Ball valve opens by turning a handle attached to a ball inside the valve. The ball has a hole, or port, through the middle, so that when the port is in line with both ends of the valve, flow will occur. When the valve is closed, the hole is perpendicular to the ends of the valve, and flow is blocked. Ball valve was evolved from plug valve, so it's also named ball type plug valve. The ball, which can make a quarter turn (90°) around the spin axis, is the on/off control of the Ball valve. 
Ball valves in the piping are used to cut, distribute and change the flow direction of the fluid. If the opening were designed to be V-shaped, it would also have the excellent function of flow control. Ball valves, which need a little rotating force and turn a quarter, can be closed tightly. The completely equal lumen provides a littler-resistance "green passage". Ball valve not only has the advantages of simplicity in system structure and good performance in sealing Properties, but also smaller in size, less in weight, less material, smaller dimension, less drive torque, easy-operating, easy-repaired, can be applied to general media, such as water, solvent, acid and natural gas. It still can be used in poor working conditions, such as oxygen, hydrogen peroxide, methane, ethylene and so on. The body of ball valves can be a whole or a combined one.
Ball valve is a new type introduction came out in 1950. In a short span of 30 years, it has become the fastest-growing valve, especially in the United States, Germany, Japan, France, Italy, Spain, Britain, and other industrial developed country. Ball valves are widely used, the demand of quantity is still growing up, and the current trend is to develop high-temperature, high pressure, heavy caliber, high tightness, long life-span, excellent adjusting performance and multi-function valves. The reliability and other performance indexes are all reached a comparable high level, and ball valves have partly replaced gate valves, globe valves and throttle valves. Due to the outstanding advantages of the ball valves, it has been widely used in the areas of aerospace, Petroleum, long-distance pipeline, light industry and food industry, construction and so on.

(1) Fluid resistance is zero
Generally, Ball valve has 2 kinds of structures which are RP (reduced port) and FP(full port). The fluid resistances of both structures are very small.
The diameter of channel equals to the inner diameter of pipe, the local resistance loss also equals to the friction resistance of the pipe, and so the full port Model, also called full flow type, is the Ball valve with the min fluid resistance. In the rocket launching and test system, it required the resistance of the pipe the less the better. There are two ways to reduce the resistance of the system: First, to reduce the speed of fluid, which can be achieved by increasing the diameter of the channel and the full port of the valve, but this may have a negative impact on the pipeline system, particularly the type of low-temperature delivery system (Hydrogen). The second is to reduce the local resistance, so theBall valve becomes the best choice.
(2) Easy and rapid open-close operation
Under normal circumstances, ball valves can finish the open-close operation easily and rapidly by quarter turn (90°). In order to be used in the automation system of the test platform, the time of open-close operation is limited between 0.05 ~ 0.1s. Fast open-close operation, no operation shock.
(3) Outstanding seal property
At present, the enormous majority of the Ball valve seats are made in flexible materials, such as PTEF, the seal pair combined by metal and non-metallic materials called soft seal. Generally, it's easy to make sure the tightness of the soft seal, what's more, the requirement of the machining accuracy and surface roughness of the seal does not high.
(4) Long life-span
Due to the good self-lubricating of PTFE, small friction with the ball, the advancement of ball processing technology, reducing of roughness, the ball valve's life-span has been greatly improved. It reported that as a result of the life-span test made by the company of W-K-M of the United States, the number of switches can be over 100,000 times.
(5) Main reason of high reliability
① Ball and the pair seal part of seat will be no mechanical abrasion, no severe wear and tear, and will not be locked in the working hour (in the absence of lubricants), so it can be reliably applied with the corrosive medium and low boiling point liquid;
② Built-in stem structure can remove the potential accidents of the fly-out of the stem, caused by the loosen of packing under the fluid pressure.
③ Ball valve with anti-static, fire-resistant structure can be apply to the transport of oil, natural gas, the gas pipeline
(6) Valve body with smooth channel is more suits to convey viscous fluid, serous, as well as solid particles.
(7)It will not be locked (in the absence of lubricants) in the working hour, so it can be reliably applied with the corrosive medium and low boiling point liquid.
(8)The open-close control of the Ball valve can realize the automatic location, and bear the high pressure differential when it closed.
(9)In a big pressure and temperature range, can achieve a completely two-way seal.
(10) When full-open or full-close, the seal of the ball and the seat isolate the medium, so the medium passing with high speed will not cause the erosion of the seal.
(11) The valve of Compact structure, light weight, can be regarded as the most ideal choice in the low temperature medium system.
(12) Valve body symmetry, especially the welding structure, is able to bear the stress from the pipeline.
(13) The fully welded ball valves can be buried underground; the trim would not be corroded, so the maximum useable life span can be as long as 30 years, this kind of ball valve is the best choice for oil, natural gas pipeline.