OVIKO TOP ENTRY BALL VALVE is mainly used in pipeline and industry systemand it has a top entry and on line maintenance function.It has a lot of advantages,such as small fluid resistance,simple structure,small volume,light weight,reliable saaling,convenience for operation and maintenance,open and close quickly,as well as start and close flexibly. Its most difference from common ball valve is that its maintenance can be made on pipe line and without dismounting from the pipe line.The back space seat structure is adopted for the seat and the rearportion of seat retainer is oblique angle to prevent accumulation of impurityfrom affecting back space of seat