Ball valve and plug valves is belong to one type of valve, its closing member is a ball. Ball valve body rotates around the center line to attain open and close. In the pipeline ball valve is mainly used for cutting off, distribution and change flow direction of medium. It's a new type valve that has been wildly used in petroleum, chemical industry, power generation, paper making, atomic energy, aviation, the rockets and so on various sectors, as well as People's Daily life.