Advantages of ball valves 

 (1) It has the lowest flow resistance (actually 0); 

 (2) Because it will not get stuck when working (without lubricant), it can be reliably used in corrosive media and low-boiling liquids; 

 (3) Under a large pressure and temperature range, it can achieve complete sealing; 

 (4) It can achieve rapid opening and closing. The opening and closing time of some structures is only 0.05~0.1s to ensure that it can be used in the automated system of the test bench. When opening and closing the valve quickly, there is no impact in the operation. 

 (5) The spherical closure can be automatically positioned at the boundary position; 

 (6) The working medium is sealed on both sides and reliable; 

 (7) When fully open and fully closed, the sealing surface of the sphere and the valve seat is isolated from the medium, so the medium passing through the valve at high speed will not cause erosion of the sealing surface; 

 (8) With compact structure and light weight, it can be regarded as a reasonable valve structure for low-temperature medium systems; 

 (9) The valve body is symmetrical, especially the welded valve body structure, which can withstand the stress from the pipeline well; 

 (10) The closing part can withstand the high pressure difference when closing. 

 (11) The ball valve of the fully welded valve body can be buried directly in the ground, so that the inner parts of the valve are not eroded, and the service life of ≤ can reach 30 years. It is an ideal valve for oil and natural gas pipelines. 

 Disadvantages of ball valves 

 (1) Because the main seat sealing ring material of ball valves is polytetrafluoroethylene, it is inert to almost all chemicals, and has the comprehensive characteristics of small friction coefficient, stable performance, not easy to age, wide temperature application range and excellent sealing performance. 

 However, the physical properties of polytetrafluoroethylene, including high expansion coefficient, sensitivity to cold flow and poor thermal conductivity, require the design of the valve seat seal to be based on these characteristics. Therefore, when the sealing material hardens, the reliability of the seal is destroyed. 

 Moreover, the temperature resistance of polytetrafluoroethylene is low and can only be used at less than 180 ℃. If it exceeds this temperature, the sealing material will age. Considering long-term use, it is generally only used at 120 ℃. 

 (2) Its adjustment performance is worse than that of shut-off valves, especially pneumatic valves (or electric valves). 

Scope of application of ball valve 

 Because ball valves usually use rubber, nylon and polytetrafluoroethylene as seat sealing ring materials, its use temperature is limited by the seat sealing ring material. The cut-off effect of the ball valve is achieved by the metal sphere pressing each other between the plastic valve seat under the action of the medium (floating ball ball valve). Under the action of a certain contact pressure, the valve seat sealing ring undergoes elastic plastic deformation in local areas. This deformation can compensate for the manufacturing accuracy and surface roughness of the ball and ensure the sealing performance of the ball valve. In addition, because the seat seal of ball valves is usually made of plastic, the structure and performance of ball valves should be selected, the fire resistance and fire protection of ball valves should be considered, especially in petroleum, chemical industry, metallurgy and other departments. When using ball valves in equipment and pipeline systems of flammable and explosive media, more attention should be paid to fire resistance and fire prevention. Generally, it is recommended to use ball valves in pipeline systems with double-position adjustment, strict sealing performance, mud, wear, shrinkage channel, rapid opening and closing action (1/4 turn opening and closing), high-pressure cut-off (large pressure difference), low noise, air holes and gasification phenomena, a small amount of leakage into the atmosphere, small operating moment and small fluid resistance. 

 Ball valves are also suitable for pipeline systems with light structure, low-pressure cut-off (small pressure difference) and corrosive media. Ball valves can also be used in low-temperature (deep-cooled) devices and pipeline systems. In the oxygen pipeline system of the metallurgical industry, ball valves with strict degreasing treatment are required. When the main line in the oil pipeline and gas pipeline needs to be buried underground, a full-diameter welded ball valve should be used. When adjusting performance is required, it is necessary to choose a special ball valve with a V-shaped opening. In petroleum, petrochemical, chemical, electric power and urban construction, metal-to-metal sealed ball valves can be selected for pipeline systems with a working temperature of more than 200 degrees.