Cargo tanks are to be provided with a high level alarm independent of the gauging device or with equivalent means to guard against liquid rising in the venting system to a height exceeding the design head of the cargo tanks.
Pressure and vacuum valves may be set higher during voyage for the prevention of cargo losses than for controlled venting during loading.
Pressure/vacuum valves which are located in masthead risers may be fitted with a by-pass arrangement which can be opened during cargo operations.
Indicators shall clearly show whether the by-pass valve is in the open or closed position.
