Allow ballast piping from one ballast tank to be run through another ballast tank without check valve installed inside the ballast tank or at tank boundary. Same to apply for void compartment bilge piping run through another void tank (Note: both tanks should be from the same piping system). Check valves are not required by Class and API-RP-2T if ballast piping does not run through void compartment or void compartment bilge piping does not run through ballast tank.
This will allow all ballast and bilge valves to be located in central location such as pump room/service space for Operator’s convenience, easy operation, inspection and maintenance and will eliminate valves inside access tunnels.
It is not recommended to install check valves inside tanks/confined space due to accessibility for inspection and replacement and system operation due to valve failure.