Two ball valves and flanged gate valve is the same type, the difference in its closure is a sphere, a sphere around the body centerline rotation to achieve open and closed a valve. Ball valve in the pipe is mainly used to cut distribution and change the media flow direction. Two ball, three ball, in recent years has been the widespread adoption of a new type of valve, the valve in the pipeline should generally be horizontal mounting. 
 A, two ball valve has the following advantages: 
 A. Fluid resistance is small, equal to the drag coefficient with the length of the barrel. 
 Two. Simple structure, small size and light weight. 
 3. Reliable, close the valve sealing surface material widely used plastic, good sealing, has been widely used in the vacuum system. 
 4. Easy to operate, opening and closing rapidly, from fully open to fully closed as long as the rotation of 90 °, to facilitate remote control. 
 5 Easy maintenance, simple valve structure, the seals are generally activities, removal of the replacement is more convenient. 
 6. In the fully open or fully closed, the ball and seat sealing surface and the dielectric isolation, through the media, does not cause erosion of the valve sealing surface. 
 7. Wide scope of application, the path from childhood to a few millimeters to a few meters from the high vacuum to high pressure can be applied. 
 Two ball valve according to the position of the channel can be divided into straight-through, three links and rectangular Type. The latter two ball valves for the distribution media and change the flow of media. Three ball valve installation and maintenance should note the following: 
 (1) to leave the position of the valve stem rotation. 
 2 can not be used as a throttle. 
 With transmission of the ball valve should be installed upright. 
 Second, the works of the two ball valves smooth or occlusion rely on rotary valve Love. The ball valve switch is lightweight, small size, can be made into a large caliber, reliable sealing, simple structure, easy maintenance, sealing surface and the spherical often in the closed state, is not easy to be medium erosion, has been widely used in various industries. 
 Three, two ball valves in the pipeline is mainly used to cut distribution and change the media flow direction. The ball valve is a new type of valve in recent years has been widely used, it has the following advantages: 
 A. Fluid resistance is small, equal to the drag coefficient with the length of the barrel. 
 Two. Simple structure, small size and light weight. 
 3. Reliable, close the valve sealing surface material widely used plastic, good sealing, has been widely used in the vacuum system. 
 4. Easy to operate, opening and closing rapidly, from fully open to fully closed as long as the rotation of 90 °, to facilitate remote control. 
 5 Easy maintenance, simple valve structure, the seals are generally activities, removal of the replacement is more convenient. 
 6. In the fully open or fully closed, the ball and seat sealing surface and the dielectric isolation, through the media, does not cause erosion of the valve sealing surface. 
 7. Wide scope of application, the path from childhood to a few millimeters to a few meters from the high vacuum to high pressure can be applied. The ball is rotated 90 degrees in the import and export of Department should be fully rendered sphere, thus cutting off the flow. 
 Two ball valve is a relatively new category of ball valves, it has some advantages unique to its own structure, such as switching non-friction seal easy to wear, opening and closing torque is small. This can be reduced with the specifications of the actuator. Accompanied by multi-turn electric actuators on media regulation and tight cut. Widely applied in petroleum, chemical, and urban drainage requirements of strict cut off conditions. 
 Fourth, it works as follows: 
 A, open process 
 1 in the closed position, the sphere by the machinery put pressure on the role of the valve stem, pressed on the seat. 
 Turn handwheel, the valve stem is the reverse movement, the bottom of the angular plane so that the sphere to disengage the valve seat. 
 3 stem continue to enhance the interaction and stem the spiral groove of the guide pin, the sphere began to friction-free to rotate. 
 4 up to the fully open position, the stem raised to the limit position, the sphere rotated to the fully open position. 
 B, the closing process 
 A closed, clockwise rotation of the handwheel, stem began to decline and make a sphere out of the seat begins to rotate. 
 2 Continue turning the handwheel, the valve stem by the spiral groove embedded in its role of guide pins, so that the stem and the sphere at the same time rotated 90 °. 
 3 near the closed sphere in the case of contact with the seat rotated 90 °. 
 4 handwheel is turned the final laps, the stem at the bottom of the angular plane mechanical wedge to the oppression of the sphere, so that it closely pressed on the seat, to achieve complete seal. 
 The structural characteristics of the two type ball valve: 
 1, open and close without friction. This feature completely solved the traditional valve seal problems affect the mutual friction between the sealing surface. 
 2, the coat structure. Valve installed on the pipe directly on-line inspection and maintenance, can effectively reduce the plant closings, and reduce costs. 
 3, single-seat design. Elimination of the valve in the cavity medium due to abnormal pressure and affect the use of safety problems. 
 4, low-torque design. Special structural design of the stem, just with a small hand valve can open and close easily. 
 5, wedge-shaped sealing structure. Valve by stem provides the mechanical force, the ball wedge pressure to a seat on and seal, the sealing of the valve from the pipeline pressure changes affect the sealing performance under various conditions have a reliable guarantee. 
 6, self-cleaning of the sealing surface of the structure. When the sphere is tilting away from the valve seat, the fluid in the pipeline along the sphere sealing surface as evenly through 360 °, not only eliminates the high-speed fluid on the seat of local erosion, but also washed away the accumulation of material of the sealing surface of the, to achieve the purpose of self-cleaning .