Armaş “NSC” model valve is hydraulically controlled non-slam check valve which operates with line pressure and prevents back-flow in system. Valve works with double chambers. Upstream pressure controls one of chambers and downstream pressure controls the other one. When downstream pressure value exceeds upstream pressure value (back-flow), valve is closed as wholly sealed without causing surge because of double chambers. When upstream pressure value exceeds downstream pressure value, non-slam check valve is opened by itself slowly. So pressure surges formed during start-up, stop and working sysytems are dumped.