double beat valve 环形阀 ; 圆环阀 ; 双座阀 ; 双层阀

double-beat valve [机] 双座阀

single-beat valve 单层阀

single beat valve 单层阀

double-beat drop valve 双座阀

double-beat poppet valve 双层提升阀

single-beat main stop valve 单座式主汽门

single beat poppet valve 单层提动阀

double beat drop valve 双座阀