non return valve meaning in Chinese

单向阈
止回阀

Shipbuilding . discharges with non return valve . general manufacturing conditions
造船工业.带止回阀排放装置.通用制造条件
Technical specifications for valves for shipboard use - part 5 : cutt off type non return valves
船用阀门技术规范.第5部分:截止止回阀
Non return valves for shipboard use , cutt off type , of cast iron , with flanges , dn 15 to 500
造船用dn15至500规格的带法兰的铸铁单向阀
Non return valves for shipboard use , cutt off type , of gun metall , with flanges , dn 15 to 500
造船用dn15至500规格的带法兰的截止型炮铜单向阀
Pn1 ships and marine technology - non return valves non shutt off type extra light duty dn 32 to dn 125 , pn 10
船舶与海上技术.超轻型非截止型单向阀dn32 - dn125