Check valves are intended for use in naval vessel and military piping systems to automatically prevent a reversal of flow through the line. Critical shipboard piping systems should be outfitted with regrindable or renewable check valves to permit at-sea and forward repair. Swing check valves offer less resistance to flow than lift checks and are generally used in systems where gate valves are employed. Lift checks are generally used where frequent reversals of direction are encountered and a pressure drop comparable to globe or angle valves is allowable. Ball lift checks are especially suited for viscous fluids. Non-metallic disks, when rated for media temperatures involved, result in quieter operation, will seat even when the media contains small particulate matter, and provide tighter closure at lower pressures, especially for air and gas service. Tilting disk check valves and spring-loaded check valves are characterized by rapid closure action, which tends to minimize flow reversal and resultant hydraulic hammer. Class 125, 150, and 200 bronze-body swing check valves and class 150 and 200 bronze-body horizontal, guided-disk lift check valves with metallic disks should be procured in accordance with MSS SP-80 if the regrindable seats covered by this specification are not required. Current stock of valves covered by this specification may be used until depleted; future requisitions for these valves should refer to the current