The main differences between ball valves and plug valves are their structure, working principle, operation mode, flow control, sealing performance and application scenarios. 

 I. Structural differences 

 The ball valve evolved from the plug valve. Its opening and closing part is a sphere, which can be opened and closed by rotating the sphere by 90° around the axis of the valve stem. The structure of the ball valve is relatively simple, consisting of a spherical valve body and a hole through the ball. 

 The closing part of the plug valve is a plunger-shaped rotary valve, which rotates 90° to make the channel on the plug connected or separated from the channel on the valve body. The structure of the plug valve is relatively complex, consisting of valve body, valve cover, valve core, valve seat and valve stem. 

II. Working principle 

 The working principle of the ball valve is to control the opening and closing of the fluid by rotating the ball. When the ball rotates to contact with the valve seat, it forms a seal to prevent fluid leakage; when the ball rotates to separate from the valve seat, the fluid can flow through the channel in the valve body. 

 The working principle of the plug valve is to open or close the channel by rotating the plug body, and the plug body rotates with the valve stem to achieve the opening and closing action. The opening and closing parts of the plug valve are conical plugs with holes, and the fluid channel is perpendicular to the axis of the plug. 

III. Different operation methods 

 The operation of the ball valve is relatively simple. Usually, it only needs to rotate 90 degrees to complete the switching action. The design of the ball valve allows the fluid channel to be quickly opened or closed after the sphere rotates 90 degrees, which is convenient and fast to operate. In addition, the sealing performance of the ball valve is excellent, especially when it is fully open or fully closed, and the fluid resistance is relatively small, which is suitable for occasions that require quick switching. 

 The operation of the plug valve is relatively complicated, and it needs to be rotated several times to complete the switching action. The core of the plug valve is usually cylindrical or conical, and the fluid flow is controlled by rotation. Due to its structural characteristics, the plug valve performs well in flow regulation and can accurately control the diameter of the fluid channel, but it is not suitable for frequent operation. 

 IV. Different flow control 

 The main difference between ball valves and plug valves in terms of flow control is that plug valves perform better in flow regulation, while ball valves have relatively poor flow regulation performance. 

 Due to its structural characteristics, the plug valve can accurately control the diameter of the fluid channel, so as to achieve precise adjustment of the flow rate. In contrast, although the ball valve can adjust the opening by rotation, it is not as flexible as the plug valve. 

V. Different sealing effects 

 The sealing performance of ball valves is theoretically slightly inferior to that of plug valves, but with the improvement of technology, the sealing effect of ball valves is getting better and better, and the scope of application is gradually expanding. 

 The sealing performance of the plug valve is good, and it usually has a multi-channel sealing design, which is suitable for occasions with high sealing requirements. The ball valve is simple in structure, light in weight, small in size, and more convenient to use. The structure of the plug valve is complex, but the switch is fast and the fluid resistance is small. 

VI. Applicable occasions are different 

 Ball valves are widely used in petroleum, chemical, papermaking, pharmaceutical and other industries, and are suitable for application scenarios that need to be opened or closed quickly. 

 Plug valves are widely used in oilfield mining, conveying and refining equipment, and are suitable for application scenarios that require accurate flow control and good sealing. 

 Therefore, when selecting the type, it is necessary to choose the appropriate valve according to different occasions, media and working conditions.