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 the valve to leak and make the valve unable to seal, which is very similar to the plug valve. 

Similarly, the ball valve cannot be applied to high-temperature conditions, because at high temperature, the seat of the ball valve will undergo plastic deformation due to heat, creating a gap between the ball and the valve seat, resulting in internal leakage.