..............page:4-6,10
Analysis and research on sealing structure of ball valve
wang jia xin 1; yin feng ping 2; xu ming hua 3(1 shanghai zhenyu valve manufacturing co.ltd; shanghai 200030; china; 2 shanghai gas design institute; shanghai 200030; china; 3 shanghai butterfly & ball valve plant; shanghai 200030; china)
..............page:29-32
..............page:36-38,42